Persistent Overheating?
 

I've got a 96M, with an FMII (the Link model) with intercooler, M-tuned reroute, and now a Mishimoto radiator with two of the largest fans I've seen this side of a helicopter. Shop has added a 140 degree thermostat, and Evans waterless coolant. All of this is supposed to conquer an overheating problem.

Except that it doesn't. Yesterday, on an hour-long freeway drive, turning on the AC drove the temperature gauge needle to the right. It didn't make it all the way to "H", among other reasons because I turned the AC off and the heater on to bleed off excess heat.

The car has never been tracked; it's a fair-weather daily driver here in the Washington DC area. My daily commute ranges from 45 minutes to two hours.

The Evans coolant has a much higher boiling point than conventional coolants. My fear is that the coolant's heat tolerance may be greater than the head can stand.

Suggestions? Thoughts? Love the car, but hate the feeling that I'm going to be left stranded on the side of the road with a warped head - or worse.

Bruce MacKay

Do you still have the stock under tray? What thermostat did you use. Not all function correctly in a Miata head.

Is the system fully bled?

140* thermostat is stupid. That won't fix anything. Put a normal one back in.

When I installed an aftermarket radiator in my NB, it left a large gap under the radiator. I have no idea if this gap is stock because I never looked. After installing the new rad my AC didn't work as good as it used to, more so and low speed. The gap under the rad was letting hot air from behind the rad right back around to the front. I was basically recirculating hot air through the rad. I made a simple block of plate and tested it in my garage. With the plate installed I got 5 degree cooler AC vent temps. Although I wasn't overheating, something like this could influence your taxed cooling system. My car is not turbo'd yet, and I run stock fans on the stock shroud.

Car has undertray in place. Not sure how the trigger temperature of the thermostat would affect overheating. Worse, the waterless coolant's boiling point (375 degrees) is supposed to be so high that overheating is impossible...yet the car overheated, and the coolant overflow tank that was loaded to the "full" line is now empty. SOMETHING is forcing coolant out of the car, and we can't figure out what.

Work is being done by PBC Automotive in Chantilly, VA; they're well-known in the local community for the quality of their work.

I'm perplexed - grasping for straws.

If the coolant overflow is empty you're not forcing coolant out of the car, but you're sucking it in. Your cooling system was not been properly bled. Now it's replaced some of the air in the system with coolant from your overflow, just as it's designed to. Drain that Evans crap out of your system, fill with 50/50 coolant mix. Bleed it with a funnel.as per procedure outlined here on this forum a million times. Abandon the shop you've been using immediately.

We can already tell:

- They used some pointless high-tech coolant that may actually DAMAGE your car. Why? Regular coolant works for ALL daily drivers.
- They installed a 140* thermostat. Again: why? Absolutely pointless. If you track your car, you may go to a 185 or 180 themostat to have a little more reserve, but street driven uses stock thermostat
- They didn't bleed your system properly
- They seem to be taking your money without fixing your problem

Please post the name of the shop, so others can avoid it!

He posted the name, it is PBC, which at one point in time was the best miata shop in northern VA. That point was 10 years ago or so. Since then the shop had been sold and it all sort of went down hill.

Switch back to oem thermostat. Get a magic funnel and burp the system like stated above.

Reading comprehension fail :inout:

The reason you want a proper temp t-stat is to cycle the coolant through the system, giving it time to expel heat in the radiator as well as absorb heat in the engine. too low a temp just has the coolant flow wide open.

IIRC, your son works at the shop so guessing the coolant and thermostat were thrown in as you say "grasping at straws".

In any case, have they lifted the car up on stands and burped the system?

They are putting an ineffective bandaid on a bigger problem. +1 for don't go back to that shop

Update:

Issue was a brand-new yet leaking Mishimoto radiator cap. The trial lawyer in me wonders why a vendor would knowingly sell a defective product...but that's where we are. Car is running well.

Son is an ASE Master Tech, but does not/not work at PBC.

So far, I've been pleased with the work they've done.