compression test : should I be worried ?

Hello,

I am looking into buying a used 2005 aveo, 60 000km (37 300miles). I had it inspected and they performed a compression test that resulted in the following numbers :
#1 : 180
#2 : 180
#3 : 180
#4 : 110

They tried to locate the problem quickly by pouring some oil into the faulty cylinder, which helped the pressure go almost as high as the 3 other cyl. The conclusion was that it seems the compression ring has a slight problem.

So my question :

How problematic is that ? Is such a pressure difference common or not ? Is it likely to become a lot worse ? What could it result into ?

Thanks a lot for your help,

Pete, a potential aveo owner.

That is not normal no.

It would appear cylinder 4 has a broken piston or damaged rings.

It could also be a headgasket failure close to cylinder 4 or leaking valves.

what nemasys said is correct, with one exception, how the did the test.

if you are seriously considering the car, have them test it again after its been back together and run a few miles starting on the #4 cylinder. if it is the same low cylinder nemasys is correct, if the number is high, they might have allowed the cylinder to dry rev too many times during the last test. A better test would be a cylinder leak down, and see where the problem comes out..

a slight variation (10-15 lbs) is kind of common on engines with some mileage. one low cylinder indicates problem. putting oil (depending on the amount of oil) only cures ring and piston gap issues, a lot of oil will change the compression ratio and raise the number falsely. low compression due to valves can be solved with a lot of oil as well.. or end cylinders could be a head gasket..

if two cylinders are low, and beside each other it typically indicates a bad head gasket. plus you would have a power issue.

Wow that was quick !! Thanks a lot !

Quote:

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Originally Posted by Nemasys

That is not normal no.
It would appear cylinder 4 has a broken piston or damaged rings.
It could also be a headgasket failure close to cylinder 4 or leaking valves.

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Hmm :-(

Not a good news then... As I dont know much about cars, would you advise me to stay away from it ? Or should I try to know how much fixing such a problem would cost and bargain the price ? (currently, it's around CAN$4000).

Thanks.

if you dont know what you are walking into then either stay away, and or negotiate and have them include a 2-4 year warranty that will cover the engine (make sure that issue is specifically covered) in the new price..

if the car ran good, it might not be all that much of an issue, but i drive broken cars a lot and have a lot of experience.

for $4000, it seems like you could find an aveo without the issue easily.. maybe not?

Well the car is being sold from a individual, not from a shop... I'll make some calls tomorrow to try to talk with some GM mechanician and see what it could result into (esp. in terms of how much this could cost). With that in my hands, I'll see wether the seller will be willing to lower its price enough.

Thanks again for you precious help !

Pete.