REMOVING/REFITTING THE ALTERNATOR
Well it seems that my manifold gasket diagnosis was the correct one – my engine block is as dry as a bone and is as oil free as I’ve ever seen it, so pretty happy with that. However, all of that oil spraying around caused a few problems that needed fixing in themselves. After a few months of wondering why my alternator would only charge intermittently, changing the regulator, cleaning the brushes, I figured that the oil being heated by the exhaust manifold was condensing in the alternator itself, and causing a bad contact between the brushes and the commutator. Nothing that a quick strip down and clean wouldn’t fix.
An alternator swap is well within the capabilities of anyone with a set of spanners, so here’s a quick how-to....
First, disconnect the battery. One lead at the back of the alternator is connected straight to the battery, and it’s all too easy to ground it accidentally.
The alternator in a 300tdi is located on the left-hand side of the engine bay, directly under the top radiator hose, and is driven by the auxiliary drive belt – which will need to be removed.
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To do this, first slacken the nut that the tensioner arm pivots on, then use a 15mm socket on the centre of the tensioner pulley to pull it towards the driver’s side. This will release pulley tension from belt, and you can remove it from the alternator pulley.
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Once the belt has been removed, it’s time to free up the electrical connections from the back of the alternator so that it can be removed. Depending on the model, there may be a heat shield on the back of the alternator – remove it. Then note the position of the wires, and disconnect them.
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Now it’s time to get underneath the landy, and find the bottom fixing bolt for the alternator. It’s a pain in the @ss to get at, so be patient. I couldn’t get a socket to fit on it, and it had been ringed, so I welded another bolt to the head of the original in order to remove it. If you do this, be careful, the welder can fry your alternator pretty easily.
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Back out from under the car, and stick your head under the bonnet again. Now remove the long through bolt from top alternator fixing, taking the weight of the alternator at the same time. Once the bolt has been completely removed, you can lift out the alternator.
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From here on in, most people would be popping in a replacement alternator, but mine was in need of a cleaning, nothing more, so I stripped it down. First remove the regulator – it’s the silver wedge shaped block bolted to the alternator in the photo below, in the six o’clock position. The regulator contains the brushes, or carbon contacts that conduct the current generated by the alternator, and the circuitry that controls how that current is passed to the battery. If you don’t remove it and dismantle the alternator, you’ll break the brushes and it’s a $60 replacement
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The regulator is held on by the most evil bastard size of bolt known to man – 5.5mm. A 5 or 6mm won’t do, and I ended up using needle nose pliers in the end. Now you can see both brushes exposed – they seem to be in pretty good condition.
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Unbolt the three retaining nuts that hold the halves of the alternator together and pull it apart. Although you can’t see it in the photos, the alternator, both inside and out, was coated in a layer of oil that I could write my name in.
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Clean the alternator thoroughly with your favourite degreaser – I used petrol simply because it’s what I had at hand. Make sure that the commutator is thoroughly clean, and reassemble.
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Refitting is a matter of reversing the above procedure. Fit the alternator to the engine mounting bracket and secure with top and bottom fixing bolts. Reconnect the electrical leads, and pull the tensioner back and put the belt back on - making sure it's located in all the pulley wheels. One shiny clean alternator reinstalled.
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Finally, reconnect the battery and start up the engine. I had fitted an ammeter a few months back when I was trying to figure out what was happening with the alternator, and it shows straight away that the alternator is charging. Job done!
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