missing my boost

67Amazon · Post by **67Amazon** » 23 Mar 2023, 17:20

1997 850 GLT (LPT) 200K miles

Car is down on power, acting like my old NA 850. Fuel mileage has tanked.

I can hear what sounds like boost pressure leaking from somewhere when I am accelerating.
Not seeing any bad/blown hoses from the turbo to intercooler to TB intake.
Do intercoolers even go bad? I'm see a small hole (factory?) with a smudge of oil around it at the bottom low point of the intercooler. Weep hole ???

I attached a vacuum/pressure gauge to the vac. tree (no stock "boost" gauge) and I get a reading of around 18" of vac. at idle, 9" at cruise & 0" of vac. at WOT, normal?
Gauge never registers any real "boost".
Is there an easy way to attach a gauge to measure actual/real boost pressure ??

Sort of sounds like the wastegate is stuck open, but I don't think that's it.
Bad bypass valve ?
Can't reproduce the sound unless under load (driving).
Will fabricating a way to manually add some low PSI to the TB intake hose be a viable way to listen for a leak ???

What are the most likely places I should be looking at.

Thanks
Peter

Post by **matthew1** » 23 Mar 2023, 17:35

A boost gauge is good for problem solving/data and just plain fun. Here's my boost gauge install DIY from 11 years ago. Your boost numbers are normal, however... roughly 10psi under WOT is in the neighborhood for a correct number for LPT if I recall correctly.

Yes, intercoolers do fail. Weep holes are normal. You wouldn't be getting that high boost if your IC has a big hole somewhere, so it's not that.

Post by **hausmeister** » 24 Mar 2023, 13:38

Sounds like a boost leak or some kind of hose failure. Check the hoses or get a pressure tester... a hose can split and it is not obvious unless under pressure, for example.

Post by **Sveedy** » 24 Mar 2023, 19:10

Chased similar problem before finding out that my intercooler had a crack, so yes they do fail. Particularly the stock unit with the plastic tank. It took a smoke test to find it.

67Amazon · Post by **67Amazon** » 04 Apr 2023, 20:37

gonna use some diy tools to find out where my coolant & boost are going .....

: this is my "boost" gauge

: custom tool to find coolant leak

: diy smoke machine to find missing "boost"

67Amazon · Post by **67Amazon** » 04 Apr 2023, 20:42

sorry, I don't know how to rotate photos .....

Post by **matthew1** » 04 Apr 2023, 20:49

I'll fix them tomorrow, 67. Sometimes the forum software gets rotation wrong...

Post by **matthew1** » 05 Apr 2023, 11:09

Photos fixed.

Great DIY leak finder tool! I love it.

I'm confident you'll find it's one of the vacuum lines or elbows.

Post by **BlackBart** » 05 Apr 2023, 11:14

Cotton balls, ah ha! My son and I made one with oily rags in a paint can. The hose got hot, kinked, and it blew the lid off the can!

67Amazon · Post by **67Amazon** » 06 Apr 2023, 18:26

Good news, Bad news
Good news, I found the leaks, bad news, I found the leaks.
need both a new radiator & intercooler.
smoke test reveled a leak from somewhere on the upper left-side of the intercooler (couldn't see exactly where).
pressurizing the cooling system with the test cap revealed a small leak at the bottom right side-tank seal.