Firstly, love this site, very informative. My problem ( 94' 850 / Auto with ordinary 10 valve): Radiator had a split under the top rad hose. Changed it out (wrecker swore that a V70 is exactly the same, not the case as the tranny connections are different - 850 clip over and V70 click inside).
In any case found correct radiator - recoed unit. Refilled with coolant (with the Glycol as recommended) but not anti-freeze / anti-boil.
Anyway, topped up expansion tank, brought it to Temp. let it sit 10 minutes and topped up to MAX again.
Went onto the freeway... Temp. went up to 1mm under the boil, and then it went back down to 1/2 again... stopped, waited 10 minutes, took off cap, started car... and slowly added more coolant.
Drove further and same result again. Bought more coolant, topped up again, same again.
Stopped at destination for 2 1/2 hours, topped system again and drove home about 80 km's over some hills (500 metres high) no problem... next mrning it needed about 400mls to top up.
Drove the car about 50km's and needed the same to top up again! I did notice some hissing from the Rad. Cap when I turned off the car...
No mayonaise in the engine or oil in the coolant, no drips under the car when stopped. The cap is black rated to 75Kg. Thermostat rating unknown.
Replace these or just see if the coolant levels sort themselves out with air in the system?
Any thoughts or similar experiences to share would be much appreciated.
Thanks in advance from 'down under'.

 

My thoughts are to alway figure out how much coolant the system holds. Then count on adding that much coolant to the sytem before you are sure you have added enough. If you have a lot of air in the system it can act irratic. So, if your system holds 2 gallons, (not sure what that is in metric measurements), count on adding that much. Once you have added that amount and it still appears to be loosing fluid, it has to be leaking somewhere. If you can't find an external leak, you may want to do an oil change just to be 100% sure you are not leaking into the motor. Usually if it is leaking into the motor it will smoke like crazy out of the tail pipe.

I'm not a pro so check back here in the event that someone else comes in behind me with better information.

 

I would replace the thermostat if you have not done it already.
Also if you hear hissing the cap may not be working properly.

 

Hi RSPI,
Thanks for the input. My Haynes says 7.2 Litres. I have about 15 in now. I did stuff up by opening the cap after a 'run' and it did bubble out under pressure, so it could have been me, but 15 litres seems a lot.
The crackling of the cap is the only way I can think that the coolant is venting. Maybe, I should drain the coolant and replace it with an Anti-Freeze / Anti-Boil. The coolant was rated as a 60 and manufacturer recommmended their 90 or 100 for higher temperature ratings.
Luckily it is fairly cool here at the moment (winter). Oh, my heater has always been disconnected as well since when I bought her. She has 310k. Will probably give her a compression test tomorrow, 1 cold then 1 hot to check and compare the values.
Got some platinum plugs to put in in any case.
Funny too, my engine light (triangle with sideways T) is on after my Rad. swap. Checked all connectors and are good. light wasn't on prior to swap over.
Im stumped. Motor runs smooth...

 

I'm thinking exactly that thanks Tech. Really it makes sense. After that...coolant blowing past the pistons??? There should be a $(*$load of steam coming from the exhaust eh! Especially in our cool weather.
Grrr this makes me think too much.

 

Start by checking the thermostat. The thermostat might be broke(Common issue)
Also if it had been run low on coolant the light might be on for the coolant temp sensor code. If it is run really low on coolant that will set the light.

 

Check that Tech. Will change both. I know they have a Thermostat in stock, hopefully a cap as well. What do you think about a higher grade anti-Freeze Anti-Boil? A bit of hype?
How do I reset the code? Just get a readout, does it then reset? Go Webber (sorry watching F1) Thanks in advance.

 

I think the coolant is a hype. Just use what you already have.
You should be able to read and clear the codes yourself.
See link to learn how to read and clear the codes.

http://www.troublecodes.net/Volvo/

 

Great Site. Thanks for your help, very much appreciated.
Hoffa

 

Your welcome anytime!