V70 D5 Coolant Problem
 

Hi
I have a V70 D5 and I do long commutes every week. Everything has been fine but recently my coolant warning indicator has come on saying low coolant.
I have changed the cap and two garages have done pressure tests and flush outs and can find no problems and are saying I might need to wait till the problem gets worse. There is no indication of any coolant loss, or of a head gasket problem and no apparent overheating (I assume a light might come on or be other indications).
Sometimes the light comes on and then goes off whilst I'm on a long commute (180 miles). Sometimes it's still on when I reach my destination.
When that happens I wait for the car to cool and then the reservoir is showing below minimum. When I unscrew the reservoir cap the coolant level rises back to where it should be just below maximum.
Someone has suggested that the coolant pipes are spongy but then the pressure tests show no issues.
Does anyone know why this would start happening? The car is 4.5 years old and this started about 6 months ago.
V70 D5 2012

This is not uncommon - I had vey slight coolant loss: couldn't trace any leaks at all until I noticed a very light drip on the drive. As predicted by Clan, there was a very slight weep from the bottom left hand corner of the radiator (the right can also have the same problem).

For the very small amount of coolant loss, I couldn't be bothered removing everything to fix/inspect it so chucked some K-seal in it......so far, so good

I assume you are losing coolant? You don't specifically mention needing to top-up???

Water expanding when you undo the cap....perfectly normal. The system is pressurised.

Spongy hoses...of course they're spongy: they're just reinforced hose. Are you expecting them to be solid?

Hi
I'm not losing any coolant at all. I wouldn't have thought it was normal for this to happen. I had the car serviced yesterday and drove it home - about 1.5 miles. I then drove about 2 miles today and the light came back on. I let the car cool and it was still on. The water level had fallen down to about 1 cm below minimum. I unscrewed the expansion tank cap and the water level,rose back above the maximum level.
I have noticed some metallic sunstance around the rim - one of the garages said they thought that some radiator leak sealant had been added although I've had the car for 4 years and it's only just appeared.
I'm not losing any water at all but it's not as blue looking as it used to be - could it be a pump problem? Garage folk didn't think so as its not overheating.
Thanks

Are you sure it's full to just below max? The level indicator can be a bit hard to see.

If it was me I'd ever so slightly overfill it, try and "burp it" by kneading the hoses and see what happens.

After that I'd be looking at the level sensor in the expansion tank as the most obvious cause, given that you're not losing coolant.

Hi
Yes - I checked the level just after the service yesterday and it has returned to that level.
I went out an hour ago after the car had cooled and the warning light was still on and the level was at least 1 cm below minimum.
After releasing the cap the level returned back to where it was after the service and the warning light went off.
It's not a faulty warning light as the water level is well below minimum. There's different pressure tests show ok and the two garages don't think it's a gasket.
Only one has said that the radiator hoses seem spongy - or more so that they have seen and that there's a bit of give in them.
Otherwise am I faced with an ongoing unscrewing of my radiator expansion tank - would be great if someone could shed some light.
I checked the forum and someone else has reported the problem but there was no solution posted - http://www.volvoforums.org.uk/archiv.../t-176770.html
Thanks

I was referring to the float switch/sensor, not the light.

What about the expansion tank pressure cap? Might be worth replacing for the relatively small cost as it needs to function correctly for pressure and vacuum. Sounds like yours may be working for pressure but not vacuum? ie when the water cools it's not returning to normal atmospheric pressure.

Hi
I replaced the cap a couple of months ago as the garage had spotted some white residue near the cap. They ten pressure tested and checked it and saw no problems.
After about a few days of driving the warning light came on again.
It's a shame as I really like the car and didn't think I'd get a problem like this that's not got a straightforward fix.
Thanks

Have you tried a coolant flush and putting in new fluid? Do that and make sure the system is properly bled of all air.

As tt82 says try flushing and refilling . The rising level you describe suggests that air is trapped somewhere in the system . Don't forget water cannot be compressed so the rising level when you open the tank can only be air expanding when the pressure is released causing the level to rise. When the engine is cool enough to open the cap try squeezing the hoses vigorously to push any trapped air out of the system (burping) .

Update
Waited till the car cooled yesterday and unscrewed the cap and the coolant level returned back to just at maximum and the warning indicator went off.
Drove over 100 miles on motorway and during that time no lights came on. When I stopped the fan came on for a few minutes but when I restarted the car to drive another 50 miles the Engine System Service Required light came on.
When I reached my destination I checked the oil level via the in car electronic sensor and it was saying it was one block above maximum - could this have caused the Engine System light?
It was just serviced on Saturday and the coolant system drained and pressure tested so will monitor to see if that problem returns.
Going to go for a drive after lunch to see if the Engine System warning light is still on.
Any further advice gratefully accepted.
Thanks