Overcooling
 

I recently did a coolant reroute, and now I'm having an overcooling issue with my car.

Cooling system:

-Koyo 55mm rad
-190 deg t-stat
-FM oil cooler/thermostat
-OEM oil cooler
-Beatrush undertray
-water temp sensors in the BEGI spacer
-single 12" slim fan
-deleted the t-stat neck from the front of the motor
-oil temp sensor in the sump by the drain plug, pass side
-70/30 water/coolant mix, with a bottle of redline water wetter
-no other duct work

I'm seeing water temps no higher than 180 while I'm on it (drops down to 160 during cruise), and oil temps around 150. Even sitting in 90 deg traffic the temp barely came up to 190 (I have my fan set to come on at 194). I'm still using the OEM oil cooler as I'm running the water line for my turbo off the IACV water outlet.

Should I block off a portion of the radiator? I've never been in a situation like this before. This is one of those problems every other turbo miata owner is going to hate me for, haha.

I have about the same temperatures, what's the problem?

Something may be weird with your reroute - can you show us pictures? Or give a lot more information on what you did?

It sounds like you are bypassing a lot of water somewhere past the thermostat. I fucked up like that and had the same symptoms with my first reroute when I originally put it together.

Run a stock tstat
Set the fan to come on after 200


I think never going past 160 or 180 is definitely a problem. You could put a lot of wear/damage on bearings/motor if your oil isn't up to operating temps. Just my .02 though.

Heater core delete?

My FE3 with a reroute 180F thermostat and heater core was staying just as cool so I blocked off half the rad (alum godspeed) and it started running proper temps again.

That's well below normal IMO.

Standard reroute using that big SUV hose and the BEGI spacer/KIA waterneck.

I agree, hence why I started this thread. What is the stock T-stat rated at just out of curiosity? I have a 190 in there right now. The fan is set to come on at 194, and as it doesn't get over 190, it doesn't need to come on. Switching to a higher T-stat and changing the fan to a higher temp isn't going to do anything for me.

Nope, still have it.

How did you secure it? I have some scrap aluminum sheet laying around I was planning on using, if that seemed to be the consensus.

Mighty, let me be clear about something.

If you aren't putting water through the rad (thermostat is closed and water shouldn't still be going by it), you shouldn't be getting much cooling from the radiator. I mean, you'll get some by default, but it shouldn't cause what you are talking about.

This was the problem I had. I had a hole in my thermostat to bypass water, and it caused me all sorts of headaches as a result.

Sounds like the thermostat stuck open. After you drive the car, measure the temp on the radiator if its around your coolant temp then the thermo is stuck open. if its 190+ then your temp sensor is not functioning correctly, and if its like ambient then... dafaq?

I just secured it to the rad support, in the process of redoing alot of stuff on the car now so might try some other ideas

Cover the oil cooler in duct tape and forget about the rest. The 150*F oil temps are more concerning than the 180*F coolant temps.

There's no hole in my t-stat other than the little jiggle valve; everything else is "normal". Only thing I can think of is the water line running to the OEM oil cooler, IACV, and now to my turbo is bypassing the t-stat. That isn't a very big line though.

I'm fairly confident it isn't stuck open. Car warms up to temp as it normally does. I also verified it to be a working t-stat before I put everything back together. Temp sensor worked fine before the reroute, so I find it hard to believe all of a sudden it now reads too low. The location of said sensor is more or less in the same place as in my previous setup.

The FM kit has a t-stat, so until it gets to a certain temp, the oil cooler is essentially not there. I looked again last night and the oil temps were up around 170, not 150 as previously stated.

Well if your T-stat doesnt open to 190 on either the coolant or the oil, neither of them should even be flowing through the rad/cooler. The only thing that really causes the car to never heat up is a stuck open t-stat, or the sensor not reading right. It your rad/oil cooler were doing too good of a job your temps would just be stuck at the thermo opening temp.

Or the temp sensors arent working right. But both sensors are reading funny at the same time, so its very unlikely they both died. It must be a ground offset issue that just popped up. Are these two sending units grounded to the normal sensor ground or just to the engine? And does your coolant gauge match the engine temp reading in the standalone?

*edit: Leafy beat me to it

Trying to figure out why a cooling reroute would suddenly cause the system to over-cool.

hmm good point I can verify it against tunerstudio. The sensors are autometer electric gauges (single wire senders). I have a 4 ga ground coming off the block, head, and an 8ga off the intake manifold. The only thing that changed was the coolant reroute. I'm puzzled.

hence why I started this thread.

You could have tweaked something fumbling around by the head. If it was only the coolant sender reading low I'd say it could be just an air pocket around the sensor. But since its both reading low, and they're both ground to block and not to the normal sensor ground the best bet is you'll find the temp sensor in MS working properly and its a ground offset issue. Do both gauges read ambient when the car has sat overnight?

Not entirely true. If the oil cooler were totally bypassed, the oil pressure drop that would happen when the thermostat opened would kill motors. The Mocal adapter maintains ~10% flow through the oil cooler core to keep oil pressure up and eliminate that dangerous drop. Regardless of where the thermostat opens up (it's like 180*F IIRC), covering the core with a couple of strips of duct tape will bring oil temps up.

170*F is too low, still. I would prefer to see 200*F in every day use.

Well that does make sense. I'll give it a try then.