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Low vacuum reading. Head gasket??

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12sec92Tsi

15+ Year Contributor
187
2
Jul 20, 2004
Hagerstown, Maryland
My boost gauge only reads 10-12 in hg at idle and about 15 on decel. I did a compression test while it was warm the other week and got 150 across all four. Would a cold compression test show different results and tell me if my head gasket is blown?? Thanks. :talon:
 
No, you're suppose to test when the car is fully warmed up and apply full throttle during cranking. Sounds like you have vacuum leak some where between the TB and intake valves. I suggest performing a pressure test and make sure you open the oil cap to listen to any hissing so you cover the possibility of bad pcv valve and valve seals. Good luck.
 
Yes I did perform the test when the car was warm and applied full throttle, so I guess I'll check for vacuum leaks somewhere in the system. I have my pcv valve removed and routed to my catch can so that eliminates that possibility. I will build a leak tester soon and try and find where the air is escaping. Thanks for the reply. :talon:
 
Defiant said:
You have a kinked vac line, or are tapped in at the wrong location. Hook up to the FPR line.
Okay I'll check all my vac lines this weekend. The previous owner had a boost gauge tapped into the line that runs from the bov to the intake manifold, I guess this causes a low reading. I switch to the fpr line this weekend also. Thanks Defiant. :thumb:
 
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