Overheating Volvo DL--how to pinpoint/fix the problem

Hi,

My 1980 240 DL has been overheating (boiling radiator). This happens after a few miles of driving (10 miles) even on flat freeway in not very hot weather.

The fan runs fine, and I can feel it pushing hot air backwards (testing this only when standing still, of course). So I guess it's not the fan clutch.

For further testing, I have disabled the thermostat, meaning that I have clipped out the valve completely so that now the thermostat is always completely open (there is just a hole where the valve was (since I've clipped out the valve).

Still overheating!

So I guess the next things to test are:

1. Is the radiator completely blockec?

1. Is the water pump defective?

Any suggestions for simple tests for those? I'd also be happy for any other suggestions for how to go about solving this problem.

Thanks, Wolfgang, Santa Barbara, CA

Does the temperatur gauge show to high temperatur or do you only see air bubbles in the expansion tank? Is the fan belt tensioned enough?

Niels

The gauge shows high temperature above red, and the radiator water starts boiling over.

Haven't checked the fan belt, but since the fan moves fast and I feel hot air being pushed backward, I suspect that fan belt isn't the problem.

Thanks.

Wolfgang

"Niels Bengaard" wrote:

Check the compression of all cillinders. May be your head gasket.

Pieter

I don't see any bubbles in the coolant. If I drive fairly slowly in cool conditions, like early morning, I can go 10 miles without overheating (though high temperature), but no bubbles in coolant reservoir. So can how can the head gasket be the problem?

Wolfgang

Sounds like a shot radiator to me. Thankfully, a good metal

Check the center of the radiator (carefully) to see if it's hot (or as hot as the upper hose). If it's significantly cooler, that will narrow it down to a water flow problem--three prime suspects are a water pump problem (loose pulley, broken vanes, jammed, slipping belt), a clogged radiator, or a collapsing hose (lower is the prime suspect).

Gary

There have been other suggestions, but ...

What coolant have you been using ? Topping up with hard water will cause scale build-up, which wrecks heat exchange properties. The block and radiator may need a de-scale.

I had the same problem on my 87 240 DL with 196 k & removed the radiator to replace it but noticed the road grime, so laid it flat & sprayed something like "Greased lightning" all over the vanes from side to side & top to bottom, front and back,, actually, any strong cleaner will work, but I let it soak in till it was almost dry, then shot it with the garden hose. I was amazed at what came out. So, I did the whole thing again & got almost as much. I might add that it worked better by spraying the hose from the engine side out. After 3 or 4 times, I was satisfied so I put it back in & topped it off with new antifreeze & haven't had a problem to this day. This will definitely help your cooling system, regardless. I hope you get this in time to try it before you wind up spending unnecessary $$ & time on it or creating more problems. Try it,, you'll be amazed. Oh,, and put a new "fail safe" thermostat back in it. It needs it to run properly. Good Luck Richard