Cooling system diagnosis/upgrade
 

Copy paste from cooling system thread:

My current cooling system- Stock WP, 20psi radiator cap, FM crossflow from 2016, FM Stage 2 Fans, OEM 2002 coolant routing, minimal ducting but aluminum under tray is installed, 70/30 distilled water/coolant, 185F thermostat

Problems- My car runs generally hotter than I would like to see city driving (210-220) and will hit 230 in stop and go traffic when using AC.

Upgrade path:
1. FM reroute, leave everything else the same.
2. TSE radiator and the recommended single spal fan for ac cars.

What route do you think I should take here? I don't mind spending the cash on the TSE I just cant believe I don't see other people having this problem. Maybe less people have AC turbo street cars than I think.

Things I wont do:
Hood vents


Originally Posted by shuiend https://www.miataturbo.net/mt2011/im...s/viewpost.gif
How do you burp the coolant? Those temps seem way high for what you are doing.
I totally agree they're way too high. I burp the coolant using on of those radiator filling funnels. I let the car idle with some periods of holding the rpms at 2000 with the funnel attached and filled up the whole time. I will usually then let the car cool down and repeat for another heat cycle.

Quote:
Originally Posted by skylinecalvin https://www.miataturbo.net/mt2011/im...s/viewpost.gif
My assumptions would be one of the following
1) Air in system
2) Head gasket
3) Bad radiator cap
4) pinhole leak somehwere

Are you losing any coolant? When's the last time you checked.
A mechanical problem has crossed my mind before as-well.

1. My burping procedure is as above so I think I should be air free, also with a few thousand miles since I last flushed coolant I would expect any minor bubbles left to have been worked out.
2. No signs of a head gasket. Oil comes out coolant free, coolant in overflow is clean and car makes good power. No white smoke out of exhaust.
3. Just swapped from the one FM supplies to a 20PSI CSF unit same results with both.
4. I'm not loosing any visible amount of coolant. No spots under the car ever, no signs of it in the engine bay, overflow pretty much always at the same level.

I should mention crusing the highway or backroads is fine the only time I experience these heat issues is when using the AC in stop and go traffic. Even on track my temps stay pretty cool for a long time and improving that is just a ducting issue which I am waiting to address.

Edit: To confirm the pinhole leak/headgasket theory I'll rent a radiator pressure tester this weekend and see if it holds pressure.

Update: Rented a pressure tester from autozone and checked my system for leaks. The pressure tester itself would slowly leak out at the connection to the radiator but I was still able to pressurize it up to 25psi and besides the slow leak from the tester did not see or hear any other leaks.

I have confirmed both fans come on and are pulling air the proper way.

Coolant flow issue?

I'd give the system a good flush to try and clear out any crap in the coolant galleries.
And if that doesnt work, take the rad to a shop for flow testing and/or a proper clean (ie: remove end tanks, pressure clean core)


It's possible that if there's a blockage somewhere the coolant isnt able to flow quickly enough at low engine speeds, and it gets warmer.




I presume you've replace the thermostat to confirm it's not just sticky.

Thermostat is a year old Stant SuperStat that I tested in boiling water when new and confirmed good.

System was always flushed often. A few months ago I swapped coolant colors so filled, ran and dumped 3x with distilled water between and it was coming out crystal clear by the second cycle.

The flow restriction is a tempting possibility because it seems the car always runs cooler at higher rpms than it does at idle.

If it's cool at speed but over heats at idle, check your fans are working AND blowing in the correct direction. It's easy to wire the Spal fans backwards. Make sure they are sucking air through the radiator, not blowing forward.

As stated above I confirmed both fans turn on at the setpoints I have in MS and both are pulling air the correct way.

How much power is your car making? What mods have you done? Are you running a turbo? If so, which intercooler are you running?

Car is turbo makes about 250whp. Full FM2 setup for intercooler/turbo/mani so gt2560r and I use hardlines for coolant to it. 180-190kpa. Fm oil cooler and the radiator setup as stated above. Those are the only mods that should affect cooling.

With what you’ve said, I can’t see how you’re having overheating issues.
How are you measuring the water temp? OBD/ECU sensor or after market gauge? If aftermarket ecu, is the sensor calibrated correctly?
i had an aftermarket water gauge that matched calibrated ecu water temp from 50-90 degrees C but then reads 8degs C high above that which made my heart skip a beat the first time I was in traffic with AC on.
New gauge sensor fixed that.

Just had an identical problem with an FM radiator, stage 2 fans, 2560r, blah. blah. On the dyno we actually had better cooling with the small fan unplugged, which gave more amps to the large fan. Food for thought.

Double check your sensor calibration in the ECU, and if that doesn't help, I would also try replacing the thermo sensor on the back of the head.

Untouched OEM sensor in OEM location read through properly calibrated ms3. I only ever have this overheat issue in no moving stop and go traffic on extremely hot days when running ac. If I turn off ac the fans will bring the temp down.

Hmmmm. I have a 5 degree higher setpoint for the small fan so if the big fan running alone was enough it would never come on. I will double check sensor calibration and next step before I spend big money will be a new sensor.

In this situation... stop and go, the turbo does not enter the picture except with regards to the FMIC.

Does all air going through the radiator have to pass through the intercooler?

I still have stock fans and do not have a problem with stop and go. So, this seems strange. My setup is Koyo 37mm (newer one), FMIC and Oil Cooler stacked in front of the condenser; good ducting that bypasses about 2" x full width of air below the intercooler. It is a small FMIC, so some air also bypasses between it and the oil cooler. Fans turn off at 45 MPH (maybe A/C fan stays on if A.C is running, I forget). Reroute with stock thermostat. I track at only 175 HP. I think if I ran full boost, I would have cooling problems.

Re-Route is #1.
Good ducting, possibly with some of the air bypassing the intercooler and going straight to the condenser / radiator stack is #2.

What temperature are the fans set to come on at?

What temps do you see when when not in traffic and moving at speed?

Since you are only complaning about low speed driving and traffic, that says, to me, that the rest of the system is cooling fine, just not enough airflow from the fans for some reason.

Same thought I have. Not sure if this was checked, but make sure the fans are pulling air through the opening vs pushing air through them. In a rush to get my FM crossflow and stage 2 fans in before the sun went down, i wired the fans backwards and noticed I had issues with the car keeping cool at idle. Quick swap of the wires and car was sitting at tstat temp all day at idle.

I am confused with your thermostat choice. I don't think Stant makes a Superstat in 185 flavour. It's either the 180 degrees or 195 degrees.

I might have missed it, but do you have the FM fan shrouds?

The intercooler has an air gap between it and the ac condenser and is not sealed to the ac condenser or radiator. All oem ducting is in place plus I sealed from the sides of the oem undertray all the way forward to the front of the framerails

Fans come on at 195 for main fan and 200 for secondary fan. Usually see 195-200 cruising on freeway. Pulls will increase this to 203-205

Stated above but fans spin the right way. My car will stay cool just sitting idle if AC is not on.

Just checked amazon purchase history it was the 180 I was incorrect saying 185. Stant 45868 is the exact unit.

Yes I have the shroud and have it sealed to the radiator and spaced as far back as possible.

Any particular reason that you wait for the radiator to be overwhelmed by almost 20 degrees before the fans come on?

For example, on my car with a vvt engine and a 180-degree thermostat, I have my main fan come on at 192 and turn off at 187.

OEM fan turn on temperatures were greater than that so I thought I was being generous as is. Also the on temperature shouldn't matter if its climbing all the way to 230 anyways.

While true, it sure helps offset the temperature climbing if you have the fans blowing air from a lower temperature and at least helping offset how long it will get to that temperature, but that I could see as more of a bandaid if the temps are climbing regardless. But what do you have to lose by lowering fan turn-on temperature?
OEM thermostat is also hotter than 180 degrees Fahrenheit.