jake- rx7

hey, so I have an fc with ah non- turbo 13b. Checked Oil , it read half , koolant was gud. Started up, drove about 1/8 mile stopped, parked and cut off normal. When I came back to the car tried starting but the engine wasn't turning. I took out the starter and tried turning the engine manually but its locked up. Any ideas on wat could have cause this ?

Rhyno2050

possible carbon lock?? how many miles on the engine and how often do u redline the engine?

DairokutenMaoh

iTrader: (4)

carbon locks the apex and side seal from coming out and reduces compression, it does not lock the engine. A carbon locked engine will continue to turn and sometimes even run tho very rough. When a rotary engine locks(seize), there is only a couple places that can cause this which is the main and rotor bearing that holds the turning assemblies. Usually due to lack of oil supplied to the bearing. Best case scenario the bearing needs to be replaced, worst case scenario the engine is not rebuildable.

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jake- rx7

carbon lock ? can u explain that plz ? thanks ah lot .. as far as redline , not too often

jake- rx7

ohh I see thanks a lot man .. a friend was telling me as well if the apex seal slip out , it can cause the engine to lock ?

RotaryEvolution

iTrader: (30)

not quite accurate, in some cases carbon can lock the seals in the extended position keeping the engine from turning over. in this case it's best to remove the spark plugs and vacuum caps on the passenger side of the engine, pump a few shots of marvel mystery oil wherever you can get it into the engine(plugs and intake manifold ports) and let it sit for a few hours.

remove the fan and shroud and get a long breaker bar with 19mm deep socket and rock the engine back and forth with a cheater bar until it works loose.

once you get the engine free you will then know if an apex seal rolled out of the rotor or if carbon is building up inside the engine to dangerous levels. it will either build compression or it won't.

BUT this is usually the case when an engine has sat for years, not run and shut down and then attempted to restart a short period later. unfortunately you have less than a 50% chance that this is the case and the most likely explanation is the engine had lots of miles and dropped an apex seal. an engine that was just run and carbon locks usually will build no compression, not be locked up.

DairokutenMaoh

iTrader: (4)

I thought the only way for apex to slip out is through detonation and blow the seal to pieces before it can come out? I don't see how a perfectly fine seal would just slip out of the rotor even in extended position?

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RotaryEvolution

iTrader: (30)

original seals are made in 3 pieces



top half of the long seal takes the frictional wear and becomes shorter and shorter over time. eventually it wears so thin that the rotor slot cannot hold the seal in place any longer. this can occur anywhere from 150-250k miles.

mazda does not make 3 piece seals any longer, after realizing their mistake with the '86-02 engines. they were not worth the additional sealing benefit when it would eventually cost an engine. 3 piece seals were also more prone to sticking in the slot, i have never seen a 2 piece seal stick simply due to carbon deposits. i have seen 2 piece seals rust to the rotor in the extended position, which is usually the cause of a siezed engine that has sat for several years exposed to the elements, which is a curable condition.