XC70 mystery coolant issue
 

Hi
first post.

2007 Volvo XC70 - 5Cyl turbo model. Actually has really given us no issues - great car! until now...

Anyway my wife was driving and all of a sudden the coolant light comes on. She popped by our trusty mechanic who topped it up but did advise there would likely be a leak somewhere given it was basically empty. He was too busy so we booked it in at his next availability (2 weeks).

Since then we checked it every day. EVERY Day! No change...still full, no issues what so ever and there was some pretty significant driving done. She drove to the coast and back twice that week...a good 400kms.
Come the day of our appointment with the mech it was still full so of course we decide to cancel.../postpone!
the very next day - completely empty, like bone dry! Warning lights etc as she is driving.
Any idea what it could be?
The mechanic is diagnosing now - he is hoping it is a water pump issue and not a gasket issue but i thought i'd come here as well to see whether anyone had seen anything like this before?
Thanks
Gus

most common places to look are coolant reservoir and radiator tank - look for crustys on either of these

Do you have any coolant in oil or transmission fluid? If you don't have any exterior leaks, then my experience has taught me that it's internal. If you can't locate a leak and the fluids are without coolant, you have coolant going out the tail pipe. Normally happens at night with the pressure build up looking for a place to go. If you like the car and are not ready to have the head removed, what I did was buy a quart bottle of blue devil for coolant systems. Follow directions, it works but is not a permanent repair. Neither is life.

thanks so much guys. catching up with mechanic tonight so will update the thread. there is def no pressure issues...some very minor signs of coolant near to water pump but not clear if that is the issue....we'll see! might look into blue devil in the short term

Another way of checking for pressure in the coolant system and there should be pressure, not much but some. Is to, in the morning or anytime after car has been sitting for several hours, is to open the cap. There should be a small release of pressure. If it doesn't come out here, then it's going somewhere. The leak in my head gasket was sporadic, as is yours.

So mechanic did all the tests. And I mean all of them. Had it in there a couple of days.

what we know is the coolant system has full pressure. Also there was no trace of coolant in the oil or transmission etc

what we don't know is when and where it is leaking. He had it running and tested all sorts of scenarios but couldn't get it to leak again.

its a 2007 - 10 yrs old - is starting to think it might be time to trade. 😞

so problem solved

had a leaky coolant container (very minor split at the bottom that couldn't be seen unless removed) and a faulty thermostat.

The faulty thermostat was the root cause - when it didn't work (which was intermittent) the coolant would heat up and the pressure would cause the release.

all fixed now though an no issues so far!!