Hello,

I am assuming you have the original style of radiator/expansion tank where the radiator cap is just a fill cap and the pressure cap is on the plastic expansion tank.

We have seen leaks from the radiator filler cap neck and leaks from the upper radiator neck that can cause the rim of the upper radiator tank to collect coolant.

To do a proper test, you will need a pressure tester with a pressure gauge.

You might be able to rent one from Autozone or some other car/truck parts chain.

Make sure the pressure tester comes with rubber spacer ring which you may need to properly test your cooling system.

The rubber ring is used as a spacer for the pressure tester where it attaches at the expansion tank.

Although you may not need the rubber spacer if the expansion tank is the later version.

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Eric
Hi Performance Automotive Service (formerly OVO or Old Volvos Only)
Torrance, CA 90502