Compression Test = Useless?
 

I had always read here that a compression test was a great indicator of the health of an engine. The other day I called up someone selling a 94 with fairly low mileage. I asked if a compression test was done, but was told it was not needed. He said something like, "you don't need one, you can tell by the vacuum level at idle."

I was in no position to debate that, but what do you guys think?


-RedHaze

he is right that a the vacuum at idle is a good indicator of engine health. but a compression test is a BETTER indicator as it tells you what each face of the rotor is doing as well as each rotor. He's giving you some BS if he says a comp test isn't "needed", and i'd honestly be weary of an RX7 owner that says something like that. He might as well say you don't "need" to monitor your water temp.

Danny

a rotary tech at a mazda dealership told me that the standard tool or method for testing compression wouldn't work on a rotary motor, and that it you tried it, it would give false readings. He said that a special compression tester designed for rotary motors was needed. Just FYI.

There is a specal tester but if you use a regular tester with out the shrader valve in place and know what to listen for as the motor turns you can get a better than good idea of the motors condition