Heating problems 92 740

  • Thread starter Thread starter Bjorn
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Bjorn

I just lost all the heat in my heater in my 92 740 as I was driving down
the road. It worked great when I started the trip, and then just quit. At
the same time the engine coolant temp gauge was creeping up towards the red.
There is no visable leaks, the rad is not low, and there is no broken belts.
I am thinking that this has to be my water pump.
Any other suggestions??
 
Bjorn said:
I just lost all the heat in my heater in my 92 740 as I was driving down
the road. It worked great when I started the trip, and then just quit. At
the same time the engine coolant temp gauge was creeping up towards the red.
There is no visable leaks, the rad is not low, and there is no broken belts.
I am thinking that this has to be my water pump.
Any other suggestions??
Click to expand...


Rare, but it happens. I put a used radiator in my 240 once and it turned
out to have a pebble from the salvage yard in it, got into the water
pump and jammed the impeller with similar results. A bad thermostat
could conceivably cause that, but usually they fail open.
 
I have had the car for about 2 years, and there has not been any problems
with the radiator. The thermostat is functioning since the upper hose gets
hot after the engine heats up.
 
Bjorn said:
I have had the car for about 2 years, and there has not been any problems
with the radiator. The thermostat is functioning since the upper hose gets
hot after the engine heats up.
Click to expand...


I wonder if something has got in there and clogged or jammed the pump?
It's made in such a way as to let the impeller break loose if it gets
jammed so that it doesn't snap the shaft and throw the belts.

I'm not sure what the easiest way to test this is, I suppose you could
drain the coolant, remove the belt, disconnect the lower radiator hose
from the pump and poke a wire in there while rotating the shaft to see
if the impeller is turning. If you can find a piece of transparent hose
you could patch that in temporarily to see the flow. There are not too
many things to go wrong.
 
I just lost all the heat in my  heater in my 92 740 as I was driving down
the road. It worked great when I started the trip, and then just quit. At
the same time the engine coolant temp gauge was creeping up towards the red.
There is no visable leaks, the rad is not low, and there is no broken belts.
I am thinking that this has to be my water pump.
Any other suggestions??
Click to expand...

Radiator has water, expansion tank is full? Does expansion tank go up
when hot and down when cold. It might be a bad radiator pressure cap
and you have air in system, but its a guess. Do any hoses look
collapsed under pressure. I cant check the radiator on my 02 v40 just
expansion tank, so your radiator has a cap and its full cold and
expansion tank is to proper level?
 
I found a parts place that have a pump in stock, so i figure that for $55 I
might as well just change it.
 
Well, I know it is not my water pump. I just took it off, and it seems to be
in perfect working condition.
All the hoses are good. The only way to check the level is in the expansion
tank, and the level was good when the problem started.


I just lost all the heat in my heater in my 92 740 as I was driving down
the road. It worked great when I started the trip, and then just quit. At
the same time the engine coolant temp gauge was creeping up towards the
red.
There is no visable leaks, the rad is not low, and there is no broken
belts.
I am thinking that this has to be my water pump.
Any other suggestions??
Click to expand...

Radiator has water, expansion tank is full? Does expansion tank go up
when hot and down when cold. It might be a bad radiator pressure cap
and you have air in system, but its a guess. Do any hoses look
collapsed under pressure. I cant check the radiator on my 02 v40 just
expansion tank, so your radiator has a cap and its full cold and
expansion tank is to proper level?
 
Bjorn said:
Well, I know it is not my water pump. I just took it off, and it seems to be
in perfect working condition.
All the hoses are good. The only way to check the level is in the expansion
tank, and the level was good when the problem started.
Click to expand...



You must have either a lot of air in the system, or a blockage
somewhere. Kinked hose, foreign matter in the system, etc.
 
James said:
You must have either a lot of air in the system, or a blockage
somewhere. Kinked hose, foreign matter in the system, etc.
Click to expand...

Remind me again why we don't think it's the thermostat?
Pump, plugged radiator, thermostat, loose belt, fan clutch, soft
hoses... not too many choices for what can go wrong in a cooling system.

Remember those radiator hoses from way back, had a coil spring in them
to keep them from collapsing on the suction side of the pump?
 
I don't think it is the thermostat because when I let the engine warm up the
upper hose gets warm as the thermostat opens up.
I will try to get the pump back on tonight, and see what else I can find...
 
Bjorn said:
I don't think it is the thermostat because when I let the engine warm up the
upper hose gets warm as the thermostat opens up.
Click to expand...

Warm, or too hot to touch?
There's enough ambient heat in the engine compartment, everythings going
to be 'warm'.
Probably move enough water through the steam hole on the thermostat to
get it warm.

....or not.
 
I just lost all the heat in my  heater in my 92 740 as I was driving down
the road. It worked great when I started the trip, and then just quit. At
the same time the engine coolant temp gauge was creeping up towards the red.
There is no visable leaks, the rad is not low, and there is no broken belts.
I am thinking that this has to be my water pump.
Any other suggestions??
Click to expand...

I'm wondering if you have an air lock in the cooling system.
 
Well, I know it is not my water pump. I just took it off, and it seems tobe
in perfect working condition.
All the hoses are good. The only way to check the level is in the expansion
tank, and the level was good when the problem started.




Radiator has water, expansion tank is full? Does expansion tank go up
when hot and down when cold. It might be a bad radiator pressure cap
and you have air in system, but its a guess. Do any hoses look
collapsed under pressure. I cant check the radiator on my 02 v40 just
expansion tank, so your radiator has a cap and its full cold and
expansion tank is to proper level?
Click to expand...

It sounds like air, I dont know that system but there has to be a
pressure cap, its a pressurised system of maybe 15lb, I guess its the
pressure cap or blockage. If you cant open the radiator you dont know
its full. Air-low coolant does what you describe.
 
Replaced the gasket and O-rings, put the water pump back on, and refilled
the coolant fluid.
Ran the engine until it warmed up with the cap off the reservoir and
everything seems to work as normal.
It must have been an air lock.
Thanks for all the advice and opinions expressed.


I just lost all the heat in my heater in my 92 740 as I was driving down
the road. It worked great when I started the trip, and then just quit. At
the same time the engine coolant temp gauge was creeping up towards the
red.
There is no visable leaks, the rad is not low, and there is no broken
belts.
I am thinking that this has to be my water pump.
Any other suggestions??
Click to expand...

I'm wondering if you have an air lock in the cooling system.
 
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