Alpine951

Been having a hell of a time this year trying to track down what I think is a vacuum leak. Car has idles bad and way lean ever since a WOT run one night. I pressure tested the car a few times and even bought one of those ebay smoke detectors but have not had any luck. All the previous pressure tests have been when the car is cold but I am doing one now after drive the car so it is hot. Is there supposed to be any washers on the intercoller banj bolt. It is making nice bubbles when I spray soapy water on it. I also have Laust's vacuum manifold and is leaking in between the intake manifold and the vacuum manifold. no washer is in between there. should there be one? I think I hear some air under the TB area. the vacuum line under there isn't leaking. what else could be under there. wonder if bottom of TB where it mates to manifols is leaking?

mtnman82

I'm not saying this is right or wrong and hope someone in the know chimes in, but presently I have washers between Laust's manifold and the intake, but not between the bolts and the manifold. On the intercooler pipe banjo bolt I have no washer between the nipple/port piece and the pipe, but do have a washer between the bolt and the nipple/port. I don't think I have a leak but am also wondering if I might have a situation similar to yours where things look good cold but not when things warm up... Where & how are you applying air to pressure test (just curious)?

If I had enough washers I'd put them in on both sides. Anyone have a source for these?

Tom M'Guinn

To run lean at idle, you'd need more than a missing washer or two on a small line like that. You can pull the hose off the bypass for example, and will hardly notice the difference at idle. Have you removed the two I/c couplers, and the hose coming off the turbo, cleaned them up spick and span, and inspected for cracks? Have you checked your wastegate to ensure it holds vacuum? The bypass valve shouldn't make it go leave, but if you have one of the billet versions have you checked to make sure it's not stuck open? Have you check the O2 sensor to make sure it's not responsible for the AFR? Have you set the base idle? Check the lines to the wastegate? I'm not sure how much comfort I'd take from those smoke things -- the admittedly lousy one I used was close to worthless...

Mtnman-- I think you always want a crush washer on both sides of any banjo bolt to improve the seal. You can get them at McMaster or any of the Porsche places like Lindsey, Parts Heaven, etc.

Laust Pedersen

The vacuum manifold substitutes for a banjo nut and should have sealing washers on both sides.

McMaster has them as aluminum crush washers M8x12x1.0, PN 97725A700 at $9.57 for 50 (and I have 50 in front of me) .

Laust

mtnman82

Thanks guys. Will place an order tonight.

Humboldtgrin

You should use washers. Also do you still have the Venturi booster for the brakes? Mine came apart and created a huge vacuum leak. Super glued it back together and it works great and my brakes do to now. May want to check the brake booster as well to make sure it's holding vacuum. Injector o rings could also be an issue. Check the couplers from the intake hard pipes to the intercooler and to the manifold and turbocharger. And check your intercooler for leaks. Check the throttle body o ring and idle screw on top of the TB for its o ring. Your turbo compressor housing may also have a leak(hard to check in the car). Hope you find the problem.

Alpine951

Thanks Tom. I too thought my leak can't bee from those small ones. I/c couplers are a few months old and spic and span. O2 sensor is a few months old. I have not checked it. How would I check it? My car does not have an idle stabilizer valve. The ports are closed off. Currently the idle speed will not increase by turning the throttle body screw. Why would that be? I have not checked the wastegate to see if it holds vacuum but since it boosts fine would that mean that it is OK?

Tom M'Guinn

Why don't you have an ISV?

Simple O2 check is to just unplug it and see if the AFR changes at idle.

Wastegate "probably" ok if it boosts normally, but its lines and diaphragm are potential sources of biggish leaks, and a good turbo can make (inefficient) boost even if there's some leaking.

Can't say for sure why the throttle screw does nothing. Probably too lean already to have much effect, but that's a good vital to monitor.

What's your vacuum at idle?

Alpine951

I ripped out the ISV years ago because it was leaking. new one arrived the other day but I need the curved for the intake manifold port. vacuum is around 16 to 18, and has been for years.