Last Tueday, I had some Detroit Rocker cams installed, and the car dyno tuned. They place i took it to is 2 hours away. (made 477 RWHP on a mustang dyno ) I picked it up Wednesday, and friday morning, the car wouldnt start. Turns out it's just a tune issue with cold starting. So friday afternoon, i drive it back over to the shop, he fixes it, and i get it back sunday.

So, in all of those trips, I have 8 hours of driving. 2 hours each way. No problems. been driving it all week, no problems. Today, I go to meet up with some friends in Houston for a car show, drive all the way there on the highway with no problem. The place im headed, the last 15 mins of driving is stop lights.... car overheats. I pulled over, let it cool down, and after doing this a couple times, I finally get where im going.

After sitting at the car show for about 3 hours with the hood up, and the 65 degree wind hitting it, temp seems fine, drive the 2 hours back, hit about 3 stop lights, and im over heating again...

I dont even know where to start... I have no problems at highway speeds, just when i get into city driving. I reloaded my tune with all fan speeds set to turn on as low as i can while i was over at the show, but obviously, that didnt help.

Any ideas?? im lost at this point...

Mods (that are relevant): 10 psi vortech v3 with cooler, CMDP, Detroit rocker cams, OBX LT headers

 

If you have all the fan settings at the lowest it should be on high fan when sitting there idling. Can you hear the fan on max when you are just sitting there? (i have the same settings on my car and I can hear it roaring away)

 

low coolent level?

 

I have never heard the fan on actually, in the 3 years i've owned the car...

I was gonna check that yesterday, but considering that the car was overheating, i wasnt about to open the cap. When the tuner did cam install, he drained and refilled my coolant. The aftercooler moves the coolant tank from front of the engine to the passenger side of the engine, so he had to drain it to remove the tank.

 

Have you checked to make sure the fan actually works?

 

In addition to that, was the cooling system properly "burped"? Could be an air pocket formed that is preventing adequate coolant circulation. Just throwing that out there.

 

Also check for any blockage on the radiator fins preventing any air flow through radiator at idle.

 

I remember reading threads about tunes - and some were surprised the fan comes on more often with the tune. Apparently they want a cooler engine to get the most out of their tune setting.

Since your dyno shop failed to dial in cold start settings (), did they fail to keep the fan on?

As a test for the fan itself my fan comes on pretty fast with the AC on.

 

I reloaded the tune yesterday with the fan temps set to as low as possible. Also, I talked to my tuner, and he didn't touch the fan settings. But I don't think it's that anyways, cause this is my daily driver, and I drive it 20 mins to and from work, and havnt had a problem all week long.

Anyways, I cold started the car this morning, and the fan was immediately on. I drove to Auto Zone and picked up a thermostat. When I got to my mom's house (where all my tools are) I checked the fan again. It was not spinning... So apparently it works at low temp and not at high temp.

Edit: car has been sitting for over 30 mins, just started it and the fan kicked on...

 

Ok, I've been reading that it could be the Coolant Temp Sensor, so I went to auto parts store, and bought one. Got back, pulled the intake manifold off, and found out that sensor on the side of the head was a Cylindar Head Temp Sensor. So more reading online tells me that there is not a coolant temp sensor on a 07 gt... But the guy at the auto parts store told me it's on the side of the engine

Does a 07 GT have a coolant temp sensor, or not? And if I does, where is it? I've searched all over the engine and can't find it.

 

My 08 manual says ECT engine coolant temp (if equipped), next CHT cylinder head temp (if equipped). Doesn't say which models have which sensor. Still looking but wouldn't CHT also be a way of calculating coolant temp?


btw, when it overheated, did the gauge go hot? did you go into safe mode? says to look for DTC's - do you have any error codes?

 

The V6 has the coolant temp sensor (ECT), the V8 has the cylinder head temp sensor (CHT).

Also, there are separate relays for the high and low speed fans in the engine fuse and relay box. Maybe test the high fan speed relay?

 

Confirmed. The Index shows the 4.0 has the ECT, the 4.6 has the CHT, the 5.4 has both.

Shows the 4.6 CHT in the valley.


Should have some codes stored to help.

 

Thanks guys, I ended up breaking the cyl head temp sensor when I put it back in, so I'm waiting on one to get here Tuesday. =(

 

Good luck with troubleshooting it!

 

ooops!

says tighten to 89 lb-in (10Nm) and should not reuse an old one.

 

How is the coolent level when its cold?

 

Ok, so new fail-safe thermostat, and new cyl head temp sensor... Fan still not on at normal operating temp...

 

I assume you mean normal op temp according to the water temp gauge. Mine doesn't come on as soon as the gauge is up. My fan comes and goes - but when I have the AC on it's cycle is much more frequent.

In fact when I take mine out of winter storage every 6 weeks or so, I have to let it idle longer than I like, drive in 1st gear out my road to the mailbox on the highway (about a mile round trip), and then come back to the driveway. The fan usually still isn't on. But at that point if I hit the AC, the fan comes on right away.

 

I started doing some data logging with my X3, an trying different fan temps. For a while, the fan was cutting off at exactly 190 degrees. I called sct and talked to them. They said that the low speed fan is set to turn off at 190. So I set my high speed at 196, and let the car idle. The fan stayed on until it reached the temp for high speed fan, then cut off. I tried different temps, all same results.

I even tried a different tune from a different tuner, and still got same results. So I don't think it Is the tune itself.

Edit: I also tried a new high speed fan relay, and still no luck.