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Old 01-07-2019, 07:49 PM
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Hello

Hey all! I'm a rx7 guy who's broadening his appetite! I've been parting a 1991 fc vert for a while, got a few engines for rebuild and diagnosis in the garage, and I have some rx8 goods for sale. I'm new here, so making my way to 10 for classified postings. I have a 1984 gsl-se for rallycross and drifting, BTW and have been enjoying it thoroughly, as a true rotor head should! I'm local to Indianapolis and meet with other Mazda guys around here for meets. Hope to see some of you around (look for the Buell rider at the Dragon that waves at all the rotaries!).
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Old 01-08-2019, 07:59 AM
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S2 engines

So I bought a S2 engine with over 120k miles for pretty cheap, just don't have a rotary compression tester, yet, to test it. Seller said that the cat glowed red hot and the car was in "limp" mode until he got home. Then he replaced the engine and posted this for sale. Should I just rip it open, or would it be worth my time and energy to get it tested for possible straight sale? Thoughts?
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Old 01-08-2019, 08:51 AM
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Welcome!

IIRC, it's 10 posts and 30 days to get out of the new member sandbox.

You aren't going to get a valid compression test result cold. At least not one that anybody is going to accept or could correlate with a proper warm compression test result.

Glowing cat just means he neglected his ignition the unburned fuel destroyed his cat, causing it to clog. The most common result from that is a coolant seal failure. I'm not really sure how to test that with the engine out of the car. I suppose you could close up all of the coolant inlets/outlets and try to pressurize it with a MityVac hand pump. Short of that, you'll need to disassemble the motor to see what's what.
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Old 01-08-2019, 09:37 AM
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That's very helpful advice! I think I will open it then cause I doubt I'll get much for it without doing that. What would broken water seals look like when inspected?
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Old 01-08-2019, 10:20 AM
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Originally Posted by Jonny5zaliv View Post
That's very helpful advice! I think I will open it then cause I doubt I'll get much for it without doing that. What would broken water seals look like when inspected?
Once you crack the keg, look at the inner rubber/silicone/viton/whatever seal that separates the water jacket from the combustion chamber. Heat will build up near the exhaust ports with a clogged cat so check there first.

This is a different failure mode (pinched seal) but it will probably look similar.


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Old 01-08-2019, 10:37 AM
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OK, I've taken apart a S1 RX8 engine, S2 shouldn't be much different, right? Thanks so much for the help! One last note, it wouldn't make much difference that the sounds coming from the spark plug holes make it sound like good compression when manually turned, correct? I known it's not scientific, or anything, it sounds perfectly fine, though, lol.
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Old 01-08-2019, 11:23 AM
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The only major changes with S2 motors are the extra oiling ports and electric OMP.

Anything in the 75 - 120 psi range will probably sound the same to most people. A blown coolant seal will probably not drop compression enough to be audible via air escaping the spark plug holes.
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