belt tensioner for 987.2 ? seized

[jonnyspyder]

Hi all, I have just fitted a new serpentine belt to my 987.2 Spyder, the car is 12 years old and has done 58k miles, I fear the belt I took off was the original - although tbh it looked ok. The tensioner 30mm nut/body was quite stiff to adjust - clockwise to loosen tension on the belt took a lot of effort and the tensioner would not spring back from "fully clockwise" on its own at first - once anticlockwise force was applied the tensioner pulley nut it then returned to a position that tensioned the belt. I only have a socket so could not see whether the smaller nut-head at the tensioner 30mm nut centre was free to move independently of the 30mm part thus I'm not sure whether the thing is seized or not. Does the way my tensioner is operating sound normal or, because the belt not been off for 12 years, is the tensioner part seized and should move freely against its spring or is this behaviour normal? Thanks!!

 

[P9XX]

The belt tensioner should spring back to re-tension the serpentine belt automatically.

I believe the serpentine belt tensioner on your car is the same or very similar to that fitted to the 997.2, DFI engine.
DeMort has replaced many, my own was replaced by a local Porsche specialist a few years ago.

The 987 DFI engines tensioner also suffers the same corrosion and seizure problems as the 911 except less frequently due to the engines position and orientation in the car.

The following link should give you a good idea as to the source and rectification of the problem:

http://911uk.com/viewtopic.php?t=132158&postdays=0&postorder=asc&start=0

The attached diagram shows the tensioner assembly as parts 1 - 6.

 

[jonnyspyder]

thank you P9XX, very helpful - my tensioner looks similar in every way to the one in the diagram... without wishing to offend those with any degree of mechanical sympathy I attempted to rotate the 30mm "nut"/corner of the tensioner with an adjustable wrench so I could see the parts that would be hidden by a socket and the entire assembly inc the centre of the 30mm "nut"/corner Torx 50 screw rotated as well. I have removed the tensioner, I assume the bush/collar assy that runs through the centre of the 30mm "nut"/corner should be free to rotate? (the bush is seized solid in to the tensioner body) When I cracked the top Torx the pulley immediately released and behaved as I believe it should - therefore I assume the top assy Torx should hold the centre of the body bush tight with the body then being free to rotate about the bush and thus allow movement with the pulley to take up belt wear- can you confirm? That being the case is there any way or point in pulling the bush and treating to prevent it seizing? Finally is there any way to test the hydraulic spring that provides the tension? The sassy was coated in black goo - pretty sure it included oil rather than just belt dust. Thank you again

 

[P9XX]

I think you are correct in your diagnosis of what is happening to your tensioner.

The "Tensioner Arm" comprises an aluminum casting with a steel sleeve.
The pivot bolt (No 4 in the diagram) grips the steel sleeve against the water pump back plate.
In normal action, the aluminium arm rotates around the steel sleeve.
I think the dissimilar metals of the arm and sleeve corrode together aided by rusting of the steel.
On my car, this happened. Rotating the 30mm tensioner nut turned the arm, sleeve and the Tx50 M8 x 60 bolt.

The hydraulic tensioner (No 3 in the diagram) contains a strong spring and hydraulic oil. Oil leaking out of this tensioner means it has failed.

In my case, all items 1 to 6 were replaced at about 40k miles.

Regarding refurbishment of a seized lever / sleeve, I don't believe this is recommended.
Please note from the part number list (above) that there are 2 part numbers for the lever, indicating a revised part from that originally fitted at the factory.

The tensioner part numbers for your car are identical to mine.

 

[jonnyspyder]

Thank you, I have purchased and fitted a new tensioner lever and hydraulic spring... the new spring has free oil inside the rubber boot which I think forms part of the damping, the lever is a mystery to me as the new item appears to have no moving parts - the bush and internal appear to be fixed to the aluminium body however where as my old lever refuses to rotate about the hex bolt when the latter is tight the new one rotates quite freely - the Porsche tech guy I spoke to explained that there is an internal sleeve but I'm buggered if I could see one... anyway all fitted and I now have a belt that tensions correctly. Frustratingly I dropped the tensioner pulley cap into the bottom of the engine bay, no doubt lying on the under cover, I have no way of getting to it so I've had to order another!! Thanks again for your help...