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Wet Serpentine Belt Slips


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My 2004 turbo Tip does this strange (or not so strange) thing that whenever I have washed the car or it has rained quite heavily, the serpentine belt slips on the alternator pulley when the engine is first started for about 10-40 seconds with the voltmeter registering at 12V until the belt stops slipping. Looking in the engine bay, the alternator pulley is turning but obviously not enough to give a charge until a little chirrup when the belt grips fully. It doesn't happen with a light drizzle but any moderate rain (which in the U.K can happen daily) would make the car do this. When I park the car the rear is slightly up hill and I wonder if this is enough to angle the water directly on the belt.

I've tried a new Porsche, Contitech and Gates belt and all do the same thing. Looking at a previous post, I've checked the routing as the belt can be installed a couple of ways in the car. There is no oil leak but i cleaned all the pulleys with brake cleaner anyway. My alternator is a brand new Bosch one.

Anyone else have this problem?

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First I have heard of this --

I'm not that familiar with the Turbo's -- is it possible the tensioning pully is weakening? How much deflection do you get in the belt with the engine off,

I'm not sure if the best way is to measure at a common point lateral deflection -- or rotation/twisting?

I don't think the tensioner is adjustable, but it might be.

Just a quick cheap thought....

A little more elaborate -- one could fashion up some sort of rain diverter around the belt.

Mike

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You claim that an new alternator is mounted, maybe the current alternator has no freewheel pulley and the previous does have one? I would consider that first, you never know.

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My original alternator had a fixed pulley but the brand new Bosch replacement had a freewheeling pulley. I thought that was it so tried a new Bosch one with a fixed pulley but problem persisted.

I am starting to wonder if it is the tensioner. It feels as strong but this is subjective. I need to exert about 13kg using a 23.5cm long socket and bar to turn the tensioner using the 15mm bolt. At about 10kg force it's just starting to move.

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I can honestly say that I have never encountered this problem. First thing I would do is to pull the belt and check its length against a new OEM unit, then install the new OEM belt (they are really not that expensive). Could be just stretch or glazing on the face of the old belt. Then I would look at each pulley for any signs of unusual wear or texture on the pulley faces where the belt rides. I would also consider replacing the tensioner.

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I've done all the above except the tensioner which I suspect is the problem. I've used 2 Porsche belts on top of the Gates and Contitech one in the last year and 8k miles. My water pump and alternator is new. Replaced the P/S pump pulley and also the 2 idler rollers. Only thing left is the crankshaft pulley and tensioner. Can the tensioner be replaced with the alternator out and engine in situ or is access too awkward? I was hoping that with the alternator out I can reach round the back of the tensioner to get at the bolts holding it to the block.

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I've done all the above except the tensioner which I suspect is the problem. I've used 2 Porsche belts on top of the Gates and Contitech one in the last year and 8k miles. My water pump and alternator is new. Replaced the P/S pump pulley and also the 2 idler rollers. Only thing left is the crankshaft pulley and tensioner. Can the tensioner be replaced with the alternator out and engine in situ or is access too awkward? I was hoping that with the alternator out I can reach round the back of the tensioner to get at the bolts holding it to the block.

If you scroll down several pages on the following PDF file, you will see both instructions and photos on a DIY for the tensioner: http://bd8ba3c866c8cbc330ab-7b26c6f3e01bf511d4da3315c66902d6.r6.cf1.rackcdn.com/Porsche_996_Turbo_Accessory_%20Serpentine_Belt_Pulley%20Replacement.pdf

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Thank you JFP as usual. Your advice is always invaluable. The instructions in the link show the tensioner roller replacement. I will probably try to replace the actual tensioner body as well. From the parts diagram and turbo technical manual, it looks like it can be done once the alternator is out of the car.

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Thank you JFP as usual. Your advice is always invaluable. The instructions in the link show the tensioner roller replacement. I will probably try to replace the actual tensioner body as well. From the parts diagram and turbo technical manual, it looks like it can be done once the alternator is out of the car.

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Thank you JFP as usual. Your advice is always invaluable. The instructions in the link show the tensioner roller replacement. I will probably try to replace the actual tensioner body as well. From the parts diagram and turbo technical manual, it looks like it can be done once the alternator is out of the car.

Changing the belt roller is straight forward, changing the tensioner itself is a bit more complicated. That L shaped arm in the photo passes through the bracket and into a small black canister that houses a clock spring. When you twist the pulley to get the belt on, you are actually winding the clock spring tighter, which is how it holds tension:

151115350074.jpg?itok=gRJuau7A

Problem is getting at it. On the normal 996 or Boxster (diagram below), it is under the AC compressor at the rear of the bracket that the AC and alternator mount on (item #10):

tensioner.JPG

The layout on a Metzger engine is not exactly the same, so I have no exact diagram, but it is similar. This is no picnic to get at and replace as it is in very tight confines, but the part is about $150-200 US.

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It is the black spring bit that I am thinking of changing as I've replaced the pulleys, idler rollers and various belts. Might take off the alternator first and have a good look to see how accessible the bolts are before attempting to do it.

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Hi, I have an 02 TT tip and the same happens to me: either in heavy rain days or after a thorough exterior wash, I have the same slippage for a few seconds. Never worried about it but it may have begun to happen 2 or 3 years ago when the alternator quit and had it replaced under warranty. They even threw in a new battery. Best warranty I had in any car.

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Hi-

I have a 2003 996 TT with the same issue. Bought it with 9,800 miles and only have 12k now. The belt is original and if it gets soaked during washing it will slip and even stop (done this once so far) right after the wash when I turn the steering wheel quickly (loading the belt). I assume its slipping at the crank as the alt light comes on and power steering goes away. If I leave the car running when I wash it, the belt squeeks when spraying water around the rear lid. Plan to replace the belt later this fall but don't expect this issue to go away completely. Live in Seattle and have never had an issue while driving the car in the rain athough the car is new to me and I try to avoid the rain. Not sure this is an issue with tensioner etc or just a poor design. Appreciate everyones input on the topic.

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In your case the belt is nearly 10 so would have hardened or become glazed. I would replace it in the first instance as it's cheap and easy to do.

My problem only relates to the belt slipping on the alternator pulley when it is very wet and first started. It doesn't affect the steering or occur during driving. I've replaced my belt 4 times in the last year but it still occurs.

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  • 4 weeks later...
  • 3 months later...

I haven't had the chance to sort it and mine is still doing the same thing after a storm or washing the car. I cleaned all the pulleys and put a new belt on again with no change to the problem. I have a new Febi tensioner to put on but inertia ( and terrible UK weather ) is a terrible thing. I guess I've lived with the problem for 2 years it's becoming something I've accepted will happen when it's very wet and hasn't caused any harm. If I get round to changing the tensioner I will update this post.

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  • 3 months later...

Just happened to me today after car sat out in a heavy rainstorm (at the local garage for the annual inspection). I ordered a new belt since I have no record of this one being replaced and it might be 12 years old!

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  • 10 months later...

Finally decided to try to replace the tensioner. Got a Febi one for only £55. Removed the alternator and the tensioner was clearly visible. The 2 bolts holding it to the mount were just about accessible but the middle one holding the rod to the pulley was obstructed by a pipe. There was no way of moving the pipe as it is rigid. To change the tensioner would have entailed more dismantling so I chickened out and replace everything. I guess I just have to put up with the belt slip after a heavy shower or washing the car. As I can get Gates belts for £15-20, I've been changing it every other year (about 12 k miles) case it's weakened by the slipping.

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  • 3 weeks later...

I have a 2001 996TT that I bought with 17,500 miles on it.  The belt also squealed after I washed the car (I don't know about heavy rain).  I thought it may be the belt, so I put a new belt on.  It seemed a little better, but if I get a lot of water in there, it still squeals for a few seconds. 

I pretty much brushed it off as a bad design, but if someone finds out otherwise, please share the fix!

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  • 2 weeks later...

Happens to me all the time after a wash (especially since the soapy water provides even more lubrication than just rain I assume, since I don't drive it in the rain).   Dealer confirmed that it's a typical 996TT issue.  Happens more often than not.   As long as it doesn't slip for more than 5 to 10 seconds, you're good.  If it slips more, than you can be "polishing" the belt, or it is already worn.

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