Thermo Valve boost leak advice

Talk and Tech about turbocharged 924/944/968 cars
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Spencan
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I have been chasing boost leaks for a while now. I rebuilt the throttle body (thanks Tom!), replaced some cheap aftermarket Intercooler clamps, and replaced the original ISV hoses.

Now when I pressurize my intake system, I can hear air coming from the thermo valve under the intake. I connected a handheld vacuum pump to the tube that connects to the intake and it holds 18 psi with no leaking. When I connect the pump to the other side of the thermo valve (to the evaporator system side) it does not hold any vacuum. I did this with the engine cold. Do have the lines mixed up or do I need a new thermo valve?
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'89 Turbo S-Glacier Metallic Mods: Evergreen Turbo-"Raptor" stage II, Bell custom intercooler, FTech 9 DME & OBD+, Tial 38 Wastegate, GFB EBC, A-Tune, 3" Turbo Back Exhaust, Cross-Drilled rotors, refreshed suspension

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Spencan
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I bought a new one and will replace it soon.
'89 Turbo S-Glacier Metallic Mods: Evergreen Turbo-"Raptor" stage II, Bell custom intercooler, FTech 9 DME & OBD+, Tial 38 Wastegate, GFB EBC, A-Tune, 3" Turbo Back Exhaust, Cross-Drilled rotors, refreshed suspension

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Tom
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Sorry I missed this. As far as I understand, that valve simply opens when hot to let evap vapors flow to the brass tube on the throttle body. What were you trying to draw a vacuum on? One the little bunny ear ports?

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Spencan
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Yes, during my research on how to test it, I found some information that read that if both sides hold vacuum, then it’s working properly. One side does but the other side doesn’t.
'89 Turbo S-Glacier Metallic Mods: Evergreen Turbo-"Raptor" stage II, Bell custom intercooler, FTech 9 DME & OBD+, Tial 38 Wastegate, GFB EBC, A-Tune, 3" Turbo Back Exhaust, Cross-Drilled rotors, refreshed suspension

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Tom
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Pretty sure I have a spare one in the garage. As far as the valve itself is concerned, I've always understood it was just closed when cold and open when hot. I'll see if I can confirm that... If you take the hoses off and test those, I would not expect the hose going to the throttle body to hold vacuum; the line to the evap system I'm not sure, but if the downstream valves are open I imagine you'd have have to pump the mightvac a long time to see any real vacuum since there's a lot of air volume in the tank/canister, lines, etc.

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Spencan
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My new one came today from AutohausAZ. I think that I will test it the same way, just to see if it’s an accurate test. Either way, my original one does leak when air pressure is applied to it, so it needs to be replaced.
'89 Turbo S-Glacier Metallic Mods: Evergreen Turbo-"Raptor" stage II, Bell custom intercooler, FTech 9 DME & OBD+, Tial 38 Wastegate, GFB EBC, A-Tune, 3" Turbo Back Exhaust, Cross-Drilled rotors, refreshed suspension

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Spencan
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Here’s the new one.
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As you can see, both sides hold vacuum.
'89 Turbo S-Glacier Metallic Mods: Evergreen Turbo-"Raptor" stage II, Bell custom intercooler, FTech 9 DME & OBD+, Tial 38 Wastegate, GFB EBC, A-Tune, 3" Turbo Back Exhaust, Cross-Drilled rotors, refreshed suspension

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Tom
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if you put a heat gun on it, or submerge the metal part in boiling water, it should open inside such that neither side will hold vacuum if the other side is uncapped.

Did your original not hold vacuum like that even when cold?

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Spencan
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Yes, the side that is connected to the intake held vacuum and the canister side did not.
'89 Turbo S-Glacier Metallic Mods: Evergreen Turbo-"Raptor" stage II, Bell custom intercooler, FTech 9 DME & OBD+, Tial 38 Wastegate, GFB EBC, A-Tune, 3" Turbo Back Exhaust, Cross-Drilled rotors, refreshed suspension

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mwc951
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Clean up the engine compartment and simplify things.
Pull all that stuff out.
viewtopic.php?t=3215

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