testing boost pressure leak?

[EMurillo]

does anybody know how to test for boost pressure leaks, i suspect i have

a leak somewhere because when is a hot day i don't get a reading unless

i bring the rpms really high. i read on a thread that you use a 4" inch pvc

pipe cap on the turbo intake hose and an old tire valve stem. so i suppose

i have to take the air intake off ?. to pressurize the system or is there another way to do this. one more question what is the maximum boost pressure i should be getting. ? ______________________________________________________________

2004. 5 CTD HO, 325/600, swb slt, 4 x 4, 48re, 3. 73, 27. 5 f/er wanderer toy

hauler, k & n air intake, gages, pyro, trans, boost, westin step bars, rancho rs9000x shock, billet grille, BF goodrich all terrain,

 

[jelag]

You can't test your engine this way... . I'm guessing there never will be a time when at least 1 or 2 valves aren't open letting the compressed air out... .



Most engines don't develop much boost when the truck is sitting still. . the engine isn't doing any work and there is not enough heat generated... (heat being burnt air and fuel)



Purchase a boost gauge and tap the intake manifold and test it...



We just had our 04 in for some work... and we pull a trailer that often will weight 18-20K lbs... . the diver on the first trip out got almost 200 miles from the shop before he called saying he couldn't pull the hills... . we found 2 hose clamps loose between the turbo and intake manifold... . once we got those tight all was fine... . he never noticed the difference on a level road... .



I don't remember the maximum boost but it seems its around 26-28 lbs... . My 01 was turned up... and I saw over 35 many times... but my 04 and 05 don't have any performance enhancements... ... so no gauges... .



Hope this helps...

 

[Bob4x4]

The 600/610's can see mid 30's stock



Bob

 

[Luke Warmwater]

You can't test your engine this way... . I'm guessing there never will be a time when at least 1 or 2 valves aren't open letting the compressed air out... .

I got to thinking about this myself since I want to test my system for leaks. So let's ponder this together... we are working with a 4 stroke that will have a small degree of valve overlap. The question is how much... In a 6-cylinder, 4-stroke engine, there are three power strokes per revolution, meaning that there's a power stroke occuring every 120 degrees of crankshaft rotation. I have no idea how much valve overlap a Cummins has but if I remember right, gassers usually have roughly 40 degrees of overlap. That being the case it would not be very hard to rotate the engine by hand to find a point in the firing rotation, where you are not in an overlap condition. I'll find out tonight as I'm going to give it a try.



EMurillo, you're on the right track.

 

[rweis]

Well, maybe you can't make a PVC adapter to find a leak, but mine sure works.



True there is some valve leakage, but I could hold a constant 20 psi on the boost gauge (and on the compressor gauge). Soapy water sprayer, and there it was. A second time it was the hose from the intake manifold to the boost gauge.



I would say the adapter works if you are looking for boost leaks.



Bob Weis

 

[nps]

Can't pressurize the intake? Guess I must have valves that are stuck closed. :-laf



You can most certainly hear major air leaks - the leakage through the valves can't be heard outside the motor.



Sure the pressure bleeds down, but it's not like you are doing a 24 hour pressure test or anything.

 

[rweis]

I had a thread on how to make one from Home Depot parts. The search will find it.



Bob Weis