Brehon47
The discolouration and deposit on the inside has defied all attempts to remove it. Suggestions welcome. Tiny
pauljloz
New tank - given age and risk if / when it fails? Agressive cleaning may accelerate degredation of the plastic.
jlfents
Use soapy water and a little bit of sand (or something similar). Shake it around a bunch and flush out when finished.
ramrod
Replace it with a new tank
Brehon47
Cheeky bloke aren't you Ramrod
Brehon47
Thanks Jeremy - I did something similar but it was not successful. Very tencious film of unknown composition but common to older vehicles. There will be some homespun wizard with the knowledge I reckon.
I could strap the tank down and hit is with an high pressure water jet but the tank may be brittle - or end up next door! Tiny
ramrod
You're wasting your time. Look at the inlet where the hose connects. There is a steel sleeve fitting, which when heat and age take its toll the sleeve starts corroding, then it swells, cracks the plastic and guess what, coolant leak. It's not worth worrying about when a new one is $50 or so
Brehon47
Thanks ramrod - I saw the capillary tube -i it's not corroded nor is the tank leading. I just want to clean it inside so I can accurately check the level of coolant at a glance. Tiny
Philia_Bear
The plastic itself gets chemically altered
Depending on age this can actually be through the entirety of the plastic
Sanding might work...
lasercowboy
Yeah it's mostly from corrosion inhibitors or corrosion products permeating into the plastic itself.
You can leach some of them out with a bit of acid (kettle cleaner works well, or vinegar works slowly) but you're fighting a losing battle, and the thing will eventually get too brittle to bother with.
Brehon47
Thanks Gents - it comes down to putting a value on the time that would have to be spent cleaning without any certainty it will work out - compared to how long it takes to make the cost of a new one. Who is the best source of a new one? Tiny
DCW242
I've been able to get them looking pretty good by filling them with fine sharp gravel and cleaning vinegar, blanking off all the ports and shaking it. It looks better but they will never look like new.
850 ones probably aren't worth doing that to though, they are known to fail and easy to buy new.
FCP stocks aftermarket and genuine ones.
https://www.fcpeuro.com/products/volvo-engine-coolant-recovery-tank-850-c70-s70-v70-9141095my#reviews
https://www.fcpeuro.com/products/volvo-expansion-tank-850-c70-s70-v70-1
Brehon47
OK Thanks Duncan - I'll proceed to purchase. Tiny
Brehon47
Gents - I was replying to Philia_Bear and Tim - got through most of what I wanted to write when my PC shutdown (twice). I have lost your comments but recall:
The Bear - thanks - the gears lockup and the vehicle has to be restarted Or sometimes it idles and the gearbox is still inoperable. return to start procedure from scratch and it works.
Tim - it's a 5spd non turbo - and I'll buy a new tank for my 850.... aftter22 years it has earnt one! Tiny
Ex850R
I think I have a new or near new one fella!
@Brehon47
jamesinc
Pretty sure you can put them in an ultrasonic bath to clean them
Ex850R
Phosphoric Acid.
ramrod
That may eat the plastic.
Adrian if you're keeping the car, anything other than buying a new tank is false economy. You're extending it's life expectancy by putting a new tank on it. Cooling system failure is the death of these cars
jlfents
From what you guys are saying it sounds like the 850 tanks use a crappy plastic. Either way I don't see what the big deal is - its just a plastic tank. If it holds liquid it still has life in it. When it gives in clean up the mess and replace it.
1/4 tank of sand/gravel should do the trick in regards to deposits- heck you may even have to violently shake it a whole bunch for the stubborn pieces. You won't get discolouration out unless if you use something that chemically eats plastic to reveal a new clean surface.
Brehon47
Thanks Gents (Jeremy, Snoopy, James, Rico, Blacktown Bear, Duncan, Pauljloz & Ramrod ors
I was hoping to find a solvent and will purchase Snoopy's suggestion for any relevant future task. It would have been a bit quicker to have cleaned my present tank but the scale/deposit must be etched into the plastic as it has resisted all methods so far,..maybe a shade lighter but not enough to sight the level of coolant.
Onwards and upwards - thanks to all of you for assisting so generously - and wisely. Tiny