More questions '92 740 cooling system....

James (or anyone):


Re: '92 740 GLturbo overheating. replaced shorted electric cooling
fan...still running hot.
I am swapping in my spare 740 radiator, and have a new cooolant
recovery tank coming from FCP Groton. I was just wondering if there
is any way that you could overfill the system? The cap has an integral
relief valve in it though doesn't it? An overheat or overpressure is
supposed to vent out of the cap, saving the tank from cracking, isn't
it?

When I have the new radiator installed, what is proper way to fill the
system? With no fill cap on the radiator itself, how do you get the
air out and ensure that the system is really full? What I have been
doing is just addding water until mid-way on the reservoir; start car,
and then add enough to bring it back to mid-level.

2nd question is... does your 740 have working AC, and do you switch in
a second fan when the AC is on? Seems like the 89 Volvo sedan I used
to have had an auxiliary fan that normally ran when the AC was on....
If yes is the answer, then I definitely need to get a second 12 in.
fan and wire it up to come on with the AC....or just have two fans
running all the time.
With only one 12 in. fan alone, no mechanical fan, should it be
sufficient in S.Texas summer climate...if you have a healthy cooling
system, proper coolant mix, etc? (here in summer is the closest thing
to hell imaginable) Geronimo

 

consider a leaking head gasket, allowing hot gases to escape from
cylinder(s) into the coolant, causing the high temp and possibly rupturing
the overflow tank....

 

I am running my 945 with a 960 radiator fan having removed the mechanical
item. So far I have not needed to switch it on to avoid overheating.

All the best, Peter.

700/900/90 Register Keeper,
Volvo Owners Club (UK).

 

The rad from your '89 is not the same as on the '92. The one from the
'89 is smaller, and had no heat exchanger for the engine oil. The
filler cap on the expansion tank includes 2 valves - one to let excess
pressure out, and another to break the vacuum that occurs upon cooling.
I would suggest a new cap to make sure all that is working properly.
The expansion tank is the highest point in the system, pressure changes
and flow will ensure that the air ends up there. Just keep topping it
up as necessary after any work on the cooling system that results in any
loss of coolant.
You'll probably see 3 nearly identical switches on the condenser
(visible with the grille removed). These switches send pressure signals
to turn on the standard 2 speed electric fan on low speed, then at a
higher pressure, high speed, then at a higher pressure still, turn the
compressor off. (Note that the fuel computer actually does the
switching of the relay - so it can turn the fan on as needed based on
coolant temperature as well.) Whether one 12 inch fan is enough, that
depends on the fan. Since you don't seem to have the original fan, and
have room for a second one, find the fan relay (or the wires to it) and
use one fan as low speed, and the second as high speed.

--
Mike F.
Thornhill (near Toronto), Ont.

Replace tt with t (twice!) and remove parentheses to email me directly.
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