94 Gt Running Extremely Cold

SN95KnightMare

New Member
Jan 18, 2016
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I'm new to stangnet as a member but not to browsing the forums I've been trying to diagnose a cooling issue on my SN95 for a while with no luck. No matter how long I leave the car idle for it will not reach operating temperature. in 1 hours time it might reach operating temperature once with me reving it. At that time the gauges is in the middle but almost immediately the thermostat and fan kick on sending the gauge plummeting. now I've replaced all correlating sensors, thermostat, CCRM and coolant flush still no luck.

94 5.0 with only cold air intake and exhaust
 
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Do you have an alternate means of checking temperature? If nothing else, an infrared non-contact thermometer can be helpful.
The stock gauge is not super useful so you might not have anything wrong...........
 
I will hit the thermostat housing with a temp gun when I get home. It just seems extremely odd that the thermostat won't open up after idling for 45 mins. But if I get on it around town temp will go up thermostat will open and then engine temp plummets. Sometimes I go a whole 30 min drive to work with out hearing the thermostat open and cycle the fan on.

Cabin heat is working, so I don't have a clue.
 
I still think everything might be fine. It's cold out, so if you're moving at all, the fan will never come on; it might only come on after an extended drive and then a period of idling.
Remember, the stat opens very slowly (most non-performance stats require around 15-20* to go from barely opening to fully opened). In cooler weather, it might not even open all the way: it opens enough to cycle some of that cold radiator electrolyte into the motor and the stat can close right back up or stay only slightly open, depending upon conditions.
 
As Hissin said, the stock gauge is unreliable but I can give you my experience with the stock gauge on an engine that's in good condition. I've owned a 94 GT, a 95 GT and a 94 Cobra Clone, and the stock gauge on all three has acted in basically the same way. Hopefully this general description will help you figure out if your car is acting "normal".

The average operating temperature while driving should have the needle somewhere around the "N" or "O" of the word "NORMAL" behind the gauge. Exactly where depends on what temperature thermostat you have, the type and condition of your radiator and the accuracy of the stock gauge. The low-speed fan should kick on when the needle is somewhere around the "M" in "NORMAL", and the fan should stay on until the gauge drops to somewhere in the "R" range.

When you start the car and the engine is cold, the gauge will slowly rise from the left edge until the thermostat opens. At this point, the needle should be somewhere around the "N" or "O" in "NORMAL". Once the thermostat opens, the temperature will drop somewhat but will rise back up again. The thermostat will then open and close as needed to keep the engine at a minimum temperature. So if it's cold out it's possible the temperature may never get very high.

If I'm driving under 35mph, and usually stuck in traffic, the temperature gauge will slowly rise until the fan kicks in. If I'm driving 40mph or faster, the temperature will never rise over the "O" in "NORMAL". The temp will rise a bit after exiting the freeway, especially if it was a long drive, but it won't ever reach halfway unless I run into traffic like I mentioned above.
 
I was out of town for a couple weeks my apologies on going incognito. Any ways I hit the thermostat housing it read in in the mid to high 170s after driving home from work. I'll hit it once more today after I get home to get another reading.
 
I was out of town for a couple weeks my apologies on going incognito. Any ways I hit the thermostat housing it read in in the mid to high 170s after driving home from work. I'll hit it once more today after I get home to get another reading.

That's indicative of the T-stat being open or partially open all the time. What are the ambient air temperatures?
 
I might have missed what stat is in there now, but to add to Richard's thoughts (which are spot-on), it could also be indicative of a performance 180* t-stat (the ones I've tested start to open at just over 170* and are fully open just shy of 180*).
 
Get that stock T-stat back in there if it isn't. Should be 192F stat. There's no advantage to going with a colder T-Stat unless you're in an area with extremely hot climate. Running a colder one could actually prove detrimental.
 
Another note I unplugged my fan car warmed up and started to overheat vary slowly. After plugging the fan back in it cooled it down to operating temp. Then Shut off. Car then proceeded to hold temp for 20 seconds then dropped back down.
 
I'm getting confused by the seemingly conflicting posts................
With everything connected properly, is it running too hot or too cold?
 
If it gets up to temp with the fan disconnected, can we assume it does the same with it connected? The fan will not naturally come on till over 200*F (AC off), so you should reach 200* without issue.

Even if the fan is coming on earlier than stock, the mechanical t-stat you replaced should limit how cool the engine gets.
 
In my opinion the car should have stated to generate heat a lot quicker than 10 minutes with the fan unplugged with a little reving. With it plugged in it rarely ever reaches temp and when it does it goes down instantly. Gas milage is horrible. The state housing is in the 170 180 area temp wise, something is keeping it to cool.
 
Ok, I understand now. IMHO 10 minutes to reach operating temps while in the 60's isn't super unusual, but if you're not reaching your t-stat's rated temp, something is going on.
I generally don't recommend it since one could get burned, but if you remove the rad cap and let it warm up, you can see coolant start to move when the stat starts to open. At that moment, you can take an IR reading of the stat housing and then use a kitchen thermo (never to be used for human consumption again) in the radiator (to confirm the IR reading, or indicate how much offset there is between the coolant and the housing reading). That info might be enlightening. And it would help purge any air out of the system......

Alternatively, have you measured the voltage across the ECT and checked temperature that way? That's useful because if your ECT is out of calibration, you'll see its reading.
 
If you've made a rig to check ECT temps, keep it in there for further testing. See what temp it reads when you think the car should be at operating temperature.

How bad is your mileage? I'm just curious (it might not be related).