“Water Cooled” Alternator, Really???

2004 VW Passat W8 at Nelsons Automotive of Pewaukee   


This 2004 Volkswagen Passat W8 has one and it failed in a big way when the Battery, (the original 7 year old one) died. Driving the car you wouldn’t have thought there was a problem with the battery other than it turning over a little slower than normal. The car originally came to us for new skins (tires) and the customer mentioned the battery light illuminating a few days earlier and then went out. He said the car still performed normally other than a new whining noise coming from under the hood.

During our inspection we noticed the noise and immediately suspected the charging system. We decided to start with a quick battery test which showed a battery rated for 680 CCA only producing 300 CCA, definitely a failed battery. We replaced it with the hopes it was pulling too much out of the alternator and causing the noise. Unfortunately after the battery, the noise was unchanged and upon further testing, we found the charging system producing an abnormal amount of A/C and traced the issue down to a failed stator inside the alternator.

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To our surprise, when pulling out the old unit, we discovered coolant pipes bolted to the rear case of the alternator and thought “now that’s an interesting idea” as 99% of the alternators are air cooled. If you notice in the pictures, the alternator is tucked tightly under the right lower corner of the engine and removal of the front of the car is needed to access this little gem. More than likely the reasoning for this type of additional cooling as the area it lives in is really tight. We were able to repair said alternator and sent it happily down the road with a clean bill of health.

Think of it, a V8 4.0L in a Passat, now that’s special, and kind of cool if you’re like me and get a kick out of German engineering.

Jim Nelson

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4 Responses to “Water Cooled” Alternator, Really???

  1. Jud says:

    So its not a 1 person job to replace the alternator or did you mean just the front clip? Also, any VW specific tools needed to replace it?

    • Jim Nelson says:

      its a 1 person job if you are a master certified tech that has the correct tools and training to perform this level of repair. The tech that performed this repair has been servicing cars like this for 20 years and will tell you its not the kind of repair you would recommend doing in your home garage. There are no VW specific tools for this but there are tools used that most guys don’t have. The question you are asking is if you can do this yourself, without service information and i’m assuming with a basic set of tools. Will the car just work when you are done or will it appear that no one has ever had it apart when you are done. if you are adventurous and OK with things not being as they were prior to you taking it apart then you should be able to try it. I would not recommend it.

  2. Jud says:

    How are was it to replace the alternator? I have a W8 and I’m a good mechanic and DIYer . Was it difficult getting the front clip back on?

    • Jim Nelson says:

      It’s not a do it yourself job, the a/c also needs to get charged in the process. Major pain of a job but fun, if you like puzzles:)

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