alternator problem?

[arry911]

Hi I have a 911 sc 1982 has just come back from run and its making what I thought was a scraping baring failing type noise. I have turned the fan with a spanner and there is no noise and no noise from bottom pulley. I let the car cool down and its seems to have gone. I wonder then that its the alternator baring going as it gets warm, Also I am charging the battery up every two weeks. No alternator light coming on so I thought it was charging . Light on with ignition on. So I thought I would run it with the fan belt off but I if its not hot I guess it wont do it. Any ideas!

[Jdub]

I am not clear with this - you are charging every two weeks because you have to, or because you decide to? If the battery is draining then you will want to find out why. A bad battery cell or similar can put stress on your alternator but not a physical issue, such as a bearing going bad.

Be sure your fan belt has the correct tension.

[T77911S]

when it is hot and making the noise, remove the fan belt and run the engine, it will be fine for a few minutes

[arry911]

I run the engine with the fan belt off , nice and quite. So I am pulling the alternator which was going well till I try to remove the six nuts on the back which hold the plastic cover on , I have got two off the rest are turning with the stud attached so I thought I would unwind them and pull them out. I have stuck a lever between the two parts as I am turning the nuts but they have only open up a bit. Do I cut through the studs to remove the cover? I had to charge the battery as it kept going flat ( new battery) no light on so I thought it was charging ok.

[Jdub]

Consider first purchasing a new battery. This is especially important since a bad battery will kill the diodes in the alternator. If the battery is more than 5 years old, I would replace it.

Be SURE to rebuild your old alternator. Many stories on this BBS about trying to fit a "new" alternator and plenty of issues. Keep your old one and rebuild it so that it will go right back into the car without issues.

Good luck! You might have a current draw - that is about hooking up a fresh battery and then pulling fuses in the fuse box until the current draw disappears - there is the beginning of your current draw.

[arry911]

Thanks jdub, I had to cut through the bolts to get it off so rebuild out of the question now. I have a new one on the way so hope its ok.The battery is only two years old. I think something is draining it plus I suspect the alternator was not charging it.

[Jdub]

Hey be sure to hold on to that old alternator! Do not core it if you can help it - do bring it to a rebuilder and they can R&R those threaded posts in no time. It is worth money to folks exactly in your position.

Keep in mind you may have either a drain or a bad charge or both, so approach the two separate issues first, then both as a combined issue. Also, fuss around in the fuse area to see if there are any modifications.

[rick-l]

There is a lot of misinformation about alternators in this thread.

Unless the battery is a dead short, not the case here, it will not kill the diodes in the alternator. The alternator is designed to charge batteries and the components are sized appropriately.

You won't notice any bearing noise in a healthy alternator between no load and full load. In addition the bearings are sized for the fan load.

Also these cars, from personal experience, draw current when off and there is nothing wrong with topping off the battery every two weeks and is sometimes required. 100 milli Amps is the pass/fail criteria I see batted about and at that discharge rate in 336 hours (2 weeks) you have lost 33.6 Amp-hours, about half the capacity of the battery.

Getting a rebuilt alternator in my vintage car is dicey because the typical re-builders don't replace the slip rings and for some reason the brushes wear deep grooves in them.

[arry911]

Thanks rick-1, What you say sounds right .The battery has half charge after two weeks and the baring was making some noise so I thought it was best to go for a new alternator my one looks old. Also a chance for a clean up and a respray of my fan.

[arry911]

Well i took the car into the Porsche garage , need to drop the engine out not good

[rick-l]

Originally Posted by arry911

Well i took the car into the Porsche garage , need to drop the engine out not good

Not just to replace the alternator.

[arry911]

No it was not the alternator after all , could be a big end gone.

[Scott Douglas]

If they're removing the engine to get the alternator out, they aren't trying hard enough.

[Scott Douglas]

Sorry to hear that.

[arry911]

Originally Posted by Scott Douglas

If they're removing the engine to get the alternator out, they aren't trying hard enough.

Well I know the alternator is ok as its new, wish it was that. Engine is not turning very well by hand its catching on something

[timmy2]

Maybe just a tensioner failure and the chain skipped a tooth. New tensioner and cam timing adjustment if you are lucky.
More if you aren't....

[arry911]

Originally Posted by timmy2

Maybe just a tensioner failure and the chain skipped a tooth. New tensioner and cam timing adjustment if you are lucky.
More if you aren't....

I can only hope.

[arry911]

Update , I had a blockage so no oil on the camshaft on #6. So new camshaft (964) and follows.

[arry911]

Originally Posted by arry911

Update , I had a blockage so no oil on the camshaft on #6. So new camshaft (964) and follows.

Just got the car back and it runs great. Well it should it cost me £2800 (nearly $4000 )