Overheating?

[WarrenG]

My 289FIA has approx 1900 miles on it. Equiped with 1965 289 stroked to 331. Last night on my way home after driving approximately 25 miles and 40 minutes I thought I caught a whiff of coolant. When I looked at my temp gauge, it was up to 240-245 degrees F. After approximately 1-2 minutes it quickly dropped back to its normal 180. Approximately 15 minutes later while accellerating from a stop light, it moved back up to about 225-230, then within a few seconds quickly dropped to 180 again. This happened three more times with the top out at between 210 and 225 degrees. With the exception of the first episode, each time the peak never lasted for more than about 30-45 seconds and the gauge returned to normal operating temperature in less than 1 minute. For the last 38 miles and 45 minutes of the trip, mostly on the capital beltway, the temperature remained normal.
Other than the water temp everything else was normal. Oil temp remained between 175 and 185 degrees and pressure at 45-55 psi depending upon RPM. It was about 10PM and the air temp was probably around 70.
Upon shutdown, I checked the engine compartment but didn't find any sign of leakage however there was only about 1/4-3/8 of coolant in the Hamilton overflow tank.
Any ideas what might have caused this before I start taking things apart? My first guess was faulty thermostat, but was wondering if a faulty sensor, gauge or wiring might also cause the indicated fluctuations. Any help here would be appreciated.

[jwoodard]

I had a similar situation with my Lone Star Cobra when I owned it. After much checking I determined it was a faulty ground in my dash wiring. You might start there and make certain your ground for your gauge is good.

[DonC]

After you check the gauge and sending unit check the fan belt. Sounds like the water pump may not be doing all it should for you.
DonC

[strictlypersonl]

Since it's a mechanical gage, I doubt whether that's the problem.

I would suspect (in order):

Air in the system. Bleed any air from the highest point - probably a fitting in the intake manifold.

Bad thermostat.

Bad water pump.

[WarrenG]

Thanks Bob. I'll start on that tonight. BTW, since I'll probably have to add some coolant, what coolant mix do you put in the cars? Do you recommend any wetting agent?

[patrickt]

Warren, do you remember when I posted a note to you on the CACC forum to keep an eye on the connector plug to the left (driver's side) of the radiator that is the hot feed to the fans? On my car that plug was put together as correctly as it could be put but it still had an intermittent fault so my fans would sometimes come on and sometimes not. It finally culminated in my engine overheating and throwing up all over the garage floor. Before you go to any extravagant remedies, double check that connection; it’s always possible there was a batch of faulty ones that got through the ERA QA tests. Do this: With the engine off, throw the fan bypass switch on the dash so your fans are running, then wiggle the connections that are just to the left of the top of the radiator almost under the fender well. If you can get any sort of interruption in the fans by doing this wiggle test then you’ve found the problem. Instead of replacing the connector I just cut and soldered around them. Even with my stroked and bored FE, I run at 85-90 Celsius on 95+ degree days - even in stop and go traffic. Usually closer to the 85 mark, and that’s for both oil and water.

[WarrenG]

Patrick, I'll check that too. The fan was operating when I got home. Not sure about while on the road, couldn't hear much over the exhaust and the other road noise.

[Rick Parker]

I had the exact symtoms: fast rising temps after thermostat opened, temp gauge would swing wildly and peaked at 230-240 within a few seconds and then the gauge S/W mechanical would swing down to 140 and start the process over. Mine was on a fresh build. 289Hipo with the aluminum waterpump without a backing plate (1st generation). I had not run the combination previously. I fought it for several months, but the solution turned out to be a different waterpump with cast iron impellor instead of "sheet metal type", the one being used was a rebuilt unit from an Auto Parts store. The pump was apparently cavitating. I ended up purchasing a OEM Ford pump. No problem since then.
I will assume yours has run OK without prior issues(?) until this point. Check to be sure your pump is still functioning (impellor tight on shaft). Check your head gaskets.

[Dwight]

Not more than a 50/50 mix, but less antifreeze is better. Water (distilled) is more efficient at removing heat. I noticed that you live in the North. If your Cobra is exposed to temputatures below 32 degrees, you should check the ratio to be sure you are protected during very cold weather. Most Cobras are stored inside during winter months and do not need a lot of antifreeze to protect them. Too much antifreeze makes a Cobra run hot. We know this from experience.

Dwight

[strictlypersonl]

Warren,

For your conditions, I'd use about 1/3 antifreeze (0F freezing point) for its anti-corrosion additives. You engine shouldn't come close to straining the cooling system, but if you sit in traffic a lot, some Water Wetter might be good.