420A Compression test results. Should I be worried?

[Kyle97-clipse]

Today I decied to do a compression test on my 97 eclipse 420a with 105,000 miles. These were my results

Cylinder1 - 205
Cylinder2 - 205
Cylinder3 - 160
Cylinder4 - 205

My Question is should I be concerned with number 3 being lower. I know that 160 is not bad because the service limit is 100 but because it is lower than the other ones it has me wondering. What are some of your opinions on this?

 

[fastasseclips95]

Im pretty sure your lowest number should be within 10 percent of you highest. Someone correct me if im wrong. Whats the reason you are doing a compression test?

 

[Kyle97-clipse]

No, no problems, no smoke and im not burning or losing any oil. It's just that the previous owner had it turbo'd and beat on it pretty good so I just wanted to see what shape the engine was in. I don't think it's to bad tho ### 160 is still pretty high.

 

[tqmx1]

Drive it a bit and recheck it, It could have some crap between the valve and seat. And if that does not do it take it to a shop and have a leak down check run on it to find out if it's getting past the valves or rings.

 

[Defiant]

Burned valve. Yes, you should be concerned.

 

[Kyle97-clipse]

Burned valve. Yes, you should be concerned.

Why do you think that the valve is burned?

 

[DSM1G90]

160 is still pretty high.

..against those 205 readings? I'd say that this cylinder is a bit on the low side (a good 22% lower) compared to the other three readings. You got some issues with this one cylinder.

Forget about the service limits. You just want uniformity. Now, if all four are close to service limits, then it's time for a ring and bearing job.

Why do you think that the valve is burned?

If you were using oil, that'd be rings. But if you're not using oil, something isn't right with the valves.

 

[Kyle97-clipse]

What is my next step then, to take the valve cover off? And how do i check if any of the 4 valves on that cylinder are having problems?

 

[DSM1G90]

You can leave the cover on.

Trick is to do another compression test, BUT, put a couple of tablespoons of oil down each cylinder and do the readings again.

If the numbers comes up, especially in that 3rd cylinder, the rings are going. But, if the numbers don't increase with the compression test, you got a bad valve.

Bad valves means a head removal and rebuild - can't get out of that.

- good luck ... DSM

 

[Kyle97-clipse]

Well I just thought I would post an update I decided to test cylinder #3 and the compression was right up there with the others at 205psi so I guess there was a piece of carbon or somethin that got dislodged all i can say is im happy

 

[bigf4]

Good to hear that. sucks rebuilding the motor

 

[DSM1G90]

..dang, pretty tight motor then with compression that high .. 205..!

Yea, good luck to you - DSM