Radiator plug problem

Dec 03, 2003 5 Replies
N
1988............740 Volvo Estate.


My son is away with the above car, he has had the plug for the temperature gauge for the electric fan pop out and cause the engine to over heat. The engine does not have an electric fan it is pulley driven so. The radiator has been temporarily repaired at the roadside by the roadside recovery service ( RAC ) in the U.K. How do I replace the plug that has popped out.


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B

I replaced a radiator on my (ex) 740 a couple of years ago and re fitted the temperature sensor with a new grommet and remember thinking "this thing could pop out". Not happy with just leaving it as it was, I made a two pronged clamp that conveniently bolted to some lugs moulded into the plastic top tank of the radiator. I didn't worry after that!

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M

Get a new seal (and plug if it was lost) and install like normal. The plug has a slotted top, position it so that you can wrap a long plastic tie through the slot and around the tank to hold it in.

Anybody else with this rad design, I'd suggest doing this before that plug (or temp sensor) pops out on you!

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N

What would cause the plug to go other than the plug itself. Could there be a fault in the rad or engine

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M

The plug is not the problem, the seal is. There's nothing but friction of the seal holding the plug in. The pressure inside the rad goes from

0 to 150 kPa (the pressure of the cap) and from freezing cold to above 100 degrees C, repeatedly over a period of years. The seal rubber gets harder, the coolant functions as a lubricant as it slowly creeps its way out. Then one day, Poof! and you have problems. If the cap is defective the pressure can get way higher, so it's a good idea to have the cap checked (or replace it) since you've had this problem.
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