M923a2 air compressor mystery

I just want to add that since the original issue and it fixing itself I have not had any other air delivery issues. I have also not fixed, rebuilt, or replaced any part of the air compressor system.

I know this does not help anybody with similiar issues but it is what it is.

I will revisit this thread if anything else related comes up.

Ok, the unloader stuck again. The compressor filled the tanks but would not refill them while driving.

I also had another issue. While priming the system after a fuel filter change I noticed the unloader/ compressor blowing bubbles around the top four bolts and at the gasket at the top of the assembly (not the round part up top but the upper square shaped gasket).

A gas compressor in the bed got me home again and also the air system started working properly again.

Time to rebuild and clean the unloader and compressor. I tore it apart and cleaned a ton of gunk out of the unloader assembly and lightly lubed it. I also removed the old gaskets and replaced them. All that went well and back together with minimal cursing. I was hoping the unloader assembly would come out alone but I had to take the whole top off the compressor to get it out.

The compressor pumps and it all went back together as expected. The whole thing still leaks though! All four bolts and the upper gasket again.

What would be the best gasket sealer that would hold up to the heat and pressure of the compressor? I could ask at the auto parts store but I just wanted to see if someone on here had good luck with a particular product for this application.

I plan to tear it apart again next weekend in an attempt to stop the leaks.

Thanks again for any advise.

And yes, I did see that the two bolts on the circle part have to be tightened last. If they are tightened first the whole assembly will not tighten properly. I loosened them when I saw it leaking again but it didn't help.

There's got to be something wrong Andy and I took the four bolts out also the unloader bolts removed everything.
Put new gasket in reinstalled everything and it's been working fine.

Well, in all honesty, with time constraints and no access to a dealer I cut my own gaskets from gasket sheet material. But it is leaking just like it did before. I am scared to torque the bolts more as they are pretty small.

It is just a bunch of small leaks, nothing major. I think the correct gasket sealer will seal it up.

Check to see if the head is flat, most I have checked needed some work.

A gasket is 7 bucks if needed we can get you one and mail it to you.
It's a fairly hard gasket not pliable.

Csm Davis said:

Check to see if the head is flat, most I have checked needed some work.

Click to expand...

That is what I am thinking the issue is.

I am going to try the gasket sealer and then go from there.

dawico said:

That is what I am thinking the issue is.

I am going to try the gasket sealer and then go from there.

Click to expand...

Order the correct gasket it won't cost much more than the sealer.

Just wanted to give a little update on this issue. This is copied from a response I gave in another thread so some info may be a repeat.

I took the unloader to an auto parts store and ended up with a gasket sheet and cut my own. I didn't replace anything else. I cleaned everything up and lubed the moving parts. I had my unloader stick on me before so the copper colored slider got special attention. All the seals were in good shape, I don't have a local Cummins dealer, and don't like to wait for shipping so I just went for it.

The first time I tore it apart I just replaced the gaskets and it leaked pretty bad. The second time I used new gaskets and hardening gasket sealer. It still leaked just as bad. This time I used a new gasket and silver Permatex RTV gasket maker. Now I just have a little foam on one side with soapy water spray.

The gasket at the compressor head has held fine (below the two coolant lines and the air outlet). It was just the gasket at the unloader that was causing problems and leaking. I put a bead on both sides of the gasket and finger tightened it like the directions said. I let it sit for about two hours and tightened it up. I also spread some on the shanks of the bolts as it leaked there too. Then it sat overnight.

With very little leaking the compressor definitely has more time between cycles. My secondary tank holds pressure much better too. It used to be empty overnight but now it stayed up at 70 psi. The primary usually stayed up there overnight. It may be unrelated but it is a change.

I wasn't sure if the silver Permatex was the one to go with over the red, so time will tell. I probably wouldn't have had so many issues if I got factory gaskets but it is what it is.

I will update this thread if I have any more issues with the compressor or unloader.

Glad you have it working, I think I might be doing much the same soon. About using the 1 inch impact of the front gladhand I found that there isn't nearly the volume of air needed to run mine. It might be the cheap gun but I think it is a line size and pressure issue. I mention only because if you haven't bought the 1 inch impact then I recommend buying the 3/4 instead. A 3/4 should still have the jones to twist lugnuts.

Ken

Dawico,
Just started have a leak like yours. With the noise and heat it was a challenge figuring out where that high pitched leak was until I grabbed the soapy water and finally realized it was the top gasket on the air compressor. Did you remove the entire unit ( i think ) or where any of you able to get the top off whit pump installed? Where do you others recommend I source the part from?

CARMAN said:

Dawico,
Just started have a leak like yours. With the noise and heat it was a challenge figuring out where that high pitched leak was until I grabbed the soapy water and finally realized it was the top gasket on the air compressor. Did you remove the entire unit ( i think ) or where any of you able to get the top off whit pump installed? Where do you others recommend I source the part from?

Click to expand...

The head can be removed with the compressor in place. Back bolts are the worse part of the job. I highly recommend checking the head for warpage and lapping it flat if needed. It took me 2 gasket changes before I figured this out. After fixing the head, mine has been trouble free for over 2 years.

shadowdd said:

I had the exact same thing happen at Christmas time and it ultimately was the unloader on the top of the compressor. I was not able to pull the whole unloader off since it contacted the bottom of the injector pump. I ended up pulling the line from the top of the unloader and loosening both bolts that hold the unloader in the compressor head. I pulled up the unloader as much as I could and saturated the entire unloader with WD-40. I let that sit and repeated the process a couple of times. I then put everything back together and started the truck up and the compressor was filling the tanks once again. Now it seems to fill the air tanks much quicker. I hope this helps.

Bryan

Click to expand...

I am doing this procedure right now....did you have to put any sealer around the housing when you put it back together?

Thanks,
John

jminker said:

I am doing this procedure right now....did you have to put any sealer around the housing when you put it back together?

Thanks,
John

Click to expand...

If memory serves me correctly I did. I have since pulled everything apart and rebuilt the compressor with new seals and rings and a new unloader.

jminker said:

I am doing this procedure right now....did you have to put any sealer around the housing when you put it back together?

Thanks,
John

Click to expand...

I had similar problems with my compressor after I loaded a large deck worth of lumber into my truck. Thank you Hagerty for the free tow home. Long story short the head gasket was old and crumbling and preventing pressure from building. Parts I needed to rebuild the top end were hard to source so I asked a friend at napa if he could get me a new(rebuilt) compressor. $275 later no more compressor problems. (He was the owner of the store) he recently sold the store so deals like that will be harder to come by

925a2Tim said:

I had similar problems with my compressor after I loaded a large deck worth of lumber into my truck. Thank you Hagerty for the free tow home. Long story short the head gasket was old and crumbling and preventing pressure from building. Parts I needed to rebuild the top end were hard to source so I asked a friend at napa if he could get me a new(rebuilt) compressor. $275 later no more compressor problems. (He was the owner of the store) he recently sold the store so deals like that will be harder to come by

Click to expand...

.
Nice! At least you found a solution. Maybe the old compressor can be rebuilt with some gasket material.
Spare parts are always great to have around

Hate to hear that your parts contact won't be around any longer
Hope he has a new mission now.