Balancing a fan/clutch/pulley assembly?

[Mike F.]

Based on my previous thread, https://www.forums.ncrs.org/showthre...ump-amp-pulley , is there a way to balance or check the balance on a fan/clutch/pulley assembly?

First water pump rebuild lasted about an hour ($100)- ran engine to 5000rpm, water pump bearing grenaded (roller bearings everywhere).
Second water pump rebuild (warranty) lasted about 30 miles - run engine to 5000rpm, fan/clutch/pulley start to wobble. Water pump shaft has play in it. Not sure if the problem is the pump rebuilder or an unbalanced fan/clutch/pulley assembly prematurely wearing the water pump bearing.

I've ordered a new "date correct" water pump ($250), but other than ordering a new fan/clutch/pulley ($400???, it's getting expensive for a lousy water pump repair). Is there a way to eliminate the rotating parts as the problem?

TIA,
Mike

[Kurt G.]

Re: Balancing a fan/clutch/pulley assembly?

It's. not easy but you could do the old "bubble" balance trick, or go to your local lawnmower supply shop and get a blade balancing kit. Set the fan assembly on the balance tool and check it out. I'm not sure your fan assembly is the problem though. I don't think the fan turns enough rpm's or has enough mass to trash your water pump bearings. Make sure you have the fan snug to he water pump shaft and check the pulley to make sure it is straight. It could be that the pulley is slightly warped and causing a wobble on the shaft. Could, and probably is the rebuilder, though. I've had a pump rebuilt by Hite in Columbus, OH for about 5 years ago. No problems, yet.

[Edward J.]

Re: Balancing a fan/clutch/pulley assembly?

Mike, I am thinking the Rebuilder is doing something wrong. I have not ever heard of a fan clutch being that out of balance before. 30 miles on a pump bearing is just wayyyy to short for a brg. to fail. I know that 70 uses a smaller dia hub and shaft that other years, Is the hub of the fan clutch fit snugly on the water pump shaft? belts are not over tightened?

The factory did have marks on the water pump shaft as did the clutch fan for balance purposes. once these parts are replaced there lost. Ive done many water pump replacements over the years and have never had a balance issue, but then I don't think they will see 5000 RPMS as they are regular drivers.

[Mike F.]

Re: Balancing a fan/clutch/pulley assembly?

Mike, I am thinking the Rebuilder is doing something wrong. I have not ever heard of a fan clutch being that out of balance before. 30 miles on a pump bearing is just wayyyy to short for a brg. to fail. I know that 70 uses a smaller dia hub and shaft that other years, Is the hub of the fan clutch fit snugly on the water pump shaft? belts are not over tightened?

The factory did have marks on the water pump shaft as did the clutch fan for balance purposes. once these parts are replaced there lost. Ive done many water pump replacements over the years and have never had a balance issue, but then I don't think they will see 5000 RPMS as they are regular drivers.

First time I've had a problem like this with a water pump. The pump was on the car for about 20 years, started dripping, etc.. Then the rebuilds started, bolted everything together just like any other water pump replacement.
Either I assembled it wrong twice, the rebuilder rebuilt it wrong twice, or I have something out of balance.

Mine's a driver and I spin it to 6000rpm cause that's where the redline is.

[Patrick B.]

Re: Balancing a fan/clutch/pulley assembly?

I had the original 5 blade fan on my 70 LT-1 loose its balance back in the 70's. It was real obvious because the shifter would vibrate even with the car stopped in neutral at certain RPM's. However, it did not harm the waterpump. and I replaced it with a 7 blade fan which is still on it. If your shifter is not buzzing, your fan balance is probably OK.

[Joe L.]

Re: Balancing a fan/clutch/pulley assembly?

First time I've had a problem like this with a water pump. The pump was on the car for about 20 years, started dripping, etc.. Then the rebuilds started, bolted everything together just like any other water pump replacement.
Either I assembled it wrong twice, the rebuilder rebuilt it wrong twice, or I have something out of balance.

Mine's a driver and I spin it to 6000rpm cause that's where the redline is.

Mike-----


If you installed the same fan and clutch on the car that had previously been on the car for 20 years, or so, without problems, I find it very hard to believe that it got out-of-balance at the exact same time you replaced the waterpump. That's just way too much of a coincidence (unless you somehow damaged the fan during removal and installation).

Check this: what size is the pilot hole in the fan clutch? If it's 5/8" everything is as it should be. If it's 3/4" you MUST use a reducing bushing. That may have been there before but perhaps you lost it when you removed the clutch and fan. The bushing is not an interference fit; it simply slides onto the waterpump shaft or into the clutch fan orifice.

Also, when you get the new waterpump check the flange for runout with a dial indicator. GM never published a spec on this (but I'm sure there was one) but runout should be minimal. I'd say less than .003".

One other thing I don't understand is something you said in a previous post. You said when the waterpump failed there were roller bearings everywhere. The bearing assemblies used in these 5/8" shaft pumps are double row BALL bearings. I've never seen or heard of one that used roller bearings or one row of balls and one row of roller. The latter is common in the 3/4" shaft bearings used for big blocks and 71+ small blocks, though.

[Mike F.]

Re: Balancing a fan/clutch/pulley assembly?

Fan clutch pilot hole is 5/8".

This is what the bearing looked like after it grenaded. All I found were roller bearings. When it came apart the fan pulled the water pump shaft forward, pulling the inner race of the bearing forward with it. I found roller bearings laying in the driveway and inside the pulley.

[Edward J.]

Re: Balancing a fan/clutch/pulley assembly?

Mike, why the nuts on the back of the studs? would they be possible there are interfering with something at high RPMS. Ed

[Mike F.]

Re: Balancing a fan/clutch/pulley assembly?

Mike, why the nuts on the back of the studs? would they be possible there are interfering with something at high RPMS. Ed

Not sure why the nuts are there, but they've been there for 20+ years. In the past I've run the car/engine on a chassis dyno and engine dyno without any problems. I regularly run the car up to or close to redline and hadn't had any problems until the first water pump rebuild.

[Edward J.]

Re: Balancing a fan/clutch/pulley assembly?

Mike the closer I look at those pump bearing that were left, It looks like the really got hot, there discolored.

[Mike F.]

Re: Balancing a fan/clutch/pulley assembly?

Mike the closer I look at those pump bearing that were left It looks like the really got hot, there discolored.

I agree with you, it got hot. How or why is the question.

[Edward J.]

Re: Balancing a fan/clutch/pulley assembly?

Mike, I would say that lack of lubrication. and it appears the the bearings were held in place by a nylon cage which I am not sure the a good idea since coolant temps. run a constant 195 degrees, so once the heat has got to the cage its not long before the bear seal fails and the greased bearing rollers fails.

Being in the automotive field theres a lot of parts made in China, Where quality control seems to be a problem. I am sure the the bearing that was installed on your pump was made there. The High Rpms that your were turing Likely made lunch meat out of the nylon cage in the brg.

I hope the next water pump you install holds up for you.

[Don H.]

Re: Balancing a fan/clutch/pulley assembly?

Stop torturing yourself and send your pump to Arthur Gould Rebuilders. Your pump problems will be over.

http://arthurgouldrebuilders.com/

[Mike F.]

Re: Balancing a fan/clutch/pulley assembly?

Stop torturing yourself and send your pump to Arthur Gould Rebuilders. Your pump problems will be over.
http://arthurgouldrebuilders.com/

New pump is already on the way via Bill Mock.

[Joe L.]

Re: Balancing a fan/clutch/pulley assembly?

Fan clutch pilot hole is 5/8".

This is what the bearing looked like after it grenaded. All I found were roller bearings. When it came apart the fan pulled the water pump shaft forward, pulling the inner race of the bearing forward with it. I found roller bearings laying in the driveway and inside the pulley.

Mike------


I was not aware that any manufacturer was making these 5/8" shaft bearings with roller bearings but, obviously, some are. Is there any sort of manufacturer's ID seen on the end of the shaft? It might be hard to see.

I agree with Edward on the nuts. They should not be there. The studs should thread right into the hub. The nuts imply stripped threads in the hub in which case the best plan is to replace the hub.