Volvo: v70 XC, 2000, Coolant tank leaks from Lid, coolant tank, tank leaks

Question
QUESTION:   For a few months the coolant reservoir would require refilling with no signs of any leakage.  I do not have any type of link under the dash, yet the car never ran hot.  The temperature was always just below the half way point on the gauge.  I recently had a new tank and thermostat installed with what appeared to be the cure-all.  Now periodically the coolant reservoir gets pressurized and antifreeze / steam are forced through the top of the reservoir.  Of course this is a random event.  It occurred a couple weeks ago after a 3 hour trip.  I filled the tank and all was fine until yesterday afternoon.  The temperature gauge is still normal, but when I stop after a 15-20 minute drive the tanks leaks from the top.  

Any thoughts would be appreciated!

Thank you,

Tom

ANSWER: Tom,
So after running for 15/20 minutes it will blow coolant out of the tank. That tells me when the engine heats up you maybe pushing compression into the cooling system. That would mean a bad head gasket or warped, cracked head. Now are you sure that the tank itself is not cracked and just the hot coolant expands the crack and leaks? If you are not sure see a Volvo shop for some help.

---------- FOLLOW-UP ----------

QUESTION: Good points!  The shop that replaced the thermostat and tank ran a pressure test.  I would assume that would catch a gasket problem.  The tank appears to be free from cracks.  Could the cap be an issue.  I am sure it is designed to relieve pressure at some point in order to prevent major issues.

Again, the engine does not run hot.  My wife took the car on a 6  round hour trip on Tuesday with no issues.  I would think that a cracked block or bad gasket would eventually drain the radiator.  I appreciate your response and will take the car to another shop.

Have a great day!

Tom

Answer
Tom,
Ok it does not overheat, no leaks with a pressure test, but at times it blows coolant from the cap. Maybe a cap that is defective or will not seal on the bottle, unless there is a head gasket issue. Put a new cap on it and see how that works. If it overheats, try and remove the cap and preform the test to determind if there is compression getting into the cooling system. That is done one of two ways using a H/C C/O tester or there is a kit with a fluid that will turn color if exhasut is present.