Overheating Bad Problem
 

So a few weeks ago my 1993 1.6 turbo miata with a megasquirt plug n play 2 started overheating very bad. I was hitting 250 degrees on my coolant. I assumed it was a head gasket because I had problems with it before, but I used a sealer and it worked. That was around 6 months ago. So about a week ago I decided to replace the head gasket because I assumed that was my problem. So today I got the car on the ground with the new head gasket and took it for a drive. I was hitting 240 degrees on my coolant and climbing. If anyone knows why my car is still overheating very bad please let me know if you have had similar problems. I have a combustion gas detector so I can check the head gasket but I doubt thats my problem. I used an oem head gasket and sprayed it with copper spray as well. Maybe its because the heater core house is right next to the manifold?? Maybe its because my intercooler pretty much blocks my entire radiator and my secondary fan isn't turning on? I have no idea. Any help would be greatly appreciated. Thank you!!

Over heating will typically nuke your thermostat, was it replaced? What radiator are you using? What is your bleed procedure? How old is the water pump? Have you pressure tested the coolant system?

stock radiator and brand new mishimoto thermostat. to bleed it I fill it and then start the car and add more as necessary and also squeeze the upper radiator hose to get the bubbles out. I have not pressure tested my system and not sure about the water pump.

Any oil/grime build up on either side of the crank pulley? VC leaking? Look on the back of the rear timing cover (the metal one behind the cams), is there any oil? These are all signs of requiring cam seals, crank seal, and VC gasket. Great time to replace the water pump, timing belt, idler and tensioner pulleys.

How is your ducting? Is your stock undertray in place? How far from the radiator is the intercooler?

My decking is pretty bad and my stock under tray is not installed. Radiator is about an inch and a half away from the intercooler. I drove around with no hood or front bumper and i didn't really overheat. I was pinned at 210 which is a bit hot but didn't go over 210. So I guess airflow is part of the problem. Any suggestions on that??

That's a big contributor right there. You need the undertray to create a low pressure zone under the engine. Without it, you hardly pull any air through your radiator.

Yeah, move the intercooler as close to the radiator as possible, duct in front, and replace any missing under panels. That'll help a lot.

You said you used a can of stop leak? That'll clog up and coat they inside of the radiator.,.... Not even sure how you would clean that crap out, might be best to replace the radiator.

Install stock under tray. Burp coolant using the Lisle magic funnel with the front of the car raised.

Don't let it get that hot. If you're passing 230 and climbing shut the car down. You're going to be stopping soon anyway; better to do it when it's your idea than when the car decides to stop.

Is this a new random issue or did it come after changing something? If its a new issue double check that your fans are working. I've had a fan motor die and a fan relay die, both causing me to overheat at different times. When warming the car up, does it drop a little when it passes your thermostat temp? If no, then the thermostat is likely stuck closed.

My car was running warm when the intercooler covered the entire mouth of the car. I have ac though. I switched to a taller IC and problems went away. I wasn't seeing temps as high as you. I let it get to 230 once, and that was with ac on. I would get an undertray on the car and block off any places air can be diverted away from the radiator. +1 on making sure your fans are coming on and staying on. I would try having the fan come on earlier and just go ahead and put in a new thermostat, they're cheap.

so my secondary fan doesn't turn on so i will probably buy some powerful aftermarket fans and install my stock under tray and hope that fixes my problem

Oem fans are strong. Nothing short of some SPALs will outperform them.

Seems cheaper to figure out why your secondary fan isn't being triggered.

Doesn't the secondary fan (AC) fan get triggered to on with AC? And don't the MSPNP2s have wonky AC support? I'm thinking there could be something going on there.
Also, its not hard to just wire the fans in parallel, so that when the main fan kicks on, the pass side does too.

Update: i took the car out for a short drive yesterday and this morning i just let it get up to operating temp at idle. I look in my radiator. I dont see anything but my overflow tank is filled to the brim. What does this mean!! I had the same problem before i changed the head gasket. If anyone knows why this is happening please let me know!! Thanks

With the engine running, grab one of the radiator hoses. Is it rock hard? You could have combustion gases leaking into your coolant system and pressurizing it. Did you check your block and head for straightness when you did your head gasket?

You can also test for this with the engine off. Plug in a compression tester, and pull off the radiator cap. If pressurizing any cylinder makes bubbles come out of the coolant, or pushes up the level, you know you're leaking.

Ok I will try the compression test. Could the water pump be the issue?

Water pump wouldn't drive extra coolant into your overflow tank, but who knows.

How old is the radiator cap? I would pressure test the cap too if you have the tool.

installed a brand new cap today still overheated