What Do These Compression Test Results Mean?

B

Ben R

New Member
#1
#1
I have a 2002 Toyota Corolla, 1.8L engine. It is burning a lot of oil, maybe like a quart every 700 miles or so. If I'm not mistaken, I also think it is losing coolant as well (was far below low when I checked it recently). I checked the compression on the engine and got the following results. My Haynes manual says that the minimum compression should be about 145, and the maximum be about 210.

Cylinder: #1 #2 #3 #4
PSI: 190 190 180 192

I saw that cylinder #3 was slightly less, and took more turns to build up than the others. It would go above 100 really quickly, and then take about 8 more jumps until it reached 180. The other cylinders would take about 5 jumps to reach maximum compression. I added some oil into #3 and retested, but I got over 270 psi! I figured I put in too much oil, so I vacuumed most of it out. (I only put in about 2 1/2 caps full of oil.) I then retested and got over 240, still climbing. I didn't want to push it much more.

I'm wondering why the wet compression is so much higher than it was, and why it's way higher than the normal maximum pressure. Also why would every cylinder's compression be so high yet burn so much oil? Thanks, Ben.
 
Donabed Kopoian

Donabed Kopoian

6 Speed Master
#4
#4
Couple things you did wrong.

One, you do the dry test, all cylinders, exactly the same way, exactly the same amount of cranks.

Two, when you do the wet test, you do it on all four cylinders, again, exact same way. (Use one capful, and wait a minute for it to get into the piston, using too much pushes it into your gauge, artificially jacking up the pressure)

If compression on the wet test is significantly higher, then you have bad rings, and that is where you are burning oil. If the wet and dry test turn out the same, then the valve stem seals are where the oil leak is coming from.
 
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