Air tanks

[j.m.jackson]

Any idea where the wet tank is on a GMC 5303 suburban? The tank behind the passenger rear wheel well is a dry tank, and the one under the driver is also a dry tank. Replacing drain valves with decent 1/4 turn valves, and there's some moisture in those supposed dry tanks. I suspect that there is an automatic purge on the wet tank. I also suspect that it's disconnected, as there is a flex line going to the air compressor governor that is disconnected and hanging. Fitting is plugged with a bolt on the governor side.

[TomC]

Simple-trace the output air line from the compressor to the wet tank. Mine had an air/water separator from the factory.

[j.m.jackson]

I agree, it just involves getting my head in some very low clearance spaces. Looking at the maintenance manual, it looks like there are 4 tanks. I think I may know where the wet and dry tanks are, tucked between the spare tire compartment (which is right in front of the drivers side rear tire) and the battery box. No outside access, only access from underneath. I still suspect that the moisture ejector is disconnected. I'm tempted to put some pressure on that line that's disconnected at the governor and see what it does.

[Paso One]

This picture is from a transit but you can see the air dryer and the tank after is the wet tank.

[j.m.jackson]

I can see two round things between the batteries and spare tire on the drivers side. I'll take pictures and see.

[j.m.jackson]

Yes, that's the tanks. They are oriented vertically, with the wet tank on the outside. The dry tank has that drain valve that takes the special key. The wet tank has a line coming off the bottom of it, going into the spare tire compartment, and then going into the heat ductwork inside. Any idea where the ejector is? There are also two lines coming down, to drains. I suspect these are the outlets of the ejector. I'll pull the interior duct this afternoon and see if the ejector is right there inside the coach. I hope so. Any ideas? I want the air system fully functional, as it's a safety thing.

The book says the ejector can be triggered by the governor or the air brakes. Hopefully when I put my hands on it, i can verify which one it is.

[j.m.jackson]

The tanks are between those two doors. Front is battery, rear is spare tire.


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[j.m.jackson]

Found the moisture ejector valve, it's in the heater duct on the drivers side. I'm 95% sure the disconnected line at the governor goes to this. Both exhaust lines were plugged with dirt dobbers.

I've got a trip to Lowes this afternoon for a faucet valve in the non-mobile house, so while I'm there I'll get a rubber tip for my blow gun to run some air down the control line at the governor and see if the valve activates. If not, I'll try it at the valve itself. Who knows how much water is in that wet tank.

Also, anyone have experience getting one of those turnkey valves out? I'd like to replace it with a 1/4 ball valve like I have everywhere else.

[chessie4905]

Shouldn't be too hard to remove.they should be brass or copper. The drain in tank could be plugged after removing valve. If so, you can probe with small screwdriver. Careful that you don't get a bath. If it has water and oil sludge, let it drain over night to get all the oil out. GM mentions this in their shop manuals.

[j.m.jackson]

I can't imagine what's in that wet tank. A mess, for sure. Good call on the point of not taking a nasty, nasty bath.

[j.m.jackson]

Pulled the line off the bottom of the wet tank. Great googley moogley. Looks like grey paint. 2 gallons, maybe more once the temp cycles today.

[muldoonman]

Pulled the line off the bottom of the wet tank. Great googley moogley. Looks like grey paint. 2 gallons, maybe more once the temp cycles today.

That can't be good.

[Oonrahnjay]

That can't be good.  

     Agree.  ILTM like you've got a combo of water and oil.  Water happens (although if you have an air dryer and this is past it in the system, that's another thing to think about) but I think your biggest question now is "how much oil".  Drain that tank as well as possible and air it up (maybe a few short drives at highway speeds with a drain after each?) and see if you're getting oil out of the tank once all the "old stuff" is out of there.

[chessie4905]

Just goes to show what can happen when tanks are never drained or moisture ejectors are disabled. Probably was disabled because of air leakage and couldn't find repair kit or rebuilt unit or didn't want to be bothered with proper repair. Makes you wonder about proper perotic maintenance or service being done prior.

[j.m.jackson]

Chessie,

Yes, that's why I'm touching every system to make sure they're roadworthy.

I'm looking forward to seeing what's up with the ejector valve.