Volvo Maintenance Hints for 7xx/9xx - Bill Garland's Nuclear ...

the coolant drain is at the end of the short hose leading from the oil cooler, about five inches
behind the oil filter beneath the car. It points down from the tubing on which it is mounted.
Draining Coolant. [Inquiry:] I must be missing something here. My 944 needed an antifreeze
flush and refill, so off I went. I set the heater on "high", disconnected the vacuum to the water
valve to make sure it was open, disconnected the upper and lower radiator hoses and drained a
large quantity of coolant out of the radiator, water pump and overflow bottle. The heater hose
was stuck on to the firewall pipe; not wanting to cut the hose, I did not disconnect it, thinking that
the upper radiator hose disconnection would encourage the head and heater to drain. I also
drained the block via the block plug screw. After refilling and draining again once, I put in what I
thought was exactly half (5 qts) of the system capacity in new Dexcool antifreeze. This filled the
system, so I obviously had another five qts of undrained water sitting in there somewhere. Has
anyone figured out how to drain the cooling system down to zero? Can the heater actually hold
that much fluid? [Response:] You will never be able to get all the coolant out. Have you ever
replaced an engine thinking you got all the fluids out only to have a mess all over the floor. The
engine has areas that can't be drained unless the block is tipped over. You did as thoroughly as
the job can be done. When refilling premix the coolant so that when you top off, the mixture is
still 50/50 .
Engine Flush Procedure. [KenC] For a thorough flush, try this technique. You will need sockets
for the clamps' nuts, a garden hose and a couple of feet of 1" I.D. RBU (reinforced with braided
vinyl) or solid vinyl transparent hose (transparent, so you can see the quality of the water
coming out). This hose is available in all hardware/plumbing stores, and it's external diameter
lets it snugly fit into the upper radiator hose forming a good connection.
1. Turn the heater temperature control to "hot" to open the water valve.
2. Drain the cooliing system (preferably when cool, so there won't be a temperature shock or
overheating to the engine). If you can reach the engine block drain, so much the better,
but at least pull off the lower radiator hose where it goes in the radiator. Be careful pulling
off this hose so you don't break the plastic outlet.
3. Remove the thermostat and then reinstall the thermostat housing without the thermostat.
Don't worry about a gasket -- there's no pressure in this process, so just finger tighten the
two nuts. And throw away the old thermostat -- treat the car to a new one and its gasket,
after all this effort, it deserves it.
4. After draining, slip the lower radiator hose back onto the radiator's "neck", but don't bother
with a clamp (again, no pressure).
5. Pull off the upper radiator hose from the thermostat housing. Now, stick the transparent
hose into the housing, so that the transparent hose extends forward over the radiator (so
discharged coolant doesn't fall into the engine compartment) -- later you'll be watching the
appearance of the coolant in the hose before being discharged, a more reliable view than
watching the stream of coolant. Be careful in this process that you do not lean on or crack
the plastic upper radiator hose inlet: it can be brittle.
6. Wrap a little tape around the end of an ordinary garden hose, and jam it (gently) into the
open end of the upper radiator hose -- it will fit nicely. Now, turn on the garden hose's
water supply.
7. Watch as the fresh water circulates throughout the cooling system, flushing out the old
stuff. Keep an eye on the color of the solution in the transparent hose before it spills out.