Rebuild, Low compression, Over heated
 

Ok, it looks like I may have toasted my newly rebuilt S4T. After fixing may other things that were wrong with the car, including building a custom wiring harness, I have found the motor to have low compression.

I don't seem to be able to get any bumps on the rear rotor, and very small bumps on the front. When I go for a cumulative total, I reach about 85 on the front, and 40 on the rear. I can only attribute this to an over heating that occured in heavy traffic when my fan clutch went.

Oddly enough, I still hear 3 bumps from each rotor when the plugs are removed. I can only guess that over heating it has warped an iron or a housing. My question is, what should I do? I can rebuild it again, but I don't want to go through that if the new seals are shot....I'd rather just buy an atkins? motor maybe.

Which is more likely the warped piece? Iron, or housing?

Could it just be a stuck seal? (Unlikely)

1300 miles on rebuild suffering an over heat, are the seals warped, cracked or malformed in any way usually?

If you were buying a motor, who would you go with?

Nothing? No one has any input?

How does it run (if it does run anymore?)

It runs. When I tryt to start it cold, I can get it to start after about 30 seconds. It will hold a rock steady idle at about 1100 or so, and seems to drive fine.

Any noticable smoke/lack of low-end power/etc? How well does it hot-start? Are you holding the throtle open when doing a compression check? Is there anything that directly prompted you or worried you to check it again other than just being curious? Sorry for the million questions, just kind of helps explain what it's behavior is thus far.

Sonic, I'll take any questions you can think of, I appreciate the advice. I did the compression check because of a hot start issue. I had my brother start the car while holding the throttle down, so I can't be 100% sure obviously, but he swears he had the pedal to the floor. I'm heading home from work, and I can re try in an hour. As for starting, there is a small amount of smoke....very, very small, when first started. No more than my NA engine used to make. It clears up in about 10 seconds...but less me stress again...it is Very minimal.

I know my tolerances were all good, so over heating is the only place I have left to look, or so I think.

How long/hot did it get? I've overheated a few times for more than i'd like to admit to, and it's managed to be OK. Did you ever do a compression check before then and notice a difference? How do the chugs sound in comparrison to each other? Say if you left the front plugs in and turned it over with the rear leading missing, then swaped to the front leading missing. Is there an overly noticable difference? I asked about hot-start because that's a damned frustrating issue most commonly caused by lower compression.

Well, it climbed to almost the top of the S4's gauge, and I turned it off. Unfortunately, it did boil over. The bitch about it, is that I didn't do a compression test when I first built the motor. I relied on the fact that I had three good chugs on each rotor, and the knowledge that my build was good( I assumed)

I'll check to see if there's a big difference in the sound between rotors, but off the top of my head, I'd say they're pretty close in sound. I just don't want to yank this motor if I don't have to. Honestly, at this point, I'd just get an atkins motor to drop in, and rebuild this one....but I really don't want to do that if it's just something I'm not thinking of

does it start normaly? or do you have to mash the throtle to get it started?

I have to play with the throttle.

did you have to play w/ the throtle befor it was over heated?

Yes I did.

I went through most of the other reasons for a hot start problem. Many things have changed in the 1300 miles since I rebuilt it. Having the hard start had me chasing a bunch of stuff. I actually found my wiring to be faulty when I pulled on the TPS clip. I heard a clicking and immediately figured it was the injectors. When I found that, I thought I had it. I figured the rear injector was firing when it shouldn't, and flooding the rear rotor. I rebuilt the wiring harness and removed all of the pins I didn't want anymore. Hmmm....I have of rotor wash or something? Might I have done that to the rear rotor? MMO?

It's hard to say why all 3 rear faces would be so low.

Ugh, I got caught up yesterday, and was unable to do another compression test.

I would say it would be worth it to take the car for a proper compression test just to have a better idea (mazda rotary compression tester) before going through the work of taking the engine out for further investigation.

That is assuming you have a dealer or other place with the tester relatively near.

I doubt overheated enough to warp a housing. But were your housings good condition in the first place when you rebuilt? My rebuild after 3k miles still has some hot-start problems but I dont think compression ever was really good in the first place as I used worn housings.

The motor was running when I bought it. I decided I would do a rebuild on it, to ensure it's proper running. When I reassembled it, there was no damage, but I replaced one of the housings with one that I bought from judge ITO, because it had that slight groove from the 3 piece apex seals. As for the plates, the step wear was all with in spec, and the housings seemed to check out as far as their thickness was concerned, when measuring across a few different spots.

As for this rotor wash I've heard of....I haven't heard much. Does it happen? Could a primary injector that was firing when it shouldn't, have soaked down the rotor and washed away any oil which would help with compression? Or is that just too far fetched?

Let's try to get some compression back in case of rotor wash...and no, this isn't far fetched if you happen to have severe flooding. The following is a brief description of what I do - you can find better writeups by searching...

Turn the engine over with the fuel disabled (EGI Inj fuse out) after removing all spark plugs (I prefer to remove all). Put the lower ones in (make sure you put the leading spark plugs in), pour a tablespoon of oil or ATF into the chamber (yeah, a bit much :) ) and re-test compression. See if this helps either chamber restore compression.

I used MMO on the rear rotor only, and I saw a slight improvement in compression, but nothing to write home about. However, after adding the MMO, I started it up, and it only took 4 or 5 seconds as opposed to the usual 10 - 15 seconds to start. After starting, It holds an idle about 1100, and revs up to the higher rpm ranges with no issues at all. I'm wondering if I should just drive this shit in to the ground.

Thous testers can be inaccurate at times. However I have found low compression numbers to be culprit usualy to on fresher motors related to, high amounts of lube still in motor, leaking oil seals, hard seals on used housings, flooded engine, rotor grooves damaged or warped causing seals to ride tight.

If I pulled it, would the seals still be useable after 1300 miles? Should I just drive it like this, and shop for a new motor? The crappy part, is that I can start it and drive it. Oce I turn it off, I'm done for the day. I can actually start it, let it run for 2 minutes, kill it....and it will not start back up. Even with my fuel cut switch, I can not get it to start again. I imagine that I could do the MMO trick again, but who wants to be doing that shit all the time?

If you do not remove the oil control rings and did not use OEM coolant seals everything but generally the front cover is reusable.

I used a complete atkins seal and gasket kit. Why would it matter if I remove the oil control rings?

because the oil seals will not reseat