muller1
Senior Member
- Joined
- Sep 21, 2008
- Messages
- 263
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- Your Mercedes
- ML 270 Cdi and S type Jag 2.7 Diesel Sport Saloon, and now a VW diesel GT golf
I have an ML 270 and for the last few weeks I have sometimes heard a peculiar "chirp" or slight "rattle" from the front of the engine when idling.
The noise got louder and seemed to be coming from the alternator area.
A couple of days ago the noise was getting worse and I went to my local indi and we had a look under the bonnet.
There was some glittering metal flakes lying on the under engine tray around the alternator area and there seemed to be flaked metal dust lying around that area.
With the engine at idle , there was a noise and when i put the High beam full lighting load on the alternator the noise changed and got deeper.
It seemed as if there was something up with the pulley but he*l a pulley is a pulley.
WRONG, MB use an INA clutch pulley, why, I cannot fathom out.
The pulley drives one way and slips the other.
In other words when the engine runs the correct way, RH or CW looking from the front of the engine it drives the alternator BUT, if you were able to run the engine backwards (which is impossible) it would NOT drive the alternator but it would slip instead.
It seems as if the sprag clutch rollers have started to fail and are chewing up the rollers and the cage hence the noise from the pulley and the nice glittery shiny flakes.
I priced a new alternator and almost fainted when I was given prices form £290 for a Delfi (old name was Lucas) one and Bosch at £325.
My indi said that he would just order the new pulley which arrived yesterday but true to MB you need special tools to change the pulley.
The pulley screws on to the shaft and to allow the fitting and removal they have put a female spline in to the end of the alternator shaft and a female larger spline on the inner ring of the pulley.
This measn that you have a hollow male larger spline tool to fit the pulley and you put a smaller splined tool inside this one to hold the alternator shaft.
Now you can hold the shaft locked and use the larger splined tool to screw off the pulley.
You then do the reverse to fit and tighten the new clutch pulley back on.
Why the need a slipping clutch pulley I cannot understand but I am only a dumb marine engineer after all.
In all my life I have never seen this on a fixed drive like this.
I could understand is it were possible to reverse the rotation but in this case it is impossible.
I am now waiting for the special tool to come to change the pulley and I want to open up the old one to see what has happened to this one.
I think it could be welded in a fixed position with no ill effects.
An other strange thing I found out was the alternator is WATER COOLED, yes you read this correctly the alternator has a water cooling jacket built in to it.
Why, I will never know. The only other water cooled alternators I know about are on nuclear powered subs and ships where the output is so great from a compact power source air cooling is not sufficient as there is so much heat rejection when working hard.
I will let you all know what the removed pulley looks like once I have it off and cut in half.
Regards.
Mike
The noise got louder and seemed to be coming from the alternator area.
A couple of days ago the noise was getting worse and I went to my local indi and we had a look under the bonnet.
There was some glittering metal flakes lying on the under engine tray around the alternator area and there seemed to be flaked metal dust lying around that area.
With the engine at idle , there was a noise and when i put the High beam full lighting load on the alternator the noise changed and got deeper.
It seemed as if there was something up with the pulley but he*l a pulley is a pulley.
WRONG, MB use an INA clutch pulley, why, I cannot fathom out.
The pulley drives one way and slips the other.
In other words when the engine runs the correct way, RH or CW looking from the front of the engine it drives the alternator BUT, if you were able to run the engine backwards (which is impossible) it would NOT drive the alternator but it would slip instead.
It seems as if the sprag clutch rollers have started to fail and are chewing up the rollers and the cage hence the noise from the pulley and the nice glittery shiny flakes.
I priced a new alternator and almost fainted when I was given prices form £290 for a Delfi (old name was Lucas) one and Bosch at £325.
My indi said that he would just order the new pulley which arrived yesterday but true to MB you need special tools to change the pulley.
The pulley screws on to the shaft and to allow the fitting and removal they have put a female spline in to the end of the alternator shaft and a female larger spline on the inner ring of the pulley.
This measn that you have a hollow male larger spline tool to fit the pulley and you put a smaller splined tool inside this one to hold the alternator shaft.
Now you can hold the shaft locked and use the larger splined tool to screw off the pulley.
You then do the reverse to fit and tighten the new clutch pulley back on.
Why the need a slipping clutch pulley I cannot understand but I am only a dumb marine engineer after all.
In all my life I have never seen this on a fixed drive like this.
I could understand is it were possible to reverse the rotation but in this case it is impossible.
I am now waiting for the special tool to come to change the pulley and I want to open up the old one to see what has happened to this one.
I think it could be welded in a fixed position with no ill effects.
An other strange thing I found out was the alternator is WATER COOLED, yes you read this correctly the alternator has a water cooling jacket built in to it.
Why, I will never know. The only other water cooled alternators I know about are on nuclear powered subs and ships where the output is so great from a compact power source air cooling is not sufficient as there is so much heat rejection when working hard.
I will let you all know what the removed pulley looks like once I have it off and cut in half.
Regards.
Mike
