Cooling Issues

[jwdawson]

I am working on a March 1970 FJ40 that is having a cooling issue. It first started the other day with the Temp Gauge going all the way over to the left. It did not overheat the first time that this happened and then the second time I drove it, it did in fact overheat. I was at home luckly. I took the thermostat out and checked it and looked at the water pump as well. I ended up replacing both items and not wanting to fight with the "maybes". I now have the vehicle back together and just started it this morning for a gas run. After driving it to the gas station and back home the gauge was all the way back to the left again and stayed there. I checked the oil for maybe a blown head gasket and nothing there either that I can see. The vehicle seems to be running nice and smooth as well. The radiator doesn't seem to be clogged either. What else is there that might be causing this problem? Any help would be appreciated.

 

[dgangle]

bad T-stat, guage, sending unit? Did you burp the cooling system?

Can you provide more info on how you know it overheated? Were you relying on the guage alone for this info?

 

[jwdawson]

Cooling

I was relying on the Gauge inside the vehicle. I guess that is was wrong to do as well. Like I said it was working fine up until now and then this. The reason I said it was overheating was after I shut it down the radiator back flowed and the hot water came out through the overflow tank. After I replaced the T-Stat and water pump it doesn't seem to be as bad now but the gauge is still going most of the way to the left. I have ordered an OEM temp sending unit from Toyota (which was cheaper $19.00) than the orther guys out there. That will be here around Friday and it will get replaced as well.

 

[Melloj123]

Had this same problem with both a 70 and a 77 and in both cases it was a clogged radiator. New radiators solved the problem. Also with the 70 I had blockage at the back of the block where the block drain is. Check this drain for flow. IF you get good flow, fine. Mine was completely blocked but I was able to clear it up by digging around with an ice pick.

 

[Varty Yo]

i dealt with the clooged block also. but i couldnt get mine cleared out. i finally gave up and got a new engine. if you search there is a very long thread that was started when my cooling probs began.