I have been reading old post about air leaks and it is a little confusing, I have changed all 8 air bags so it stays put and does not drop, I rebuilt dryer a few years ago and it has not gone to many miles I replaced 2 air solenoids on front 6 pack (lower- up/down RF) so I can't hear anything leaking, But in a period of 8 hours, PSI gauge drops most of the way down both white & red evenly, Any suggestions?
Welcome to the wonderful world of air leaks!
First question, about the red (front tank) and white (rear tank) needle movement. Do they stop, or at least pause for a day or two, around 55-60 psi, or do they drop straight down to zero? The answer will indicate the condition of your
protection valves.
In an 8 hours period it falls pretty much all the way down
OK, this indicates your protection valves are not functioning properly. I would suggest your first step should be to replace these valves. There are two reasons for this priority.
First, the protection valves serve a very important safety function. If you are driving down the road, and have a massive failure (hose blows, fitting breaks off, etc) in one of your air components (air suspension, air step, air horns, etc), properly functioning protection valves will prevent the pressure in your front and rear air tanks from falling below 60 psi. This will insure that you have enough air pressure to operate your service brakes and bring the coach to a safe stop.
Second, if the protection valves are working, it greatly reduces the possible places you might be leaking air. Replacing the valves will make the job of tracking your air leak a LOT easier.
Here is my thread on replacing the air tank valves. It is not a difficult job, and your air system will thank you for the time spent.
Air Tank Valves R&R (http://www.foreforums.com/index.php?topic=27638.msg226700#msg226700)
Art,
Here is another suggestion. If you do decide to tackle replacing your air tank valves, you should also check the condition of your tank inlet check valves. This is easy to do. Pressure up your air system to about 120 psi. With engine off, open the water drain valve on your wet tank, and let the pressure bleed down to zero. Close the drain valve. Go inside and check your air gauge. Both needles should still be showing around 120 psi. If one or both of the tanks has dropped to around zero, this would indicate the check valve on that tank is totally inoperative. If the pressure in one of the tanks has gone down some, but not to zero, then the check valve is leaking.
Either way, you will want to repair the offending check valve. Remove the valve, and take it apart. If it is just plugged up with gunk, but otherwise OK, it can be cleaned out and reinstalled. If it is corroded, seat destroyed, spring broken, etc...replace it.
The check valves are important - they keep a leak in the wet tank from totally draining the pressure in the front and rear tanks. Once again, this is a safety issue, for exactly the same reason as stated above for the protection valves.
So if I air up and drain wet tank should the pressure protection hold pressure in front & rear tanks?
Also Chuck are those part # for protection valve& shuttle valve good for my coach?
When you air up the coach, and drain the wet tank, what you are testing is the
inlet check valve on the front and rear tanks. This valve keeps air pressure from escaping
backwards through the supply line from the wet tank. The
protection valve is on the
outlet port of the tanks. Both valves are intended to preserve braking pressure in the tanks in the event of system malfunction. The two terms are often confused.
As to the part numbers...since you have a newer model coach, I cannot know if it uses the same part numbers. You need to take a close look at the valves on your coach, and see if they look like the photos I posted. If so, the part numbers I used should work. If yours look different, you might be able to find part numbers on the old valves, and see if they are still available or if crossover parts are available.
Art,
If you have the white FT book you might find an air system schematic near the back. If not, see if you can get one for your specific coach from FT. It is important to get one for your coach because while there are many common elements the details change from year to year. Just as my 2001 is significantly different from a 2003 and is certainly different from your 1996, your 1996 maybe different from a 1993.
Roger
This is what I got with coach
That
is the air system schematic, and it is
very handy for tracing the layout of the air lines. Almost every air line installed by Foretravel is marked with a unique number, which can be referenced on the schematic. Unfortunately, it does
not list part numbers for all the various valves. There is no such listing, as far as I know. The only way to find part numbers is like I said: look at the old part and hope to find a number on it. If you are lucky, the OEM part number will still be available. If not, you will have to find a suitable substitute.
That is the one, different from mine. The number in the CN box (4722) is the coach number for which this drawing first became effective. Your coach number is 4871. Glad you found it.
Took a couple of pictures
Sometimes the part number is stamped on the part but it is hard to see. Wipe it off and rub it with some sidewalk chalk or plain white chalk and then wipe it off again. Usually the part number will be pretty easy to see.
There may also still be the tag with id# on. I know most of my valves have it still on. You may have to clean the valve to see it but it is a small white sticker.
JohnH
Some of those fittings can be very difficult to access and in some cases require partially dropping the air tank to get clearance to remove one. The air plumbing "trees" which pile fitting on fitting can leave the innermost one almost inaccessible. When removing the check valves from the front and rear air tanks, it was almost impossible to get at the check valve for the front tank. removing some of the mounting hardware from the tank and loosening the rest let one end of the tank down just enough to back out the fittings at the top of the "tree". When I replace the check valves again, I am going to put in stainless steel pipe unions on the root of the "tree" so I can remove those parts without the bad words.
Don
Edit: I should mention that this was done at John H's pit. Without that, it would have been impossible get the necessary leverage to remove those fittings, bad words or not!
I have never been under a Unicoach...from what you say the tanks must be
much harder to access. I sympathize, and I feel your pain. One of the many benefits of the Unihome - everything up front is fairly easy to reach and work on.
I agree with you about the check valves...those suckers were in there
TIGHT. I had to use a serious "cheater" on my wrench to break them loose. I was hoping my valves were non-typical in that respect, but apparently not.
The good thing is, once you have removed them and then reinstalled with fresh pipe dope, the NEXT time they should come off a lot easier. ^.^d
I'm sorry, Art, but I can't see enough in your photos to tell what you've got.
Chuck,
I have sent a PM to you. Did you receive it?
Rudy,
No, I have not received your PM.
Can you take a minute and call me please, 7 one 3 8 one 8 3234, Thanks
So looking at schematics it looks like there is a check valve on all 3 tanks, For maintenance do you remove and clean or replace?
Already answered. See reply #4 above.
Nice! I see , Is there anything in book that explains letters on schematics like( I ) must be check valves (H) is protection valve (K) Is another shuttle valve? only on front tank (U) is the shuttle valve ? I took a few pictures and down loaded to computer so I can check it out Is
The only "legend" I know of is the one in the lower right corner of the schematic. Somewhere, buried deep in a long-lost file drawer at FOT, there is a "Key" to all the letters on every model year air schematic. Only Indiana Jones would be able to find it, and he retired.
Correct. "U" is the 4-way shuttle valve. "H" is the protection valve. "I" is a 1-way check valve. "K" (front tank) is a 2-way check valve, which is very similar (internally) to a shuttle valve.
Your air schematic actually has a lot better notation than the one for our '93 model coach. I have to "guess" about the function of just about everything on our diagram.
To any members who might be watching this thread:
While we're talking about air leaks, I would like to make another suggestion. If you have any interest in really knowing what is going on in your air system, you need a way to monitor the pressure in your wet tank. Foretravel, to my knowledge, did not ever install a wet tank pressure gauge.
There are two ways to rectify this situation. I decided to mount my gauge in the engine compartment. There is a unused tapped "reservoir" port on the D2 governor. I installed a small needle valve in this port, then ran a line to my gauge. I hung it where it is visible looking through the slats in the engine compartment cover. See photos.
An even easier way is available, and it works just as well. I believe all the Foretravel coaches have the factory installed air hose for filling the tires. This hose comes directly off the wet tank. You simply rig up a pressure gauge with a male quick connect air hose fitting. Then when you want to read wet tank pressure, plug the gauge into your air hose and open the valve. Voila!
Knowing your wet tank pressure can help you isolate and identify pesky hard-to-find air leaks. It is also handy for checking/adjusting the setting of the D2 governor, without having to run all the way up to the driver compartment. A highly recommended mod! 8)
Chuck:
What is the 0-30 psi gauge reading?
Fuel pressure - comes off the inlet line to the injection pump, using a Tork Tek snubber.
Definitely a worthwhile and easy to accomplish mod... I did both methods you described back when I had the air dryer failure. Speaking of which, today I let it idle while watching the wet tank gauge and can confirm that the wet tank pressure drops while the front and rear tanks hold steady at 120psi. I had a feeling of dejavu while doing this and now remember that I had already done this a year or so ago. The pressure drops until the governor kicks in and engages the compressor. Funny thing though, at fast idle, it didn't seem to drop much if at all... I didn't watch it very long so I may just be obfuscating the issue, because I can't think of any mechanism that would make a difference between fast idle and regular idle as regards the wet tank losing pressure from 120psi. Of course, it builds pressure much faster with fast idle... scratching head and moving on. For now...
Don
Hey Chuck. In our 2001 coach the aux air comes off the rear brake tank after the protection valve. Adding air to this aux air connection does allow you to adjust height using the air bags but does not add air to either front or rear tanks or the wet tank.
I have an air pressure gauge that I can plug into the aux air connection. If all of those tanks are empty and I air up the air bags using the aux air and disconnect the air supply I will read about 110 lbs (what is in the retarder accumulator and the aux air line) assuming the check valves are working. Concept is similar, details change.
Chuck,
I ran the test this morning and the dash white needle went to zero and the red down about 5 lbs. indicating the rear tank inlet check valve is not working and perhaps the front one is leaking. Time to remove and see what's going on. This is an excellent and easy way to test these valves. A healthy air system is also a safe one! ^.^d
Jerry
So, we both have basically the same problem: something that comes
directly off the wet tank is leaking air. You lose 20 psi in 5-6 minutes; I lose 120 psi overnight. In both cases, our check valves on the front and rear tanks are holding - that is good!
On our '93 GV, if I rule out the inlet line from the dryer (protected by a known good check valve), that only leaves 4 other outlets from the wet tank.
1. 3/8" nylon line that terminates at the air hose (tire filler hose).
2. 1/4" nylon line to air tank remote drain valve.
3. Main 1/2" braided cloth line going to front and rear air tanks.
4. Multi-outlet manifold with 3 ports. One port is the safety pressure relief valve (I have already removed, cleaned & reinstalled). One port is the 1/4" braided cloth supply line going to RES port on the D2 governor. The last port is a 3/8" nylon line that goes to the isolation valve (I think that is what it is called) on the air dryer.
Rusty Socket has recommended spraying the braided cloth supply line to the D2 with soap solution. I plan to try this at the next opportunity.
Jerry (coastprt) suggests trying to tighten the packing on the brass valve on the (tire filler) air hose. I did that this morning, but have not yet tested to see if it helped.
If neither of these pan out, I plan to put a ball valve on every line coming off the wet tank, and close them all. Then open them, one at a time, until I find the leaky hose. I'll let you know if I have any success!
Glad the test worked, and successfully indicated items needing attention.
Eat Your Wheaties before you tackle removing the check valves!
Some definitions needed please
What is the "D2 governor"?
How is the "Protection Valve" different from a check (one-way) valve?
What is the "PIE Interface Mod". On my air schematic each of the front tanks go to this. (2004 295)
Hi Larry,
The D2 governor, operating in conjunction with the unloading mechanism, automatically controls the air pressure in the air brake or air supply system between a maximum (cut- out) pressure and a minimum (cut-in) pressure. The compressor runs continually while the engine runs, but the actual compression of air is controlled by the governor actuating the compressor unloading mechanism which stops or starts the compression of air when the maximum or minimum reservoir pressures are reached. D-2TM governors are provided with mounting holes which allow direct mounting to the compressor or remote mounting. Porting consists of three reservoir ports (1/8 inch P.T.), three unloader ports (1/8 inch P.T.) and one exhaust port (1/8 inch P.T.).
Haldex D2 Governor Service Data (http://beamalarm.com/Documents/haldex_d2_governor_service_data.html)
The protection valve is like a check valve but it stops any leakdown at a preset minimum pressure. This keeps a minimum pressure available for the braking system. Probably a better description somewhere but that is what I understand.
No PIE interface on my air schematic. There is however a PIE interface just below my nose. Apple anyone?
LOTS of discussion on the forum about the governor - just do a quick search and you'll get more info that you thought you wanted ;) It controls upper and lower limits for the engine-driven compressor.
PIE Interface module is likely the blue module in the dash that takes air pressure and displays it on your dash gauges. A couple of folks have had it fail (Dan Spoor I recall being one). Search on "blue module" for his posts on the subject.
Oh, the dreaded Blue Module, mine is gray. They seem to fail incrementally. My air gauges and volt meter have died. Replaced air gauges with direct connected mechanical gauges. As these fail they casue your "annunciator" to beep all the time. A switch fixes that. VMSpc shows voltage as reported by the engine ECM.
You've received some good suggestions on the safety side of the air system, but they may not solve all the air leak problems. Some other places to look based on my experience.
In my case (1997 U295) I had a similar situation which was initially traced to leaking air cylinders for the step and step cover. When these were replaced the leaking slowed considerably but did not stop completely (pressure would gradually fall off over about 36 hours). One remaining leak is in the body of the antilock brake control valve for the front brakes.
It seems that this last one could fool a protection valve as it might be seen as a steady application of service brake, but I don't know that with any certainty as it's not clear to me just how the protection valve functions to allow air to the service brakes.
Unfortunately, there is no easy solution to the valve body leak. Haldex lists the valve as obsolete with no replacement. FOT service said they had researched it once and Haldex suggested a non antilock replacement but didn't know what that replacement was.
Kieth Risch at MOT recommended just continuing to drive the coach and said many others are driving coaches with more severe leaks than this one.
The purpose of the protection valve is to "protect" brake function in the event of failure in one of the auxiliary air systems. The air lines to the brake system come off the front and rear tanks
upstream of the protection valve. The protection valve can do nothing to prevent air loss due to a leak in one of the brake components. A leak in either front or rear brake components will drain the corresponding "brake" tank
and the wet tank. When driving, if the engine air compressor was unable to keep up with the air loss, then brake failure would be the inevitable result. Leaks in the brake system should not be ignored. If the original component is no longer available, a suitable replacement might be available, but may require some modification of the system. Any modification of the brake system should only be performed by a qualified (certified) air brake technician.
In addition to what Chuck said maybe this will help. The brake system protection valve is a check valve with a pre-set cutoff pressure. It stays open until the cutoff pressure is reached and then it closes. So, let's say you park and your coach pressure starts at 120 psi. If there is a slow leak, say in one of your air bags for example, the pressure will slowly go down in a few hours, until the brake system protection valves shut off at 65 psi. Then if your brake system is solid, the pressure (both needles) will stay at 65 psi (hopefully) for many more hours.
Note: This type of slow leak, say overnight or a few days, in the coach auxiliary system is not necessarily a problem, many coaches have small leaks, but a lot of us enjoy tracking them down ;). A fast leak (pressure loss in say in an hour or 2) should be addressed. (The DOT pressure loss requirement is 120 psi in an hour).
As Chuck said, if the source of the leak is in the brake system - or in the coach auxiliary system and the protection valve(s) are faulty, your air pressure will go all the way to zero, without a noticeable time period holding at 65 psi.
In this case the problem should be found and fixed as soon as possible.
I fully intend to get a replacement for the bad anti-lock control valve once I find someone that I trust to work on the air system. In the meantime, the leak is well below any DOT specs. (it takes 36 hours to drop from 120 to 0) so I'll drive it until I find that person/company.
Mostly I put this out for Art to consider other sources of leaks based upon my experience.
Chuck,
I successfully replaced the the protection valves, the one way check valves, and the tank inlet check valves on the front tanks. I also replaced the inlet check valve on the wet tank along with the safety blow out valve. Tough going at first but thanks to your instructions along with pics made it not so complicated. It took a lot of elbow grease but got it done.
I'm now in the process of replacing the ad-4 dryer with an ad-9. I built an emergency air dryer bypass to check things as they progressed. Removing the rusted/seized hoses from the old dryer fittings was a royal PITA and a real test of my manhood! I didn't have an air wrench so I finally had to break them loose with a couple of pipe wrenches. It's hard to get a good bite on those fittings in that cramped compartment. I finally had to take the dryer off the bracket and move it around to get enough torque.
The by-pass works and the compressor builds air but doesn't stop at the governor cut-off. I replaced the governor with a new one and the problem still persists. The compressor is a Bendix 501 and the governor has two lines coming out. One for the dryer control from the unloader port and the other one for the wet tank. I'm beginning to think the unloader mechanism (valve) is stuck and won't stop building air. Does yours work the same way or do I have to have the dryer hooked up for the governor to work properly? It worked fine before with the old dryer and d2 governor. I changed back to the old d2 with the same results. I noticed on your pics it looked like there was an extra line other than the one from the d2 that you used for the wet tank air pressure gauge. I sure hope that I don't have to service the unloader mechanism on the compressor. I don't know if the compressor has to be taken off the engine to do this. It would would probably be easier to remove the compressor and replace with an upgraded model with more cfms.
Thanks.
Jerry
Jerry,
Sounds like you are deep into your "Air System" investigation. I feel your pain from removing the old frozen dryer connections! It took every tool I had, and the longest "cheater" pipe I could get into position, to break those big suckers loose! I am sure you have already seen my old thread on this subject, but if not:
Air Dryer Bypass Demo (http://www.foreforums.com/index.php?topic=22007.50)
We (myself and all the other contributors to that thread) got into a very detailed discussion about what needs to be plugged, and how, when using the bypass. We finally decided on this basic procedure:
"You disconnect the big air line that attaches to the isolation valve. You disconnect the big air line that attaches to the bottom of the dryer. You connect those two hoses together with the EDB. That takes the air dryer (with isolation valve still attached) completely out of service. The next step is to plug the line that runs from the D2 governor to the dryer. The last step is to plug the black nylon air line (from wet tank) that is attached to the Isolation Valve. That completes the bypass procedure."
You have a different engine, and it sound like your air compressor/D2 governor setup is different from mine. Is your D2 mounted directly on the air compressor? My coach had the AD-9 Dryer as original equipment. My D2 governor is mounted on the frame and had (originally) three small air lines connected to it. One (reservoir pressure port) comes from the wet tank to the D2. One (unloader port) goes from the D2 directly to the air compressor (which is mounted on the engine block about 15" inches away). The 3rd line (unloader port) goes from the D2 to the air dryer. I also added a 4th line (reservoir pressure port) to the D2 for a pressure gauge.
On my coach, if I follow the steps listed above, the D2 will still function correctly to control the compressor. The fact that the dryer has been removed has no bearing on the D2/compressor operation. The D2 only needs one input to operate: reservoir pressure. As long as it can see this input, it should supply the "load" and "unload" signals to the compressor at the preset pressures.
When using the dryer bypass, be sure you have plugged the small line that goes from your D2 (unloader port) to the dryer. If this line is left open to atmosphere, the D2 cannot send a "unload" (pressure) signal to the compressor.
Chuck.
My D2 is mounted directly on the compressor. I connected the big inlet and outlet lines from the dryer together and put a plug on the small line for the dryer control. I think I forgot to include the isolation valve from the delivery port on the by-pass. I'll go check.
Thanks,
Jerry
Chuck,
I finally figured out my problem. After getting the intake hose and fitting off the compressor, I was able to get a look at the unloader valves and my suspicions were correct. The unloader valves were rusted shut and not working at all! They probably had been that way for a long time due to never being checked for operation by the prior owners. I didn't realize the compressor was never unloading and the air pressure was only being controlled by the governor cut-off and the blast purge of the air dryer. With the dryer by-pass connected the governor should still control the pressure cut-off if the unloaders are working properly.
Unfortunately with a Bendix Tu-Flo 501 compressor you have to remove the head to service the unloaders properly if they are stuck. Also on the 6V92 the compressor is mounted on a slant with the intake connector facing down. You have to have a mirror to see inside! The hardest part is breaking the intake, discharge and coolant lines loose. You also want to be careful to not break any of the six head bolts when taking the head off. If you have a Bendix Tu-Flo 550 or above you can easily change the unloaders without removing the head.
Since I had to remove the head I bought a field service maintenance kit and plan to service the intake and discharge valves at the same time. I didn't detect any air leaks with my shop compressor but the inside showed a lot of rust and crud buildup. Internal air leaks can go undetected and regular maintenance on the unloaders, air lines, etc will help the compressor run more efficiently and last longer. My compressor was never unloading and never getting a break to cool off. Might even help with the hp and mpg too!
Jerry
Very interesting post! I have never seen the inside of any of the air compressors mounted to Foretravel coaches, so the photos are a big help. Glad you discovered your problem. One more "symptom" we will need to be aware of and watch out for: failure of compressor to unload. Thanks for the report!
Air leaks are very hard to detect for sure. The corrosion by very highly oxygenated water in an compressed air system is a problem along with bits of rust fouling up control components. Dryers help when maintained (BTW some desiccant dryer filter crystals can be revived by baking in an electric oven to drive the moisture out). To reduce the amount of moisture going through the system it may be a step forward to relocate the intake to inside the coach to take advantage of somewhat dehumidified air while running our air conditioning. Additional desiccant air dryers/micron filters may be beneficial at the inlets of $$$$ leveling system components. Just don't add them to the brakes or other safety systems. JMO
Chuck,
Thanks to your posts on the air dryer by-pass I was able to figure what was wrong. If there are no major leaks and the governor and dryer are working properly, you shouldn't be building air after cut-out and before cut-in. The Bendix tech support also told me that in my situation the unloaders were the likely suspect. Here's a pdf on the Bendix Tu-Flo 501 air compressor and a short video on how the unloaders work. You can see how the valves are pushed up with air pressure from the unloader port via the governor at cut-off to unseat the intake valves and make the compressor unload.
Jerry
BENDIX TU-FLO 501 AIR COMPRESSOR MANUAL Pdf Download. (http://www.manualslib.com/manual/392715/Bendix-Tu-Flo-501-Air-Compressor.html#manual)
http://www.youtube.com/watch?v=y6u_hFztHZo
I just skimmed through the manual you linked. I'm trying to understand what the coach owner can do to avoid the situation you encountered. Being a typical owner, I never give any thought to "maintaining" my air compressor...it either works, or it doesn't. On our coaches, is the air going into the compressor being filtered by the big engine intake air filter? I ask because I have never actually investigated the flow of air into the compressor. Besides providing clean filtered air to the compressor inlet, and watching for leaks or unusual behavior, what else can the owner do?
Yes, the most common source for intake air for the air compressor on a diesel engine is the engine intake manifold.
But, easy to verify on any coach. Just trace the lines from the compressor. One will go to the source of air, the other to the air dryer.
So the air is filtered by the main air filter, the turbo boosts pressure and the CAC cools it. Gives the compressor a big jump on doing it's job.
Chuck,
"On our coaches"?
As you know, there are different compressors for different engines, depending upon OE manufacturer, year, size of engine, etc. and even then mounting configurations may well be different (D2 mounted directly on compressor or remotely, for instance).
For the 8.3 Cummins with Holset compressors, I posted a bit about this, trying to help Don (Acousticart) about 2 years ago. It's a bit more complex than just clean air in, demand (and leaks) going out. And there is not a wealth of built-in instrumentation to monitor compressor, D2 governor and air dryer normal/abnormal operation. However, the following may help in understanding a bit more about normal operation.
Air Dryer Rapid cycling? (http://www.foreforums.com/index.php?topic=22077.msg166882#msg166882)
HTH,
Neal
Chuck,
I would think the most important maintenance for the compressor would be air dryer maintenance. Moisture from the wet tank line to the governor would be a source if it's not dry. Also sitting up for long periods would allow for the rust and buildup to accumulate in the valves and their bores and cause them to stick. I don't think my air dryer was ever serviced and draining the tanks wouldn't be enough. We already saw the same problem with the one way check and protection valves on the tanks!
The advanced troubleshooting chart starting on page 13 will give all the info you need for maintenance on the 501. Look for rust, buildup, and kinks in the discharge line and soap test the compressor for air leaks. 60 psi is the minimum pressure required to unload. Recommended maximum inlet air temperature is 250F and discharge is 400F. A small shop air compressor with the correct fittings will help you test for leaks in the unloader, inlet, and discharge valves. Small leaks are acceptable. When I tested my unloaders not only were they not leaking they they were frozen shut! I had to use a pair of locking long nose pliers and a lot of effort to pull the valve stems out. After that the valves came out easily with some air pressure applied to the unloader port.
Jerry
See, this is what I love about this Forum and the many knowledgeable members - I learn something new almost every time I check in.
Thanks for the great link, Neal. I remember reading the first part of Don's ordeal with his mysterious air leak, but for some reason I missed your long and informative post concerning air compressor operation. Great stuff, and much to absorb (I learn by osmosis).
And thanks, Jerry, for bringing this whole subject to the attention of the group. I bet you have inspired more than one member to take a more active interest in their air compressor. I know i am going to continue to study the subject, and learn how to best take care of mine!
Chuck,
Here's some pics of the discharge valves and springs and the field maintenance kit for the 501. The discharge valve seats were really tough to unscrew. I had to use a lot of PB blaster and 1/2" air impact wrench with a 14mm Hex bit to break them loose. You can see all the rust and buildup after 20+ years. They were working okay but I decided to replace the springs and valve plates with new ones. I'll clean up as much of the head as I can with brake cleaner before installing. The inlet valves will get new springs, valve guides and valve plates also. The maintenance kit OEM # 287043 or DMK-4410 contains all of the necessary parts and gaskets plus an unloader kit. Sure hope it makes a difference with all this effort and back strain on this old compressor!
Jerry
Great photos! Be sure to add a final post to this thread when you get it all put back together and have had a chance to test it. Always nice to know the end result of these mechanical adventures.
Chuck,
Looks like success!
I cleaned the compressor head up with some brake cleaner and emory cloth. Replaced discharge springs and valves and tightened them to 50 ft lbs. Painted the head with silver engine paint. I also cleaned off all the old gasket material on the compressor along with the the head and the inlet fitting. After tightening the 6 head bolts to 20 ft lbs. I tested the unloaders with my small compressor air pressure at the unloader port and they worked like they were supposed to!
I reconnected the inlet and discharge fittings. After those were in place I reconnected both coolant lines and the inlet and discharge hoses. I lost about 2 gallons of coolant and replaced that also. After reconnecting governor I started the engine and watched it build air to the cut-off psi and the unloaders worked to stop the compression. I know they were working because I wasn't fooled by the dryer purge blast. I had the dryer off and the by-pass hooked up.
After pumping the brakes about 5 times watching for compression between pumps, the cut-in pressure was reached and compressor loading started again and continued till cut-off. After trying this test about 5 times I was convinced the system was working properly.
I'll do some soap testing tomorrow on the fittings and put an air gauge on the governor at one of the reserve ports for wet tank pressure. I'll also do some testing on how quickly the system builds air and holds pressure overnight after the compressor service.
Jerry
Great report, Jerry! You have blazed a path I hope I DON'T need to follow. (But if I do, I know it is "do-able").
Here's the compressor head installed after the maintenance work and soap testing. The gauge on the governor shows the pressure in the wet tank. Extensive soap testing so far shows no leaks.
I also removed the dryer and changed the filter, purge valve, discharge check valve, and seals. It's a Bendix AD-4 which is obsolete. You can still get parts and seals for it but there's no core allowance for it if you want to upgrade. When I took it apart I found one seal missing, two other seals broken and no discharge check valve! After cleaning, new seals, purge valve, o-ring, and filter, it works like new. The purge is much stronger and shorter in duration. I'm going to keep it for a backup and later upgrade to the much lighter spin on type AD-IP or Wabco 1200 like Pierce just installed on his rig.
Jerry