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FIXING A VOLVO RADIATOR SENSOR PLUG LEAK
By Rick Fletcher
NOT to be reproduced or copied without the express permission of the TR Register Australia Inc.
If you carry out the Volvo Radiator modification using a second-hand radiator with plastic side tanks, there is a chance that the temperature sender unit may leak. This is located in the top of the driver's side plastic tank as shown below.
The sender unit, when not fitted, has a blanking plug to fill the hole. There is a rubber grommet which fits here to seal the blanking plug and it softens with age. The correct Volvo spare part for this no. 1378869 ("Rubber Bushing" - I paid only $2.75 for one of these from Manning Valley Motors at Taree).
Unfortunately, when it failed at Mungo Brush, I had no spare and needed to improvise. The repair below works fine for a temporary seal of the 3/4" hole.

The plastic
blanking plug
back in place.

None of this is required
if you use the brass
tank radiator.

 

These bits came from my spare parts odds & ends that I carry. The hose is about 1/2" ID (might have been ex. brake booster?) and the bolt is 2" x 3/8".
This is it assembled. Push about 1/2" of the left hand end into the hole and tighten the nut on the engine compartment side. (I did it back-to-front with the potential disaster of losing the nut inside the radiator when removing it)
The head of the bolt pulls in to the tube ...
... gradually expanding it. You need to hold it such that the expanded bit fills the hole in the plastic tank.

There is no need to make it too tight, just so that it is firm. I used a LITTLE bit of silastic around the bolt head but I don't think it was necessary. The water pressure wedges the repair in tightly and it got me home from Taree to the Central Coast without losing a drop of water.

When you fit the correct rubber bushing, the plastic blanking plug is a "push" fit into it. Actually it is a "b###" tight fit.
I ended up lubricating it with a tiny little bit of teflon grease. There is NO taper or lip on the plug - yet it seals!

PS - thanks to Brian Richards, Bob Slender & John Muddle who issued soothing advice and replacement water during this exercise.