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blue62 · 07-18-2021, 08:05 AM

So if your only getting 8 in.hg at idle!!
Is the needle steady??? drifting??? ticking??
What action if any is there from the needle???

Also how many miles on the car.????

8 in.hg at idle says you have a major vacuum leak at the intake manifold.
big enough that you should be able to hear it and find it easily.
It can also indicate that you have late valve timing..
Or a combination of both.

I would do the vacuum test again with a standard vacuum gauge just to verify readings from the mini vac gauge.
If you still have low vacuum readings I would do a compression test to compare cyl. to cyl and bank to bank.
a compression test will help tell us if you have valve train issues.

You can get low vacuum readings from leaks, poor valve timing, poor valve seating, any kind of issue with the valve train, head gasket leaks, worn rings, all manner of things.

The action of the needle can tell you where the problem is.

07-18-2021, 08:05 AM	#45
blue62 Registered User Join Date: Aug 2018 Location: Woodland Wa Posts: 1,313	So if your only getting 8 in.hg at idle!! Is the needle steady??? drifting??? ticking?? What action if any is there from the needle??? Also how many miles on the car.???? 8 in.hg at idle says you have a major vacuum leak at the intake manifold. big enough that you should be able to hear it and find it easily. It can also indicate that you have late valve timing.. Or a combination of both. I would do the vacuum test again with a standard vacuum gauge just to verify readings from the mini vac gauge. If you still have low vacuum readings I would do a compression test to compare cyl. to cyl and bank to bank. a compression test will help tell us if you have valve train issues. You can get low vacuum readings from leaks, poor valve timing, poor valve seating, any kind of issue with the valve train, head gasket leaks, worn rings, all manner of things. The action of the needle can tell you where the problem is.