Skip to main content ↑ ↓
Topic: Likely air leak locations  (Read 2900 times) previous topic - next topic

Re: Likely air leak locations

Reply #51 –
Whenever I work on any of the air system valves or components, I always use the Super Lube.  I coat every O-ring and every metal part lightly with lube before reassembling and installing it.  Don't get carried away - just a thin coating.  Helps hold things in correct position while you assemble the valve.  Protects the rubber O-ring surface from "friction" damage between moving parts.  It will also actually help fill in microscopic defects in the sealing surfaces within the valve, and thereby (hopefully) forestall minor leaks.

Will not degrade rubber parts, tolerant of high and low temperature operating conditions, water resistant, chemically inert.  Excellent stuff!
1993 U280 SE 40' WTBI, Build: 4359
C8.3 300hp, 6-Speed, Exhaust Brake
960 watts on the roof (6 x 160)
Sorento (or BOLT) on a Kar Kaddy SS
"It goes without saying..."

Re: Likely air leak locations

Reply #52 –
Went and got o-rings today.  Could not find metric ones anywhere but found some at Lowe's that were a near exact match.  The box had half of them missing and since it was the only one they had they let me have them for half the price, for a grand total of $1.53.  Could not find super lube anywhere but the throttle rebuild kit came in today so I used some of the silicone grease that came with it.  No more leaking from the solenoids!  I'm pretty pumped that I was able to fix it! :)) The tanks are holding much better now, only lost about 15psi in an hour.  There's still some  leaks to be found but it's getting better! 
Hannah and Tyler Phillips
1993 U280 Grand Villa AKA Pearl
Basement Air
Cummins 6CT8.3
Build Number 4196

Re: Likely air leak locations

Reply #53 –
Got the throttle out and rebuilt last night.  Removal, rebuild and reinstall was pretty easy.  Getting the foot pedal back in place was kind of a bugger but I used a piece of braided fishing line tied to the top of the spring to hold up on it and a mirror behind the pedal so I could see what was going on.  The pedal took about 15 minutes to install and the rebuild took about the same.  I checked for leaks and also the actuation of the throttle cable as per the instructions.  There are no leaks and the throttle moves as it should although I'm not sure how to check if it's moving the proper amount.  All in all it was a fun project.  We're still losing air steadily from somewhere so the search continues!
Hannah and Tyler Phillips
1993 U280 Grand Villa AKA Pearl
Basement Air
Cummins 6CT8.3
Build Number 4196

Re: Likely air leak locations

Reply #54 –
Quote from: 1985 –
i found a leak in my parking brake switch and one that i chased forever was an air chamber diaphragm

I'm not sure what the air chamber diaphragm is but would like to check it.  Can anyone enlighten me?
Hannah and Tyler Phillips
1993 U280 Grand Villa AKA Pearl
Basement Air
Cummins 6CT8.3
Build Number 4196

Re: Likely air leak locations

Reply #55 –
Quote from: The Soft Boulders –
Getting the foot pedal back in place was kind of a bugger...
Took me a LOT longer than you to get that pedal reinstalled......

Ah, to be young and flexible again.  My old body don't fold up so good anymore, and looking through trifocals makes working in close quarters more difficult than it should be.

Glad you got this project done successfully!  That's one item that won't need repair again for about 20-30 years.  ^.^d
1993 U280 SE 40' WTBI, Build: 4359
C8.3 300hp, 6-Speed, Exhaust Brake
960 watts on the roof (6 x 160)
Sorento (or BOLT) on a Kar Kaddy SS
"It goes without saying..."

Re: Likely air leak locations

Reply #56 –
Quote from: The Soft Boulders –
I'm not sure what the air chamber diaphragm is but would like to check it.  Can anyone enlighten me?
Only "air chamber diaphragm" I can think of is a part of the brake assemblies.  Air pressure is used to release the spring brakes (parking brake) on the rear axle.  Don't mess with the air brakes or rear spring brake mechanism unless you know what you are doing.  That's a job for qualified brake techs.

Photo (not very good) of rear brake can below:
1993 U280 SE 40' WTBI, Build: 4359
C8.3 300hp, 6-Speed, Exhaust Brake
960 watts on the roof (6 x 160)
Sorento (or BOLT) on a Kar Kaddy SS
"It goes without saying..."

Re: Likely air leak locations

Reply #57 –
Quote from: Chuck & Jeannie –
Took me a LOT longer than you to get that pedal reinstalled......

I may have just gotten lucky!  We'll go with that because it doesn't happen very often. haha
Hannah and Tyler Phillips
1993 U280 Grand Villa AKA Pearl
Basement Air
Cummins 6CT8.3
Build Number 4196

Re: Likely air leak locations

Reply #58 –
Quote from: Chuck & Jeannie –
Only "air chamber diaphragm" I can think of is a part of the rear brake assemblies.  Air pressure is used to release the spring brakes (parking brake) on the rear axle.  Don't mess with the air brakes or rear spring brake mechanism unless you know what you are doing.  That's a job for qualified brake techs.

That's what I was coming up with when I did a search but wasn't for sure.  When I was under the coach look for our wet tank I noticed that our brake cans were pretty badly corroded.  I'm definitely not comfortable with messing with our brakes!
Hannah and Tyler Phillips
1993 U280 Grand Villa AKA Pearl
Basement Air
Cummins 6CT8.3
Build Number 4196

Re: Likely air leak locations

Reply #59 –
The brake chambers won't leak until the brake pedal is pushed.

Re: Likely air leak locations

Reply #60 –
Quote from: Protech Racing –
The brake chambers won't leak until the brake pedal is pushed.

Correct.  The parking brake/emergency brake is SPRING applied, AIR PRESSURE released.

So, when parked, should not be source of air leak.
Brett Wolfe
EX: 1993 U240
Moderator, ForeForum 2001-
Moderator Diesel RV Club 2002-
Moderator, FMCA Forum 2009-2020
Chairman FMCA Technical Advisory Committee 2011-2020

Re: Likely air leak locations

Reply #61 –
Speaking of air leaks, I have a "waiting to happen" braided stainless steel air line from compressor to air dryer.  Is there a reason for it to be so long?  It comes out of compressor "I think it is compressor" goes forward to transmission then loops back to back of engine compartment across back to air dryer.  It has 2 spots That the stainless braid is missing-- looks like it was kinked!
Would a shorter line do the job? 
Thanks
Chris
1999 U 320 DGFE
Build Number 5523
Chris & Elka Lang
In the field, Lonoke AR

Re: Likely air leak locations

Reply #62 –
Quote from: Chris m lang –
Speaking of air leaks, I have a "waiting to happen" braided stainless steel air line from compressor to air dryer.  Is there a reason for it to be so long?  It comes out of compressor "I think it is compressor" goes forward to transmission then loops back to back of engine compartment across back to air dryer.  It has 2 spots That the stainless braid is missing-- looks like it was kinked!
Would a shorter line do the job? 
Thanks
Chris
If that big air line was kinked its leaking. Its that type of  stainless nylon hose because of the heat produced by the air compressor. That type of hose can not be kinked no matter what.
92 Grand Villa
Silver 6v92
 side isle.
build# 3973

Re: Likely air leak locations

Reply #63 –
Quote from: Protech Racing –
The brake chambers won't leak until the brake pedal is pushed.
Maybe I'll get under there tomorrow and have Hannah hit the brakes.
Hannah and Tyler Phillips
1993 U280 Grand Villa AKA Pearl
Basement Air
Cummins 6CT8.3
Build Number 4196

Re: Likely air leak locations

Reply #64 –
Quote from: Chris m lang –
1. Is there a reason for it to be so long? 
2. Would a shorter line do the job? 
3. It has 2 spots That the stainless braid is missing-- looks like it was kinked!

Chris,
1.The short answer, yes
1a.  That hose length is there so the air that has been compressed can have time to cool off some prior to getting to the dryer. I don't remember the exact numbers that Mark (he is the Cummins man that worked on this engine development) gave me but that length was what was determined to work for the Holset compressor on our age coaches. Different compressor/dryer combos have different specs.
2. It  would do the job of moving the air from point "A" to point "B"
3, Not good.

Pamela & Mike
Pamela & Mike 97 U 320

"It's not what happens to you, but how you react to it that matters."

Re: Likely air leak locations

Reply #65 –
There is real satisfaction in finding a problem then creating a solution. When I had a significant air leak, I squirted my bubble mix all over and when I got to the front (engine running) I could clearly hear it. Reaching up to the bottom of the treadle valve, I found the leak and when I plugged the exhaust port with my finger I could make the engine rev! The replacement/ remanufactured valve was easy to get, relatively easy to replace, and it solved the leak.
Now on to the next thing...
Woody & Sandy Lloyd
1993 Grand Villa
Unihome U280
Cummins / Allison
Build # 4379

Re: Likely air leak locations

Reply #66 –
Got back under the coach today and found a couple more air leaks.  One of the solenoids MoT replaced on the rear six pack is leaking around the base of it.  It may just be the o-ring but the surface of the manifold is so rough I'm not sure how they got a seal in the first place.  The other two air leaks are coming from the service brake relay valve and the spring brake relay valve.  They both look identical and from pictures I found they both look like a service brake valve but how I'm reading the schematic one is the spring brake valve. I could be wrong though.  Both have one air line entering and two lines running to the brake cans.  Both are leaking from the bottom around what appears to be a circlip. If there is a circlip, maybe they're rebuildable?  There are numbers on the bottom (T-294859-C) but I didn't come up with much of anything.
 Is anyone familiar with these valves?
Hannah and Tyler Phillips
1993 U280 Grand Villa AKA Pearl
Basement Air
Cummins 6CT8.3
Build Number 4196