compression test

Rule of thumb is 125-150 psi depending on the compression ratio of the engine. Make the compression test with all plugs removed, the ignition coil disconnected and wide open throttle. Crank for 5 seconds to get a stable reading. Log readings, do all cylinders and then repeat. Make sure you get consistent readings on each cylinder. Readings between all cylinders should be within 5-10 psi. If you get a cylinder that reads low, put a couple of squirts of oil into the cylinder and repeat the test. If the reading comes up, most likely worn piston rings. If the reading stays low, could be head gasket or valves. Don't forget to label the plug wires as you remove them to make sure they all go back in the right places.

@278,000 km my 96 SOHC 5sp pumped to

155 lbs dry and warm, and 230-270 lbs with oil added, (the 230 cylinders had less oil than the 270 ones.)

Adding more oil will seal the rings better but will also raise the compression ratio, I should have measured the added oil better by counting the oil can squirts and adding the same number.

Previous test @178,000 km pumped 130/128/131/130 warm and 128/126/128/125 cool and 220/185/225/215 oiled warm and 190/155/185/185 oiled cool. The center cylinders were retested 1,000 km later both 160 psi warm. I suspect a piece of crud on valve in #2 cyl during first oiled test.

YMMV depending on accuracy of your gauge, I think mine is OK and was top quality and quite expensive in its day but is about 35 yrs old. As Oppie topposted, your results are probably more important relative to each other cylinder after dry and wet testing, as these results will all be with the same tester. Record your results in your maintenance log and then you can compare them in another 50 or 100,000 km to detect any trends.

Many mechanics will debate the value of compression testing and will often advocate for a cylinder leak down test as being a superior test, but a plain compression test is easier and uses simpler tools and will quickly find large problems like one bad cylinder or valve.

Good luck, YMMV, make sure you have locked the throttle butterfly valve in open position for test, IMHO warm is best for reliable results and consistency.

Hi "Oppie"

Thank you very much for your help. Regards,

danielr

And thank you 'Private' for your input also.

Let's see... I've got a 92 SL1 SOHC with 553,000 km on it. Been putting Castrol Synth in it and a cheap Motomaster oil filter since the car had 100,000 km on the odometer. I change my oil every 10,000 kms. Did a compression test about a month ago and got 185-190 PSI in all cylinders dry and cold. Didn't bother putting any oil in the cylinders to do further checks, since I was happy with the readings. Hope this helps!

Alex

Thanks Alex; It certainly does, as it provides a reference to effectiveness of the same oil I'm using. Thank you very much.again danielR

No problem Daniel. Good luck!

You should be happy with these numbers and your service life. I would normally suggest verifying the compression test gauge but why tempt fate, if it aint broke, etc., it is the cylinder variation that is most important anyway.

Looks like you got a good one, keep it as long as you can and don't fix anything that doesn't need opening up.

Good luck.

Thanks for the words of encouragement. I intend to keep the car as long as I possibly can although it got really close to getting junked a couple of months ago. One of the timing chain guides has shattered leaving the chain rattling and car losing power. My wife was super happy as she wants me to get rid of the car and buy something "decent".... well, I stuck to my guns, ordered a new kit and replaced the chain, guides, sprockets, etc... Now the car runs like new and my wife ain't very happy about that! LOL

BTW... guys at work are having a tough time believing that the car being as old as it is (18+ years) still runs on the original clutch and the exhaust system (well, the muffler was replaced a few times, but everything else is original)

Alex

The Stainless Steel exhaust systems popular now (because of the acids in catalytic converter exhaust eating out steel pipes) go on just about forever. I used to have a Chrysler product that had 208K miles on the original pipes. As with you, muffler only had been replaced three times. Pipes were still good when we junked the rest of the car.