2010 GT Overheating

Stuck in real slow traffic jam last monday, taking my disabled older brother home.
Temp gauge on dash lit up red.

Switched Aeroforce gauges to read Cyl head temp and also coolant temp.
CHT's were 252 deg F.... and coolant temps hit aprx 242 deg F.

It didn't go into limp mode, but I did a U turn and got the hell outa there..and took
an alternate route. It was 49 F outside, around 4:30 PM. Cranked up the
heat on top, full bore, with blower on full bore, then had both windows down.

That seemed to do the trick a bit, dropped it down a few degs.

IF the T stat was stuck closed, I was under the assumption that the heater would not work
inside the cabin ? Both heaters hoses were blazing hot. Overflow container was hot, and
up to the top..since the hot coolant inside was expanding. Pipe from top of eng rad to eng block
is hot. Car has a small Roush M90 blower, and the Roush aluminum intake manifold has the coolant cross over built into it's leading edge.

Both the low speed and also high speed ENG fan do NOT kick in. Normally with AC on, or heat / cold
coming out the defroster by window, the eng fan defaults to high speed.

I checked the 40A fuse, and its good. And also both the low speed fan relay..and also the high speed fan relay.

Only thing I can think of is either a defective eng fan unit, or a stuck closed T stat, ( assuming that the
cabin heater hoses have hot coolant in em with T stat closed, which I don't know for sure is the case. )

On a 2010 GT, the electric eng fan fuse is a 40A, located in slot #7.
Cooling fan relay (high) is in slot #50.
Cooling fan relay ( low) is in slot # 55

Both relays are simple SPST-NO types..with a 12 vdc coil.

Connector right at the fan is ok.

I have the low speed fan set to come on at 204 F....and high speed fan to come on a aprx 213. ( X3 with VMP software)
T stat is a 190 F unit. Normal deal, with eng idling, and hood up, in summer, in driveway, when coolant hits 204 F... low speed fan kicks in...and coolant drops to 194F, then low speed fan shuts off. Then coolant temp starts to climb..and once back up to 204F, low speed fan again kicks in.... then the cycle just repeats.

Apparently there is a voltage drop resistor in the fan housing somewhere. Resistor just drops the voltage down to aprx 9 vdc. High speed relay just shunts out the resistor for the full 14 vdc high speed mode.

What else should I be looking at ?

Water pump? Is your belt slipping?

groundpounder said:

Water pump? Is your belt slipping?

Click to expand...

Belt is tight. The M90 setup for the 2010 GT comes with the Roush heavy duty tensioner, same one as used on the larger TV-2300 blower setups. Water pump is spinning fine. Now whether its fried internally, I don't know. I highly suspect the electric eng fan assy. It won't come on. If out on the local hwy, there is enough air through the upper + lower grille, the low speed fan isn't required. It's the stop + go traffic that's the issue. I replaced the oem upper grille with the 7 bar grille, so loads of air into the upper grille.... albeit it's also an upper foglamp delete.

I'll try using my fluke IR point and shoot thermometer. Then point it at places I can't easily get at... like the inboard side of the eng rad. If its hot, I will know it's temp. If it's hot, then coolant must be circulating, which means the water pump is fine..and ditto with the T stat. Just thought about the Fluke 62 IR device now. Handy piece of gear, used it b4 for finding exhaust leaks, hot spots, issues with the home, overheated electronic devices, AC issues, etc. Think it was good down to -60 F and up to + 1100 F.

I used a 50-50 mix of water + glycol in the eng coolant...and also a full container of redline water water. Ditto with coolant for blower IC pump, inter cooler, HE loop, except 1/2 jug of water wetter used. RP 5W-30 HPS used for the eng. RP max ATF used for the auto tranny, plus a deeper pan for the tranny, so it holds an extra 4 qts.

Think I have around 51 K miles on the eng. Dunno how long the electric fans typ last. It's a bitch to get at the plug assy for the electric fan. I would like to know if there's any vdc at the pins. If there is, the fan assy is def toast. It would be easier to get to the assy with car on a lift.

I bet your fans melted down.

Check/replace the fan speed resistor at the plug in the fan shroud housing and check the wiring.

Fan, Resistor or possibly Smart Junction Box. Also check the underside of the Underhood Fuse Box. Not uncommon for the underside of the box where the Fan Relay goes to melt.

I would check the underhood BEC like mentioned. When the connection between the two halves burn up you end up with an intermittent or always open circuit.

http://www.s197forum.com/threads/cooling-fan-high-speed-relay-bec-melted.106834/

After you check the wiring and voltage feeding the fan with a voltmeter (when setpoint is made), should that check good....

There should be another fuse that provides control voltage for the relay coils to turn on and off at the desired temp settings via the PCM. It will be a 15amp fuse if the system is similar to the 2005-2009 models. Looking at the 05 diagram (sorry I have nothing on the 10) There is the 40amp fuse you mention (though labeled with another number) that feeds the fan motor when the relays are energized, AND there is a 15 amp fuse that is on the relay coil side that the PCM uses to energize the relays (the control side) as the PCM demands based on ECT setpoint.

If this all checks fine and what 46ADDICT states to check is good and you have verified 12+ feeding the low and high fan motor connector based on PCM control then you likely have a failed fan motor.

Best of luck. Hope this helps.

Hot wire the fan motor and see if she spins.

I found a discolored connector on the fan circuit, under the fuse box, that I found while doing the coyote swap.

Tnx for all the replies. It all gets taken apart tomorrow. The resistance of all the relay coils is 66 ohms. Every relay in there is identical.
14.4 v / 66 ohms = .218 A or 218 Ma. Why a 15A fuse position is required to operate relay coils that only draw 218 Ma is beyond me.
We will also try stuffing 14 vdc directly into the fan assy to see if the fan works. Just unplug the fan connector,and inject 14 vdc from an external source, like the battery etc. So far, I have not found the fuse position that supplies power to the pair of relay coils... don't see it listed in the fuse box under the hood, nor in the 2nd fuse box, next to the SJB inside the pass side cabin.

Dunno how much the actual fan draws in either low or high speed mode, but a 40A fuse position is used to provide power through the relay contacts. Relays appear to be SPST- Normally open, types. If the fan does suck anything close to 40A, that would require at least 8 gauge wire, which would never melt, discolor etc. If Ford did something stupid, and used 12-14-16 gauge wire, I can see issues. Even 10 gauge is only good for 30A.

I will let you all know what I find out. Wx is supposed to be sunny on wed.

Pentalab said:

Tnx for all the replies. It all gets taken apart tomorrow. The resistance of all the relay coils is 66 ohms. Every relay in there is identical.
14.4 v / 66 ohms = .218 A or 218 Ma. Why a 15A fuse position is required to operate relay coils that only draw 281 Ma is beyond me.
We will also try stuffing 14 vdc directly into the fan assy to see if the fan works. Just unplug the fan connector,and inject 14 vdc from an external source, like the battery etc. So far, I have not found the fuse position that supplies power to the pair of relay coils... don't see it listed in the fuse box under the hood, nor in the 2nd fuse box, next to the SJB inside the pass side cabin.

Dunno how much the actual fan draws in either low or high speed mode, but a 40A fuse position is used to provide power through the relay contacts. Relays appear to be SPST- Normally open, types. If the fan does suck anything close to 40A, that would require at least 8 gauge wire, which would never melt, discolor etc. If Ford did something stupid, and used 12-14-16 gauge wire, I can see issues. Even 10 gauge is only good for 30A.

I will let you all know what I find out. Wx is supposed to be sunny on wed.

Click to expand...

Best of luck. Like said, I only had the 2005 schem to reference. I agree that 15a in a .5a draw circuit is overkill (2-5a would have been a more logical choice). It may have been a misprint...I'm only as good as the drawing in that regard. If the relays are providing voltage to the plug on high and low demand (based on PCM temp setpoint for ECT) then there is no reason to worry about that fuse since you can't locate it. May have even been eliminated on the 2010 model.

Pentalab said:

Dunno how much the actual fan draws in either low or high speed mode, but a 40A fuse position is used to provide power through the relay contacts. Relays appear to be SPST- Normally open, types. If the fan does suck anything close to 40A, that would require at least 8 gauge wire, which would never melt, discolor etc. If Ford did something stupid, and used 12-14-16 gauge wire, I can see issues. Even 10 gauge is only good for 30A.

Click to expand...

I have bypassed the stock wiring circuit and used 10awg power and ground wires with a 40A fuse. If you keep the wire lengths as short as possible the 10awg should suffice. From eyeballing it the stock circuit uses a 12awg which may be part of the problem. The fan I'm using is an aftermarket Spal and it has held up all year with the bypassed setup.