Heater/radiator issues

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77ToyFJ40

77ToyFJ40

Joined
Jul 5, 2024
Threads
39
Messages
100
Location
Albertson, North carolina
On my 77 fj40 I am not getting heat on either heater. I have flushed the heater cores in both directions until I got good flow. After idling for a while the top radiator hose gets hot but the lower radiator hose will not. I removed the return heater hose from the fire wall with the engine running and I get no coolant flow from the heaters. It has a new thermostat in it. Does this sound like a clogged radiator? I had it idling about an hour and the temperature gauge never got past 1/4 way.
 
does your heater valve work? Not just the dash pull but is it actually opening and closing the valve on the firewall?
 
Maybe the valve is clogged with radiator sealant or the hose. Your thermostat must work or you would have over heated idling for an hour.
 
Fluid must be moving threw the radiator or the engine would over heat soon enough. But hey it could be.
 
Maybe you have an air bubble. Park on a grade so that the rad cap is the highest point in the system, let it run for a while with the cap off. Clamp off one of heater hoses for a while, then do the other heater hose. Check that the fluid level in the radiator surges as the thermostat cycles.
 
charliemeyer007 said:
Maybe you have an air bubble. Park on a grade so that the rad cap is the highest point in the system, let it run for a while with the cap off. Clamp off one of heater hoses for a while, then do the other heater hose. Check that the fluid level in the radiator surges as the thermostat cycles.
Click to expand...
I've let it run with the radiator cap for close to 30 minutes. The only thing i haven't done is park on a grade.
 
When I found out my heater wasn't working, it turned out the original owner had removed the thermostat.

The upper radiator hose getting hot means the head is getting hot. The head is the source of fluid for the heater. It could be that the water passage in the head where the heater line takeoff connects is plugged up with gunk.
 
Last edited:
73FJ40 said:
When I found out my heater wasn't working, it turned out the original owner had removed the thermostat.

The upper radiator hose getting hot means the head is getting out. The head is the source of fluid for the heater. It could be that the water passage in the head where the heater line takeoff connects is plugged up with gunk.
Click to expand...
Im getting coolant to the heater valve so it shouldn't be a problem in the head.
 
how about some pics under the hood? heater hose routing
does the thermostat have the upper ring on it?
is this a new problem?
getting coolant to the heater valve from both directions or just one?
 
77ToyFJ40 said:
Im getting coolant to the heater valve so it shouldn't be a problem in the head.
Click to expand...
If your radiator was plugged more coolant would be forced to flow through the heater lines, since the heater and radiator are parallel circuits.

You don't say if the heater valve coolant mentioned above is hot. If hot and the downstream heater lines aren't, there is a flow restriction (pluggage or air bound) in the heater system.
 
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