another nice day for a drive when suddenly...

PostPost by: chicagojeff » Mon Feb 06, 2006 3:31 am

saw steam rising from the front of the car, and at the same time, noticed that all of a sudden, the heater was blowing cold air...

low and behold, my water pump belt was gone! I have a gilmer drive, with supposedly 37 teeth, and a half inch belt. I think I can find the replacement, but here is the basic question, how do you remove the fan (11 blade replcaement plastic blade) without removing anything else? Can it be done? thanks anyone!

Jeff
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PostPost by: Matt7c » Mon Feb 06, 2006 8:48 pm

Jeff, I hope you didn't overheat anything! I have never heard of the 11 blade replacement fan, although I would be interested to see one to see whether I could use it to eliminate the electric fan (that I haven't yet got around to re-installing).

I put the original 2 blade metal fan back on for winter. My water pump is not original, as I have the front cover conversion to enable water pump removal without taking off the front cover. On the pump itself, the pulley part is only a cover over the main pump body. 4 bolts hold the fan and pulley assembly in place all of which can be removed easily and without extracting the pump. The pump body is secured using grub screws underneath the pulley part which just bolts onto a flange.

I don't know how similar your set up is to mine, so I don't know if this helps, but good luck.

Matt
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PostPost by: type26owner » Tue Feb 07, 2006 2:36 pm

Hey Jeff,
A toothed timing belt makes sense to drive an oil pump that has low inertia and a somewhat constant load. The same type of belt especially a 1/2" wide wimpy one to drive an alternator or generator is just asking for trouble. I've done this type of engineering many times and I would always choose to go with a vee belt in that situation. It's the instantaneous load from rapidly accelerating which is the killer of timing belts with teeth. I would call the Gates Corporation engineering help for advice. Bet they will tell you the same thing. :wink:

Just aligning the pulleys to the tight tolerance required is a problem.
Last edited by type26owner on Tue Feb 07, 2006 2:44 pm, edited 2 times in total.
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PostPost by: M100 » Tue Feb 07, 2006 2:43 pm

A Multi V pulley and belt setup ought to be a much better option to preserve water pump life. Has anyone done this?
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PostPost by: type26owner » Tue Feb 07, 2006 4:00 pm

Hey Martin,
You're making an assumption that the belt load is the root cause of the waterpump bearings failing after about 50k miles. I have first-hand evidence that clearly shows that is not true. I have cut open the last few bearing to see what the hell happened. The front bearing race and the balls were in pristine condition. The normal process of fatigue wear that causes a dulling and pitting of the surfaces but there was almost none of that. The rear bearing was destroyed from the grease being contaminated with coolant. The inner bearing races are intregal with the shaft and the shaft was severely rusted and took out the grease lipseal. Believe that's the actual cause of most of the waterpump failures. By spraying some rust preventative up into the weephole, the rusting problem can be prevented.

I still have the bits from one waterpump. If you'd like I can try and take some pictures to prove my point. Seeing is believing, at least for me!
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PostPost by: twincamman » Tue Feb 07, 2006 4:11 pm

I would remove the fan blades completely and install an electric fan ---extended the life of both my tc water pumps 8) ---ed
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PostPost by: chicagojeff » Wed Feb 08, 2006 1:47 am

I should be clear...I have a 1/2 inch gilmer belt connecting the lower gear and the water pump / fan pulley. The alternatior is on a separate pulley to the lower gear with a v shaped typical-looking toothed alternator belt.

I measured the teeth again on the mysterious water pump pulley arrangement...it is 37 teeth on the top, and I think 32 on the bottom.

Has anyone ever seen this before?

If I replace the fan with an electric one, which makes a lot of sense, I still need a drive belt to connect the water pump. It seems to make sense to me that it need not be looped through the alternator as well, but I aint sure what to do now. No idea of what length belt must be right.
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PostPost by: twincamman » Wed Feb 08, 2006 2:06 am

the belt only contacts 3 points --the pulley the pump and the alternator ---- I don't understand the problem ???? :?: ed
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PostPost by: chicagojeff » Wed Feb 08, 2006 3:28 am

i have two belts going to the lower drive pulley. One from the allternator only, and one to the pump only. Most set ups are one belt that hits all three points--the pulley, pump, and alternator.

Or, put another way, I have two pulleys located down on the drive shaft. One to the alternator, and one going up to the water pump.

crazy?
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PostPost by: rgh0 » Wed Feb 08, 2006 9:46 am

Jeff

Using a tooth belt drive between the crank and water pump in mid engined racing cars with twin cams is quite common. These cars have no alternator so no need for a second belt to the alternator.

Fitting 2 pulleys onto the front of the crank must have given some problems with alignment and rigidity of the assembly and if not done right could have caused problems leading to stripping the teeth off the belt.

I have not seen problems with half inch toothed belt drives on race cars and these engines certainly accelerate and decelerate much quicker than a road car. But they also do a lot less miles as well so hard to judge if the design works on a higher mileage road car.

I have seen toothed belt drives advertised for road twin cams in the UK over the years but I thought these used a single belt for alternator and water pump.

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PostPost by: M100 » Wed Feb 08, 2006 11:05 am

Keith, my water pump has [touch wood] lasted a bit longer than that running with the belt tight enough to drive the dynamo with the belt regularly coated with belt dressing I keep expecting it to go at any time though! The water pump tight belt myth has perpetuated for years probably incorrectly but I recall checking over a +2 many years ago a friend was thinking of buying. The car had something like three water pumps and a new alternator in about 10000 miles and the owner was getting rid and buying a Porsche 924 <snigger> The belt on that car was so tight it was about an octave up in tension from what I run mine at and I can't help thinking that was the primary cause (the car had very dodgy electrics, we checked it over early evening and the headlights seriously dimmed when the heater fan was turned on)

I turn my water pump a few turns every month during winter layup to avoid "stiction" of the seal but the spray up the weephole looks a good preventative measure to add. I'd be interested in the pictures of the bearing. I often wondered how big the bearing area was.
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PostPost by: type26owner » Wed Feb 08, 2006 2:39 pm

Jeff,
Driving just the waterpump with a toothed belt makes a lot more sense for that size of belt. This type of belt will reduce the preloading if the belt manufacturer's engineering advice is obeyed. But like I indicated earlier the tension of the belt is not the root cause of the waterpump bearing failures as far as I can tell.

Good luck finding that exact size belt. I have a stockpile for the special ones I need to spin the fuel pump on the racecar. I know what a pain it can be tracking down a supplier. :roll:

Martin,
I'll have to RTFM for my digital camera so I can overide the auto-focus. I can never do good closeups but I'll try extra hard this time!
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