Fan belt replacement on F motor

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Nov 21, 2017
Hi All,
I've had a 1974 FJ40 for 17 years, bringing it with me from the US to Australia and now in Canada. I used to have an account here years ago but I lost track of my old username and email has changed.

I'd appreciate a little help on what must be a stupid question...this is an F engine with a mechanical radiator fan driven by belt directly to the crank pulley. The water pump, power steering and alternator (drivers side) are all driven off a second belt.

Although I have maintained the motor regularly, I have never changed the fan belt. It is ancient but still works. I want to replace it along with some other refurbishment work I am doing. Because the fan and the crank have no obvious adjustment to them I am wondering how to put a new belt on there without disassembling the entire fan and shroud. What am I missing here? Is it really right to take the fan shroud off, thread the new belt over the fan blades and stretch the new belt onto the crank pulley and fan pulley witha screwdriver? Seems awefully primative?



You should be able to loosen the tension via the alternator bracket/power steering bracket. This should allow for enough slack to slip the belt off of the other pulleys and over the fan.

From the picture that you provided, the belts look ok. If you do not see any visible cracking or wear, I wouldn't worry about replacing them.
Thanks Krondor, but I am referring to the other belt to the right. There is nothing on it besides teh fan and crank directly. No alternator or other tension adjustment mechanism I can find?
That belt seems to be unnecessary??
That there is a custom job. The inside belt towards the engine would have run just the alternator, fan/waterpump from the main crank pulley. The outside groove was for a narrower belt that ran off the fan and main crank to a smog pump mounted high on the right side of the head via three bolts. I'm assuming someone added a saginaw power steering pump your truck, probably bolted down with two head bolts on the left side of the engine and decided to run it with a longer belt, using the alternator to tension it.

The question is, why they decided to run the second belt. In order to replace it, there are four long bolts in the front of the fan, take those loose, while also loosening the other belt of course, and the pulley, spacer and fan will come off the hub of the waterpump. The fan will lay in the shroud and you can get the belt off. The longer belt would most likely go around the fan without taking it off, like a stock belt would have. The hard part will be getting a belt the exact same length and getting it stretched on there and then lining up the four bolts and getting the pulley, spacer and fan bolted back on under tension like that. It is tough with no tension. As I said, the question is why do this. The outside grooves are narrower and actually take a narrower belt than what you have to ride in the groove properly. I suspect the one single belt would turn everything OK without the second belt, unless it was slipping or something and overheating and someone decided to add the second belt.

Either way, each belt is a custom deal, and you will have to match them at the parts store to replace them, as neither would be a stock belt cross reference-able to your model and year. They both have a number on them still so that is good. I would just cut the short belt off and see if runs OK without it. If so , just replace the long one and be done with it.
Thanks so much for the thoughtful replies. I had to look at it again to realize why my head was so twisted over this...the forward belt between the crank and the fan should be redundant. I am taking the whole cooling system off and refurbishing it so will find out a better routing for the belts.

A pic from the other side would really help. From what you’re saying it seems someone just stretched on the forward belt over the crank and water pump to provide a backup for the water pump should the other belt fail. I guess it works but having no adjustment is kind of half a**ed.

It also appears you pulleys on the crank and water pump have one wide and one narrow groove. Running the narrow belt in the wide groove is probably to accommodate a narrow groove on the power steering pump. Can't tell without a pic from the other side. (hint) With a bracket from a 2F engine you could move the alternator to the other side and have the belt configuration in the pic that mdsims posted. That would be ideal with two adjustable belts and redundancy for the water pump.

Also you might consider replacing that steel four blade fan with the six blade plastic. It will mover more air and there's been some stories of the metal fans coming apart and taking out the radiator.

"More Pics"
I would assume that the second belt was added because the departure angle from the water pump to the alternator/pw steering pump was not steep enough. This would cause too much slip on the water pump and cause an overheating issue.

Krondor is on to something. A rule of thumb for belt wrap on water pumps is 90 degrees.

Regarding the wider belt than design for the water pump/harmonic balancer sheaves, since it will sit higher in the sheaves, it would seem to be easier to stretch the belt over the sheaves, than a narrower belt that would sit deeper. IMO, anyway! :beer:

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