FC slow overheat
 

I have an 88 vert with a slow overheat issue. Less than 2000 miles on a rebuild and it ever so slowly overheats under a load. If I'm driving up a canyon the car will be running at approx 195 and slowly creep up to 215 to 220. As soon as I go downhill and take the load off the engine it cools back down below 200. Brand new Koyorad radiator with electric fan and recent flush. Custom undertray and overtray (between radiator and bumper). New fill cap. No white smoke. No overflow. Did champagne bleed. I unfortunately suspect bad coolant seal but hoping I'm missing so
https://cimg4.ibsrv.net/gimg/www.rx7...5bdfdc624c.jpg
mething. Any help is appreciated..

welcome to the board. :)

you very well may be right. which water seals are in the engine?

i have a few thoughts. take them in no particular order ....

1. is your lower hose collapsing?
2. start trying to find ways to plug any gaps and force air through the radiator AND the oil cooler
3. maybe try another cap
4. are those numbers from an aftermarket gauge?
5. what fan did you get for it?

you might get more ideas here: https://www.racingbeat.com/mazda/per...r-cooling.html

I think the engine builder used OEM seals.
Lower hose does not appear to be collapsing but obviously I can't see it while driving. When I bled the system, I throttled up the engine and tried to see if it would collapse but it didn't.
I have been working on airflow. I have a custom under tray between the intercooler and the radiator and a new oil cooler thermostat. I also did a custom overtray from front of engine bay to radiator.
already 2nd OEM cap.
GuageART multi modal guage. I have been getting even higher oil temps which makes me suspect of the oil cooler but I've heard those almost never fail.
I'm not sure on the brand of the fan but it is running at 180 I believe.

Thanks for your help.

i didn't realize you're turbocharged as well.

so, you have a lot going on up there, in a limited space. i think you should go ahead and start focusing on getting the airflow channeled through the coolers - maybe some sort of rearrangement is in order as well?

for the coolant seals ... you can pressure test the system and/or check for signs of combustion gasses in the coolant itself. by virtue of the fact that you have isolated a specific circumstance where the car will run hotter than usual (and given that you are turbocharged), the coolant seals seem a little less likely, but still possible.

you're probably right about the oil cooler. i don't readily remember hearing any stories of them failing (short of sometimes cracking around the fitting for the lines). i have certainly never SEEN one fail. they are very reliable. i don't know how your intercooler is arranged under there, but i suspect it may be part of the reason the other two coolers are not operating like they should.

maybe someone smarter, or more experienced will chime in.

Thanks. Pretty much where my thoughts are at this point.

well, i just want to revisit this in light of the new info.

it would probably be a good idea to see if you can figure out the fan you have because now the flow rate (cfm) will be a little more critical than if you only had the radiator and oil cooler.

It's 17" Derale. I believe it's the two speed at 2400CFM max and it's pulling not pushing. I am travelling at over 40mph minimum when it starts getting hot so the fan shouldn't be doing much at that point. I have definitely been considering trying a v-mount intercooler but that's a pricey upgrade.

i get that part. i was just thinking maybe it may have been running warmer than it should before you got to the point where the natural airflow over from the airflow of the fan. you indicated that the car runs at around 195° before it starts to creep upward, which is about 10° more than RB said "should be" normal.