Strange coolant loss issue

[derbybiker]

09 XC90 D5
Had a strange coolant loss recently.
Now I'm a regular checker or tyre pressure, oil, coolant etc so I know its not a gradual leak.

Few weeks ago on my commute I got the red warning triangle and low coolant message. Was a few hundred yards from work so parked up and checked the tank and sure enough the level was down towards the bottom of the tank. Topped up and commute home (26 miles) stopped a couple of times to check the level and all good.

It stayed at that level for a couple of weeks and then I got the message again. Similar level in tank. Again topped up and was good again for a couple of weeks. Have been regularly checking the level so hence I know its not a slow leak.

So that's three times I've had a sudden loss of coolant.
Checked the engine bay when its been running at normal temperature and no signs of a leak.

Anybody got any idea's whats going on?

[The Ridge Rider]

I had a similer thing happen to my Jeep Cherokee, coolant loss was small, pressure test was ok so was the sniff test, no signs of exterior leaks, eventualy had to have the head off, turned out that there was a small crack near exhaust valve, so coolant was going down exhaust manifold, which is a bit hot causing coolant to turn to steam and out it went via exhaust pipe, only cost me just over three grand to get it fixed.

[xco]

Originally Posted by derbybiker

09 XC90 D5
Had a strange coolant loss recently.
Now I'm a regular checker or tyre pressure, oil, coolant etc so I know its not a gradual leak.

Few weeks ago on my commute I got the red warning triangle and low coolant message. Was a few hundred yards from work so parked up and checked the tank and sure enough the level was down towards the bottom of the tank. Topped up and commute home (26 miles) stopped a couple of times to check the level and all good.

It stayed at that level for a couple of weeks and then I got the message again. Similar level in tank. Again topped up and was good again for a couple of weeks. Have been regularly checking the level so hence I know its not a slow leak.

So that's three times I've had a sudden loss of coolant.
Checked the engine bay when its been running at normal temperature and no signs of a leak.

Anybody got any idea's whats going on?

I had a leak similar to this many years ago on a sierra sapphire with a 1600 pinto engine.

it would lose coolant on a run but when you stopped to check everything you could not find a leak anywhere.

To cut a long story short it was the hose from the expansion bottle had worn under the clip that holds it to the bottle (the squeeze together with pliers type wire clip... not a jubilee type clip) but would not leak until the engine caused flow under pressure.

A relatively cheap fix but a bugger to find. Worth a look maybe??

Hope this helps.

[cheshired5]

OP, look here.

[derbybiker]

Originally Posted by cheshired5

OP, look here.

Thanks for the link, I'll use that as a start.

[derbybiker]

Just to bring closure to this thread.

The leak was from the thermostat housing, specifically the gasket in the middle of it.

Just happened to be lucky one night when I got home and checked under the bonnet and saw the leak. Still don't understand why it was an intermittent leak though.

[xco]

Glad you found it in the end