FC Rotory Help

Postby **RX-7 Chris** » Thu Apr 21, 2011 9:14

Eric, give me a call tomorrow (can't talk tonight) and I'll be able to help you out with your questions.

D Walker · Postby **D Walker** » Thu Apr 21, 2011 9:14

Compression on a rotary is argueable, especially at altitude, but I would want to see 85-90 with nice even bumps on all faces.

Overheat on a rotary is usually caused by lack of coolant, lack of fans, or poor airflow (clogged radiator fins or front end damage) and its actually pretty hard to overheat one by running it lean. Air bubbles can be a true PITA and it can bevery difficult to get them out.

If you have overheated it (anything over 200deg for any length of time) your killing the motor. it might not be "blown", but its on its way and the best thing to do is to STOP and have the engine rebuilt ASAP before housings, rotors, and plates are ruined which only add to the butchers bill. As we all should know, overheating a 13B can and will cause the o-ring grooves in the irons to crack, causing them to leak coolant into the combustion chamber and burn the o-rings out. There are other failure modes as well, so the overheating really needs to be addressed.

No way I can help this weekend unless it was in my shop, and even then the best I could do would be to sort of oversee someone else doing stuff. After the first I may have some time to help.

ecam8000 · Postby **ecam8000** » Thu Apr 21, 2011 9:14

D Walker wrote:
Overheat on a rotary is usually caused by lack of coolant, lack of fans, or poor airflow (clogged radiator fins or front end damage) and its actually pretty hard to overheat one by running it lean. Air bubbles can be a true PITA and it can bevery difficult to get them out.

If you have overheated it (anything over 200deg for any length of time) your killing the motor. it might not be "blown", but its on its way and the best thing to do is to STOP and have the engine rebuilt ASAP before housings, rotors, and plates are ruined which only add to the butchers bill. As we all should know, overheating a 13B can and will cause the o-ring grooves in the irons to crack, causing them to leak coolant into the combustion chamber and burn the o-rings out. There are other failure modes as well, so the overheating really needs to be addressed.

Thanks guys.

Christi, how many times has this been hot and how long? What we are trying to fix, may be due to an already overheated engine. If that is the case, a new radiator, fan and fan shroud would not fix the "problem".

christi · Postby **christi** » Thu Apr 21, 2011 9:14

Okay, sorry just got up, about to head out for the door for work but:

The car has overheated twice. Once driving to my buddies to fix the t stat / oring and change to the E-fan. The second time was up on Lookout Mountain.

Postby **RX-7 Chris** » Thu Apr 21, 2011 9:14

why did you change to an e-fan?

ecam8000 · Postby **ecam8000** » Thu Apr 21, 2011 9:14

I will install the new t-stat and radiator cap tonight. I will burp all the air I can out of the system. And I will do a cooling system pressure test before starting the engine. If there is no white smoke or coolant smell from the tail pipe once the engine starts, is it safe to assume the engine is O.K? I will look for all signs of leaks. Tonight/tomorrow I will post to let you know the results.

D Walker · Postby **D Walker** » Thu Apr 21, 2011 9:14

No coollant smell in a rotary is a positive sign. pressure testing is a good idea as well.

Thermostat that is opening should not need replacing, but I understand the why behind it

Bubble of air is most likely thought right now, but if it has overheated before and this seems to be an ongoing issue I would start looking for a deeper cause

Postby **RX-7 Chris** » Thu Apr 21, 2011 9:14

has the car ever gotten a complete coolant flush or has it just had the coolant replaced that was lost?

christi · Postby **christi** » Thu Apr 21, 2011 9:14

Eric, you got a new t stat? Did you also get mine for the 3 as well?
In feburary I had greese monkey do my coolant flush. I know the car also needs a oil change ....

I've always wanted a e-fan. I've alway heard it's better airflow for the car....

Postby **RX-7 Chris** » Thu Apr 21, 2011 9:14

that depends on the e-fan you used and how it is wired up.

ecam8000 · Postby **ecam8000** » Thu Apr 21, 2011 9:14

christi wrote:Eric, you got a new t stat? Did you also get mine for the 3 as well?
In feburary I had greese monkey do my coolant flush. I know the car also needs a oil change ....

I've always wanted a e-fan. I've alway heard it's better airflow for the car....

Yes I have two t-stats, one for each of your Mazda's.

Coolant came out clean no signs of garbage. Current blend is about 25-30% coolant to water. Tonight I will change that back to 50/50. When the fan came on it did pull a fair amount of (warm) air through. Like I said before, even with extended idling, it seemed to keep its' cool (pun). Only after the hard test drive did it seem to heat up. When the engined shut down it pushed a quart or so of coolant into the overflow (gurgling sound) and later (30 minutes) it had pulled the coolant back into the radiator. No coolant on ground. That is why I ordered a replacement Radiator cap as well. But with the flash and push - I have to believe there is air created with each hot shut down.

christi · Postby **christi** » Thu Apr 21, 2011 9:14

I can't thank you enough for doing this during the week while I'm stuck here for work, Eric. Hopefully it is not a blown engine and it is possibly the cap if not the radiator.

I can say that the e-fan shouldn't be the issue. The oveheating started to happen in the first place when the t stat wasn't working and I had no o ring in the rad neck. like I said the first time it ever overheated was when I was driving to my buddies place (the one ho is doing my exhaust system) to change out the o ring/t stat and change to the e fan. So I'm not sure.

Sent from my iPhone.

chickenwafer · Postby **chickenwafer** » Thu Apr 21, 2011 9:14

D Walker wrote:If you have overheated it (anything over 200deg for any length of time) your killing the motor.

200* is just past the optimal operating temperature for a rotary...hell, Mazda doesn't even have the fans kick on in an FD until 221*F and the RX-8 doesn't kick on it's first fan until 202*F and the second at 212! While I agree these are high temperatures (when I tune I set the fans on the FD to kick on at 84*C) 200*F is not overheating.

Every rotary from the factory runs at 200*F plus with the way Mazda has set it up. Not to mention I was told by Jim Mederer himself, in person at SevenStock, that overheating a rotary isn't until about 235* when you do real damage. Now is it good or even advisible to run 225* then? Hell no, but I don't sweat 105*C coolant temps.

ecam8000 · Postby **ecam8000** » Thu Apr 21, 2011 9:14

Good info, the only things that make me think there is a heat issue, is that Christi says the car shuts down when it gets too hot. The gurgle past the radiator cap (and not violent) may be just a weak cap.

christi · Postby **christi** » Thu Apr 21, 2011 9:14

Eric, secondgenpat is gonna stop by as well

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