Balto

First off, yes I know I should have gone turbo but that ship has sailed so far its found the Malaysia flight 370.

Edit due to not enough information on my part causing confusion, note to self, don't write a thread on a 20hr shift.

Backstory. I installed a TDR intercooler kit on my MP62 supercharged Miata. Shortly after I noticed the car was overheating when cruising above 65mph (was never a problem in the past, even on 120F California days with the AC on).

​​​​​I'll list what I have done below.

Replaced WP/TB (needed to be done anyway).
All coolant leaks fixed.
M-Tuned coolant reroute.
TDR aluminum radiator.
All underbelly paneling (purchased new, mine was missing).
Replaced all hoses with MAZDA factory rubber. No BS Silicone here.
Different coolant ratios, 50/50, 70/30, 80/20, and 90/10. I even ran straight water with WW at one point.

I don't think the head is blown, all my spark plugs look normal, and I'm not getting any coolant in the cylinders, or coolant in the oil due to leak down through the ring gaps (the car gets driven around town for a bit then parked for 2-3 weeks at a time). I have experience with blown heads, I own a 95 4runner with the 3vze engine (A.K.A 3.SL0).

Anyway, weekend before last when I worked on it (the fan shrouds needed trimming so the radiator would sit right) I was able to put the top radiator cover on. It wouldn't go on due to the radiator not sitting proper in the past and it really seemed to help with temps(all air entering the grill is going through the radiator now), but it still didn't solve the issue. At cruise (70) it got up to 92C (fan kickon temp, thermostat is a 80C) and stopped there. However when I parked it, and turned it off the temp rapidly spiked to 102C. Other than cutting the intercooler in half (its a TDR intercooler for the MP62) I don't know what else I can do. On a 85F day I can't imagine that at 70mph it would be getting that hot with all the coolant upgrades. If the thermo is 80C it should be hovering at, or just a few C above 80 at cruise right? Also keep in mind the AC is OFF.

Any help would be appreciated.
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Joe Perez

iTrader: (8)

This seems normal and healthy to me.


What would you expect to happen when you stop the engine? There's still a ton of heat in the block and head, and it's no longer being active dissipated by the radiator.


No.

Balto

WELP. Maybe I did fix it then. I only got to drive it for about 10 minutes at 70, I shredded a tire en-route to my brothers house so I couldn't drive it faster than 40 limping it home. I'll report back when I get some new rubber and take it out again.

Joe Perez

iTrader: (8)

Think for a moment about the underlying reason behind why automotive cooling systems are sealed with a pressure cap. They are expected to operate above 100°C. If you increase the pressure on a sealed container of water, you also raise the temperature which it can reach without boiling.

Godless Commie

iTrader: (2)

Your cooling system seems to be working as it should.

90 or 100 C is perfectly normal, and the engine is designed/supposed to run at those temps.
Do not worry about ambient temps, that's why you have a thermostat in the system. It will just open sooner and cycle more if ti is hot, that's all.

Also, running an engine below operating temps is not advisable, either (improper oiling, reduced fuel economy, etc..)

Balto

Maybe I didn't give enough backstory.

No, I know I didn't give enough backstory.
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At cruise at 65+, within a minute it would go up to 108C (this happened the first time it ever happened, I quickly pulled over and did the universal 'wtf' hand gesture at the gauge and my FM link module). Every little bit I did helped a small amount, but I was still slowly creeping up to 102-104C (which is when I would back off) at cruise. This last time I took it out, was the first time since March that it didn't immediately creep up to 100C+.
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One other question. What temp should I set for the fan kick on temp? What do you guys with 80C thermostats run?
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Joe Perez

iTrader: (8)

At 65 MPH, the amount of air hitting the front of the car vastly exceeds what the fans are capable of pulling through the radiator. The fans are nearly irrelevant when the car is moving at speed.

A few posts ago, you said that highway cruise temps stabilized at 92°, which is perfectly normal. Now you're saying that they quickly shot up to 108°. I'm confused by this narrative.

Balto

It only stabilized after the fans kicked on. In the past even with the fans it would shoot up to over 100C.

Joe Perez

iTrader: (8)

So what changed?

I assume I'm reading this correctly. To summarize my assumptions:

What accounts for this change in behavior?

And, do you have confidence in whatever instrument you are using to make these observations? (You mentioned FM Link earlier, which automatically makes me question the rest of the electronics on the car.)





Also, @IB Nolan, the[INDENT] function is still more broken than Congress. I'm going to start executing kittens if this madness does not end.

Balto

I updated the OP with a small Backstory.

Only thing that changed is I trimmed the fan shrouds so the radiator would sit flush, therefore allowing me to install the upper radiator shroud. So now all the air that enters the bumper is passing through the intercooler and the radiator.

FM link and the stock gauge is the only instrumentation that I'm using. I measured the coolant temp at the reroute at the back of the head in the past and confirmed that what the gauge is reading is correct, at least at idle. I obviously can't get a temp gun on it at cruise lol. (housing was ~90C when the gauge read 86-88).
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Joe Perez

iTrader: (8)

I read the updated backstory, and I'm still confused.

80° is the point at which the thermostat just barely starts to open. Equilibrium in the system will be reached at a point somewhat higher than this, after the thermostat has opened more fully. (It's not an on/off thing- thermostats are analog devices.) I shot an embarrassing and highly amateurish video documenting this phenomenon about ten years ago. Can't seem to find it at the moment, which is probably for the best. The production quality was really bad. (It was shot on VHS, and I was quite intoxicated throughout the whole video.)

The point I'm not clear on is whether the temp is settling in at around 92° (which is perfectly normal, and in fact a tad low), or if it's still creeping up towards 108° (which is not catastrophic, but a bit high.) I've not been able to form a solid picture of this based on the last few posts.

Balto

Ok ok ok, now I'm home from work. I'll try to be as absolutely thorough as possible in this post. I'm REALLY bad at explaining things, as I'm sure you can already tell.

So I supercharged my Miata, and I didn't like the intake temps (the coolant temps were fine at this time). So I bought a TDR intercooler kit for my car.

2 Days after I installed it, I went to leave to a buddies house, after about 10 minutes cruising on the freeway I look down and see my temp gauge on the car at about 3/4 on the gauge. I quickly grabbed my FM link module, toggled on the coolant temp screen, and it was at 108C. This is when I quickly pulled over and shut the car off, cursed a lot, let it cool, then turned around and limped home and got my DD.

First thing I did was order the underbelly panel for the car. The PO had removed it and I guess threw it away or whatever, because I didn't get it when I bought the car (had no idea it was even supposed to have one).

I installed it and buttoned it up, did nothing, still overheating. This is when I tried different coolant ratios, replaced the WP/TB (both needed to be replaced anyway) and installed a 80C thermostat. It did nothing.

Next, I noticed I had quite a few coolant leaks. Lower radiator hose, both heater hoses, and that STUPID O-Ring below the exhaust manifold. I also found a M-Tuned coolant reroute for cheap, so I picked it up, and fixed the leaks/installed the reroute all at the same time. Once again, it did nothing.

Somewhere in between this I installed a 6-speed/3.63 combo. This is irrelevant information, but I figured I would add it.

Next I installed a TDR intercooler. I figured this would help, and it seemed to make it get hot 'less fast', but alas, eventually it would still overheat at sustained cruise.

The last thing that I could think of was to install the upper radiator shroud(Picture attached). In order to do this I had to trim the radiator fan shrouds so they would stop hitting on the sway bar. I did.

I took it for a short cruise, only about 15 minutes in length. About 5-7 minutes of this was spent at 70mph (85F day). During this cruise I noticed the temps slowly rose up to 92C, which is where my fans are set to kick on, then it stopped. It stayed there for probably the next 2-3 mins or so (never done this before, it always continued to rise in the past). Then I took a corner to fast, hit a loose chunk of asphalt, and shredded 1/5th of the tread off my rear tire.

So that's where I'm at. The car is sitting, waiting for me to buy new tires for it (old ones were at 3/32 anyway). It's an hour drive away from me at my parents, and I won't have time to get to it for another week and a half or so, so I thought I would get some ideas here.

I have always assumed that at cruise, on a 85F day, if the cooling system was doing what it was supposed to, the car wouldn't get much higher than the thermostat temp, and certainly wouldn't need the fans to help it stay cool. But after you saying what you said about the thermostat barely starting to open at 80C, I guess it wouldn't anyway. However, it may not even be fixed, I didn't get to drive it that long after it seemed to 'settle', I may need to stress it more and see what really happens.

I hope this was descriptive enough.

Joe Perez

iTrader: (8)

So, prior to the car being disabled due to shitty tires, it was working normally? (Asking seriously.)






I do not see a supercharger or intercooler in this photo.






I managed to find a copy of the video where I boiled a couple of thermostats in a clear glass bowl, so we can observe their operation in real-time. As per my previous disclaimer, it's amateurish, but yielded useful data:







Ok, we'll wait for you to get the car running again before proceeding with the diagnosis.

Godless Commie

iTrader: (2)

Just for giggles, what's your cruise timing?
Cruise AFR would be helpful, too.

Balto

The circled thing is what i installed. I was just using the photo as a reference :P.

Also yes, it appeared to be working 'normally'.

I'll come back to this thread when i get new tires and take it out for a spin again.

[Edit]: That video is retro as fuuuuck but was fun to watch tbh (I'm a nerd w.e). The format had me laughing a couple of times, 10/10 will watch again.

Balto

14.7, and I'm running the stock numbers that's for the FM link with a supercharged 1.8. I think it's just stock timing that the engine would run in a NA. I thought timing was an issue, but I checked it and it's where it's supposed to be at idle (10°).

sixshooter

iTrader: (12)

To recap, your car was not overheating, you installed an intercooler, car began overheating, you changed a bunch of other stuff that was not related to the intercooler, car still overheating.

I'm rubbing both my brain cells together trying to ascertain why it was not determined that the intercooler bears some responsibility here? Wouldn't it be even more obvious when swapping intercoolers caused a variation in the effect?

I am guessing that the intercooler is blocking up the bumper mouth, possibly very close to the cross bar behind the bumper support. I'm secondarily going to wager that the bumper mouth opening is not sealed all the way to the radiator.

Balto

I never swapped intercoolers. But yes I know that the intercooler is indeed the problem, which is why I'm considering cutting it in half to allow more airflow into the radiator. Even now it keeps air at +/- 10F over ambient, so I think even with it half the size it would still do its job.

The opening is pretty damn sealed up. I wish I had the car with me so I could take some pictures, but alas.

[Edit]: I have an MS3X from Braineack that's ready to install as well. Again somewhat irrelevant information, but yea.

​​​​​​Next time I'm up there, I'll take a datalog of just the coolant temp so you guys can see what's going on.

sixshooter

iTrader: (12)

You must allow space for air to get around the intercooler to the radiator in large amounts. Radiator is more important.

pdexta

iTrader: (17)

That was not the case with my car. Streetcar, stock radiator, no ducting, 3 stacked heat exchangers. On a hot day my car was overheating at 80mph with the fans set to shut off. I raised the fans off speed and now it'll cruise as fast as I've been willing to go and sit just below my "fan on" temp.

I'm sure it'd be a different story with ducting, a proper radiator, and no AC, but on my car fans are still beneficial at high speeds.