1996 Cobra Overheating Issue!!!

[Marz89]

So I know this is a known issue across cobra's in general.

I have replaced radiator (OEM), Fan (OEM), waterpump (OEM) and CTS (Coolant Temp Sensor)

Fan comes on but does not seem to do a whole lot. I have already had my system flushed and I do not believe there are any air pockets in my system anymore but it seems when on freeway I still overheat all the way up to about L on NORMAL. Downshifting seems to help a little, not sure if it makes waterpump spin faster or why it helps.

I am not exactly looking for answers as to why or what to do, more looking for advise as to high end fans/rad/waterpump to see what others are using that may have helped your issue with overheating. I noticed that most, if not all, aftermarket fans are single speed and the OEM is two speed so not sure how you guys are making that connection, are you using the low speed as the trigger for the fan or the high speed? I am not looking to put a toggle switch inside my car...

Thanks in advance.

 

[wmburns]

I'm pretty good with electrical and could help you interface an after market fan to your car.

But...........

It's seems to me that there's something else wrong here. There are tons of these cars on the road with the same OEM fan and radiator that don't overheat.

Allow me to relate an experience helping someone else. They were POSITIVE the motor was overheating because the dash gauge said so. Upon interview the motor was NOT showing the other typical signs of overheating.

I gave the guy some advice which he ignored. He finally come back to me after replacing almost EVERY part in the cooling system and still had the same symptom (apparent overheating).

I told him to measure the voltage at the battery when the fan was not running and repeat the measurement when the fan was running. Also measure the voltage at the alternator case and the battery negative (this reads the quality of the ground path to carry current. Should be low).

To make a LONG story short, he found that the motor grounding strap between the left hand motor mount and the frame rail was not installed correctly. The caused the alternator to be poorly grounded. When the high amp drawing fans kicked on the alternator could NOT keep up and the system voltage dropped.

What do you suppose the driving factor is for the dash temperature gauge is? Give yourself a big pat on the back if you said voltage. When the system voltage dropped this caused the dash gauge to read HIGH.

Could your problem be related to the charging system? IDK. But your comment about the fans "but does not seem to do a whole lot" could be a clue that they aren't getting enough electrical power. I got to say that my experience with OEM fans is there's isn't any doubt that they are "doing something" when they run.

Bottom line. Today's cars simply will NOT run right without a strong battery and charging system. IMO every trouble shooting activity should start with the review/tune up of the charging system. Are the battery terminals clean and tight? Has the alternator been tested for correct output and excessive AC ripple (bad diode)? Are the grounds around the radiator core support clean and tight?

No excuse cut corners here as almost all auto parts stores will test batteries and alternators for FREE.

 

[Marz89]

Wow... I did not expect a detailed reply like this and it makes total sense. I mean the engine was rebuilt about 2 years ago as well. It seems like the Low speed might never actually turn on but I also can't hear it so it is hard to say but the high speed does kick on and seems to not really move the temp gauge at all, only thing that helps is down shifting when slowing down. Not even the old school "turn the heater on with Vent" doesn't even make a difference which in any other case of over heating issues, it did help.

I am going to buy a volt meter tomorrow after work and test your theory this weekend and will report back to you about this. If you are correct on this, I owe you a beer lol.

Thank you.

 

[Marz89]

So guess what?

I think the issue might be resolved. Will have to do some testing for the next couple of days to see how it works out.

I bought a Bama tuner before I posted on here and it just came in the mail. I loaded a config onto my CPU and my fan turns on sooner than it was before, much sooner, basically as soon as it hits between "R" and "M" on "NORMAL" it kicks on. Before, the high speed did not kick on until "L" which tells me that the asshat I bought the car from probably loaded a bad config onto the CPU which messed it all up.

Took it out on the freeway a bit and it did not go past "M" on "NORMAL" at all while in California heat and traffic. But was only tested for a few minutes on a pre-warmed engine which was running on "L" when I got home.

Will update in a couple days with results.

 

[wmburns]

Sigh........I have failed.

Why? From your reply it appears that the only measurement device being used is the dash temperature gauge. A measurement device that can be inaccurate and is subject to possible false readings. At the least some cross check of how hot the motor really is.

A good trouble shooting should start with the basics and then move on from there until the problem is understood.

Consider for a moment what IF the problem is really in the low speed fan (just a thought experiment). Your new PCM configuration now turns the high speed fan on sooner. IF this is the case, you really haven't fixed anything but instead masked the symptom.

Regardless. Good luck. I suspect that this solution beats what you were considering doing (replacing the stock radiator with an after market unit).

 

[Marz89]

Well to be honest, before, I could never hear my low speed kick on and only would hear the high speed kick on at "L" but considering how loud the car is in general, could not confirm if it was coming on or not as when I would get home and pop the hood, the fan would not be running at all unless the temp was at "L" which the high speed was on.

I had the battery and alternator tested and confirmed working fine. I checked ground connection and tightened it to be sure but did not seem to make a difference. I have not gotten around to buying a voltmeter which is why I had not reported back about the voltages as you requested. When I got the tuner in the mail today, (I have been impatiently waiting on this), I immediately plugged her in and uploaded the config and fan came on immediately while engine temp gauge was still above middle. Also, on the tuner, it also shows the engine temp which even when sitting at the In N' Out drive thru, (before I would never sit in drive thru as it was always getting hot but decided to try it today after the tune), the temp sat steady at 178F easily. Got her on the freeway and opened her up and never got past 185F.

P.S.

I forgot to mention in original post that when the temp would get to "L" on the gauge, I could smell the coolant which seems to be a indicator of heat. Also, when it would get hot on the freeway, I would notice a decent power loss and boogyness so to speak. I have only had one other vehicle that would over heat (Ford of course) but it was over 10 years ago that I had it so I do not remember if I could smell anything or notice any power loss.

 

[wmburns]

FWIIW, smelling coolant is a sign of a coolant leak.

The stock T-stat for your car is 192 degrees F. So at 185 degrees your motor is not actually up to full operating temperature.

Note, the 1996-1998 Model year Mustangs have TWO temperature sensors. One for the PCM and one for the dash. So you see it is possible for the two sensors to disagree. The PCM uses a different sensor IF making decisions about pulling timing if it thinks the motor is too hot.

Note2, the DOHC motor is very difficult to bleed all of the air from the cooling jacket. Any air trapped inside the cooling jacket will migrate to the highest spot in the motor as will as blocking the flow of coolant. Guess what else is there. Temperature sensors. IF the temperature sensors are in contact with air instead of coolant this will make them read LOWer than they should. Which may offer an explaining HOW a motor could be running hotter than the dash gauge.

Many people report the only way to remove all of the air is by vacuum re-filling the cooling system.

If this were my car, I would double check the motor's actually temperature. An inexpensive way is by pointing an infrared thermometer at the T-stat housing. THEN you will know if the temperatures (dash and PCM) being reported are "reasonable".

Next I would double check there isn't any air in the system.

The low speed fan should come on IF the AC is on. Does it? If you let the motor idle in the driveway you should hear the low speed fan kick on/off. The high speed fan should only run after the low speed can can't keep up. Finally the fan should cut off whenever the car's speed is above 45 MPH as the fan isn't needed then. So if the motor is overheating above 45 MPH the reason isn't fan related.

The stock fan set points are a compromise between fuel savings, motor temperature, AC performance, noise, and fan wear/tear. The Ford engineers actually know a lot about cars.