VaSSagO

I have heard different stories about rotories, that they are fine then one day they just seize or when they are on there way out they take longer to start. Is this true and if not is there a way of telling?

This would be nice to know as i really can't afford to rebuid. I ran a search but could not find anything.

yayarx7

A compression check is really the only way to tell what shape your engine is in. But it will not tell you when you are going to loose an apex seal, or a water seal, or when the o-rings are gonna leak, if they are.

You just drive it till you can't. Some people get 200,000miles +, some get less than 100,000. But a well taken care of motor will last you quite a while.

VaSSagO

It is a 13B, when i bought it 6 months ago i got the car checked over by a mechanic, the compression was 100 - 100 PSI. Does that sound about right?

82streetracer

iTrader: (1)

eveness is a good thing

peejay

Warning? What warning?

Mine ran great until the moment an apex seal decided to exit stage left. Then it was a very inefficient one-rotor engine.

Engine death can happen two ways - the coolant seals fail or the rotor seals fail.

Coolant seal death means you get combustion gases in the coolant, which makes it run hot, blow white smoke (from the coolant getting back into the combustion chamber) and it only gets worse. It can get so bad that you have to pull the spark plugs out and crank the engine a few times before starting it to blow the coolant out of the chambers!

Rotor seal death is USUALLY slow. You first notice it as the engine being hard to start when hot, but starts fine when cold. Pretty soon it is hard to start when cold. Once it's running it's okay, though. (I've heard an old way of checking the compression is "If the engine can start then compression is good enough!") And then there is of course the hard failure - an apex seal (or less often a side seal) breaks and causes all kinds of damage. Mine died because I overrevved it which weakened the seals and caused one to shatter as I went up past 6200 (the point as which iron seals start to chatter - stressful)

There's also what I call "elective death" which happens two ways - excessive oil burning (blue smoke on startup/high RPM, eventually leading to blue smoke all the time, even though it still runs great) or the dowel O-rings leaking. The oil pressure goes through the upper dowel pins, and (normally only on '83-85 12As with the ****-poor oil cooler) the oil cooks the O-rings that seal the dowels between each housing, and oil leaks out at the top of the engine, right where it says "Mazda 12A" on the rotor housings. (That's where the upper dowel pins are) Both of these are "elective" because, while annoying, they are not fatal and the engine can still be driven for white a long time, as long as you don't let the engine run out of oil.

yayarx7

There should be 3 readings per rotor, one for each rotor face, and only the $1500 Mazda tool can give you the correct readings.

MIKE-P-28

iTrader: (1)

Yelp rotary motors give ZERO , NONE , NADA, warning... My 85 ran fine that day, as a matter of fact earlier I took her up till about 6k, then me and my son were sitting there idleing and POOF... Gravel sound inside motor (Ive been there before I knew what happened), i just put my foot on the gas and limped it home. About 10 miles used probally 1/4 tank of gas. Foot all the way to the floor fast as she'd go was about 35 mph

85RX7GS

iTrader: (1)

I was driving home and all of a sudden, the rear seal went out. It sounded like I was driving a huge lawnmower home after that, with maybe 30HP.

rxtasy

my '84 GS actually started to run GREAT for a few days then BANG!! driving home from work, don't think i was even going the speed limit on a side street. happened about 30 sec after thinking 'Man, the rex is running great these days' needless to say, i always tell my '85 it's running like ****

nimrodTT

The two I had blow apex seals seemed to run especially well right before they let go, but I was running both at the limit right before the catostrophic failures. One was in the driveway after a hot lap on a back street and another was on the way home from an autocross.

MIKE-P-28

iTrader: (1)

I remember now that my 85, smelled really really rich that day, didnt think much about it. And she died!

diabolical1

iTrader: (3)

i've had 4 Rx-7's and i've blown 8 motors between 3 of them. only one gave warning ... and that was the one that i have now. the guy that i bought it from put a 7 lb. radiator cap on it and cooked the motor.

it ran hot from the day i bought it until the night it blew the reservoir tank up. however, up to that point it just got harder and harder to start and when it was running, i don't think it could get out of it's own way ...

nope ... they usually don't give any warning before they depart.

AZ85RX7

peejay, you're talking about the o-rings beneath the oil cooler right? Mine was leaking from there (had oil on the top of the engine, by 12A sign) when I bought the car, and soon spend the $5 each for the new rings and replaced them. Took a while to put them in, but now it doesn't leak from there anymore. The old o-rings were so old and dry, that they felt like hard plastic, and broke easily when I tried to bend them

peejay

I'm talking about the DOWEL O-rings - they require engine disassembly to replace.