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Discussion Starter · #1 ·
I have a 1987 JETTA 8V. When the engine starts up and runs the intake manifold actually gets cold to the touch. It stays cool no matter how long the engine runs. Anybody have any ideas of why this would happen?
Thanks in advance!
Jim http://****************.com/smile/emthup.gif
 

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Re: What would cause a cold intake manifold? (vdubdrivenfool)

THere is a gremlin pour liquid nitrogen on it when you arent looking?


my real guess is the constant air flow going through it into the engine wicking heat away. If you really want a crazy guess...your FPR is busted, and the vacuum line that hooks up to it, is allowing gasoline to be sucked into the intake manifold, which is then evaporating fast (as gas does) and super-cooling the intake manifold. same idea as when you get rubbing alcohol on your hands and they get cold as it vaporizes off.
Now if you tell me you drive your car for 1/2 hour, let it idle 10 min at a stop, then pop the hood and your intake mani is cool? that would be some strange shat.
 

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Discussion Starter · #3 ·
Re: What would cause a cold intake manifold? (Banditt007)

Quote, originally posted by Banditt007 »

Now if you tell me you drive your car for 1/2 hour, let it idle 10 min at a stop, then pop the hood and your intake mani is cool? that would be some strange shat.

That is what I am telling you. No matter how long I drive it stays cool to the touch?
REALLY......
 

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Re: What would cause a cold intake manifold? (vwfanforlife)

Quote, originally posted by vwfanforlife »
I'm also curious, cos i have a friend with a '78 bug which is actually icing up the intake... and our ambient temp is around 22 celsius......

That's not that unheard of at all for a carbed motor, especially if running on alcohol or a high alcohol blended fuel, the fuel evaporating in the intake manifold absorbs a lot of heat. That explains how this could happen in a 78 bug. The 87 Jetta of the O.P. is a much more puzzling, the only thing I can think of is maybe raw fuel's getting into the manifold from a leaking cold start valve, but if that were the case, I'd expect the motor to run poorly.
 

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Discussion Starter · #6 ·
Re: What would cause a cold intake manifold? (ABA Scirocco)

I think I may have found the problem? It was a bad thermo time switch. I disconnected the cold start valve and the car ran perfect with no cold manifold. Then I jumped the CS valve to see if the thermo switch was good. I got constant power. It is supposed to only power up for 10 seconds or less. Now I need to get a TTS and install it and the car should run perfectly! http://****************.com/smile/emthup.gif
 

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Re: What would cause a cold intake manifold? (vdubdrivenfool)

Quote, originally posted by vdubdrivenfool »
I think I may have found the problem? It was a bad thermo time switch.

That certainly fits the symptoms, everything makes perfect sense now. Good stuff http://****************.com/smile/emthup.gif
 
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