Hi guys this is my first post on this forum. I have a compound turbo 1999 5.9 cummins. About 3 weeks ago I developed a boost leak. I have since replaced all of my boots and the exhaust manifold gaskets and have failed to stop it. It starts a 4 pounds of boost and stops at 37... Any ideas of where to look next? Thanks

 

You can get some Fernco fittings, a PVC pipe cap, and a compressed air fitting and make a leak checker. That will attach where the intake hose would go to your first turbo. Use about 10 lbs of pressure and listen and feel for leaks without the engine running, and that should help pinpoint your leak/leaks.

 

I will try to get a way to run that test. I did the starting fluid trick and wasn't able to isolate where it is. I really think it's on the drivers side. Thanks for your info!

 

No problem. Much eeasier to find a leak when the big loud Cummins isn't running

Here's a couple threads on the Fernco fitting leak tester:

https://www.dieseltruckresource.com/...tester-214239/

https://www.dieseltruckresource.com/...finder-185000/

https://www.dieseltruckresource.com/...nt-find-74481/

 

I'd stay away from starting fluid...

You can remove the fan clutch and dust baby powder around any potential leak areas...

Its hard to get boost up on an unloaded Cummins isn't it?

 

It wasn't hard at all until I got this boost leak. It's a five speed manual and used to boost a little at 1800 in neutral. I have also been warned it could be my intercooler. How would one go about testing that? the same way?

 

Yep, rig up a pressure tester, apply compressed air, and listen for leaks. Most spots you can also spray with soapy water, and see if it's making bubbles.