Stang runs hotter then it should...ideas? (warning, long post)

[Chythar]

I've had similar issues that vladasap is describing in his thread. I didn't want to hijack his thread, so here's a new one. Now, I'm basing all this off the stock gauge. Yes, I know it's notoriously inaccurate. But it reacts just like the temp gauge on my 94 V6 does, so I don't think it's off by much. Also, most of my troubleshooting skills are with my V6, so I'm learning how to apply those skills to my GT.

The ECT and CTS sensors are the same between the V6 and GT, and the temp gauge is also the same. So I think it's fair enough to compare how the two heat up. Just ignore the 2-cylinder difference.

The GT heats up at about the same rate as my V6. Both have a 180 deg thermostat, and I can see the thermostat open when the temp needle is between "N" and "O" (the temp drops almost back to "N"). The GT then continues to heat up at about the same rate, until it reaches halfway up the gauge. This happens irregardless if I'm cruising city streets or stuck in rush hour traffic. Eventually, the temp will rise over halfway to the"M". Then the fan kicks on, and drags the temp back to about halfway again. This is also the same time the fan in my V6 kicks in. The temp bounces between halfway and the "M" the rest of the time I drive the GT.

I've installed these parts, with no real change:

Mishimoto radiator (fits great)
Mr. Gasket 180 deg thermostat
Black Magic fan (86-93 model, made my own brackets)
swapped the thermostat/gas gauges with ones from a spare cluster
Checked for vacuum leaks (fixed a couple)
New spark plugs (stock Autolite) and wires (MSD)
Seafoam'ed the engine (love the James Bond smokescreen)
Installed the two air dams beneath the radiator support

I've run both the KOEO and KOER tests and fixed the codes, that's how I found my vacuum leaks. Both tests now return 111.

The original engine in the GT never did this, its temp always sat right around the thermostat temp. I pulled it 'cause of worn crank bearings (they had a lot of brass showing). I ended up replacing the stock AODE at the same time. Tranny is a Dynamic Racing Transmissions Street/Strip AODE with the 4R70W gearset. The new engine is a 91 Thunderbird engine. According to SorsCode, the longblock is the same as the 94-95 GT EXCEPT it has the 93-95 Cobra cam in it. Heads are stock GT, not the Cobra heads. Would the Cobra cam heat up the engine like this? If so, I would think the Cobras would have the same heating problems.

The engine runs really smooth now after the fixes above. The new plugs, wires and Seafoam were just done today, and the engine purrs like a kitten. They also solved my pinging at WOT.

Any ideas? I could use 'em.

I think the CTS sensor is fine, it's what feeds the gauge in the car. Is there anyway to check what the ECT sensor is reading? I had a similar situation with my V6 years ago, the ECT sensor value was bouncing everywhere and the computer always thought the engine was cold. It kept heating up almost to boiling over.The OBDII tool for my V6 will report the ECT temperature that the computer sees. I could use that test to see if the ECT was reading the right temperature. But I don't think there's any way to do that in the OBDI GT. I guess I could check the voltage and see if it's bouncing all over.

 

[HISSIN50]

If you have a scanner (not reader) you can view PIDs, and ECT is one of them that's viewable. I've done this to see how the ECT and my mech gauge relate (they're always within 5* of eachother and within 2* of eachother above 178*F).


Are you totally sure your fan is up to par and coming on at 208*F (do the V6's have different fan speed thresholds that could explain the disparity?)?

The Black Magics have a bit of a negative following in some circles. I only mention it because it's hot in LA and even our stock fans (which flow wonderfully - I have a Taurus fan in mine now [almost 4000 CFM at 14 volts] and I dont think it does quite as well as our stocker. I can tell you for sure next summer when it's 115* outside) are sometimes not enough.

Have you been able to take it for a cruise on the highway (over 50 mph) to see where the gauge settles? If it's where you want it, you know it's probably a fan issue.

Honestly, though it seems you have your reasons not to, I'd put a mech gauge in. Even if you just run it for a week and remove it (or hide it under the dash or mount it in the engine bay), it would be really useful and less work than swapping parts back and forth.

Lastly, though I'm sure you've seen it, here's a little tech note on cooling systems. In the tech note, there are hyper-links to CCRM testing (for the fan) and manual fan switches in the article too.

Good luck bud.

 

[vladasap]

well im attacking the problem by installing gauges first, to get an exact reading of whats goin on
so far i replaced the thermostat and flushed the coolant but no diff really - the temp might be slightly lower (very slightly)

ill keep you updated on whats goin on and we'll see whats up soon (btw the fact that you have an aftermarket radiator and the same issue kinda rules out the radiator being the issue which im SOOO happy about *thumbs up*

***btw i noticed that the moment i put either the heat or the AC on, the fan comes on and the temp goes way down and the gauge reads real cool ..... ??? so confusing ???

GOOD LUCK

 

[HISSIN50]

well im attacking the problem by installing gauges first, to get an exact reading of whats goin on
so far i replaced the thermostat and flushed the coolant but no diff really - the temp might be slightly lower (very slightly)

ill keep you updated on whats goin on and we'll see whats up soon (btw the fact that you have an aftermarket radiator and the same issue kinda rules out the radiator being the issue which im SOOO happy about *thumbs up*

***btw i noticed that the moment i put either the heat or the AC on, the fan comes on and the temp goes way down and the gauge reads real cool ..... ??? so confusing ???

GOOD LUCK

In your case, let the car idle with the HVAC turned off. Put a DMM on CCRM Pin 14 and see if the DMM shows 12 volts at 208*F (the low speed fan should be on).

Good luck.

 

[parchisi]

I'd make sure that the e-fan is up to snuff. I had a hell of a time figuring out a cooling problem on the '93 Cobra. For some reason, it actually cooled WORSE when the fan was turned on...must have been something to do with airflow disruption or something. Fan on and driving at 50 mph, it would overheat. Turn the fan off and drive, it would stay cool. Replaced the unit with the stock clutch driven fan and shroud, and now there's no problems.

 

[Chythar]

I'd make sure that the e-fan is up to snuff. I had a hell of a time figuring out a cooling problem on the '93 Cobra. For some reason, it actually cooled WORSE when the fan was turned on...must have been something to do with airflow disruption or something. Fan on and driving at 50 mph, it would overheat. Turn the fan off and drive, it would stay cool. Replaced the unit with the stock clutch driven fan and shroud, and now there's no problems.

Fair enough. I have the stock GT fan on my 94 V6, it's easy to swap and test.

 

[SuperStang83]

Do you still have the fan shroud on? I have seen people take them off and the temp will rise higher than normal. Neddless to say they put the shroud back on shortly after taking it off.

 

[vladasap]

sorry im kinda stealing the thread
but i've came to the conclusion that my fan comes on too late ( hey cythar - i believe that might be ur issue as well - i mentioned ur post to my mechanic and he says its almost deff that same prob)
what is it that controls that? i believe it some sort of a relay or something but i have no idea where to get it, what its called or how to change it??
help us

 

[HISSIN50]

sorry im kinda stealing the thread
but i've came to the conclusion that my fan comes on too late ( hey cythar - i believe that might be ur issue as well - i mentioned ur post to my mechanic and he says its almost deff that same prob)
what is it that controls that? i believe it some sort of a relay or something but i have no idea where to get it, what its called or how to change it??
help us

The ECT relates engine temp to the puter. You need to do some testing. See the link in my first post for assistance (I reply to many cooling threads and got sick of retyping the same info all the time, hence Wes letting me put some info on his Wiki).

Good luck.

 

[vladasap]

thanks
i cant really do any testing cause unfortunately i cant find mechanic that will boother doin that for under a $100 while i can get the ECT and put it in myself for $30-40

should i just do that ???

 

[HISSIN50]

If you have a DMM and 30 seconds, you can check your ECT calibration. I will post a couple of voltages and ECT temps if you want to do this.

Harbor Freight puts DMM's on sale for 5 bucks each all the time. Those meters work just fine and can do more than most folks care to do.

If you really want to replace the ECT, you could. It's just nice to know a part is bad before spending money on it.

Good luck.

 

[Chythar]

If you have a DMM and 30 seconds, you can check your ECT calibration. I will post a couple of voltages and ECT temps if you want to do this.

Harbor Freight puts DMM's on sale for 5 bucks each all the time. Those meters work just fine and can do more than most folks care to do.

If you really want to replace the ECT, you could. It's just nice to know a part is bad before spending money on it.

Good luck.

I also suspect my ECT is giving out bad values. Hissin, I'd very much appreciate those voltages and ECT temps. I presume I'd stick a pin through the wires leading to the ECT, or take off the connector and check the ECT directly? I don't really know how to diagnose electrical issues, but I follow instructions well. I have a DMM and I do actually know how to use it.

 

[HISSIN50]

I also suspect my ECT is giving out bad values. Hissin, I'd very much appreciate those voltages and ECT temps. I presume I'd stick a pin through the wires leading to the ECT, or take off the connector and check the ECT directly? I don't really know how to diagnose electrical issues, but I follow instructions well. I have a DMM and I do actually know how to use it.

Sorry - I got lazy with my quoting. I had actually been commenting on Vladasap's above-post (since he mentioned a mechanic).

You can test the ECT either way - dynamically (measuring voltage) or statically (measuring resistance). I prefer resistance checks but do both because checking the voltage takes the vehicle's wiring into consideration.
Remember it's a thermistor, so voltage and resistance follow the same trend.

At ~70*F, look for 3.0 volts or 37K Ohms. This is just a room temp baseline if you want to do it.

At 212*F, look for about 0.50 volts or 2.10K Ohms.

If you measure voltage, you have it right - find a way to measure the sig-return wire with the DMM set to read DC voltage. This is done with the car on (it can be KOEO).

If doing resistance, set the meter to the appropriate Ohms scale, disconnect the ECT's electrical connector and measure across the switch's terminals. This is done with the car off.

 

[Chythar]

Revived from the dead! I figured I should make an update for anyone that finds this thread in a search. My GT's temp issue turned not to be the cooling system directly, but bad timing. I had set up an adjustable timing pointer wrong, it was off by about 4 degrees. When I thought I was at 10 deg BTDC, I was really at 6 degrees. After fixing the pointer setting and resetting to an accurate 10 deg BTDC, the engine runs a lot cooler. Most of the time, the temperature gauge sits right between "N" and "O". If I idle in traffic to long, the temp does rise to halfway but the low speed fan now keeps it under control. It's much more manageable now.

Who knew?