I have a 245 with an unusual overheating problem. About 4 years ago, while driving out to Yosimite on a hot summer day, and going up a steap grade, I looked down to see the tempurature almost in the red. by the time that I found a spot to pull over, less than a minute later, the temp had gone into the red.

I have never had problems like this before so this was very shocking to me. After letting it cool down, everything was fine.

Within the next few months I noticed that the coolant levels slowly when down, white smoke out the tail pipe, and a milky residue in the oil. Then, I failed a SMOG test. So, I decided it was do or die and took on the largest project I had taken on a car. I changed out the head gasket, and put in a new cat. She started right up and passed the next SMOG with flying colors.

Ever since then she overheats every now and then, but since I am now trained to look at the temp guage more than the road, it never comes close to critical levels. All I have to do is blast the heater for a minute and she drops back down.

In my feeble, by brute force methods to fix the problem I have done the following:

Changed the coolant every few months, replaced the heater with a heavy duty one from IPD, 3 row. Put in a new fan clutch. Recently I changed out the heater hoses that goes to the back firewall, and I put in a new engine wiring harness. Also, I have replaced the thermostat.

I have checked the mixture, and watched the O2 sensor to make sure than she wasn't running extremely lean. And the timing is on. I have run out of ideas. Does anyone have any ideas?

She doesn't do it all of the time, maybe 5% of the time. And when she does act up, it will often happen a few minutes after she reaches operating temp. But I have seen it when I had 4 people in and going up a hill on a warm day.

The only thing I haven't done is to actually flush the system. But I have changed the coolant so often within the past couple years that I sort of feel like there is something else going on than a little restricted flow in the engine. I am wrong about this, and this could be the source of all my problems?

Any responces are apprieciated.

Thanks,

Mike

Given the age of your car, I would just invest in a new radiator (or have the flow of the existing one tested). Out here in the desert I couldn't drive in traffic last summer with AC on without the temp needle crowding the red zone. A new (OEM style) radiator (yes, with new 'stat and hoses) took care of that. The needle is steady even at 115 F ambient, driving up to 9000' in Flafstaff or cruising at 85 mph on I-10 down to Tucson. A new rad isn't all that expensive... $165 or so.

are you sure it's REALLY getting hot? the 86-up temp gauges have a bad rep for being inaccurate.

did you give the head to a machine shop to see if it was flat and not cracked? sounds like a cracked head to me. good luck, chuck.

I doubt that you have a problem with the head or cooling system that will respond to any of the normal efforts to correct the problem. I also do not agree with Porkface (with all due respect) in that if you had a bad head there would be other symptoms.

My opinon based on experience with my daughters 88 240 is that that the cooling system just does not have sufficient capacity under extreme heat loads as you described to do the job. I did the thermostat thing, flush thing etc etc, no good result. Her problem was a gradual rise of the guage while stopped at a long light or in slow traffic during hot weather (90F plus) with AC on. I trained her to turn off the AC and flip on the heater to avoid severe overheating and possible damage when this happened.

Final solution was to install an electric fan in front of the rad controlled by a relay and dash switch. She just flips it on when she sees the heat going up and guage soon drops towards normal.

Fortunately she is observant and quite trainable even though she is under 25 yrs of age. What a girl she is!
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David Hunter