akageals

Guys,

Well....bad news (I guess).
Recap:
Car ran at 1/4 - 1/3 in town with or without A/C running
Car ran at 1/4 - 1/3 on interstate (70 MPH or so) WITHOUT A/C
Car ran at 3/4 - on interstate with A/C running
Underbelly tray and all ducts/shields are in place

What I tried:
Replaced thermostat (2x with Mazda OEM units)
Replaced upper and lower rad. hoses
Replaced water pump and housing (mine was corroded a little)
Flushed system with Zerex Heavy Duty Cleaner (6 hour type)

Ran car today for first time with all the new parts and after flushing everything. I still get exactly the same behavior as indicated above. When I flushed the cooling system I did not see ANY thing other than the water and cleaner come out so.....I'm at a loss now.

The only thing I did notice was that the front shields did not have any of the fasteners to hold them in place. I replaced the fasteners and will see if that makes any difference tomorrow. Let me know if you have any new ideas.

Todd

SureShot

The fan clutch starts to wear out after 120000 mi. On the series 4 version the fan should pull hard up to about 4k, and then maintains ~4k as the engine revs higher. Mine was slipping at 2500. You can get the fan clutch to bite better by bending the bimetal strip outward. Check it out.
Bill

autocrash

That sounds right.... maybe consider getting an electric fan?

NZConvertible

The problem is occuring at interstate speeds, where the fan does nothing.

Akageals, you've replaced all the things I'd normally suggest. A radiator and/or A/C condenser airflow blockage might cause this. Someone in another thread cured their temp probs by steam cleaning the outside of the radiator. Cleared all the crud from the fins.

SureShot

At highway speed, the fan still helps, and under high stress conditions, that little extra can make all the difference. I had several contributing minor problems on my 87, but it was the new fan clutch that finally fixed it..
Bill

Six Rotors

iTrader: (17)

Actually looking at all the information you give,your car appears to behave in a similar fashion to mine in hot weather(say 90F plus).Last year on the RT66 Trip I noticed that picking up the speed cooled it off somewhat,like 90+ mph.

RX7BEAR

I was having the same problems too running hotter then normal 1/2 way to 3/4 and climbing big hills on highways would make the temp climb too!!!!!!!!!! I just spent 200.00 on the black magic efan which is a bitch to mount had to hack saw the brackets to get it to fit right . Now Im waiting on my pass front caliper to get here so I can drive it a test it.

christi

This sounds like what my car is doing now. I'm draining the coolant tomorrow (obvious reasons I have orange instead of the recommand coolant in there) and changingthat out .. I'll be getting my mazda t-stat friday, I hope. Should I wait til I get the t-stat before draining the coolant?

Also, I never had heating probs until the summer hit. I guess it must be the weather, all during winter through spring... it stayed at it's normal temp.

Atleast I'm not the ONLY one having this problem.

Oh, and how can you tell if your clutch fan is slipping?

akageals

I tried two different fan clutches.....the spare one I put on was used but it made absolutely no difference so I don't THINK it's the problem. I removed the rad. and cleaned it well....although steam cleaning would have been a good idea...wish I had though of it. Anyway...it's debris free and fairly clean. So....the only thing I could do is to put a new radiator on it. Only thing is I'm questioning if it would make a difference. A Fluidyne is about $420.00 so it's a big gamble. I'm almost to the point of just leaving it alone since it does not overheat and in about 8 weeks it will be cool enough that I won't need the A/C. Anybody think this could be A/C related? I converted to R134A and have had this problem ever since.

Todd

deadRX7Conv

One of the issues when the automakers switched to 134a was that the condensor/compressor needed to be larger in order to perform as well as the r12. I would think that the r12 components aren't sized properly for 134a. And, in your situation, your condensor may be preheating the air going to the radiator. This reduces the radiators ability to cool. I don't understand why you would have a problem on the highway when you consider the windchill/supercharger effect of the wind blowing on the radiator.

Try a bottle of redline water wetter or whatever brand is available in your area(crc tow cool/royal purple ice/NOS coolant additive...)
Make sure that you are using green antifreeze and distilled water.
Do you have the electric pusher fan on the condensor? If not, you could buy a small 8-12" thin fan($65) and wire/relay it for A/C use only and keep your normal fan. Or you could just replace the fan with an electric radiator mounted 15-17" fan($100-300).
My NA stick RX-7 doesn't have the electric fan assist. I am under the impression that it was used with T2's or automatics.

RXTASY1

A stock fan with a shroud will out flow an electric fan hands down.
Here is what I have done to get my temps down.
Flushed radiator and added water wetter and 25% water, 75% coolant. Water cools way better than coolant does!

I blew an oil cooler line last year and oil sprayed all over my radiator. The front of it was caked and could not breath. I took it down and had it steam cleaned! That helped a lot! While you are at it, steam clean your oil cooler also.

If you have removed the under tray, put it back on! This will "ram" the air thru your radiator instead of under it.

Rxmfn7

iTrader: (4)

Just out of curiosity, why green coolant only? I just flushed my system and put the red (orangeish) coolant in, because it is supposed to corrode less. What's the disadvantage of the red compared to the green?

Rotorific

iTrader: (1)

Hey man this sounds scary but you water seals may have blown or are going bad. Anything over 1/2 way is considered overheating in an rx7 and i too had the same problem thus i got another engine sitting in my friends garage waiting to be put in. I replaced everything and nothing changed. So now im replacing my engine woopie... Two things to look for sitting at idle or driving around town how far do you go rpms wise? Anywhere under 4k and your temp will maintain go past that or even to redline once or twice and youll see the needle pay a visit to the H. Another thing is after hard driving look in your coolant overflow see if it is blowing bubbles into your tank make sure the tube is still in the coolant. If it is that is a sign your seals are gone because of the exhaust fumes blowing into there. Just a thought - Gabe Medo

akageals

Guys,

Well....it's about 95 degrees here today. I took my car up on the interstate and up a mountain road (55 - 70 MPH) and the car ran at 1/2 or below. The only thing I did was to put some tie wraps on the plastic shields in front of the radiator. My shields were on there but all of the plastic rivets were missing so I think that at high speeds the air pressure may have been pushing them away from the frame and allowing air to escape. Anyway.....I'm going to go for another test drive in the hottest part of the day and see if it stays this way.

Todd