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MG MGA - Generator Bearing?

My car has just developed a new noise, a clicking type sound which changes with rpm. I beleive it may be the generator. I can move the pully back and forth a bit and the cooling fan can be spun easily by hand. The bolt holding the pully on is tight. My battery is a bit low but I am not getting a generator light on situation.

So, if that may be the cause, can I keep the battery charged and drive the car like this for a week until a new one comes in or will it fly off and do damage? I drive about 10 miles a day.
Thanks,
Randy
RAP Palsgrove

Hi Randy - I assume you are talking MGA here - the photo looks like an MGC. My dynamo expired earlier this year after making noises for about a month ( 500 miles)but I managed to drive 30 miles home with the red ignition light on. The rear bearing had completely gone through and I needed a complete dynamo to replace it ( rather than just the bearing). The pulley should not fly off but it could go like mine and damage it permanently - cheers Cam
Cam Cunningham

An overly tight fan belt can crack the pully. A cracked pully can click for a while before it fails.
Loose water pump to fan bolts can click also. Bearing sound is not usually described as a click.
Randy
R J Brown

I'll bite. I think RAP is talking about the little cooling fan behind the generator pulley. That fan should be clamped tightly between the pulley hub and a spacer on the shaft, so it should not wiggle or turn relative to the pulley, but should turn as one with the pulley. If the fan turns independent of the pulley you need to tighten the nut in front holding all this on the shaft.

If the pulley wiggles a bit in the radial direction along with the shaft, then the front ball bearing is on its last legs and needs to be replaced. If the pulley wiggles or wobbles in any other direction it may be loose on the shaft (tighten the front nut). The other possibility is loose rivets that secure the sheet metal pulley to the cast alloy hub. When the rivets work loose the outer pulley wiggles and chatters and will soon come completely off when the rivets wear through.

The crankshaft pulley is riveted together in similar manner but has an iron hub. That one can be brazed or welded together if the rivets work loose. I have never had much luck re-setting these rivets once they come loose and wear around the sides. I think you would need new rivets, and then only if the holes are not too badly worn oversize. If you are setting these rivets by hand it would be a good idea to heat the rivet, then smash it down tight, then allow it to cool and shrink to a very tight fit. I once salvaged a generator pulley (temporarily) by installing hardened steel #10-32 machine screws and nuts, and heating the screws before tightening the nuts. This held up long enough to order a replacement pulley.
Barney Gaylord

Of course Barney is head on.

I had the EXACT same problem. It drove me bonkers for a long time and I drove without issue for quite a while.

I changed over to an alternator instead of repairing the generator. Its highly, highly recommended and a very simple installation.

Tysen
T McCarthy

I repaired my crankshaft pulley (rivets were getting loose)by drilling out the rivets and replacing them with short bolts and lock nuts. Seems to be holding up fine.
Cheers,
I also had a failure of a generator pulley. I suspect because of a tight bearing. The pulley spun on the armature, detroying the key and keyway in both the pulley and the armature. Drove from Watkins Glen to my home (about an hour) and when I opened the bonnet to investigate the noise the pulley was at this very odd angle! How the belt stayed on I'll never know. The new alternator is great!

Cheers.
GTF
G T Foster

Randy, I concur with Barney, I would check the play at front and rear after you have tightened the fan.
If the bearings are shot then you may get sparks (as well as blades) coming off the small fan. I had this start a fire on the strengthener located in the front of the bonnet!! I guess I was lucky it was not the fuel line?

Neil
Neil Purves

>If you are setting these rivets by hand it would be a
>good idea to heat the rivet, then smash it down tight,
>then allow it to cool and shrink to a very tight fit.

Actually, if you heat the rivets before setting them, as they cool they will shrink in diameter, and be loose in the holes. The rivet may also contract in length, giving the appearance of tightness, but they will eventually loosen again due to the sloppy fit. Solid rivets like these are best driven cold, using either a press or air rivet gun (i.e. air hammer or aircraft rivet gun). The solid steel rivets are normally a very soft alloy and can even be driven by hand using a hammer and punch, etc. You can order them in pretty much any diameter and length (you will probably have to trim) from industrial suppliers such as MSC and Grainger. If the holes are not too badly worn, you could drill for the next oversize rivet.

When you drive a solid rivet, in addition to forming a head, the rivet will also expand to fill the hole. This is important because it creates a tight interference fit, with no motion possible between the parts. It may also prevent the part from cracking out from the rivet holes, and will normally make up for slightly damaged holes, since the rivet shank will expand to fill the void (within reason)

>I once salvaged a generator pulley (temporarily) by
>installing hardened steel #10-32 machine screws and >nuts, and heating the screws before tightening the nuts. >This held up long enough to order a replacement pulley.

I think I have a pulley around that has been repaired like that. I have a fair amount of experience driving solid rivets in my aircraft work (aluminum), and also steel rivets on some of my other projects. At some point when I run out of things to do, I will probably replace all the screws with rivets, to make a spare pulley.
Del Rawlins

As long as we are all chewing on this, I'll bite too. I have found that the older Ford tractors used the same generator that we use on our MGs, with one notable exception. The exception is that the rear plate on the generator has a bearing in it on the Ford tractor, where as the MGA version of it only has a bushing. This came to light when one of our club menbers installed a MOSS Supercharger and changed the generator rear plate to handle the load on the belt for the supercharger. The added bonus here is that it looks stock except better.
JP Jim

I've had some experience using steel rivets on aircraft gas turbine engines. Unless you have at least a 6x pnuematic rivet gun--you'll run the chance of work hardening the rivet from too many light blows. The little rigs they sell at the tool store, that come with chisels and the like for cutting exhaust pipes and sheet metal are not going to hack it. A better way is to use a hammer and large pin punch. You should only use two or three blows to set the rivet. Use a hand rivet set to draw the rivet and then hold the round head. The best solution (and the one I used) was a pnuematic rivet squeezer, which is like a small hand held hydraulic press.

The rivet is going to expand to fill the hole, and properly driven, is not going to loosen. Heating the rivet will remove the temper from the rivet and actually weaken it. Likewise--heating screws and installing them could increase the tension beyond the maximum torque value for the fastener and cause premature failure.
Rob Carleen

This thread was discussed between 27/09/2007 and 02/10/2007

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