Secondary air pressure low, Keep burning up head gaskets

[RobertoGatos]

Racked up a bunch of miles on my 923a2 converted into a 931 over the last year, but recently have ran into some issues with the air system.



Started off with a bad head gasket that I replaced, and a thousand miles later it looked like this:



Fixed that, but had it fail two more times since.



Installed a new air dryer, unloader valve, and governor. Still had a head gasket fail. Finally just swapped the compressor out of another truck, and that has been fine for the last 500 miles or so. Hoping that solves that issue...

Somewhere in the midst of all this, I noticed the secondary air gauge reading about 10 PSI lower than the primary. No obvious air leaks anywhere, and am in the process of troubleshooting, but wonder if the two are somehow connected?

The only other odd thing to ever happen was the parking brake failing to release. Truck sat outside in 30* weather for a few days, think it caused the valve under the drivers door step to freeze up. Brake eventually released on its own, and has been fine ever since.

Washed the truck today, and will be going through it tomorrow with the TM. Any ideas?

 

[Andyrv6av8r]

Just replaced the same gasket on my A2 yesterday. It had a chunk blown out of the rear and wouldn't build pressure. is this a common issue on just A2's?

 

[Suprman]

Looks like excessive heat from the pic. If it were me I would replace the entire compressor and make sure oil is circulating properly thru it. Check your governor and air dryer expello valve. If the expello valve has a small continuous leak it can cause the compressor to over work.

 

[patracy]

mating surfaces square?

 

[R Racing]

Perhaps you have a leak on the secondary side causing the compressor to have to work all the time . That would cause it to cycle more and not unload which would cause more heat to the head.

 

[R Racing]

I also noticed you are using paper gaskets. I'm wondering if the oem gaskets are reinforced and may have a metal or carbon core to help disapate heat?

 

[RobertoGatos]

I also noticed you are using paper gaskets. I'm wondering if the oem gaskets are reinforced and may have a metal or carbon core to help disapate heat?

Been using cummins part #4920062 which is a fiber gasket. The other pic is a side of the road fix. That one actually lasted the longest!

Troubleshooting today, I did notice a VERY slight leak near the fan clutch hub while the motor was not up to temperature. Stole a fan actuator valve off another truck to swap with and see what happens, will report back tomorrow.

Thanks!

 

[RobertoGatos]

I've had two trucks so far with the problem. Am wondering if there is a better air compressor that would bolt on?

Just replaced the same gasket on my A2 yesterday. It had a chunk blown out of the rear and wouldn't build pressure. is this a common issue on just A2's?

 

[R Racing]

I thought they used the same compressor on the a1s. There normally a great compressor. Maybe the CTIS pushes it over the edge? I know the 1s on the m915s -m920s get worked hard . But they hold up really well.

 

[R Racing]

Another thing to check if you haven't is the valves back by the glad hands. I have seen were the valve is open . But they have the covers on and they leak the whole time the truck is running. Just thought I'd mention it.

 

[Suprman]

The ctis is designed to shut down under 110 psi so as not to drain the air system. The unloader valve in the compressors head can get stuck and cause the compressor to over work. Rebuild kits are available for around 45 bucks. I had to do this with 2 trucks but I have never had other compressor failure issues. I had a ppv stuck partially open in combination with an intermittently bad expello valve on the air dryer that gave me a day or two of headaches before I figured it out.

 

[goldneagle]

The ctis is designed to shut down under 110 psi so as not to drain the air system. The unloader valve in the compressors head can get stuck and cause the compressor to over work. Rebuild kits are available for around 45 bucks. I had to do this with 2 trucks but I have never had other compressor failure issues. I had a ppv stuck partially open in combination with an intermittently bad expello valve on the air dryer that gave me a day or two of headaches before I figured it out.

Any info on the rebuild kit?

 

[Suprman]

Twice I called Fleetpride and gave them the compressor part number they had the kit for me the same day.

 

[M931]

i have this problem on my M931 a1, there is antifreeze in one air tank, anyone try that???

 

[Suprman]

You don't want antifreeze in your air system it is corrosive.

 

[R Racing]

Possibly another thing to look at is see if you have a clogged check valves.that would restrict the air compressor causing it to work harder to build air.

 

[bchauvette]

You don't want antifreeze in your air system it is corrosive.

I had compressed air in the cooling system. Getting coolant in the air tank might be in the same ball park. Check the pictorial stuff on my sky drive

http://1drv.ms/1EFZgXB

that gasket is fried! Any issues with the coolant going through the compressor head! It looks like your addressing the effect an haven't nailed down the cause yet.

I had terrible corrosion in coolant/air galleries, also the valving was badly gummed up.

 

[M931]

i have looked at my compressor, the head is Sealed Water,mean there is not open between Water and gasket,...... no Water leak there

 

[RobertoGatos]

Here's what I've been working on over the last few days:

Added shutoff valves for the coolant running to the air compressor head, so it can be serviced without pissing all over. Also, used 5/8'' hose instead of 1/2'' so things might stay a bit cooler.



Put in a fan actuator out of another truck, also with a shutoff valve. Figure if it ever has a leak, or is pressurizing the coolant system I can turn it off and bolt the fan to finish my trip.



Since the coolant was already drained, I also popped in a coolant filter before I put new fluid in:



Used about two bottles of soapy water under the truck looking for leaks. Found some small ones, but the secondary gauge is still reading low... The truck will hold air overnight, dropping maybe 60 psi. Don't think I'm looking for anymore leaks at this point. Headed to Vegas tomorrow, so I guess we'll see how it goes.

 

[Csm Davis]

Okay every air compressor on a 5 ton I have opened looks like the picture he posted of the burnt gasket and I have opened a bunch, all 809 and 939 series used this pump. I personally think that the top head should have been made of cast iron and cooled like the middle. the aluminum head is always warped when I have had a failure like this. I am thinking about making a steel replacement for my trucks as I believe that the main reason for the gasket failure is the difference in expansion rates of the 2 heads and a lack of sealing surface area. The top head is very thin to deal with the heat and pressure present in this application, I do believe that the increase in use has pushed these to the edge of reliability.