Ok, my story is a bit different from most of you guys..

I have an 87 T2 that has honestly been one of the best cars I have ever owned...However, I recently had to have the engine rebuilt due to a blown side seal and collapsed corner seal spring....

Before I had the engine redone, It never got above 1/4 on the temp gauge. I always wondered why everyone had all of these cooling issues...

Since I have had the new engine in (1000 miles now) It has consistantly been getting hotter and hotter, day by day. Especially on the highway, where the gauge gets up to 3/4!. I have done the following to try and rectify the problem...

Retard the timing
Checked all hoses
Flushed and filled
Changed the belts
Changed to Mazda Thermostat
checked the Rad
Checked the Fan
Changed the Gauge sender

Does this sound like it might be a coolant seal to you guys? ...I have done all I know to be a 'quick fix'. I am installing an aftermarket temp gauge tomorrow so that I will know the real temps I am running.

Thanks in advance for any feedback!

 

Are you using Redline Water Wetter in your coolant mix? It prevents 'hot pockets' in the cooling system, helping to keep overall temps down.


Do you have a clutch fan (stock) or an e-fan?

https://www.rx7club.com/forum/showth...ight=fiero+fan

How are your rad fins? Clean and clear or clogged with dirt and goo? My fav way to clean them is to pull the rad from the car and spray Aluminum Wheel Cleaner into the fins. Let it sit for half an hour and then rinse with a garden hose. Repeat until clean.
I do not recommend using compressed air on the rad fins. I tried it once a long time ago and all it did was flatten the fins.

Consider installing an aftermarket temp gauge, so that you'll know just what the temp actually is. For all you know, the stock gauge isn't reading (or reporting) correctly.

Blown coolant seal? There are a few ways to check. With the motor cold. remove the rad cap and start the car. If coolant geysers out, it's a seal. If it burps or farts out a little, you're okay.
Is there a white cloud of smoke out of the tailpipes when you start the car? If so, sniff it. Sickly sweet = coolant seal.


If you're feeling brave and want to try a controversial method, there's the 'Mod Coolant Flush.'

http://fc3s-pro.com/TECH/MODS/COOL/cooling.htm

People have used this method successfully, including me (twice.) Here is a recent (and at times very ugly) thread about this procedure. It includes the story of how the flush's author first stumbled upon it, and his observations of the results.

https://www.rx7club.com/forum/showth...hreadid=132011

 

Thanks for your reply...

I am still using the stock fan, as I had no problems of any kind with overheating with my last motor...

Checked the Rad for fin condition and flow...fine in both respects with no hot spots or cold spots while running...

I don't smell coolant in the exhaust, but the gauge does go down when I put the heat on, which makes me believe that it is actually running hot, and not just a gauge flaw...Both caps have been pressure tested and are in good shape...

I am putting in an aftermarket gauge tomorrow...

Man, this is frustrating....

 

Turning on the heat in my own 7 doesn't have a significant impact on the engine temp...

Maybe you have an air bubble. Have you burped the system yet?

Take off the rad cap, place the palm of one hand firmly over the hole and grab a rad hose with the other hand. Firmly squeeze and release the hose 5 or 6 times. Take your hand off of the hole and check the level? Did it go down? Top it up and repeat until the level stops dropping. Then move on to another hose and do it all again.
Do this with the upper and lower rad hoses, and the hoses to the heater core if you can reach them (it doesn't hurt to be thorough.)

 

thats what the bleed valve is 4 plus u can let ur car warm up and turn ur heater on high and hold the rpm;s at 3k and the level of the fluid should go down have a person hold the rpm's at 3k and fill it full at 3k still put the cap on . and tu duh its tight

 

worked every time on every car i have worked on

 

Haven't heard of that one b4. Thanks for sharing it.

 

have you made sure the front black plastic underpanel from the bottom front of the bumper to back around the lower suspension frame is installed??

Highway (as opposed to city driving) overheating can often be traced to one missing.

 

If its missing fc3s.org sells them in CF and kevlar I believe. Probably cheaper than getting one from Mazda

 

I think the easiest thing to check is the problem that I had with my car. It's pretty much unnoticable to the eye unless you're REALLY looking for it. Check the clearance to the fan shroud and the fan blades themselves. Mine was rubbing so that the fan couldn't spin freely and it'd be fine at idle and low speed, but when you start to give it something it overheats with the quickness! There are bolts up front to raise and lower the shroud if it's touching. Hope that helps...

 

Thanks for the replies...

I know it's not a fan prob, as the car stays nice and cool in traffic...Right now I am betting on 1. Bad Gauge, or 2. Air bubble..

I have the belly-pan on nice and snug...Nothing has changed on the car except having the motor rebuilt..


I am installing an aftermarket gauge tonight, so we will see after that...

 

Long shot, but- Had a Cadillac once where the spring in the lower radiator hose moved into the radiator allowing it to collapse under high RPM's. Removed hose, pulled spring down, it was fine. Also had a Chrysler where the inner layer of the lower hose come apart and inhibited the water flow. Replaced yhe hose, no problems. Also broken water pump impellers will cause the same condition.

 

They did reaplce the water pump when they did the rebuild right??? You didn't get a used water pump???

 

The waterpump is suspect from what I can tell...

 

Make sur the Water pump housing is not pitted and corroded away on the impeller area, "machined portion"

Also:
Mazda OEM thermostat and Rad Cap
Was oiler Cooler flushed during rebuild. (30% of Cooling Capacity)
Are Oil Cooler Fins clean and not bent over, clogged with road debris.
Is the Lower hose in good condition? Does it have a spring installed to prevent collapse at high RPM's?

More to come when you answer the quickies?