Overheating: Bad Fan Timer?

[Joey]

My radiator fan will not come on while my car is running.

The coolant temperature sensor on the upper radiator hose, right below the distributor, opens when the temperature gauge reads about half (it works). The green plug that attaches to it gets voltage, and turns on the radiator fan (passenger side of the engine) when it is bridged with the key either out of the ignition or in the second position (the circuit is functional and the fan itself works). When the car overheats, both the upper and lower radiator hoses are very hot to the touch (the thermostat does open). Intermittently, after turning the car off once it has overheated, the radiator fan will come on, once the key has been turned to the second position. The fan will turn off again if the key is turned to the third position or if the engine is started. The fan runs after the car has been turned off and the key removed from the ignition, and then turns off once the engine is cooled off.

So, the fan works, the circuit works, the relay works, the coolant temperature sensor works, the thermostat works, and the coolant reservoir is filled to capacity. The common factor in keeping the fan from running appears to be having the engine running.

Is this conclusively a fan timer failure? Is there anything else that could be broken?

[SN2BH22CB7]

Hmmm...does it overheat in a short time?

you stated....BOTH hoses are hot...meaning the waterpump is working...

so lets rule that out.

bleed it FIRST. theres probably air trapped in there causing it to overheat. bleed it.

then get back to us.

[Joey]

Hmmm...does it overheat in a short time?

bleed it FIRST. theres probably air trapped in there causing it to overheat. bleed it.

It warms up at a normal rate, more slowly on cold mornings and more quickly when it's hot out. I don't see how the coolant itself could be causing the fan not to work properly, but I'll bleed it when I get a chance to just to be sure.

[SN2BH22CB7]

It warms up at a normal rate, more slowly on cold mornings and more quickly when it's hot out. I don't see how the coolant itself could be causing the fan not to work properly, but I'll bleed it when I get a chance to just to be sure.

air...not enough coolant will cause it to overheat ( lack of coolant ) on a cold engine ( open the radiator cap )...does it look full?

look at your overflow tank...is it at the maximum or at least between maximum and low?

I had this same problem with one of my CBs a while back...and it came to be that there wasn't enough coolant in the system but rather MORE air than coolant...and it was up there near the red ( a sliver under red )...so..I shut it off...waited like 4 hours...open the radiator cap...and you could echo in there.

it was about 1/4 full...( ) so...I went and got 3 jugs of coolant..and put it in there until the car was running like it should...got all the air bubbles out..and the temp was UNDER the half temp mark.

just thought Id shoot you an Idea.

but if not...might be either the fan switch or the fan timer switch *( under the dash next to the MFR ( Main fuel relay ) *** you have to unbolt the fan timer switch to get to the Main fuel relay.

I hope you get this fixed ASAP!

SIDENOTE: replace BOTH the fan switch and fan timer switch...if all fails...you could always hardwire it to the ignition for it to run while the car is running ( RUN / II )


you could also test the A/C fan off the regular fan switch...

you could have either of these go bad:

A) fan timer switch
B) fan switch
C) fan itself ( works off and on )

Id just go to the JY and get all three!

[Fake Thug]

what about the condenser fan? Does it work at all? The coolant temperature sensor under the dizzy is most likely not a problem. Its not a switch. You might want to check the thermo fan switch. It goes into the thermostat housing. Has a green plug. You'll have to pull the air duct to get a good view of it. The ac fan switch goes into the water neck for the top radiator hose. you will see them. If both switches check out, then it can only be the fan timer because we know the circuit is ok. When your car runs hot both fans should kick on. Hope that helps

[Joey]

The condenser fan doesn't come on either, no matter the temperature or if the A/C is turned on or off. Not that the A/C works anyway.

But I'll run out and see if those other switches work.

[Joey]

So I replaced the fan timer and the car still overheats. I'm beginning to wonder if my head gasket could be blown?

My valve seals (or something) are worn. The car has blown a lot of oil smoke out the exhaust for a while now. Recently, coupled with my surging idle problem, a pretty big cloud of smoke forms behind my car when I start it up and drive away and if I stop in traffic. It looks kind of white and thicker than the smoke from burning oil, but I've been driving it like this for a few days and my coolant level is staying the same. I put some water in it today, drove it across town twice (with the temperature gauge pegged at the top) and when it cooled down the coolant level in the reservoir is the same. So is it just smoking more because of the idle?

Beyond that, I wired my fan directly to the battery, and it still didn't cool the car down in stop-and-go traffic. Any ideas?

[JDMxDB8]

Check your thermostat. Might be busted.

[lokuputha]

I had this problem...I needed a new waterpump. This issue is especially found in swapped motors where the water pump fins have rusted away from being exposed to air.

check out my thread, maybe you'll find something.

http://www.cb7tuner.com/vbb/showthread.php?t=75038

[timmy0tool]

2nd on the thermostat but the fan should come on at temp. do the fans turn on when you hit the a/c? both fans should spin.

[Joey]

Check your thermostat. Might be busted.

I thought if both radiator hoses got hot then the thermostat was opening? But I'll see how I can check that just to be sure.

2nd on the thermostat but the fan should come on at temp. do the fans turn on when you hit the a/c? both fans should spin.

No. Neither fan comes on, ever, regardless of engine temperature or if the A/C is on. Although, I know for a fact that my A/C has zero freon and it doesn't feel like the engine is getting an increase in load when I turn it on.

I just started it up and let it idle for a while, and the smoking actually wasn't too bad at first (just a little blue smoke) and it got drastically worse as the temperature rose. It got thicker and more white; didn't smell like coolant at any point to me, though.