1997 Volvo 850 T-5 with vacuum leak, ODB2 codes.

[Sommerfeldt]

DigiHound - I think we may have to take a step back.

- There's no correlation between your turbo and your transmission.
Just forget about that.

- Unless you put it on yourself, or a previous owner did, your car does NOT have a BOV.
Such a thing, in any case, would not be on the turbo, but on a hose with a customization for such a contraption. Now, instead, we've got wastegates and a "resirculation" system of sorts on these cars.

So, forget about BOVs, and forget about transmissions.

Here's what you should probably do, given that the techs told you you had a vacuum leak:

Tools you'll need: A good flashlight.
I ususally bring both my SureFire and my LED work-light when I go hunting in dark corners of the engine.

1: Find out where you turbo is, and take a good look at it.

There should be a few hoses, but 3 smaller vacuum hoses "on top" are the ones you're possibly having issues with. They're small (5 mm -ish), they're black, and if they haven't been changed, they're color coded with little bands. 3 of them.

2: Follow them to the TCV. Now you know where that is.

3: Check all those small, rubber or silicone hoses for leaks.

Then, when you've done that, check all your air hoses for leaks. Follow the metal pipe from the top of the turbo that goes over the engine, and check the rubber hoses you encounter for leaks. There should be 5, all in all, counting in the little "coupler" on top of the turbo, just between the turbo and the metal tube over the engine.

Don't worry about going underneath the car - you probably won't find a vacuum leak from under there.

4: Take pictures, and post them here if you want and if you get stuck, and someone will help you.

- S

[Sommerfeldt]

Riiiiight... This wouldn't leave my head, and I think I may know what you're talking about. The bypass valve, which I flippantly referred to as "a resirculation system of sorts", is the only triangular-ish part that I can think of, which looks kind of like a cover... You should definitely have one of these, and a leak there would be "at the turbo", I suppose.

Still, follow my steps above. One of the 3 vacuum hoses I talked about goes to the bypass valve... if I'm not completely lost.

- G

[DigiHound]

Sommerfeldt,

I will do so. I don't recall mentioning my transmission, though -- I've had problems with the AC (it looks like something called AC clutch gap) and with the turbo vacuum leak.

The car was throwing a catalytic converter error at one point, but my biggest question is whether a vacuum leak in a turbo can lead to an O2 sensor getting cranky and throwing a persistent CEL.

[Sommerfeldt]

only necessary if you have a manual (I have an automatic).

and I was told this is a part that's only necessary if you have a manual. BOVs don't seem to be required for automatics.

Anyway, the AC is a different issue - check out the write-ups on fixing that - breadclips and whatnot.

As for your question there, simple answer is probably "yes". So start with the vacuum leak, and go from there. But do check the bypass valve... it's kind of a triangular fitting on that thing.

- S