Miata Cooling Problems Options

[Project.D]

I'm having some cooling issues with the Miata. It starts to go past the halfway mark on the temperature gauge at lower RPMs, like when it's idling sometimes or if it's in a lower gear than necessary (i.e., 5th gear at 40 MPH to save gas). I don't understand why this would be; the water pump was just installed last year, about 2000 miles ago. The thermostat was just installed two weeks ago, along with a new temperature sending unit for the gauge. The car's engine has been opened up before, and it didn't look clogged at all in the coolant ducts. The radiator has been drained and refilled a few times as the engine's needed teardowns. The cooling fan comes on when the engine heats up. The timing is at 14 degrees, and it idles at about 800 to 1000 RPM. Lastly, the cooling system is completely stock with no leaks. Has anyone else had this problem? If so, what did you do to correct it? Figured I'd ask here with so many Miata drivers around. Thanks!

[kvenisn]

I'm having some cooling issues with the Miata. It starts to go past the halfway mark on the temperature gauge at lower RPMs, like when it's idling sometimes or if it's in a lower gear than necessary (i.e., 5th gear at 40 MPH to save gas). I don't understand why this would be; the water pump was just installed last year, about 2000 miles ago. The thermostat was just installed two weeks ago, along with a new temperature sending unit for the gauge. The car's engine has been opened up before, and it didn't look clogged at all in the coolant ducts. The radiator has been drained and refilled a few times as the engine's needed teardowns. The cooling fan comes on when the engine heats up. The timing is at 14 degrees, and it idles at about 800 to 1000 RPM. Lastly, the cooling system is completely stock with no leaks. Has anyone else had this problem? If so, what did you do to correct it? Figured I'd ask here with so many Miata drivers around. Thanks!

I'd guess you need a radiator.

[Project.D]

I'd guess you need a radiator.

That would make sense, that's the one major part of the cooling system that hasn't been replaced yet. I'm planning on doing track days with this car too starting in the fall, would a stock replacement radiator be okay for track days even in the summer? I know an aluminum radiator would be better, but I'd rather just buy the stock one if possible. Any good decently priced aluminum brands to recommend? I know Koyo's good, but I'd like to know about any decent cheaper options.

[Bob Lob Law]

Just take the hood off.

But seriously, the thing you just changed is the most likely problem. Did you test the thermostat before installing it? Put it in a pot on the stove with a thermometer to check it. With summer coming, you don't even need a thermostat in Phoenix.

[SteveAshcraft]

I know this sounds unlikely and couldn't happen to a normal person but
Make sure the fan is blowing the right direction -- I chased a cooling problem for too long because someone(??) had wired the fan backwards ;-)

Check Amazon for aluminum radiators. I found one that seems to be good for $130 including shipping.

[Project.D]

I know this sounds unlikely and couldn't happen to a normal person but
Make sure the fan is blowing the right direction -- I chased a cooling problem for too long because someone(??) had wired the fan backwards ;-)

Check Amazon for aluminum radiators. I found one that seems to be good for $130 including shipping.

I just checked the fan's direction. I think it's right, it's spinning counter-clockwise. One thing I thought of is rewiring A/C fan to run at the same time as the other fan. Has anyone else done this? I saw instructions on how to do it online, and I know it's simple, but I don't want to blow a fuse and have it ultimately not work.

[DaveM]

Hi There:

Be careful about thermostat removal ... the Miata cooling system is a bit compromised as this engine was originally designed for a front wheel drive configuration, and the location of the thermostat was at the rear of the cylinder head. When installed in the Miata there wasn't sufficient room, so the thermostat housing was moved to the front. Consequently water flow is a bit odd and the rear of the engine runs hotter because of that. It's why the temperature sender for the ECU is at the back of the engine, when it senses high temperatures the ECU pulls a bit of timing to prevent overtemperature of the number 4 cylinder. Completely removing the thermostat may indeed send more water to the radiator, but you will get less flow to the rear of the engine. If you remove the thermostat, you need to put in a flow restrictor ( a "gutted" thermostat will work). But in reality I think you will just delay the overheating issue. I think Kevin is right, replacing the radiator might just be the best way to go.

[Project.D]

Thanks for the advice everyone! I've decided to keep the thermostat in there and go ahead and replace the radiator with an aluminum one. Steve, I found the radiator you were talking about on Amazon from OPL Auto Parts. I went ahead and ordered one, and it should be here in time for the next event. Thanks for the recommendation, $130 is a really good deal for it!

[Chuckster]

Your system will also have more cooling capacity margin if you get rid of all of the antifreeze during the summer.
Using distilled water plus a surface tension reducer like Redline water wetter or Justice Brothers Super Radiator Cooler will help immensely.

I prefer Justice Brothers to Redline.
Independent tests showed Justice Bros slightly better than Redline when pure water is used.
Justice Brothers is what the Super bike racers use at Firebird in the summer.
The Distributer in Phoenix area is Diamondback 602-478-0025

Since you probably will retain the thermostat, operating temperature will usually be at the regulation point of the thermostat.
However, at times where the stat is open and the system is being stressed for cooling- the temp will not go as high above the stat set point.
Up to about 26 degrees less than using 50-50 antifreeze and no surface tension reducers.

[Project.D]

Your system will also have more cooling capacity margin if you get rid of all of the antifreeze during the summer.
Using distilled water plus a surface tension reducer like Redline water wetter or Justice Brothers Super Radiator Cooler will help immensely.

I prefer Justice Brothers to Redline.
Independent tests showed Justice Bros slightly better than Redline when pure water is used.
Justice Brothers is what the Super bike racers use at Firebird in the summer.
The Distributer in Phoenix area is Diamondback 602-478-0025

Since you probably will retain the thermostat, operating temperature will usually be at the regulation point of the thermostat.
However, at times where the stat is open and the system is being stressed for cooling- the temp will not go as high above the stat set point.
Up to about 26 degrees less than using 50-50 antifreeze and no surface tension reducers.

I've heard of the Water Wetter before, but I read mixed reviews about it. How much does the Justice Brothers version cost? The distilled water would definitely cost less than buying coolant.

[Chuckster]

I bought 4 x 14 oz. bottles and got a slight discount paying 11.99 per bottle.
I think it is $13 per bottle in single qty.
The mix is 1 to 20 for large systems.
So 14 oz. bottle is good for 2.2 gallons of water (1 gal= 128 oz).
The mix total is then 2.3 gallon if one includes the additive volume.

There are anticorrosion additives and so on in these commercial products.
However, one could explore using dishwasher detergent as an alternative to save money.

[Project.D]

I bought 4 x 14 oz. bottles and got a slight discount paying 11.99 per bottle.
I think it is $13 per bottle in single qty.
The mix is 1 to 20 for large systems.
So 14 oz. bottle is good for 2.2 gallons of water (1 gal= 128 oz).
The mix total is then 2.3 gallon if one includes the additive volume.

There are anticorrosion additives and so on in these commercial products.
However, one could explore using dishwasher detergent as an alternative to save money.

Thanks for the information. I read that Water Wetter causes a gum-like substance to show up in the cooling system and cause problems, is that common? And does the Justice Brothers version cause anything like that?

[BWeikert]

I used water wetter with distilled water in my E36 and it had a noticeable effect on the temps when running it on the track. If you never take your car to an area that has regular hard freezes, you can probably ditch the anti-freeze year around. I never ran any anti-freeze in the E36, but it also got parked in the garage and was an autocross/track car 98% of the time.