1974 FJ40 running hot

[piecemeal]

My rig, which has no coolant bottle and leaks everywhere, runs really hot. When it sits at idle the temp goes up to just past the high tick mark on the temp gauge then drops back down dramatically once I'm rolling for awhile, sometimes a long while. Is this normal?? It's 26 F here right now and it's doing this. I'm worried about what it'll be like in the summer.

 

[D'Animal]

Sounds like you have air in the system or your Thermostat is stuck.

You should have a fluid recovery bottle.

Add fluid and then start the rig with the radiator cap off. Let it run until the T-Stat opens. Add fluid and then turn your front and rear heater (if you have a rear). You should be blowing warm air. Keep adding fluid until full. If you park with the front of your rig up a slight hill, it helps burp the air out of the system. Get a fluid overflow resivoir on it ASAP. I used a water bottle zip tied until I found one.

 

[allan man]

I would try the most in expensive way first......check your radiator see if it needs topping off...pls. let it cool off first before opening that cap, then replace your thermostat, check your fan clutch,than waterpump, minus well change the hoses,if summer is a concern to you,at least if you do all this you have a piece of mind......also how old is that radiator in it might be all coroided (excuse my spelling)
hope this helps....check for leaks..

 

[Ziffdaddy]

not normal at all. I have a 74 that runs cool as a cucumber in any temp.
make sure the gauge works
use an infared gauge to check the temp when hot.
you can get a cheap overflow tank at a parts store, just make sure you get the correct radiator cap that lets fluid flow back in.
make sure you don't keep running it while pegged like that or you will be doing a lot more work on it!

 

[D'Animal]

I should add that if you add fluid and you are blowing bubbles constantly, you have a blown head gasket.

I won't add that since it would ruin your Thanksgiving.

 

[D'Animal]

I have never seen a 1974 with a Fan Clutch.

check your fan clutch,..

Not saying they did not install them, just that I have never seen one on a stock F.5.

 

[allan man]

Okey....if you dont have a clutch fan...check it anyways

 

[piecemeal]

two questions. I have access to an infrared temp gauge. what max temp should it be operating at ?? And, I do have a rear heater that doesn't seem to put out any heat. Is there a valve or knob that needs to be pulled in order for it to work??

 

[D'Animal]

Are the hoses connected to it?

It may be plugged or full of air and that is why you are having the problems you are.

 

[piecemeal]

yup. it's hooked up. must be full of air. I guess I disconnect it to see if fluid runs out or something. there isn't a special valve that needs to be turned to activate it or anything??

 

[D'Animal]

I'm not ignoring you, I live in Central California and don't have a rear heater nor have I seen one hooked up and actually working. I ahve seen them installed in FJ40's at Land Cruiser Shows, I have just never seen them working. I thought they came on when you turned the front ones on but I am probably wrong.

I have heard that they will almost cook you out of the cab when they are working though.

 

[1979fj40]

just pull the temp knob out, its in paralell with the front.(just pulled my rear out... it would run you out)

 

[1.25Ton]

There is a valve on the back of the cyl head that shuts off the flow of coolant to both heaters.
Sounds like thermostat is sticking closed. Try taking the thermostat out and then checking temp.
x2 on the overflow.

Coolerman has a great tech link on heaters too, really helpful on my '71.

 

[msapers]

A few thoughts...

Is this the rig that you picked up for $800? If so, the fact that it runs at all is a good start!

Is the engine original or has it been swapped for a V8? If there's been a swap, it's a whole new ball game, but still doable.

Was the rig sitting for a long time prior to you buying it? If so, the passages in your radiator may be clogged. Any radiator shop can "rod out" the radiator to remove any internal blockages and pressure test it for leaks for less than $100.00. (usually)

Is there a fan shroud in place? If not, this may be your problem. The cooling system is totally dependent on the fan to move air through the fins of the radiator when the vehicle is stopped or moving at low speeds. As speed increases, so does airflow and the fan becomes less important.

Is there any blockage (debris, leaves etc...) preventing air from flowing through the radiator? If so, clean it up.

Is your water pump toast? WITH THE ENGINE OFF, grip one of the fan blades and attempt to rock it back and forth while watching the pulley of the water pump. If the pulley rocks, your pump is hosed.

Hope this helps.

 

[Kroll]

yup. it's hooked up. must be full of air. I guess I disconnect it to see if fluid runs out or something. there isn't a special valve that needs to be turned to activate it or anything??

Also sometimes when you carry lots of junk in the rear and, if it's moving around lots, it can shift the rear heater shroud. Causing the fan to be jammed.