Lew

I just ran a compression test on my 84 944. Real mileage is unknown, the odometer was broken when I bought the car last Spring. Cylinders 1, 3, and 4 came it at 150+ psi. Cylinder 2 was 130. I squirted oil in the cylinder and the compression jumped to 200. This should mean the rings in that cylinder are bad. If it was normal wear all the cylinders should have read about the same. Do I have a broken ring in that cylinder? The car runs okay, but then I don't have another one to compare it to. Any thoughts? <img src="confused.gif" border="0">

Tabor

Actually, I think 150 is a little low for an NA. Anyone else want to chime in?

#2 could be scored from a foreign object.

Dave

Sounds low to me too, but my feelings won't be hurt if someone more knowlegable disagrees with me. I seem to be remembering a thread a month or so ago with 175-200 for an NA. Remember also, that an '84 has less compression than the later cars, so 150 might not be that bad.

Lew

The Haynes manual says 145 or over is okay. When I got the car the odometer was stopped at 33,000 miles, so you can guess what the mileage really is. (This car was not driven on Sunday's only by a little old lady). I can live with the 150+ for now considering the high mileage, what worries me is the number 2 cylinder being so much lower. Do I start saving for a long block? I see they're being sold for $900.

Dave

I'd be saving up the $900 , but maybe someone has other info.

TimC

My 88 NA came it at 190, 190, 170, 190. Leakdown of 3, 7, 20, and 3 (%). Now, shop advised me these are within acceptable limits (up to about 20% on comp being ok, so getting close though). However, said shop not equipped with borescope, so they couldn't take a peek and see what's up. Annoyingly, they also didn't indicate where they thought the leak was occurring (which you should be able to somewhat localize just by listening). They did say they didn't consider these numbers to indicate anything really bad like cracked ring. They also said tearing into motor to see what is up is contra-indicated with these numbers, and that it could even be crud on valve or some such (they had gotten similar or worse numbers before, on other cars, only to later retest and get fine numbers). Finally, friend's dad is a Mercedes mechanic who said he thinks the German car mfgs really specify too loose of tolerance on these things, and he said work is likely in order, but not to tear into things until ready to spend. Finally finally, of course if it is scored cylinder (so long as ring is ok) it can be pretty much run indefinitely, just with performance/efficiency hit (car still pulls to 135 + indicated, so I'm not TOO concerned). I will get it re-tested at a shop with a borescope sometime soon, and report back after that.

T