V70 Expansion tank coolant problem

[olsusana]

My 1999 V70 Turbo Wagon has 156,000 Mi. The low coolant light came on so I fillled the expansion tank to max level. I started looking for leaks and found it would leak coolant after shutdown thru the expansion tank cap. It doesn't overheat. Runs fine. Tried a different cap, same problem. There appears to be bubbles in the coolant as it fills the expansion tank. Any suggestions?

[jimmy57]

This could be as simple as a faulty pressure cap.

If the cap is cracked then replace it with no further examination. If it is not visibly cracked then the cooling system needs to be pressurized to 16-17 PSI and see if the cap holds the pressure or the cap tested on a pressure cap tester. Some parts stores can test pressure caps but the likelihood of them having the adapter to allow testing of European cap designs is slim.
If the cap holds pressure then the electric cooling fan needs to be checked. The radiator cooling fan will run soon after A/C is turned on and is cooling. If a/c is not turned on the the engine will run for as long as 15 minutes before the fan starts and runs for a time, cools the coolant down enough that the engine control module (ECM) senses the temp is low enough by reading engine coolant temp sensor and turns the fan off.
The temperature the ECM allows before it runs fan is high enough to allow coolant to boil out if the pressure cap doesn't hold pressure to make the boiling temp go up several degrees.

[olsusana]

Thanks for the time!

[cn90]

My reservoir cracked at 14y/120K miles.

Best is to replace BOTH the cap (which you already did) and the reservoir, which is $45 at dealer.
Stick to Volvo OEM part.

[xHeart]

I would idle the car in P , and without the reservoir cap, i.e cap OFF.
Once the temp needle reaches 3 0'clock, engine idling check the coolant level, it may take up to an hour of idling, and several thermostat cycle for the coolant to stabilize. The stable level is above MIN, below the middle of MAX - MIN.

[difflock54]

Bubbles means air somewhere in the coolant system.
Does the V70 have an air release bleed screw fitted on the lower radiator hose as the V40's do.
Was your heater on full when you topped up the system.
Wise especially if the coolant was very low when the warning light showed.

[rspi]

Fill it cold, drive it for 5 minutes and check to see if it is trying to overflow in the expansion tank. If so, you likely have a bad head gasket.

When we got our S70 it had a new head. I didn't know that. Whomever put it back on didn't do a perfect job and it slowly started leaking until it was loosing about 8 ounces per week. Then my daughter ran it out of coolant and overheated the motor a little. Still ran well just kept loosing coolant. I finally pulled the head and fixed it.

http://www.atthetipwebs.com/technologyi ... gasket.htm

[erikv11]

Bubbles means air somewhere in the coolant system.
Does the V70 have an air release bleed screw fitted on the lower radiator hose as the V40's do.
Was your heater on full when you topped up the system.
Wise especially if the coolant was very low when the warning light showed.

On an 850 or x70, it doesn't matter whether the heater is on or off. The coolant always circulates through the core. Always. So there is no need to think about turning the heater on or off. No on the bleed screw, there isn't one. Air just burps into the expansion tank.

I like jimmy57's reply and (unfortunately) rspi's, in that order. A simple inspection will probably tell you if the tank and the cap are good. You've already changed caps, so likely that is not the issue.

The next step is to get a tester kit to see if there are combustion gases in the coolant. If there are any at all, then the head gasket is bad.

[olsusana]

Thanks everyone, will post what is determined.

[olsusana]

Turns out is was the cap. The tank was replaced in 08' with the original cap. The cap we tried yesterday was also bad. No gasses were found in the coolant. $33, LOL. Thanks everyone, olsusana.