boost leak

[danzick]

Ive been fighting high EGT's with this twin kit. I did a boost leak check tonight and it would go from 20 psi to 0 in about 10 seconds. I could not hear a leak anywhere. I even got the soap bottle out. I found a small leak at the mouth piece for the stock turbo, but it was so small you couldn't hear it, only see the small bubbles forming. I decided to pop the oil fill cap off and try it again. well I found where all of my air is going. You could feel the air rushing out of the fill cap big time. What would cause this? truck runs great, both turbos seem ok. neither really have any in and out play.

 

[juddski88]

Where are you pressurizing it?

 

[danzick]

starting at the atmospheric turbo, and I have a plug in the down pipe.

 

[danzick]

anyone? Id like to get the truck put back together here soon. Going to mess with it some more tonight. I pulled the hot side intercooler tube off and it wasn't oily. just a little dry black stuff on the walls of the pipe.

 

[danzick]

couple questions. I have noticed a mysterious liquid dripping from my exhaust in the garage. Its a brown/orangeish color. I think I found the source. Here is a picture looking into the exhaust side of my s475. The orange puddle in the bottom is water. I hope this could be condensation from change in temperature? possibly a head gasket failure? it doesnt smell like coolant. Just smells like diesel exhaust. I havent really driven the truck in about 3 weeks. I start it every few days and pull it out of the garage to work on something else, then shut it off. When i pull it back into the garage, the whole truck condensates up from being cold outside. also, When I pressurize the system, I can take my down pipe off, and no air comes out of the exhaust? what are the chances all of the exhaust valves are closed?

 

[Moneywellspent]

If air is coming out of your oil fill cap I'd do a compression check to start.

The water could be from condensation like you said or a bad head gasket.

If your intake valves are open your exhaust valves should be closed or vise versa, that's why air doesn't come out of your exhaust when you pressurize the intake side of things.

 

[danzick]

I do not have the tools for a compression check. I may have to get one though. Balance rates on the truck are good and it runs like it always has. Could it really be a bad cylinder?

 

[danzick]

took the truck out for a drive after I put it all back together. Running strong and smooth as ever. I dont understand where all of the air is going when I do the boost leak check. going to see if the upper rad hose is hard in the morning.

 

[DAVe3283]

20 PSI to 0 in 10 seconds isn't that bad of a leak, IMO. The volume of air that moves through the motor when it is just idling, let alone wound out, makes that a rounding error.

Like Moneywellspent said, the intake and exhaust valves aren't open at the same time. The stock cam (and some aftermarket ones) have 0 overlap.

There is an old trick to see if the rings are bad. Do a compression test, then put a few drops of oil in each cylinder and redo the test. If the rings are bad, the compression will jump up when you add the oil. Though ring failure on a stock Duramax is pretty rare from what I hear.

Not sure what the liquid is from. Hopefully condensation...

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[GSXRTURBO1]

Where exactly are you pressurizing on the atmo side? Plug in the downpipe? Something doesn't seem right here....

 

[Moneywellspent]

I do not have the tools for a compression check. I may have to get one though. Balance rates on the truck are good and it runs like it always has. Could it really be a bad cylinder?

There is a chance but I'm not saying that it is. If you could get your hands on tools for the compression test I would do that first. It would eliminate or verify the possibility of bad deal rings some where.

As for the water was that in the s475 exhaust housing? Also what were your peak egt and boost pressures? If your seal rings are good and boost psi is normal and egts are the only abnormal reading then I'd suggest sending data logs to your tuner for some refinement.

 

[danzick]

Upper hose was soft, and no excess pressure in the coolant tank. Egt's were only a little above 1100 on my 3 tune which is probably in the mid to high 400s. 45 psi for boost. Egts are usually around 1300 with this tune. Not sure what's going on.

 

[BlkMax]

There is an old trick to see if the rings are bad. Do a compression test, then put a few drops of oil in each cylinder and redo the test. If the rings are bad, the compression will jump up when you add the oil. Though ring failure on a stock Duramax is pretty rare from what I hear.

The oil trick works on gassers, but is discouraged in a diesel because it is possible to get the engine to fire on that cylinder while doing the compression test.

GM specifically says NOT to put oil in the cylinders while doing a compression test.

 

[DAVe3283]

The oil trick works on gassers, but is discouraged in a diesel because it is possible to get the engine to fire on that cylinder while doing the compression test.

GM specifically says NOT to put oil in the cylinders while doing a compression test.

That makes sense. Plus, you'd have to put an incredibly small amount of oil in to avoid it burning with any significant force. It turns out 1 drop of oil is about equal to 65 mm3, more than enough to have significant combustion in that cylinder.

So yeah, don't do that on a diesel. I've done it so much on motorcycles and old cars I didn't even think about it.

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