Hi all, we have a 1998 XC70 that is having an issue with an overflowing reservoir tank. When it gets warm with the cap off it will start flowing out of the tank at a high rate. I thought it might be the head gasket so rented the Combustion Leak Detector from O'Reilly's. Test came up negative. However, it wasn't possible to do it with the car hot because too much water was spewing out. Is this something to be worried about or normal?

 

That's why the cap is there...

 

Ha ha, ok. Of course I have it on when driving. I had it off for the test. On my Honda I can take the overflow cap off even when it's hot and water doesn't come out. That is why I was curious. Thanks.

 

The system is pressurized. The cap should hold 21PSI of pressure.