how does one go about pressure testing to see if there are boost leaks on a diesel? in my previous gasser turbo i made a coupler that attached to my turbo inlet and used my air compressor to charge the system. is that safe to do on the cummins? also what is a safe psi to test too? what would be a reasonable bleed off time for the system to hold air?


i am trying to find out why i lost boost and gained more smoke. i just recentley install my GDS stage 2 and my boost stayed the same (right around 29 psi). today on my way home i noticed on a few WOT pulls i was only seeing about 18 psi and alot more smoke. the truck seem more sluggish than normal also. before i would notice the boost would rise to about 29psi and hold, then it would fall flat on it's face and drop in boost to about 20psi.

i also noticed that i got a slight exhaust leak at the downpipe exhaust housing connection. would this cause theses problems?

my thinking is that it has to be a boost leak. if you have any other suggestions as what to look for let me know.

 

Check for leaks with a suitable coupler for the air inlet, air pressure, and soapy water.

The bleed off time is going to vary depending on how many valves are open, etc.

I would check it at what ever boost level you want to see, but you probably will see it right away.

If you just put the copressor kit on, I would look at that. There's seals on the cover and outlet. Might have ripped the IC boot, wiggling it around and stuff.

The leak between the DP and turbo shouldn't affect boost.

 

thanks, i will give it a shot.

 

Ditto on checking the turbo outlet- if it doesnt seal up just right, you'll get a leak.

More smoke and less boost on the gauge will go hand in hand.

You have the right idea for testing for leaks. The Cummins head will hold 40-50psi boost (depeding on whom you talk to), but I never go above 10-15 psi when testing the intake system. If you have a leak, you'll hear it by then.

ALso, if you have a regulator and can set it to a certain pressure, it'll negate the effect of the open valve(s)- you wont have to pump it up, listen fast, pump it up again, listen again, etc, etc.....

The intercooler boots were adequate for stock outputs, but increased pressure and 15-20 years of aging will take their toll.

 

When I popped a boot completely off it was hard to do even 40 mph. It was super smokey and egts were 14 to 1500 just trying to keep 30 up a hill. ( didn't want to stop and fix it beside the road ). Went slow to get home.

 

Should be no overlap on cummins turbo, so if have a noticable leak into exhaust there is a valve problem. Try barring engine a half turn or so and retest. Fifteen PSI will generally show a leak. Pres harder if necessary to 30 or so.