I have a feeling this will be a long post, so I hope you're not busy!

As I have posted before, my boost climbs up to about 25 PSI now and dumps somewhere. It started it a time or two when I first pulled a large trailer with all my new mods installed. It has been getting worse all the time. The other day I tightened all my clamps down on all the intake air hoses and took her for a drive. I actually hit 43 PSI again and thought it was fixed. Now, a few days later, the leak is back. I have new gaskets for above and below the heater grid since I know I messed them up when taking it on and off putting in injectors and junk, but I really can't see a gap in the gaskets allowing that much air to dump. The leak has to be significant doesn't it? I mean, that turbo of mine makes a metric butt load of air. Whatever is allowing air to escape has to be big to release enough air to keep it down to 25 PSI, right? I'm electical, not mechanical, so I know a little about pneumatics, but not all the really important stuff.

What would be the first place to look if your truck was doing this?

First, I built one of those pressure testers, but I can't charge it up past 5 PSI or the dang tester blows off the turbo because the clamp won't hold or seal around the compressor housing intake because II doesn't machine the outside of the housing...those cheapos! It is just has a rough, casting texture that is hard to seal and hold to. It would help if there was a lip or something.

Second, when I do get 5 PSI in it and have it so it won't fly off, all the air leaks out somewhere real slow like. It sounds like it is coming out of the block back by the fuel filter housing or somewhere. Where could air leak in the block? Please don't tell me it is a head gasket leak!!!! If the head gasket leaked, it would be also leaking fuel or oil and I could see it or tell it easily, right? Again, electrical, not a motor man.

I also thought maybe the wastegate moved or something, but you can't really get to it on these phat shafts because it is hidden way underneath. Surely that can't be it or tightening the clamps wouldn't have cured it the first time.

Has anyone blown an inner-cooler? Maybe a rock poked it? Surely I'd hear that leak when putting air in the system. I'm out of options here. Does anyone have advice on this term paper full of crap????

Thanks for reading. JWB

PS. Isn't there a air port on the mantifold that you can tap for a guage? Maybe this is leaking? I'll do a search and see if I can find that plug.

 

I would be looking at the wastegate. That is a lot of air to be dumping. I have driven around with numerous leaks and could still boost a lot.

 

I'm with you, something BIG has to occuring. I wonder if the wastegate actuator came lose and is slowly moving itself with vibration. My truck doesn't shake or ride rougher than a log wagon or anything. How the world do I set it back if it has moved....just move it...drive it...move it...drive it...until I get it to make 40 PSI? That will severly wiss me off. That turbo is only a few months old. I sure hope it isn't that.

 

the intake manifold on the side of the head has a long approx 18"x4" aluminum cover sealed with a paper gasket. you can pull all your injection lines and remove that cover to replace the gasket if thats the case. (double check all the bolts that hold it down if you've loosened any doing injector line work)

there is a plug just below this manifold that takes a 1/2" socket drive (square) where some guys plumb the gauge, check that (like you said its near the fuel filter)

also way in the back of the head is both the MAP sensor and IAT sensor, both screw into the head and use rubber o-rings to seal. check to the be sure they are good and sealed.

i think you will find your leak in one of these places


EDIT- also check your gauge tubing, i cracked my plastic tubing and was only seeing about 20psi for a few days until i found out what it was. if you notice no increase in EGT's or decrease in power, then this will most likely be your culprit

 

Thanks! I'm going to pull her in the shop tonight and check all these. The air did sound like it was coming from that area. Maybe I can just re-torque the bolts holding down that intake. I'm not familiar with that part of the motor, but it is time to learn!

 

yup all it takes is one to be slightly loose.

example, at a dyno event i was installing my TST and used one of those intake manifold bolts at the front for my ground wire, forgot to tighten it down, on the 100 mile trip home that night i got a boost leak and it drove me nuts, cant remember if it was enough to register a loss on the gauge but i could hear it screaming out of the hole and it had me furious. got home and tightened it down...problem solved!

 

Ya, well, I found my problem and it don't look good for the home team. The air is going in to the freakin' CRANKCASE! What the heck? I'm assuming that is a head gasket problem to my best knowledge. Now I'm trying to figure out if I can do the work or pay someone a freakin' thousand bucks to do it. I'm calling Cummin's right now for a quote. Man, this stinks.

I pressurized the system with my little tester last night and my air compressor. I put 10 PSI on it once I got the tester to hold. I climbed under the truck and put my ear to the oil pan....air movement was loud. Then I took the oil fill cap off, you know the 710 cap, and I could hear and feel air. That really...really....stinks.

Now I'm going to search for how hard it is to put one on and all the new gaskets I need to buy before I start. I am going to put the marine gasket in so I need to find some info on that too. Good thing I'm not too busy at work today and have the choice to take all next week off!

 

well its not too hard to do the head gasket. are you adding o-rings or fire-rings, or just doing the marine gasket? modified 12v marine gasket is $200 from PDW (PM jetpilot or call him 717-557-7060) studs are $400-$450 and would be good for you with the fuel and air you are pushing. also add another $100 +/- for misc gaskets and supplies you will need.

if you pay someone to do the work you are looking at another $800 or more in labor (that is if you add the studs, they are alot of work to get torqued properly). its not difficult to do, just need a cherry picker and some time to do all the work. it could all be done in one weekend if you can keep at it. let me know if you need any more info/help

edit:

misc gaskets/materials you will need include
-manifold to turbo inlet gasket (could be re-used but for $5 id replace it)
-turbo oil drain gasket, they tear easily
-2 heater grid gaskets
-some good brakleen or parts cleaner
-emory paper or gasket cleaning wheel for grinder/air tool
-new coolant, 6 gallons (gonna need to flush it out because is likely there is oil in it)
-oil change materials while you are at it

*if you add studs
-12mmx1.75 bottoming tap (good idea to get at least 2 in case one breaks)

 

Ok. They guy at Cummins Tech Support was a complete ...well...horses patute. He told me that I wasn't testing it right. He said the air I was hearing was just going into the valves and that it was normal.

SO...if you charge up your intake systems and the air keeps flowing, where the heck is it going? If an intake valve happens to stop in the open position, the air will go into the cylinder. If one of the two or both of the intake valves are open, then the exhaust valves for that cylinder would be closed. Thus, the air shouldn't escape...right?

This is really stating to bug me. Now I'm thinking it is my turbo...my brand new II turbo that is the problem.

My coolant is perfectly clean...my oil is clean and normal...and my truck runs great...up to about 25 PSI. What the heck? I can't see that I would lose a tiny piece of head gasket somewhere without having MAJOR problems and not just this little air thing.

Any other words of wisdom???????

 

There is valve overlap that could cause some air movement...also, a leaky valve seal "could" let air past it, go through the push rod area, and flow into the crank case. The only way to find out for sure it to remove all the rockers so all the valves are closed...at least then you would know if it actually is going into the crankcase. It could also be rings, but not very likely unless you have lots o miles, IMHO!

Sounds like fun, Good Luck!

Chris

 

I'd sure rather romove the rockers and make sure before removing the stinking head!!! Thanks, that is good info. So, when the truck is running, during this valve overlap, some intake air actually goes into the crank? I just never would have imagined that...but that is why I don't design motors!

Maybe I need a valve adjustment???

 

Maybe I'm not pressurizing the system enough to find the "REAL" leak. I'm a little reluctant to put 20 or 30 PSI in there, but that is where it normally runs, right? Would it hurt to put that much pressure in there if it is leaking into the crank?

 

Ever hear of blowby??

Overlap doesn't really cause the air to go to the crankcase...overlap is one of the reasons you can't totally seal the cylinders, the intake and exhaust valves can both be open at the same time!!

Blowby is compression (in your case, compressed air) getting into the crankcase around the rings, valve seals, through a crack in the head, etc!

Chris

 

Well, maybe I shoud get a compression test done, eh?

 

You won't hurt anything probably going to 50psi...as long as the air can get out! Check the vent tube on the front of the engine to make sure the air is coming out there...the vent tube could also come down back by the starter, too!

If you do have a major problem like you think, you're not gonna hurt anything else by throwing compressed air into it. It's a long way from the amount of heat and pressure of the engine firing!

Chris