Low compression when cold
I previously posted regarding a vibration problem that i was having when the engine was cold in my VS V6 commodore.
I had a compression test done and found that when cold its about 90psi, but when hot its normal. I understand that this means that the rings are failing.
I also understand that this will be expensive to fix, so how long can i get away with this problem without fixing for?
Many thanks
It doesnt seem to be burning much oil at all. Havent had to top up in the last 6 months.
Why compression test a cold motor?
The test would not be accurate as the clearances have not taken up yet.
Donating Member
You should test for compression at normal operating temperature,..or near enough to......not cold.. If you are experiencing a vibration from the engine and suspect poor compression, I'd be looking more for one cylinder that had much lower compression than the others. If they are all more or less the same they should not cause vibration.
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Hi thanks for the replys.
I took it into the mechanic with a vibration - when in drive and the engine is cold. I can feel it through the steering wheel and the dash rattles. After about 10 mins it goes away. Mechanic told me that he did a compression test, when cold and then hot. When cold he said it has low compression like 90 psi, and then when hot everything is normal, 180 or so. Should i listen to this guy? He said its piston rings, and probably need a rebuild.
IMO find a new mechanic.
I would be testing spark first, followed by fuel, compression at 180 on all cylinders at running temp sounds fine to me.
Real cars are steel cars.
Dodgey lifter holding a valve open? Oil is thicker when cold.
If I told you I was a compulsive liar, would you believe me?
operation HQ under way.
sticky ring. run a bottle of tune up crap from wynns or i prefer nurlon. cant hurt, i ran a complete 140000km treatment in my old v6 and it lasted for a 1000km trip with buggerd ballance shaft berings.
Originally Posted by Adam Savage (mythbusters)
Real cars are steel cars.
^^^
Not a bad idea.
Maybe even some de carbonising spray through the intake.
If I told you I was a compulsive liar, would you believe me?
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