I'm getting ready to replace the thermostat and the upper and lower radiator hoses on my b-21. Draining and flushing sound easy enough, but how do I refill the sysytem with coolant/water? Is it done with the new thermostat inplace or through the expansion tank, or...? I'm used to those radiator caps where you fill it up and wait for the thermostat to open to put in the remainder amount. I'm afraid of air pockets or too low a coolant level in my Volvo because I ruined a ford tempo (POS that it was) by not filling it correctly.

I've drained and filled enough B21/23/230 Volvo cooling systems to last a lifetime, but I'm still alive, and probably will be doing cooling system maint. for years to come. The draining and refilling instructions by others are generally good - I've never done anything but fill the buttoned-up system via the reservoir...never a problem.

As said, just orient the new 'stat so the little jiggle pin and hole in its outer edge is at the highest position. This will bleed any air left in the upper reaches of the head. Like you, my recent dealer purchase was also a Wahler - a more robust looking unit than the Calorstat that I removed.

On my biennial maint. I always buy and use that Prestone HD Rad flush. Just follow the instructions on the container. Afterward, fill and drain the system repeatedly until the drained stuff runs clear...not just the block drain, the lower rad hose, too. Then dump in 4 litres/qts of quality antifreeze and top up with distilled water - yes, distilled water. Let sit a few minutes and top up again if needed (unlikely).

After a good run and cooldown, test the concentration of the coolant by draining a cupful from the block drain. Depending on results, top up the reservoir with what's needed to adjust the conc'n. It will probably be 50/50.
--
Bob (son's 81-244GL B21F, dtr's 83-244DL B23F, 'my' 94-944 B230FD; plus grocery-getter Dodge minivan, hobbycar 77 MGB, and a few old motorcycles)

Thanks 'Dad

There are 2 drains. One by pulling the lower rad hose. The other, a drain cock, is on the passenger side of the block under cyl 4.

To fill, use the expansion tank and use distilled water (cheap enough).

Make sure when you install the thermostat that the little valve is at the top so that air can bleed out of the block.
--
1980 245 Canadian B21A with SU carb and M46 trans

Hello,

I always make it a point to fill the block and head before installing the new thermostat. With the thermostat removed, fill the head up completely (until overflowing). Then, reinstall the upper hose and fill the expansion tank. This is a fool-proff method (I have never had any air pockets in these engines). Run the engine until the thermostat opens, then add until full. Check it over the next few days (when cold) to make sure it didn't go down at all. Anyway, that's what I'd do...

I hope this helps,

Joe S. - Volvo Master Technician

1988 760 Turbo w/276k miles, 1981 242 Turbo w/243k miles

P.S. - I would make it a point to use an original Volvo thermostat (the are very accurate). Most aftermarket thermostats do not hold the temperature as steady as the original.

Thanks for the tips. I did get a volvo thermostat which has Wahler stamped on it OEM I guess.

I always fill it up through the expansion tank, pouring slowly. After the expansion tank is at MAX, start and run hte car until the thermostat opens, run awhile at varying speeds, then when it cools, top up if necessary. Never had a problem doing it this way.

Mike

Thanks Mike, but do you ever fill the radiator before putting the upper hose back on assuming that the lower hose is in place? How about before replacing the thermostat, do you fill up at that point as well? Are you serious, no problems with just filing the expansion tank with the whole system empty? Sounds wierd (please do not take offense).

I do it the same way. Just fill through the expansion tank.
Since it's high up, it allows the radiator to fill up.
The rest can be added after the engine warms up.
--
-Cool Volvo- 1982 240 4 Spd OD w/ 227K, 1989 240 5 Spd w/ 214K. Used to own 1966 122, 1968 144, 1970 145, 1972 144, 1980 245

I've worked on '83, '86 and '89 - but not '82.

Anyway, the topmost hose on passenger side - the thin one - allows the air in the radiator to escape when filling via the reservoir tank, and also afterwards if there should be an air pocket in the radiator.