Where are the apex seals and how do I get to them to see if they are in good shape or not?


Asked by May 12, 2014 at 03:41 PM about the 2004 Mazda RX-8 4-speed

Question type: Maintenance & Repair

I am trying to see if the seals are in good shape because the dealer said it may not need a new motor if the person who changed to spark plugs might have put them in wrong in shich case it would only cost $160.00 to repair what they call a 'wash out'  verses a new motor.  I only have about 40% compression...

9 Answers


Dangerous ground there, the apex seals are inside the engine, if the wrong spark plugs were used, it not only damages the apex seals but also cracks the rotor housings thus ruining the engine, if it is indeed a "washout" it can be cured by removing the spark plugs and squirting in a little ATF into the lower spark plug holes and turning over the engine slowly, then putting in the correct spark plugs and attempt to start, this needs to be done in a well ventalated area as it will smoke till all of the ATF is burned out and the engine is at operational temp. Then the engine is shut down and a compression test it again performed to see if it recovered or if the seals are bad. Clear as mud, right?

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Best Answer Mark helpful

As stated, the apex seals in a rotary are similar to the rings in a piston engine. They "seal" the rotor edges, hence the name "apex" in the housing as it spins.

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I just bought a 2004 Rx8 it runs and drives but low compression.Engine sounds good and idles good but when coming to stop you must keep rpms up or it dies.It's Automatic trans.I was told maybe carbon build up? Since you need to not baby these engines and redline them ever so often and rev them up before shutting down is this all true.? Car has 11000 0.00 miles on it

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How do you know it has low compression? These engines use a special unit to get the compression readings so you can't use a convential compression gauge. If carbon is a problem usually they will ping during acceleration, this really sounds like you have some engine management unit that has gone bad, have you checked for any codes? And automatic transmissions really knock these little engines back quite a bit. Back in my hay days I use to race these little guys, I had my rev limiters set at 12000 RPM's but back then I seldom got to 100k on the odometer before pulling the engines and rebuilding them and usually would find a side housing would have to be replaced. So these engines do like to spin but with an automatic is going to prevent you from winding it out unless you shift kit it. HTH

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Thanks for the reply..I don't know much about these cars but like the looks.I have not even checked it out much The guy I got it from said he had compression checked and it was low.Is it hard to pull engine and put new seals in?I work mostly onold school engines with no problem.This engine looks all alien to me but I heard there's only three moving parts.

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BTW.I paid 1300.00 is that considered a good price?

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Yes it's a lot of work, you have to measure every little piece and file to get the right clearances, mess up and you have to buy another piece, side seals are critical on the clearances, if you do decide to do this yourself you have to forget everything you know about convential engines, buy a good shop manual and don't deviate from the instructions, cleaning and having a clean work area is a must, one piece of dirt and you ruin a engine really fast. I always boosted the oil injection pump setting on my engines, you have to watch the oil level more but well worth the added protection, besides I only ran the oil for 3000 miles anyway, less if I ran it harder than usual or before a race at the tracks. 1300 was just a touch high for one with engine trouble but not too bad. You might consider getting one of those engines from a Japan engine supplier, I used them in my RX's and they were mostly good only had one that failed right away and they stood behind it so I was only out my labor for R&R the engine. Hope you enjoy your project.

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And I noticed it is an auto with power shift.car is fast it just dies when you stop at light unless you put it in neutral and keep rpms up a little. Now on a cold start it takes about 10 cranks to start and idles good so hope its something simple

1 people found this helpful.

Well thanks for the great info.do you have the info and price for the low mile Japanese motors that might be my best bet and I looked at motor and scratched my head lol how does the motor come out from bottom or? Does it need any special tools or ticks to take out.?

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