Re: Which belt for the hydraulic fan pump?
Reply #4 –
Twig,
First question: Why does 8 not work but 6 does? If Detroit put 8 grooves on the crank pulley and the engineer put 8 grooves on the pump pulley, seems like all their engineering college education and experience means it was designed for an 8 groove belt. If Gates Corps's engineer says an 8 groove design needs an 8 groove belt, that's what it needs.
So with the "less belts are OK" logic, your Ford, Chevy, etc with 6 or 7 ribbed belts would be fine just putting a 4 or 5 ribbed belt on it. Correct?
The problem with the installation is the tensioner is the big heavy tensioner and pump mount is in a fixed location with 4 bolts attaching it to the block. The tensioner can be spaced out to get the belt in the middle but the big steel mount has to be taken off and the mounting holes elongated to it can be moved forward a quarter inch or so. But then the pump will move with it so what to do? Fortunately, there are 4 visible bolts on the face of the pulley and the shaft is keyed. By loosening the bolts, the pulley can be moved in or out on the shaft. Our tensioner was tilted so either a tapered shim has to be fabricated or a washer has to be placed to correct the angle.
If the tensioner is replaced with a new one and the angle discrepancy remains, the coefficient of friction on the roller face will be different and the movement may be less for a time.
For those new to this topic, the tensioner movement has long been a topic and ours was exactly as others including Gates described. If the tensioner is at an angle compared to the crank and pump pulleys, the belt will be forced to move over slightly and shorten it's overall length quite a few times a second. As it slightly changes length as it returns to the original position, the tensioner idler will jump up and down causing anxiety to the observer. At higher engine speeds, the frequency is higher and the belt does not have the time to move as far. Much like a sound speaker with the bass notes causing visible movement of the cone but the higher frequencies make the cone movement much faster and not visible.
The slight side to side belt movement combined with any pulley alignment problem will cause the belt to touch/rub on the side of the main pulley instead of being held in place by the "V" of the pulley. This causes wear, fraying and then failure of the belt.
The problem compounds itself when the belt does fail and there is no spare onboard. The belt will be a mile or so behind the coach and even when road service arrives and is able to find a belt the correct lenght, it is very unlikely to have 8 ribs so the problem is forgotten until the next time.
The fans in the cooling system consume around 60 horsepower when operating at full speed. Our Toyota has a 7 rib belt to do a lot less work. Seems like the engineers look at the maximum load and size the belt according to the load.
If you have an earlier model with only one fan, check to make sure the pump has 8 grooves as it's possible that a 6 groove belt might be used on a single fan radiator with a different model pump having fewer grooves. The alignment still has to be correct regardless of the number of grooves.
With $30,000 replacement/overhaul costs, the belt is the most important accessory on the engine. Failure to check and adjust the alignment puts your engine at risk. Anyone with basic DIY skills and a $5 investment in the angle indication I show in my post can check and correct and discrepancy. Failure to do so with that knowledge in hand is either being in denial of the problem or just plain laziness. I would never take the word of one person compared to the company that built the engine or pump motor. They are the experts.
"you can lead a horse to water, but you can't make it drink"
Pierce
Topic: Which belt for the hydraulic fan pump?