So, I finally put the turbo on my 1990 w/ VVT swap.

Last summer, the car was N/A with just the VVT swap. Worked fine on the street, but overheated at Rallycross (same duty cycle as autocross). I threw out the 24 year old radiator, and installed an aftermarket aluminum rad, and all problems went away. YAY!

Now that the intercooler is on there, it gets quite hot on the highway. Just driving at 70mph, and coolant is at 100C (212F). Previously was at 94C.

It will also get hot at idle. If I turn on the AC, the other fan kicks on, and it cools down just fine.

So, it looks like I really have two problems:
1 - Not enough airflow through the OE radiator fan at idle.
2- Not enough airflow through the radiator at highway speeds.

Seems like the root cause to both of these issues is the restriction caused by the intercooler.

Some specs:
Fab9 350hp Intercooler.
AC installed and working
Spal fan in place of AC fan
OE undertray with custom piece of plastic to attach to front bumper under the intercooler.

So, what am I missing? I bought another Spal fan to replace the OE main cooling fan, and I'm hoping that fixes issue #1.

How to fix issue #2?

 

How is your coolant burped? Are you running an MS? At what temps do you have the fans set to turn on at? At idle does the car heat up until fans turn on and then cool down to the point that they turn off?

 

A few answers:

-Coolant filled with front end jacked WAY up in the air.
-Forgot to mention that I also have a DIY coolant re-route (Moss spacer, Kia waterneck, GM hose).
-Running custom ECU.
-Fan on at 96C, off at 94C. At idle, fan comes on, stays on, and coolant climbs to 100-101C. Doesn't cycle at all. Turn on AC (second fan turns on), coolant drops to 94C and cycles.

I have the second SPAL fan now to replace the OE, just need to install it. But, that still won't help with the highway overheating...

 

I think you may have some air stuck in your system. I would suggest getting a magic funnel. Then jack up the front of the car as high as you can, install the funnel and re-burp the system. I usually run it till the fan turns on and then turns off 3 or 4 times before I call it good and that all the air is out of the system.

 

Magic funnel is bitchin, unless you have a huge bubble and the funnel goes from empty to full in 5 seconds and spill over.

Is the radiator connection to the bumper mouth air tight?

 

Magic funnel magically ordered with free 2 day shipping. I'll post some pics of my setup later tonight.

 

It helps to have your fans come on when you are burping the system. Sometimes this takes a while. I know when doing it to freshly built subie motors we would wait 20 - 30 mins depending on the air temp before the fans kicked it. However, never had an air bubble problem after doing it this way.

 

Yes you need to let the car idle until the temps hit where the fans come on, then let the fans run until it cools down the coolant until they turn off. Then repeat the process another 2 or 3 times to make sure all the air is out.

 

Glad to know I am not the only one with OCD on this. I also like letting the fans kick on 2 or 3 times. I figured I would say once to avoid any flames for my potential overkill of multiple fan cycles. I figured in my novice knowlege good burp > overheating. Spend the extra time and gas on letting it cycle a few times. Also (without chopping up your hand) squeeze your rubber coolant tubes to help get air out.

 

OK, so the magic funnel arrived. I jacked up the car and installed it on the radiator. I used the straight extension, and the two 45 degree adapters (opposing each other, so still straight up for some extra height).

I started the car, and let it warm up. When cold, no bubbles at all. Once warmed up, there were some bubbles coming through the funnel. I would grab the top hose and squeeze every once in a while, and a few more small bubbles would appear. So, everything was going well. Then it started getting hot. I have a digital gauge for coolant temp on the dash, so would have to leave the front of the car and check the gauge. So, it gets over 100C, and starts boiling like crazy IN THE FUNNEL. I run back to turn on the AC fan to cool it down, and the whole funnel collapses!! Gallons of f*cking hot coolant spilled everywhere. ARRGGGHH!!!

The two 45 adapters are what caused the turmoil. Don't use those!

Haven't taken it for a drive yet.

 

You and me both bother. And I didnt even use the 45's, thing just got to a certain point and expanded over the top of the funnel, and started getting big bubbles out, puking everywhere.

 

So the water got over 100*C and started boiling?

Weird.







Pro-tip: Next time you use the magic funnel, shut the car off *well before* the coolant reaches the boiling point.

 

The coolant will get hot if you allow the fans to cycle 2 times. I personally have used a regular short funnel with zero issues. Just have some rags around to catch any overflow. Wear gloves because it will get hot.

 

LOL That's what I was thinking. OP: No pressure, no increase in boiling point. Going to have to repeat procedure a couple times.

 

Well, I was hoping that the main cooling fan coming on would prevent it from getting above 100C, but it didn't. Which means that the bubbles in the coolant probably aren't my problem. LOL.


Also:

Ethylene Glycol Heat-Transfer Fluid

50/50 Ethylene Glycol/water mixture boiling point should be 107C. Maybe my coolant temp sensor transfer function is off.

 

Have you wired your fans to both come on at once?

I thought this was just general practice for turbo miatas especially if they're driven somewhat hard.

 

With the custom piece in place of the factory plastics is there any gap on the sides in front of the rad? The air will follow least resistance and not go through IC/AC/Rad stack - see Emilios coolant system thread for more ideas. You will not have a problem if you follow those steps and you've done the burp a couple times.

 

Update:

Installed bad *** 11" SPAL fan on drivers side in place of main cooling fan. This solved my idle overheating issue.

As noted above, also used the magic funnel to remove air from the cooling system.

Then, went for a drive on the freeway at 70mph. 103C. F*ck.

Looks like there is a bunch of space on the sides the radiator where air could escape. The next step will be to make some sort of ducting.

 

Whose radiator are you using?

 

Ebay special.

Not this exact seller, but same crap: 98 05 Mazda Miata MX5 MX 5 Manual MT Dual Core 2 Row Aluminum Racing Radiator | eBay