Engine/Transmission (1994 - 1998) Suspected boost leak

[charlessmith]

I suspect I've got a boost leak from the sounds I hear while on boost. This is the '96 12V. While under boost I hear a 'rushing air' noise, although the boost and exh gas temps look about normal.



I'm running with a 5000# camper in the truck, and this started (I think) after a 2 mile very steep uphill where I was running 68 MPH. This was running about 32 PSI boost, the exh temps were running 1250F - 1300F, and the water temp was toward the high side but not in the red. This was not full throttle, just enough to hold the speed (110 KmH). I dropped to 60 MPH out of OD, which cooled things quite a bit.



A few minutes later, after I'd topped the uphill, I noticed the rushing air noise and finally figured it came and went with boost.



MY question, how do I figure out what's leaking? I'm 3000 miles from home so I probably can't fix it right away as long as it doesn't get worse.



Also, I assume I need to be careful not to overspeed the turbo since it's pumping more air that is going into the engine - right? This probably means take it easy on the heavy foot.

 

[KYOUNG]

Are you sure your not hearing your wastegate, or fan clutch kicking in?

 

[hsmith]

If you are actually hearing a boost leak, your egt's should be out of control and you should also be low on power. Most common place is the inlet boot at the cooler. Happened to me before I installed silicone boots.

 

[HBarlow]

I don't think your turbo can produce 32psi boost with a leak in the intake tract and as another member stated above, your EGT would rise also.

 

[Bob4x4]

32 psi is possible with enough fuel and a hose that is out of place (slipped and clamp not tight) The hose does not have to be all the way off to whistle.

Tightening clamps should be on the pm list of things to do even on a stocker as they age.

 

[charlessmith]

I'm suspecting it's a small leak, like a gasket between the head and intake manifold. On another 12V truck I had a hose blow off at the intercooler, that was obvious - a new '97 with 15K miles and NO power and lots of noise. This sounds like the blower fan turned on high when I show over 10 PSI boost, and the more boost the louder it gets.

Thanks for the suggestions. I'll double check the hoses and tighten the clamps.

 

[Bob4x4]

You can try shaving cream on any suspected boost leak area. When you start it up it will show as long as the cooling fan doesn't disturb it.

 

[surfbeetle]

Follow this link to an older thread... Make the adapter with parts from a hardware store. You can then pressurize your system with 20-30 psi and look for the leak. Since you're not at home, find a place that has compressed air that you can regulate the pressure to the 20-30 psi.



https://www.turbodieselregister.com...2/185133-how-pressure-test-intake-system.html

 

[Erniek]

I just had a similar problem with my 97 12v. I heard an air rushing noise for quite sometime with just a small rise in egt over normal. It turned out to be that the hose on the cold pipe just down stream from the turbo had come off only on the bottom side. You couldnt see it looking down from the top side of the motor, but when I felt around the clamp, I could feel that it had blown off. I loosened the clamp and repositioned the hose and retightened clamp. Good to go now, no more noise, and the egt has dropped a bit.