Bendix Air Comp leaking

[GTSailor]

Looks like I have a leak. I read troubleshooting guide from Bendix. This "may" be head gasket. Air compressor is fully functional.

I did have probably about 1/4 cup of oil in my primary tank (not wet tank). I think the dessicant has not been replaced in a long time in the AD-9 air dryer so i don't jump to compressor passing oil just yet until I replace dessicant.

Any thoughts on replacement vs. trying to just replace head gasket? I assume coolant drains out when you take that head off.

If I replace compressor, will all the oil come out of the front cover? like how does that work. I know its connected into the front engine cover but is it wet?

These things appear to be pretty heavy.

[Eclipse436]

If you let it sit you shouldn't loose oil out of the front cover. I just replaced mine for ease of mind but you'll need to pull the gear off the front to put on your new compressor, this can be quite a task depending on your tools since they're press fit. The small line at the front is your oil supply, I put channel locks on the coolant lines to keep from loosing too much coolant. These are expensive though so a rebuild kit may interest you more. You should replace your governor at the same time to be sure everything is new.

As a diesel mechanic if we found oil in the tank the compressor would get rebuilt, governor replaced, and the whole air dryer would get replaced to avoid issues down the road.

[Booyah45828]

I've seen worse oil leaks then that.

Clean it all off and verify where it's leaking from.

Also, fix the bare wire you've got dangling there that we mentioned in your other thread ASAP.

There's 2 coolant lines in the head, air discharge on top, and the air supply line on the side. You've also got the oil supply line on the side and down low. In my eyes your oil leak looks to be coming from the air supply. Make sure the gasket in there is good, and that the hose isn't torn and oil isn't leaking past the fitting. Being fed from the intake manifold, there will be boost pressure there, and if that gasket is bad it can cause the leak you're seeing.

If your compressor is passing oil, and is fed air from the engine intake manifold, pull the intercooler boot and verify that the turbo isn't the source of your oil. In normal service the compressor will pass a little bit of oil to the dryer and tanks. There should be a video of testing for that on the discharge pipe to determine if it's excessive or not.

I wouldn't recommend replacing the head gasket of the compressor, because if the gasket has failed and is the source of your leak, the compressor is very likely worn out and needs rebuilt anyways.

[Booyah45828]

Originally Posted by Eclipse436

As a diesel mechanic if we found oil in the tank the compressor would get rebuilt, governor replaced, and the whole air dryer would get replaced to avoid issues down the road.

That's a good practice to follow.

[cadillackid]

Originally Posted by Booyah45828

I've seen worse oil leaks then that.

Clean it all off and verify where it's leaking from.

Also, fix the bare wire you've got dangling there that we mentioned in your other thread ASAP.

There's 2 coolant lines in the head, air discharge on top, and the air supply line on the side. You've also got the oil supply line on the side and down low. In my eyes your oil leak looks to be coming from the air supply. Make sure the gasket in there is good, and that the hose isn't torn and oil isn't leaking past the fitting. Being fed from the intake manifold, there will be boost pressure there, and if that gasket is bad it can cause the leak you're seeing.

If your compressor is passing oil, and is fed air from the engine intake manifold, pull the intercooler boot and verify that the turbo isn't the source of your oil. In normal service the compressor will pass a little bit of oil to the dryer and tanks. There should be a video of testing for that on the discharge pipe to determine if it's excessive or not.

I wouldn't recommend replacing the head gasket of the compressor, because if the gasket has failed and is the source of your leak, the compressor is very likely worn out and needs rebuilt anyways.

I converted the one on redbyrd to a filtered ambient air inlet.. my bus has that CCV recirc system by racor which always ends up with oil in the intake tubes and it was 'Y' into the compressor feed.. so It was sending a lot of oil into the air system..



the Tu-flo 550 you have there is much more serivceable than the 501.. I would definitely check for oil at the air intake from your turbo or if your bus has a CCV recirc system..



you can buy head gasket replacement kits for those 550's and its not a hard job to do.. just be sure to follow the bendix manual for bolt torqueing.. just like an engine head torque and tightening order are important ..

[Booyah45828]

I don't think there is oil through/above the head gasket. So if the head gasket is leaking oil, you likely have compressor ring issues, and changing the head gasket won't fix that. That was my point about not replacing the head gasket if it's the source of the leak.

[GTSailor]

So my intake comes from the air intake just behind the air filter. if anything it is at slight vacuum or atmospheric as it is on the suction of the turbo. So i doubt that is it.

SO if it's not the head gasket or other items in the head as part of standard rebuild kit, what else could it be but the rings. I am wondering why they make the rebuild kit?

New problem i just noticed... I don't think my dryer is purging. As I understand it every time the system meets pressure and unloads, it sends air from regulator to AD-9 dryer purge valve. I don't remember hearing it and just fired it up this weekend. So that could be bad purge valve or regulator/unloader not working and is not sending the signal to dryer. Working on replacing dessicant and likely the purge valve.

Is there anyway to test if there is excessive blow-by.

Trying to narrow down whether I need to just bite the bullet and purchase bendix reman compressor.

Lastly, and somewhat separate issue, if something had gone wrong in the head of compressor is there any way trace amounts of coolant could get into engine oil via compressor oil drain back to valve cover? I am pretty sure I had that sweet smelling vapor coming from oil fill/dipstick tube this weekend.

[Booyah45828]

Originally Posted by GTSailor

So my intake comes from the air intake just behind the air filter. if anything it is at slight vacuum or atmospheric as it is on the suction of the turbo. So i doubt that is it.

SO if it's not the head gasket or other items in the head as part of standard rebuild kit, what else could it be but the rings. I am wondering why they make the rebuild kit?

Clean it all off and verify where it's leaking from.

There is no oil through/above the head gasket. So if the head gasket is leaking oil, you likely have compressor ring issues, and changing the head gasket won't fix that. If the intake air isn't the source of oil, then your compressor rings/pistons are. They make the kit in case the head leaks coolant, or air into the cooling system.

Originally Posted by GTSailor

New problem i just noticed... I don't think my dryer is purging. As I understand it every time the system meets pressure and unloads, it sends air from regulator to AD-9 dryer purge valve. I don't remember hearing it and just fired it up this weekend. So that could be bad purge valve or regulator/unloader not working and is not sending the signal to dryer. Working on replacing dessicant and likely the purge valve.

The governor controls purging/unloading the compressor. Governor receives wet tank pressure, and once at psi, sends air to the compressor unloader valve, and to the purge valve on the drier.

If you're not hearing a pshtttt, typically the purge valve in the drier has gotten stuck or has failed. If the governor had failed and wasn't sending the air to unload, you'd continue to build pressure until the lines blew or a relief valve opened.

Originally Posted by GTSailor

Is there anyway to test if there is excessive blow-by.

Blow by where? Engine or compressor?

Originally Posted by GTSailor

Trying to narrow down whether I need to just bite the bullet and purchase bendix reman compressor.

You need to clean it off first and see where the oil leak is coming from exactly. Then you can determine your next steps.

Originally Posted by GTSailor

Lastly, and somewhat separate issue, if something had gone wrong in the head of compressor is there any way trace amounts of coolant could get into engine oil via compressor oil drain back to valve cover? I am pretty sure I had that sweet smelling vapor coming from oil fill/dipstick tube this weekend.

I'm not going to say that it's impossible, but it's highly, highly improbable. There are a multitude of other, more likely places that coolant could be getting into the oil. A sweet smell from the dipstick isn't what I would go by. If you suspect coolant in oil, drain the oil off and send in a sample for analysis. That should tell you if there is coolant in the oil.

[mmoore6856]

Originally Posted by Eclipse436

If you let it sit you shouldn't loose oil out of the front cover. I just replaced mine for ease of mind but you'll need to pull the gear off the front to put on your new compressor, this can be quite a task depending on your tools since they're press fit. The small line at the front is your oil supply, I put channel locks on the coolant lines to keep from loosing too much coolant. These are expensive though so a rebuild kit may interest you more. You should replace your governor at the same time to be sure everything is new.

As a diesel mechanic if we found oil in the tank the compressor would get rebuilt, governor replaced, and the whole air dryer would get replaced to avoid issues down the road.

kind of wierd the oil made it past the desicant without plugging it up. something is wrong here

[GTSailor]

Originally Posted by Booyah45828

Clean it all off and verify where it's leaking from.

There is no oil through/above the head gasket. So if the head gasket is leaking oil, you likely have compressor ring issues, and changing the head gasket won't fix that. If the intake air isn't the source of oil, then your compressor rings/pistons are. They make the kit in case the head leaks coolant, or air into the cooling system.

So i started disassembling the air compressor starting with the air outlet and the cover for the valves. There is oil in everything. The line leaving the compressor, the governor, the two lines leaving the governor (sense and purge). Is this too much oil? Is it typical?

Blow by where? Engine or compressor?

Compressor

You need to clean it off first and see where the oil leak is coming from exactly. Then you can determine your next steps.

Based on what I am seeing i think its past the piston rings. Should I investigate any further?

Would no purging cause this? Seems like there would just be build up in tanks and not at compressor outlet. Of course if the sensing line recycled oil back from main tank into unloader could that be possible? Seems like it wouldn't be in outlet line still.

[sportyrick]

GTsailor:I got my C7 rebuilt compressor from REI in Illinois and has worked well, there will be a core charge. So if you want check locally and then call REI and see what their price is.

[Booyah45828]

There should be trace amounts of oil above the pistons. If you have oil present above, your piston rings are shot, or the compressor is drawing in oil from the air source. You said that the air source is from the intake tube right after the air filter, so there's little chance oil is being drawn from there, so your compressor is likely worn out. There's an off chance the oil drain is plugged on it on certain units, but I believe yours dumps oil back in through the gear housing, so that chance is virtually nil.

To fix this you'll have to clean and rebuild the dryer with a purge valve kit and a fresh cartridge, as well as clean the governor, lines, and tanks of any oil as well. Or just flush all the lines/tanks and install reman'd components. Your call on how much time you want to spend on this.

[sportyrick]

I know a trucking company that had a compressor go bad and pumped ALL the oil into the air system and the engine quit because of computer shutting it down for low oil. Sounds like you caught yours in time.

[cadillackid]

Ive always some oil in all my air systems.. when I open the air drains to my tanks it will spray a small amount of oil with of course a little moisture that made it by the air dryer.. everything always looks a little oily when opened up.. ive only considered it an issue if I was actually spraying oil on the dryer purge cycles or draining actual oil when i drain my tanks..

[GTSailor]

So air dryer was full of oil and grime. The dessicant was not even attached to the head so 100% bypass of dryer for who knows how long. I replaced dessicant and purge valve (so total rebuild except for discharge check valve). Based on what I found I will run a bit and see how things go. PO apparently did zero maintenance. Like not even blowing down the tank drains. I know because the "wet" tank drain was stuck.

Sorry for no pics. Too busy and in the moment.

[mmoore6856]

so now you get to rinse out your air tanks one note here for all you that have air compressors is the fact that the pistons are always movin whenever the engine is running. the unloader is what stops it from building presure so they have as many run miles as your engine. if you know how to hone a cylinder you can replace the rings and pistons just lik a small engine.

[GTSailor]

Update. Looked under my engine and oil is everywhere. I think it's coming from two main places...oil pan gasket and bottom of air compressor.Naturally the oil from pan can't get on the air compressor.

Also, oil is coming out of the intake. I think this is just a path of least resistance thing. If oil is passing by pistons then it makes sense, I think, that it could come out here. It's not coming from the air intake line. I have confirmed that.

Unless I am missing something I am replacing my compressor.

[cadillackid]

coming from the intake could be "suck-by" as I call it into the cylinders when the comoressor is off... essentially in the off state the compressor just shuttles air back N forth between its 2 cylinders.. there is some vacuum created on the downstroke, esp if either cylinder has weak rings that result in blowby on either cylinder.. so sucking oil in would occur and end up with some runout from the head into the intake area of the compressor..


it sounds like your compressor is worn.. I have replaced compressors on 2 of my busses... one because of cracked head and other because the unloader was sticking..



the compressor in my 45 year old bus was replaced at some point since it is a 'Like-NU'