996 Carrera - tensioner pulley spinning / cannot release serpintine belt tension

Hi everyone, I�m working on reviving a 1999 Porsche 996 Carrera Cabriolet (3.4L M96, manual) that sat in a garage for about 6 years. The car currently has ~50k miles on the odometer. The engine was replaced in 2009 at ~26k miles with an AT 3.4 replacement engine. I recently purchased the car and have been going through basic service items before attempting the first startup in years. So far, I�ve installed a new battery and replaced the cabin and engine air filters. Next on the list is fresh oil and filter, siphoning old fuel, replacing the fuel filter, and installing new spark plugs. Everything was going smoothly until I attempted to replace the serpentine belt. The issue I'm running into is that the belt tensioner will not release tension. When I try to rotate the tensioner using the 24mm hex with a breaker bar, the pulley assembly just spins instead of moving the tensioner arm. The 15mm bolt behind the pulley also appears to be loose, and using an endoscope, I can see that it spins when I try to move the tensioner. I tried several 15mm wrenches (different lengths and styles), but due to the tight space, I couldn�t get a solid grip on the bolt to stop it from spinning. Has anyone run into this before on the M96? Does this sound like a failed tensioner assembly, or just a loose pulley bolt that needs to be secured? Separately, I also attempted to remove the oil drain plug (8mm hex) and could not get it to break free. After several attempts, the hex ended up stripping, so I�ll likely be dealing with extracting that and replacing the plug. Any advice or suggestions would be greatly appreciated. Thanks!

Pulley is connected to a 'spring' arm that seizes up not allowing it to compress. Work some wd-40 into the arm mount while trying to move the tensioner back and forth with a liberal heavy wd40 application into where the arm goes into.

I will definitely try that out. Thank you!

Mine had similar issues but is what it was - PO put a belt on that was about 1in too short. It Was a pain then I just remembered I had one of those BMW things you clamp on the pulley then rotate and the belt pops off.

If the belt is in the way of you trying to deal with the tensioner, why not cut the old belt off? Get it out of there and then work on the tensioner.

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That�s definitely an option, but I�m hesitant to cut the old belt off because if I end up not being able to get the tensioner sorted out right away, I�d have no way to run the car at all. The current belt actually looks visually fine (no cracks or missing ribs), it�s just old. For now, I�d prefer to leave it on, so I still have the option to start the car once I finish the rest of the service items.

Just leave it on, it looks almost new based on the stamps on it not being worn off.

If I remember correctly, when I had to replace the tensioner pulley, I was able to get an offset wrench back there and pin the other side of it to the engine casing. I'm sure if you bring it to a decent mechanic, they can figure it out.

This is the correct answer, wedge the wrench behind on the back of the bolt and it will stop the spinning. I know this because I had a belt snap and trying to get the new one on and I ran into the same problem... the only thing that saved me was contemplating the potential shame of having my car towed in because I couldnt get a stupid belt on. Good luck. edit- meant to quote 996-cab above

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I know, it seems like the problem is a spinning fastener, its not the original problem. If the tension pulley bolt spins, stop. Do not keep spinning making loser.. Problem is a seized tension spring arm shaft/bushing, the pulley assembly is mounted on. This causes many to put excess pressure on bolt because tension arm is not moving enough or at all to relieve belt tension. The idea is not to spin that bolt or even turn it to remove tension, but to use the wrench as a lever to move the whole tension pulley/spring arm at an angle, pivoting on its spring arm where it comes out of the mount.. Not pivoting on the bolt that spins. Tension spring arm shaft, at its mount bushing/shaft, is the point that needs to turn/pivot, not the bolt that holds in the pulley. So what happens on almost all these m96 eventually is the tensor spring arm shaft that comes out of the mount gets seized up and decreases arm range or complexity eliminates the spring arm from moving. That spring is what applies the tension. This does not mean you necessarily need a new tension spring pulley mount,,, as said above, working in some wd-40 or any penetration oil of your choice usually fixes this fast. Even if the bolt still spins (as long as its not real lose) the amount of pressure needed to move the spring once its tension spring arm freed up is considerably less and the bolt will probably not spin any longer. If it does spin just tighten it best as possible and you should be able to operate the spring tension arm correctly as the torque needed to move the spring arm is considerably less than it takes to spin the bolt. You must work/spray directly in penetrating oil into the bushing the shaft goes into while moving arm/shaft back and forth without belt on it. Keep doing this till full range is restored to the tension arm.... You'll be surprised once the pulley spring tension arm is freed up to full range how easy it is to take on/off the belt now...

While I'm thinking about it, now is a great time to replace the two idler pulleys and the tension pulley while you have it all apart. One of my idler pulley bearings seized and this is what broke the belt on my car, plus this is a fairly cheap repair since you're already 80% of the way there.

Get this and never have to worry about it again https://lnengineering.com/rauch-spie...6-987-996-997/

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Agreed. I replaced all of my pulleys and the tensioner with the Rauch und Spiegel. It's a lot of money but it beats the melted plastic. R&S in front. Spalled Sebro that lasted two years in back.

Thanks, everyone, for the detailed responses. I really appreciate it. That explanation about the tensioner arm pivot being seized makes a lot of sense, especially since the 24mm hex feels very stiff, but the center bolt just spins. I think I was definitely focusing too much on the bolt itself instead of the arm. I sprayed PB Blaster into the pivot area behind the pulley, and I’m going to let it soak and then try again using the method you guys suggested — wedging a wrench on the back bolt and using the pulley/hex as a lever to move the entire tensioner arm, not the bolt. I’m working on jack stands from the top right now with basic hand tools and a breaker bar, so access has been a bit tight. I’ll report back once I give it another shot. Also, while I’m working through this, I ran into another issue — the oil drain plug (8mm hex) is stripped and won’t come out, and the plastic oil filter cap is extremely tight (won’t budge even with a lot of hand force). Any recommendations on the best way to remove those on the M96 without damaging anything? I’m planning to finish the oil service, fuel filter, drain the old gas, and replace spark plugs before attempting the first start. Thanks again for all the help.

Just do a search in this forum for "stripped drain plug" Buy a strap filter wrench from the auto parts store for the oil filter canister Get a billet stainless steel oil drain plug https://lnengineering.com/products/m...c-drain-plugs/

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The area you need to spray (and work the arm up/down to loosen up the corrosion while spraying in more pen oil) is not behind the pulley, its where the arm that comes from the pulley goes into the spring mount in my above pic. The belt has to be off to work in the pen oil into the arm mount. see pic above. Look at your engine carefully with airbox removed, you'll see what I mean. Look for the spring mount in my above pic...

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Blue arrow correct?

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https://rennlist.com/forums/996-foru...l#post19713402

Is that it, where the arm enters right?

Pretty sure the 24mm head, which is effectively a nut, is held with red loctite as well. As described, wedge a thin wrench on the 15 mm bolt on the backside of the arm so that the bolt does not turn. Then use a heat gun to heat the front 24mm head to ~500 degrees to release the red loctite. Use a socket on the 24mm head and it will come off easily. Use blue loctite when reassembling.