[OFB Cafe] Engine overheating

[Peter Hollings]

Rick --

I had those symptoms once. The problem was that one of the cylinders had 
much lower compression. At idle that cylinder wasn't doing any effective 
work and was a load on the others.  Other symptoms were a rough idle and 
high (unburned) hydrocarbons on an emissions test. I got rid of the car. 
(I had bought it used. The prior owner must have had a low oil or 
overheating event.)

Peter Hollings

Rick Bowers wrote:
> Hi all,
>
> Here is a "technical" question for the Cafe, even though it's not the 
> Truck Stop Cafe. ;-)
>
> For the past several months, more frequently now that the weather is 
> hot, the engine in my Durango has been overheating.
> It actually started last year, then stopped in the fall as the 
> temperatures dropped. It hasn't overheated again until the weather 
> recently got hot. Even when stopped at lights for extended periods.
>
> Here are the symptoms:
>
> - I can drive at highway speeds all day and the temperature stays normal
> - If I get off the highway, or slow down due to heavy traffic, the 
> temperature soars.
> - If I get back above about 40 - 50mph, it cools back down.
>
> Here is an example. I drive home from Cape Cod, about 90 miles. The 
> engine is running at normal temperature.
> I get off at my exit and drive about 1.5 miles on 30 mph roads with a 
> few stop lights.
> When I arrive home, the temperature gauge is pegged in the red, the 
> radiator is bubbling, and the overflow is dumping anti-freeze.
>
> When things cool down, I check the radiator levels. It's full.
> This weekend I flushed everything as best as I could and put in new 
> antifreeze. When I drained it, the initial drainage was almost black 
> and as thick as oil. Ughh. But that was just in the bottom because 
> shortly after it turned liquid and just brown. It did need a change.
>
> After the flush and fill -- same problem. It still overheats at slow 
> speeds/stopped.
>
> During the flushing, I put the water hose into the return (water pump 
> to radiator) hose and pushed water back through the water 
> pump,  through the block and out the radiator drain.
> I ran it until the water was clear. I also ran the motor to heat it 
> enough to (I think) open the thermostat first.
>
> I don't suspect the thermostat -- it runs normal at highway speeds.
> I do suspect the fan clutch. During my flush/fill session, it 
> appeared the fan was turning slowly, so I used a piece of 2x4 and was 
> able to stop it. I could hold it still with my hands while the engine 
> was idling with little resistance. The fan clutch was replaced about 
> 2 years ago by an unscrupulous mechanic, It may be defective. But the 
> local CAP auto parts guy says "no" (even though he could have sold me 
> a new one for about $125).
>
> Any ideas? 
>
>
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