think I finally found my vacuum leak

[9dreizig]

Got the engine on the stand today, getting ready to clean it up and figure out where the vacuum leak has been all these months..
So here's what I found.. Since I"ve ripped the air pump and CAT off this.. Do I need this ? It's the thermal switch

[A930Rocket]

Good question. I've got one of my dizzy lines run to that switch, since it originally ran to it before I desmogged the car. If your dizzy isn't run to it and your desmogged, I'd say you could plug it.

Are you going to reinstall the engine if you cap or replace it? Or do you have more plans for it?

[willtel]

I capped mine and removed the cold start vacuum limiter relays as well. It hasn't caused any issues with my car. Still starts fine in 20 degree weather.

Somewhere on this forum there is an image with the bare minimum of vacuum lines that you need with the air injection system removed.

[oilonly]

Somewhere on this forum there is an image with the bare minimum of vacuum lines that you need with the air injection system removed.

That would be a good image to bookmark. I'm going to search for it.

[oilonly]

It would be nice to get rid of all that confusion shown here.

Please help identify these parts for me

[aerodyn930]

No problem in by-passing the temp switch, It was intended to reduce emmisions during the warm up phase, (cat. converter ) by promoting higher egt's.

What is interesting is a have found quite a few that have failed, You lose not only vac. advance but also vac. retard.(under boost)

my own 930 and all my customer cars have it by-passed.

Lou/ AERO DYNAMICS

[mark houghton]

Yep, 'taint needed. Just one more thing to fail. I don't run with that switch, nor the vacuum limiting solenoids.

[oilonly]

Originally Posted by willtel

I capped mine and removed the cold start vacuum limiter relays as well. It hasn't caused any issues with my car. Still starts fine in 20 degree weather.

Somewhere on this forum there is an image with the bare minimum of vacuum lines that you need with the air injection system removed.

Is this it?

Air pump removal????

[JFairman]

Originally Posted by 9dreizig

Got the engine on the stand today, getting ready to clean it up and figure out where the vacuum leak has been all these months..
So here's what I found.. Since I"ve ripped the air pump and CAT off this.. Do I need this ? It's the thermal switch

Like everyone has said, you don't need it unless you have to have all the emission crap working perfectly, and the car will run better without it because you'll have vacuum advance to give the motor a little more pep as soon as you start it cold.

Don't just bypass the goofy thing, replace the entire red vacuum line because that origonal cloth braided vacuum hose dryrots and cracks under the fabric surface and you get a vacuum leak that is impossible to see and harder to diagnose.
The origonal vacuum advance hose was red and the vacuum retard hose was a dark blue.

The purpose of that little mechanical temp switch was to block vacuum advance to the distributor vacuum advance pot during cold starts and for a little while after a cold start until heat transferred up to it - opening it and letting vacuum pass through.
That would leave the distributor with centrifical advance only so that would retard the ignition timing enough to raise exhaust temperature because then the gas is still burning a little when the exhaust valve opens and the higher exhaust temp heated up the catalytic converter faster so it would lower emissions sooner.

There were 2 electrical vacuum solenoid switches too.
One would block vacuum retard to the vacuum retard side of the distributor vacuum pot for about 1-2 minutes after a cold start so the idle would raise about 300 rpms and not stall out with all the other emission crap and lame timing settings dogging down the motor.

The other vacuum solenoid just to the left of it was wired in parallel and was plumbed to trigger manifold vacuum to the left and right side air pump diverter valves so air pump air flow would switch from the exhaust ports to the catalytic converter.

yeah i know, more than you wanted to know... but maybe it will help someone.

[oilonly]

yeah i know, more than you wanted to know... but maybe it will help someone.

I wish I didn't know. Because now that I do I want to rip all that stuff out. But yet I want to keep it all stock. It was better when I was ignorant of all this info, now I am torn.

[A930Rocket]

So where is everyone running that vacuum line or swapping out that switch for? After looking at the link, I'm not seeing any difference.

[9dreizig]

Look at the second pic on the second link
It goes from the disty to the throttle body vacuum nozzle marked V
Good stuff!!

[A930Rocket]

What about the 2nd vac line off the dizzy?

[billjam]

Hi guys. Here's an updated diagram.
Plumbing is still basically the same except for new MBC and repositioned source for boost measurement (for gauge, LMA-3 and BOV).