Replacing thermostat on my C8.3. Engine was manufactured in late 1997 and is a 325 HP with single thermostat. The coolant shut off valve for changing the coolant filter was stuck. I tried to turn it off and it broke inside the housing. You can see the valve sitting on the housing and see the nylon valve stem in the housing. I had already ordered the stainless steel valve as the nylon valves were troublesome and often fail. Anybody know the best way to remove the remnant of the stem? Only thing I know to do is attempt to drill it out a couple sizes smaller and hope for the best.
Side note: The local Cummins parts counter doesn't seem to know these C8.3 engines. When I ordered the thermostat I asked for a gasket. They said the thermostats all come with seals. Not so. Today ordered outlet gasket, thermostat seal, thermostat housing gasket, updated shut off valve and o ring. Parts guy had to enter all these parts into the computer because he had never ordered any of them.
Great post, I was able to replace the thermostats on my previous two 300hp 8.3s. My 325hp current 8.3 I got stopped replacing the single thermostat, I felt the bolts were about to twist off and break, so I stopped. This will be my next engine product. So please continue with you post, with part numbers, and your experience if posible.
Coy,
Sorry your valve broke off.
We have the same situation. We learned that original coolant valves are plastic, and Cummins upgraded the valve to metal, so we bought the upgrade.
After removing little bracket that holds valve into hole, we could not pull out plastic valve. It seemed frozen in place and also would not rotate.
It felt that forcing might break the valve, so we decided to leave it alone.
Since no coolant runs out when we remove our filter, we figured there is no need to close our valve, so we put things back together and saved the new valve in our spare parts box.
If your broken valve does not leak out coolant, I would leave it in place. Not sure how to remove without causing damage.
Good luck
As a matter of learned principle, if it's plastic and it's made in metal then it gets changed. I learned the hard way when I went to flush the water heater, plastic tap literally "fell off in my hand" when I was hand tightening the garden hose. Oh boy that was an interesting morning.
This won't help you now but I found a parts book on Ebay for $8,they are out there,then you give them the part numbers.
The complete, up to date parts listing for the specific ESN that is installed in your coach is available at Cummins QuickServe Online. All you have to do is register with your Engine Serial Number. It's FREE. ^.^d
This is the exact same info that the clueless Cummins parts counter person should see on their computer (if they knew what they were doing).
Cummins QuickServe Online (https://quickserve.cummins.com/info/index.html)
For instance, the page for the thermostat housing for MY engine is shown below:
How did I not know this? Excellent information!
Looking at your photo, and at the .pdf I posted above, I think the design of the valve shaft is similar in both cases. Looks like your valve shaft broke at the O-ring groove, which of course is the weakest part of the shaft.
If it was me, I would first drill a hole down into the broken off plastic stub in the housing. Then, fill the recess in the housing with penetrating oil and let it sit overnight. Better yet, submerge the whole thermostat housing in penetrating oil and let it soak. After allowing time for the penetrating oil to work, try threading a long screw into the drilled hole in the stub. Pry straight UP very gently on the screw and see if the stub will pull out.
With any luck, it will pop right out.
Before you install the new valve shaft, be sure the hole the shaft fits into is clean, smooth, and well lubricated. For O-ring installations I use:
O-Ring Silicone Grease (https://www.super-lube.com/o-ring-silicone-grease)
Did'nt make it difficult and did'nt need to go to Ebay,like to have a book in my hands to look thru,most of us know about the quick
serve on-line.
Yes, you're right, some prefer a book in hand. Assuming it is the correct book for your specific ESN, then just as useful. I modified my post.
And, I appologize about repeatedly mentioning QuickServe...I know it gets old. Just thought it might be useful to our newer members.
I used Quickserve to find all the parts the parts guy didn't know existed. I bumble around a lot on the website. Takes me a long time to get to where I need to go.
I'm going to follow Chuck's recommendations. Somewhere in one of my tool chests is an old slide hammer for body work. That would work with a screw and penetrating oil. Will post results.
I just Googled the part number for the valve shaft on my engine.
I had a wrong picture in my head of how the valve operated. I thought there was 2 pieces to the valve, and that the replaceable shaft meshed somehow with a rotating valve that was built into the thermostat housing. Instead, the replaceable shaft IS the valve, with 2 flow holes drilled through it. See first photo below of the original style black plastic valves.
I edited my post above to avoid confusion. I think my idea of how to remove the broken off part of the valve will still work.
It is easy to see the great improvement made in the new replacement valve by using steel instead of plastic. See second photo.
The designer of the weak original plastic valve was NOT worth whatever they paid him (or her).
Good to know there is an updated valve. I tried to turn mine, but felt it was going to break. So I just changed the filter quickly and let some coolant drip out.
Thanks Chuck. I'm going forward with the plan to use the slide hammer, especially since there are no threads at the bottom of the housing. My new parts coming from Dallas Monday afternoon. So the o ring seals the shaft it appears. Ordering silicone lubricant today as well. Hopefully not too much corrosion in housing.
If you have a shop in the area that does glass bead blasting I would consider that,will clean the housing and ports,do not use sand blasting as it will remove metal.Could you post the o-ring part number,thanks.
On my engine, the o-ring is Cummins 3818885. I think it is probably the same for all 8.3 engines.
The new steel replacement valve may come with a o-ring in the box. Realmccoy can tell us when he gets his new parts.
Chuck,
I think here is another difference in the Mechanical C8.3 and the Electronic ISC 8.3 that started around 99'. Our coolant filter is remote mounted on the street side of the engine and appears to have to standard looking gate valve similar to a hose bib, one on each side of the filter. The picture attached is looking towards the front of the coach from above with the bed open. You can just make out the valve handle. I will probably replace mine eventually with ball valves. When I first had all fluids and filters changed before our first trip to Texas, the mechanic who did it told me that both of those valves were closed and therefore the filter that was on there couldn't have been doing anything since it was out of the loop. Obviously, the coolant still circulated since the operating temperatures have always been within range. That has always puzzled me because that would mean that the coolant has multiple loops and so the coolant filter needn't be in place for the coolant system to function. I haven't looked closely at the filter mount, so there may be a bypass that happens with both valves closed. I am not sure how that could be accomplished unless these are two way valves, in which case, why would there be two of them? One of these days, I will have a closer look at the plumbing of the coolant filter. To this point, it has been one of those "if it isn't broke, don't fix it" kind of items on the potential project list. Next time I change the coolant filter, I will pay more attention.
Don
O ring is 3818885
Extraction of the nylon valve stem for the coolant filter shut off valve did not go well. Inserted screw in broken stem and it popped out without budging the stem. Called a former neighbor who is retired AF air frame and power plant mechanic and works at L3 on stuff he can't talk about. We drilled a larger hole and attached a 1/4 inch eye hook into the stem. The eye straightened out, and when we tried to remove it the hook broke at the threads. Now we had a stuck nylon stem with a 1/4 inch eye hook embedded in the middle. We put it on the drill press and drilled a series of 1/8 inch holes around the broken hook and used a punch to break the stem apart around the threads of the hook. That relieved the stem to the first passage. We then drilled a series of progressively larger holes in the stem until we could break it up with the punch. Some scaring of the valve body in the thermostat housing.
Lessons learned. Leave it alone and change the filter without using the shut off valve. Some farmers with C8.3 in ag equipment pull a vacuum on the radiator overflow and change it with minimal mess. All report problems with those blasted stems not turning, breaking, etc. I'm just hoping mine will seal with new o ring and stainless stem. If not, I'm up a creek without a thermostat housing. My stem was essentially "welded" to the valve body.
I've read Zen and the Art of Motorcycle Maintenance several times. This is what the author called a "gumption trap."
Don't have that modern device, but couldn't applying heat from a propane torch soften the plastic or is the entire housing apt to distort?
Sorry my idea didn't work out. Hard to believe that plastic piece could be stuck so tightly in that hole. Best laid plans...
At least you have given those of us who still have the original plastic valve something to think about when changing the coolant filter.
My coolant and filter was last changed several years ago. My plastic valve was opened and closed several times during the flushing operations, and worked fine. It has not been moved since, so no telling if it would work now.
I will have the parts necessary to replace it with the steel version on hand before my next coolant service appointment.
Do you think poor coolant maintenance before you could have added to the problem? If everything is good wonder why it got welded together,probably why they went to the stainless.
There is a service bulletin related to the replacement part. It was a common problem with the nylon stem.
Saw a replacement housing on Ebay but it was the dual thermostat one.
Finally got everything back together, coolant flushed, filled, and 40 mile test run in 96 degree heat.
Somehow I ordered the old nylon valve instead of the stainless. Even though they recommend replacement of the nylon valve with a stainless valve, they still manufacture and stock the nylon valve. The price differential is about $60. We gouged the valve bore in the thermostat housing removing the stuck coolant valve and I opted to use the nylon valve hoping it was more forgiving. The o ring was a real stretch to get onto the shaft, but it sealed the housing and no leaks so far.
I used the factory gaskets without gasket sealant. The internet wisdom is absolutely contradictory on sealant/no sealant. I saw no evidence of sealant when cleaning the gaskets off. My engine manual did not suggest sealant when replacing the thermostat, so I torqued to recommended levels and they appear to be well sealed so far.
The old thermostat seal (not gasket, but metal seal with rubber trim) was difficult to remove. Used seal remover from Harbor Freight and it took many attempts to pry out. After several attempts to install new seal, I realized it is simply placed around new thermostat and it seats itself when you assemble the housing to the block.
My engine manual showed the two thermostat housing. My housing, called a bypass housing, has only one. There was no valve to release air on the housing as shown in the manual or as indicated with a sticker on the engine. Instead, there was a line from the bypass housing and thermostat housing that ran to the coolant fill tank. Two lines total. I believe they provide a means for air to escape so my particular engine "bleeds off air" into the coolant housing.
I changed from the traditional green coolant with added SCAs to Fleetguard OAT. The Cummins dealership uses NOAT in all their engines, I special ordered OAT. I followed the procedure recommended by Wolfe with initial drain, flush with filtered tap water, ran at fast idle with heater on low to thermostat opening temperature, drained, filled with distilled, ran engine twenty miles, let engine cool, filled with distilled, drove 20 miles and had a brief scare as temperature jumped to 220 and then dropped 30 seconds later to about 100 and then stabilized at 185. I'm assuming that was a big air burp. Drained and cooled engine over night, filled with 7 1/2 gallons of concentrated OAT next day and then topped off with distilled water.
Test run this evening was about 40 miles in 96 degree weather, 65 miles per hour. Thermostat ran to 180/5 and then held for the entire run. My last trip before changing thermostat had seen erratic temperature mainly from 185 to 220 and average around 200. Before that trip it had run 180 to 200. Since owning, I've never seen the steady 180/5 that showed up after my change of thermostat. It was time to beak out the champagne.
My system holds approximately 15 gallons according to my Foretravel manual. I used 30 gallons of distilled water in flush and fill. I've got about 15 gallons of antifreeze to recycle. It took me at least two full days to flush and fill, not counting recycling or dealing with thermostat and housing. The location of my coolant tank makes it virtually impossible to use a funnel. I poured coolant into the tank with a small plastic cup, 5 ounces a shot. I used my fresh water fill pump running slow to fill the distilled water into the tank.
Concluding thoughts: I know my cooling system better. I understand why the local Cummins shop doesn't like working on motor homes. One C8.3 in one application isn't like another C8.3. At some point after reading everything you can find on the forum, in the manual, and online, you have to look at your coach and figure out what "is" rather than what "ought to be." My wife always says to multiply my estimate for how long something will take by four and then double it. She is usually right.
Thanks for your help.
Auto Zone will take used coolant,call first some will take all,all will take at least 5 gallons.