V70 Coolant Problem - help needed please
 

Hi,

We have a 2004 V70 2.5T. I can see no leaks in the coolant system, but from the max level mark, the coolant level drops say over 3-4 days to below the min level and the coolant light comes on. The temp gauge is bang in the middle all the time so no probs there. The top left rad hose (when looking into engine bay from front) has blown off twice now. The coolant level does not rise back up when the engine cools down, but does rise back when the expansion tank cap is undone to release the pressure from the system. When I do this, I can hear something located below and right of the engine (again when looking into engine bay from front of car) 'relaxing' when the pressure is released. Our local garage have done a sniff test etc for suspected blown head gasket but found nothing. On idle, there are no bubbles in the expansion tank. The heater did fail to heat just before the top hose blew off last time a few weeks ago but after filling coolant system back up, the heater seems fine again.

Any help/advice re coolant system problem would be really appreciated to get this sorted.

cheers.

does the pressure cap on the coolant work?

Same thought here....faulty pressure cap on reservoir?

Hi, thanks for such promp replies. sorry for sounding dumb, but how would I know if the pressure cap is working or not? it appears to be a sealed unit so if there is a pressure relief valve inside, I can't see or test it. Thanks again.

The green (?) pressure cap on top of the translucent white expansion tank. Don't know if there's a way to test them - for the relatively small outlay it's just a question of replacing them

http://www.google.co.uk/search?q=v70...bd%3B224%3B300

cool thanks. will do and see what happens! thanks v much.

Good luck with it - let us know

check to see if your cap as warped slightly i had a similar issue no hoses blowing off but mysterious coolant level replaced cap and no issues since

If the sniff test were negative does not mean that you are ok.
This mean head with micro cracks or worse main block cracks.
The only way of creating pressure into expansion tank is cracks into head / gasket / main block. Or boiling water but you said the temp gauge is ok.
You'll never see bubbles in the water tank because the cracks are very little. If the cracks were bigger you will see bubbles into water tank, white smoke, difficulty to mantain 800rpm at minimal revs and water vanishing in minutes.

Sorry for my poor english.

If the pressure cap is faulty it will allow the coolant to boil at a lower temperature than pressurised water: water/coolant under pressure has a much higher boiling point - that's why you should never remove the cap when the engine is hot. The sudden drop in pressure will cause the water to boil spraying you with boiling coolant