Pooky69x

As title says, this rotor 1 has no compression, the engine only has maybe 20 thousand kms on it. It sat for a year, was started went to take off and hasn't worked right since. Now the cars sat for another year and I got it. Just wondering what might have happened for the rotor to lose compression?

NotAPreppie

How was compression measured?
What were the results for the other rotor?

furansu

Compression tests are only valid if performed with a proper rotary compression tester. Piston testers won't return accurate, per-face results.

Anything could have happened, assuming that engine failure wasn't the reason for it sitting for a year the first time. The seals can get stuck in their bores due to corrosion or carbon build up, the springs can get weak or form a memory when sitting for long periods, and if there was a coolant leak or moisture build-up inside the motor, while very unlikely, the apex seals can corrode to the rotor housings and break when the engine is turned over. If the chambers are dry (no oil) you'll have low compression as well.

Soaking the chambers through the spark plugs with Marvel Mystery Oil or AFT and letting it sit for several days, rotating and repeating, can sometime help stuck seals -- if the car runs at all, water via the service ports of the intake can 'steam clean' the chambers, helping break down carbon and free up the seals if they are stuck.

I'd remove the spark plugs, squirt a tablespoon of oil into each chamber, and turn the engine over by hand. Inspect the exposed section of the apex seals and rotor faces as the motor turns, look for missing material, damage, corrosion, etc. If no visible damage or concerns, you can re-install the spark plugs and attempt to start the car again (use the de-flood procedure to start, and assure the battery is charged). Ideally you'd test compression with a rotary compression tester prior to trying to start it, but if you don't have one, just go for the gold.

Pooky69x

I inspected the apex vales and all 3 are missing off the rotor. So have found out why zero compression. Thanks for the replies.

CaymanRotary

It could also be flooded. Did you notice any oil on the compression tester? That happened to me before and was wrongly diagnosed because of it.

Pooky69x

The apex seals are gone off the rotor lol nothing there all 3 of them.

CaymanRotary

Well damn haha. Never mind then. Need a new engine RIP .

Brettus

iTrader: (2)

That seems highly unlikely!

200.mph

iTrader: (9)

yhea that doesnt sound right. ive seen it happen before but it was a pettit sc car

Pooky69x

ok I could be wrong but when I whirl the car over there is no puffs of air from the spark plug hole. None, I can put my finger over the hole and get nothing. On the back rotor it will pop my finger off 3 times. Unsure of actual compression but the front one has zero as far as I can tell

furansu

rotate the rotor to where one of the points of the rotor is over the spark plug hole and take a pic. You can do it for all six points (three per rotor) if you want some input on the whole set.

Pooky69x

I'll do that tomorrow and add the pictures

NotAPreppie

Time for a new engine.
Don't bother with a rebuild. With that kind of damage, the parts cost will probably be more than a Mazda reman.

CaymanRotary

That’s really strange. You should inspect the corners to see if the seals are still there. If they are, Possible they could just be carbon locked in which case you could try some Seafoam soaking. Worth a shot at this point.

Red line envy

That is true but seafoam only works when engine is warm. Right?

Pooky69x

whats the easiest way to see if they seals are still there? I've read other things to take off the exhaust manifold and inspect in there? Like I've said the car sat for a year and that's when this all started. It started ok,.drove for about 30 seconds to the gas station got gas, went to get on the highway and it started acting up. Since then then the cars sat for about another year, I just started fooling with it and now thats what I've found.

CaymanRotary

Warm engine is ideal but letting it soak cold for 24h would probably be enough to release stuck seals. At least enough to possibly get the engine going. Try all options first before writing the engine off completely. I once bought an 8 with the same problem and it was stuck seals due to flooding. After I got it running it made great compression numbers. I drove it for almost 2 years and sold it for almost double what I paid for it haha. It's still on the road. New owner loves it, still making great numbers.

CaymanRotary

Just inspect through the spark plug holes. Just turn the engine over enough that you can see the corner of the triangle through the hole. You wont see much but enough to see if the seals are still there.

Pooky69x

Ok, I did that earlier today and I thought I seen just a gap where a seal would go. How deep would that gap be? I'm new to rotary engines and don't exactly know what I'm looking for. Is it best to pull all plugs to turn the engine by hand to do this?

CaymanRotary

Ideally the seal needs to sit right on the inside of the rotor housing. If it looks really dirty and you cant tell the seal from the rest of the rotor give the Seafoam a try. If you see the seal is broken or wavy looking or worse, not there, then Seafoam isnt gonna help. Need a new engine at that point. If you can take pictures of each corner we could help more. But it is rare to get 0 compression. You should be getting some pulses unless you have catastrophic damage in that rotor housing.

Pooky69x

I know there is alot of carbon in there just by looking in the spark plug hole, I tried the ATF trick and it did nothing. May not have waiting log enough? I waited about 24 hours. I'll get a can of seafoam tomorrow. The engine will start and run off of just 1 rotor. Should I do this before adding seafoam? And what's the best way to get the seafoam in there?

CaymanRotary

Just look for YouTube videos. Search “RX8 seafoam” bunch of them explain how to do it. The car needs both rotors to run so you must be making some compression if it starts cold. If the ATF didn’t work, I don’t know if Seafoam will do anything either. Worth a shot for $8 though but I suspect there is some kind of damage in the front rotor if the atf didn’t help.

Pooky69x

The car will start and run with both plugs out of rotor 1.

CaymanRotary

Yea but it won’t run for very long. I guess technically it can run but it will sound horrible haha.

Pooky69x

True lol but it runs the exact same if there are plugs or not lol