V70 Coolant Problem - help needed please

[Adriansewell]

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.

[jgjones095]

does the pressure cap on the coolant work?

[RM955I]

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

[Adriansewell]

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.

[RM955I]

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+pressure+cap&hl=en&source=lnms&tbm=isch&sa=X&ei=PBhWUaK5F-fA0QW7roHIBA&ved=0CAcQ_AUoAQ&biw=1525&bih=692#hl=en&tbm=isch&sa=1&q=v70+coolant+reservoir+and+cap&oq=v70+coolant+reservoir+and+cap&gs_l=img.3...41944.51611.0.52399.26.26.0.0.0.0.150 .2262.20j6.26.0...0.0...1c.1.7.img.ldKtWHGDPJo&bav=on.2,or.r_qf.&bvm=bv.44442042,d.d2k&fp=e378918c9e059f96&biw=1525&bih=692&imgrc=Df2nSXTr3GADPM%3A%3BTo6wiECD5OpbbM%3Bhttp%25 3A%252F%252Fi.ebayimg.com%252Ft%252F1998-Volvo-V70-Coolant-reservoir-tank-with-cap-and-sensor-%252F00%252Fs%252FMTYwMFgxMTk1%252F%2524%28KGrHqF% 252C!o8FC1324CWeBQ-L362%29Ig~~60_35.JPG%3Bhttp%253A%252F%252Fcgi.ebay .com%252Febaymotors%252F1998-Volvo-V70-Coolant-reservoir-tank-cap-and-sensor-%252F170976391101%253Fpt%253DMotors_Car_Truck_Part s_Accessories%2526hash%253Ditem27cefcafbd%3B224%3B 300

[Adriansewell]

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

[RM955I]

Good luck with it - let us know

[GrahamBrown1]

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

[kicku]

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.

[RM955I]

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

[Adriansewell]

hi, thanks for the replies. I bought a genuine pressure cap a few days ago. I slowly removed the old cap when the engine was warmish and the coolant level rose to slightly above the max line. I fitted the new cap. I checked the coolant level this evening (2days after fiting new cap) and the level was halfway between max and min. The engine was cold and the level rose slightly when loosening the new cap. So, it appears the problem still exists...any other ideas? I do no like the sound of micro cracks in the block! any furher help appreciated. cheers.

[Georgeandkira]

Hello, I'm not sure what a sniff test is. The thing I would expect done, in part because it's so easy to do, is a compression check. Remove the spark plugs. Screw in the compression gauge into cylinder #1 and crank the engine so the needle pulses 3 or 4 times. Do each cylinder the same number of pulses. Kira

[ShadeTek]

A sniff test test checks for any combustion chemicals from the chambers, which has leaked into the coolant. If the test is positive, then it can be the head gasket or cylinder block.

[Georgeandkira]

Hello, Thanks for the education, seriously. I had never heard of the "sniff test". To Adriansewell: You should do a compression check anyway. It's soooooo easy and cheap to do. Kira

[kicku]

If leaking water only, you will not find high pressure when remove the cap at COLD engine. High pressure means when remove the cap and water will rise more then 2-3 cm in the expansion tank. If this happens mostly you have an internal leak (head gasket hope). If this is not happening but the water continous vanishing without pressure in the tank (when at cold engine removing the cap) mostly you will have leaks on hoses or so.

[JXBURNS]

I had a similar problem but coolant dropped over 2-3 weeks; not days. When I took to garage they found, after several days, that the intercooler had moved back somehow and had been rubbing against the radiator resulting in a pin hole which was definitely not obvious. It was only when the pressure tested the system did they find the answer.

And the cause? I remembered accidentally hitting the front of the car at very low speed on a high step outside a house when getting out of a tight spot some 2 months earlier. Upon inspection the plastic grille under the numberplate was cracked. This had been pushed back into the air con condenser which in turn pushed into the intercooler and then into radiator. £500 quid worth of damage later...

Not saying this is the reason here but took ages to work out what it was.

John

[BarryCambs]

I had exactly the same symptoms and it turned out to be the head gasket. However, it did show up with a sniff test, which you have already had done. I don't know how sensitive they are, as it took a while to get a positive reading from mine. I'm not sure what else could cause the system to be pressurised, which it clearly is.

[Adriansewell]

thanks for all the replies. funnily enough John, our car also has a cracked grille under the number plate which was as we bouight the car so it could well be in the radiator...but I do not want to change the rad and still be left with the same problem.

so would a compression test show up a blown head gasket or, even worse, cracks in the block? i.e. what is the best way of determining a blown head gasket before looking at other things like replacing the rad?

cheers all.

[kicku]

thanks for all the replies. funnily enough John, our car also has a cracked grille under the number plate which was as we bouight the car so it could well be in the radiator...but I do not want to change the rad and still be left with the same problem.

so would a compression test show up a blown head gasket or, even worse, cracks in the block? i.e. what is the best way of determining a blown head gasket before looking at other things like replacing the rad?

cheers all.

Compression test will not let you see nothing until the leak is very big. Maybe remake the sniff test it's a good idea.

[Georgeandkira]

Hello, Having to do any diagnostic test a second time with a second tool or even a second technician wouldn't be a first. Yes, a compression test has a crude side. That's why you do them on the engine cold, then hot. If piston seal is in question, the test is done cold then with oil shot into the cylinder. In this case a leak down test with compressed air might be in order. The hose blowing off turns me away from a radiator with a hole. Is there any visible "frostiness" (evidence of coolant residue) on the lower reaches of anything? Kira

[makouvlei]

Hi Adrian, ever found the problem? Jannie

[Darcy]

I've had the same. Coolant level drops but returns when pressure released from expansion bottle. I spent time bleeding the coolant system of air. Warm engine with coolant cap off. Coolant begins to rise in bottle as it heats, to the point of overflowing. Switch cabin heater on full and level goes back down again. Squeezing top and bottom hoses while watching air splutter out of the small return hose from top of radiator. Did this for a while (15 Mins maybe). Now no residual pressure and coolant level more stable. Hope this helps.