Compression check, 3 at 124psi, 1 at 48 psi

[jamel16]

I just bought a 1990 eagle talon TSI AWD, The guy I bought it from said that he did a compression check and three cylinders were at 124 psi and the fourth was at 48 psi. He also rebuilt the head and replaced the gaskets. What would you recommend? Rebuild the block with new pistons and rings or just replace that one piston since the service limit is 121 psi. I don't plan on running high boost or anything so can I just get o.e. pistons.

 

[RoasT BeeF]

I thought the service limit was 130?

Anyway, I would suggest that you do a leakdown test and go from there.

 

[evil_eagle]

well as soon as I read your post about him rebuilding the head, thats where I would start, did he cut the seats? (valve job) if he just threw a set of valves in then that is your problem. But yeah 48psi in 1 hole will not work out that well, crap I can't imagine how it would idle with that low of compression in 1 hole.

Best bet is to pull the head, take it to a machine shop that knows what there doing, tell them you need the seats recut and the head resurfaced, at the same time inspect the piston tops and cylinder walls for scuffing.

After you get that all done, and if the short block is in good shape, then do a compression test and leak down test. But I have seen this from time to time, people that rebuild the heads on there own do not know about cutting the seats to get the new valves to seat right.

Very common mistake from alot of dsm owners that I have seen, do not halfass it, do right the 1st time and be done with it.

good luck..

 

[Defiant]

And look for the melted edge of the piston crown in what he called "#4" (which is probably #1).

 

[jamel16]

well as soon as I read your post about him rebuilding the head, thats where I would start, did he cut the seats? (valve job) if he just threw a set of valves in then that is your problem. But yeah 48psi in 1 hole will not work out that well, crap I can't imagine how it would idle with that low of compression in 1 hole.

Best bet is to pull the head, take it to a machine shop that knows what there doing, tell them you need the seats recut and the head resurfaced, at the same time inspect the piston tops and cylinder walls for scuffing.

After you get that all done, and if the short block is in good shape, then do a compression test and leak down test. But I have seen this from time to time, people that rebuild the heads on there own do not know about cutting the seats to get the new valves to seat right.

Very common mistake from alot of dsm owners that I have seen, do not halfass it, do right the 1st time and be done with it.

good luck..

Yeah he said he drove it home from the guy he first bought it from, he also said that he could not tell that the car was running only on three cylinders.

 

[trbotaln]

He probably has a burnt valve or a cracked piston. Possibly maybe some cracked rings.