Tracing vac leak

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Tracing vac leak

Postby lotusrepair » Tue 08.12.2020, 21:33

On the advice from some here I set out to see if I had a vac leak. I hooked up my smoke machine and found two places where smoke was coming out. The first was on top where there looks to be a blanking plug. The second is behind the intake and under out of sight. I tried various mirror angles to see where the source was but just can't get a good look at what is back there. From the photo, what is under the intake that would leak? Considering taking the throttle section off and then retrying the smoke to get a better look.

Chris
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Re: Tracing vac leak

Postby Rambo » Wed 09.12.2020, 09:22

Chris - your arrow is pointing to the idle/throttle adjustment screw. All cars had the rubber blanking plug when new but it was one of the 1st things to get binned/lost when anyone set the idling speed
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Re: Tracing vac leak

Postby TorqueHorse » Wed 09.12.2020, 18:33

Hey Chris,

There are lots of vacuum take-offs on the rear, and if you still have original hoses, they may be leaking like mine were. The service manual has a great diagram labelling all the take-offs (available from Manuals link in top nav bar of site) and here is a photo of the area in question to go with the diagram.
Image
It might even be the secondary throttle take-off hose has come off of the vacuum reservoir, which is tucked wayyy under there. Also, the EEGR take-off has a non-return valve on it, so smoke could be coming from there too, and not be a problem. Before tearing down the whole throttle, I'd suggest taking off the hoses that you can reach and plugging the ports and then repeat your test. Then go in series testing each hose back on, to see if you can narrow down the culprit. After that, then I would suspect a gasket.
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Re: Tracing vac leak

Postby lotusrepair » Thu 10.12.2020, 01:58

I can see the three hose ports at the top and it is not them. The egr valve and below is where I see smoke coming from. Thanks for the photo. I was not able to see as much detail in any of the manuals. I had the idle screw out so I will have to reset that. Might wrap some teflon tape around the upper threads to see if it seals.

Chris
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Re: Tracing vac leak

Postby Rambo » Thu 10.12.2020, 12:57

lotusrepair wrote:I can see the three hose ports at the top and it is not them. The egr valve and below is where I see smoke coming from. Thanks for the photo. I was not able to see as much detail in any of the manuals. I had the idle screw out so I will have to reset that. Might wrap some teflon tape around the upper threads to see if it seals.

Chris


Don't forget to reset your idle speed in service mode @ 950 rpm
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Re: Tracing vac leak

Postby TorqueHorse » Thu 10.12.2020, 16:59

And I confused myself: I meant the EECS hose has a non-return valve, which should be buried somewhere below your EGR valve. Couple connections down there that could be leaking. Only other thing I can think of that is that low would be the Secondary Throttle Vacuum Reservoir feed hose is loose at the connection to the reservoir, which is also way down in there. You can just see the reservoir in the bottom right hand corner of the photo: a dirty white cylinder turned on its side, held with a yellow passivated clamp, and the blue of its solenoid controller peeking out its left side.
Hope you can find the source and report back. Good luck!
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Re: Tracing vac leak

Postby cliff » Thu 14.01.2021, 19:43

A little late to this, but as I am just about to troubleshoot my own vacuum leak, here is a picture of the rear of the engine. This shows the throttle actuator, vacuum solenoid valve and throttle vacuum reservoir.

PA261711 (Copy).JPG


The long pipe on the left goes to the Plenum
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