86Rx7GXL

Well i just got my turbo 2 today, the motor was out of it cause it had low compresion in the rear rotor. well after lookin in the exaust ports and turning the engine all 6 aplex seal look great. but still just by turning the motor you can tell there is low compresion, i have auto tans fluid and a engine clearner in it now trin to clean dirt and carbon out of it hoping that may be the problem it help'd but i was wondering what else other than the aplex seals would give low compresion? could it be side seals?

Mazdarules

Maybe the housings are shot? I It could be the side seals but that usually only affects one of the three sides of the rotor unless they are all shot.

copandengr

The seals may appear to be in place but they may not be working well.

All of the seals on the rotor are designed to "float" and are held against the surfaces they run on by spring pressure. Carbon builds up in the seal grooves and will cause them to stick instead of floating. This will prevent them from doing their job well. The only real cure is a rebuild and the necessary cleaning to remove the carbon.

If you have the exhaust manifold removed you can see the apex seals in the exhaust port. Take a soft instrument (a toothbrush handle works well) and see if the seal can be depressed in its groove. Odds are you will find one or more of them stuck.

86Rx7GXL

yeah the engine core is sitting in a wheel barel full of auto trans fluid and a engine cleaner it clean any **** in side there out i turn the engine to every seal and all 6 are great i can push on them and there perfect push them down in the slot all the way and sping up with ease. if i can get the flywheel off i'll take the back plate off so i can look at the rear rotor to try to see and damage.

peejay

Keep in mind that seals don't always wear "evenly" - they tend to bow in the middle so the middle wears faster than the edges.

Also I've heard of people pulling blown T2 engines apart and finding that the remaining seals had lost over 2/3rds of their original height! So they looked OK but were extremely worn, and being worn that far the springs were probably barely exerting any pressure so the low-rpm compression would have sucked bigtime.

khoney

5 years ago, Mazda service technicians told me I had low compression and would need a new short block ($$$). Well, the REAL problem was that the car wouldn't start when hot, and it was the infamous leaky injectors wiping the oil off the seals. 5 years and 50K miles later, I am still running with the original engine thanks to the addition of a fuel cut switch. Are you sure the car you bought didn't have the same problem?

mazdized

The end piece is usually what breaks, you can not see that by looking through the exhaust port. It may not leave any scuff mark on the rotor either. Or for some reason rear got hot enough and distorted the housing around the compression area.