I've been experiencing an issue with my '83. The fan clutch never seems to engage. The truck does fine in town, but whenever I drive on the highway or in the mountains, the temperature gauge climbs above 3/4 - but not all the way into the red area. This usually occurs after about 15-20 minutes of driving at sustained speeds above 40-45 MPH.

Is there anything that I can do to check it besides replacing the entire fan/clutch assembly?

Of course, it's possible that this may be a different thing altogether, perhaps a coolant flow problem or a bad reading from the temperature gauge itself, but I want to rule out the fan clutch first. I've only heard the fan spin up twice since I bought the truck two months ago.

Any advice would be much appreciated. Thanks.

 

We have a thread, search "How To Test Fan Clutch"

 

Also, the fan clutch is pretty cheap, and a really easy job.

 

This is strange because if you were having issues with the fan not spinning then you would more likely be heating up when driving in town and likely run cooler on the highway. I'm not doubting that your fan clutch isn't engaging - obviously, if the engine is hot and the fan isn't spinning then there is an issue there, but the reason the fan spins is to draw air across the radiator when there isn't air flow present (ie: at idle or in stop-and-go traffic). At highway speeds your fan shouldn't need to come on (unless you're in a ridiculously hot environment) although it may.

You can get a fan clutch for around $40 at places like Advance Auto Parts and installation is a snap - remove the fan shroud, then you can remove the fan blades and then the clutch.

While the fan clutch may not be operating properly, I don't think that is your problem. Like I said above, you should be running cooler at highway speeds so I'm thinking that you may have a flow issue in your coolant. I'd drain the coolant and flush your radiator really well to make sure that you don't have any corrosion or blockage.

 

RAD4Runner, thanks for pointing me to that thread.

As far as the fan spinning up when driving at slower speeds when there is less airflow, I completely agree. I used to own a '93 4WD Truck and the fan would occasionally spin up to a higher RPM when pulling uphill grades in the mountains, but mainly it would do so during slow driving conditions.

It very well could be a coolant flow problem - I will have to investigate further. The coolant was recently flushed and it looks very clean - no oil or other contaminants present.

Also, even while driving with the gauge about 3/4 of the way up, the coolant never boils over (doesn't happen after I stop and turn the truck off either), so it could just be a false reading on the gauge itself. If that were the case, though, I would think that it would give similar readings regardless of driving conditions.

 

Cosmo, with coolant i'd think you'd have to get way into Red till there would be a sign of boiling. If you cant see the tubes in the radiator just drain a bit to make sure theres no scale build up, thats what caused me problems till I removed radiator and cleaned. If you've been adding any coolant at all look for leaks.

I'm still trying to figure mine out as no noticable flow in radiator so next is flushing the block but it is cooling much better since the cleaning and stopping leaks. Its hard to notice leaks sometimes cause they dry out so fast. I had a cracked sensor, leaky water pump, and pin hole in radiator which i soldered after cleaning.

ps. If you can depending where you live, I myself buy parts mostly at a store like auto zone that gives a lifetime warrantee so if in doubt just replace at no charge. Also they loan tools like the pressure tester for cooling system.
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