Mechanics

PONTIAC BONNEVILLE PISTON PROBLEM

1985 Pontiac Bonneville • V8 2WD Automatic • 400 miles

I just rebuilt a 305 for a 85 pontiac bonneville it ran fine for about the first 400 miles I took the vaule covers off and I noticed white smoke cmming from the left head. Then it started to come out of the left exaust and I have no clue why. And its only coming out of one side. I just took all the spark plugs out and
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Quenticar789
August 8, 2011.



Are you using any coolant?

Mhpautos
Aug 8, 2011.
No its just straight water. I wasnt gonna put coolant in it till I get all the kinks out of it. Could that be the reason its doing what its doing?

Tiny
Quenticar789
Aug 8, 2011.
I mean do you have to keep topping it up.

Mhpautos
Aug 8, 2011.
No its holding it fine. I did a compression test and on the side its smoking from the first piston is reading around 20 to 25 psi and all the other ones are reading around 60. So should I go ahead and take that piston out or can you think of something else that could cause that piston to be so low?

Tiny
Quenticar789
Aug 9, 2011.
Pull the head and check the valves especially the exhaust valve, a leak down test will determine exactly where the leak is, that is if you have access to this equipment.

Mhpautos
Aug 9, 2011.