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Thread: Low compression in 2 cylinders after overheating

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2011-10-24 06:47:38
Low compression in 2 cylinders after overheating
Was letting my friend borrow my car and it over heated and by the time he noticed it was too late.. Car feels a little shaky like if it was out of timing. Checked the compression in order from crank to flywheel and is as followed, 138 152 130 154. When its on I don't see bubbles from the radiator... Previously the compression was all around
#1- 167 down to 138
#2 - 163 down to 152
#3 - 162 down to 130
#4 - 168 down to 154

130 is not too bad of a number so that makes me wonder... Headgasket or head warp? I'm 100% for sure not going to put a new engine in this thing and I'm not going to spend a bunch of money to get this one shaved and cleaned up. Whats the worst possible thing that it could be and whats the worst?
2011-10-24 07:35:55
Do a leak down test. Lower compression = poor gas mileage, less power, oil / coolant consumption, and / or it will get progressively worse.
2011-10-24 07:53:16
Could be sagged rings, if your not getting coolant into the cylinder or pressurizing the cooling system and pushing coolant out into the overflow then the headgasket is probably fine. Like he said do a leakdown. Basicly take compressed air and pressurize the cylinders through the spark plug hole and listen to where the air comes out. you need to be at TDC on the compression stroke when doing this test, pressurize the cylinder to about 100-120psi at least and listen.

If it is bubbling the coolant= headgasket, if its coming out of the crankcase breather=rings, if its going through the exhaust=bad exhaust valve sealing on the valve seats, out the intake=bad intake valve sealing on the valve seats.
2011-10-24 08:58:51
Hopefully autozone will allow me to rent the leakdown tester because I don't feel like wasting 40 bucks to test it lol. I'll have to see what I can do. It's currently at my brothers house, I'm going to need to drive it home though... I might just sell it to the junk yard at this point..
2011-10-25 08:28:18
Hoping to be able to get it to my house by tomorrow and pull the head this weekend... Guess we'll see...
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