My expansion tank was leaking. Someone said it is caused by high pressure from the head gasket getting bad. What I think is that fatigue from each cold and hot cycle on the tank caused the leak. Has any body experienced that before?

 

Put enough miles on any car and they will eventually break. Heat and pressure on a plastic component over time.

 

That is correct mkc70, but i am afraid of a bad head gasket as my car has 100k miles (160.000 kilometers) and was wondering if too early for the damage on the tank. What is the expected pressure during normal operation inside the tank? I can add a pressure gauge to see if the pressure is going too high.
What is the pressure relief valve in the cap set at?

 

I have already replaced my coolant reservoir. Car has 101k miles and it was partially cracked at 70k when I bought it. Saying that your head gasket is bad because an old plastic part is cracked really is not convincing enough evidence at least to me. Just replaced one on my Taurus as well, head gasket is fine on both. Good luck.

 

My 98 V70XC AWD; w/163000 miles, expansion tank has had a slow leak for a year. Just finished doing an A/C Evap and Heater core change and ordered a new expansion tank too. The old one was leaking at the base of the lower hose bib. It had a small hair line crack in the tube. It is just the age of the hard plastic tank. I did order the Volvo tank from eEuroparts. To many others have said the aftermarket ones don't last as long. End result, you will spend the same for a one genuine Volvo tank as you would for two aftermarket ones. Couple of other things, you can use old level sensor in the new tank and I would get a new cap.