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Replace Belt Tensioners - Porsche 911 Carrera
 
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Pelican Technical Article:

Replace Belt Tensioners - Porsche 911 Carrera

Time:

1 hour1 hr

Tab:

$150

Talent:

**

Tools:

24mm wrench

Applicable Models:

Porsche 996 Carrera models (1999-05)
Porsche 997 Carrera models (2005-08)

Parts Required:

Three tensioner pulleys

Hot Tip:

The top and bottom pulleys are different, despite them looking the same

Performance Gain:

Quiet running engine

Complementary Modification:

Replace drive belt

The 911 Carrera uses a complex belt path to drive all of the accessories of the engine off of a single belt. Even when I change the belt in my 911, the path is so difficult to remember off the top of my head that I have to refer to my own diagram in Figure 3 of Project 5 (belt replacement). The bottom line is that the three belt pulleys that are located on the crankshaft pulley side of the motor get a lot of wear and tear over their life. It's not uncommon for one or more of them to fail and begin to start squeaking.

When you get a high-pitched squeaking noise from your engine compartment, it's typically very difficult to diagnose where it's coming from. I like to run the engine and open the engine access lid while I'm carefully listening for the origin of the squeak. Be very careful of your hands and any items that might get stuck or caught in the engine if you're running it with the rear panel off. I often use a can of WD-40 with the spray nozzle extender attached to try to isolate which pulley or piece of equipment is making the noise. With the engine running, I typically soak the bearing shaft of each belt pulley, listening carefully for changes in the squeaking noise. Check every one, including the water pump, power steering pump, alternator, and the air conditioning compressor. Often, the noise will go away when the lubricant finds its way to the bearing. This works about 50 percent of the time to isolate the noise.

Another way to check the pulleys is to remove the drive belt and actually turn them with your hand. Sometimes you can feel significant resistance or hear a grinding noise as you turn each shaft by hand. Again, check each one, including the shafts of all of the accessories. All three of the idler pulleys should feel about the same. The accessories (alternator, water pump, etc.) will each feel different, so it's difficult to tell if there's anything wrong with the bearing unless you spin these on multiple cars every day.

Sometimes a squeaking noise may be caused by a belt that is deteriorating. As belts age they sometimes get worn out and smooth, and that may cause them to slip, which can result in a squeaking noise. If you suspect the belt may be the problem, then I recommend you replace it first. Or, you can try out some of the spray-on belt dressing that is available at your local auto parts store. The belt dressing is a temporary fix that makes the belt a little stickier and less prone to slipping.

Fortunately, the tensioners are very easy to replace. Simply remove air cleaner and open up access to the back of the engine (as detailed in Pelican Technical Article: Replacing Belts on the Porsche 911 Carrera). Then remove the drive belt from the engine. Removal of the two idler pulleys is as simple as unbolting them and replacing them with a new one. Be careful not to drop the large washer that is on the front of the two idlers and the spacers in back either. Although they look almost identical, the top and bottom idler pulleys have two different part numbers, so be careful not to mix them up if you are replacing them both at the same time. Reinstallation is a snap; simply install the bolts and tighten. The bolts that are used on the pulleys originally had self-locking compound on them when they were new, so if you are reusing them again, simply add a little bit of blue Loctite 242 to the threads prior to installing them.

The tensioner pulley is a little bit different. It is attached to a spring-loaded arm via a single bolt that is backwards in orientation from the other two idler pulleys. You need to get a 15mm wrench on the head of the bolt behind the pulley and then loosen the pulley with a 24mm wrench on the front. Be careful not to drop the spacer located behind the pulley when you pull it off. Reinstall the new pulley in the same manner, using a small bed of blue Loctite 242. Tighten the assembly to 44 ft-lb (60 Nm).

This photo shows the back of the engine and the three pulleys discussed in the text.
Figure 1

This photo shows the back of the engine and the three pulleys discussed in the text. The yellow arrow points to the top idler pulley, and the green arrow points to the lower idler pulley. Although they look the same visually, there are two different part numbers for these two rollers. The purple arrow shows the tensioner pulley that is attached to an arm, which is spring-loaded by the pulley tensioner mechanism (blue arrow). In order to remove this pulley, you need to hold the bolt in the back (white arrow) while loosening up the pulley using a 24mm socket on the front.

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Comments and Suggestions:
Cj Comments: Any technical articles for replacing the tensioner on an 09 997 3.8 DFI. I need to do one.
July 22, 2016
  Followup from the Pelican Staff: We don't currently have that tech article. If we get a chance to perform the procedure, we will be sure to document it.

I would grab a repair manual. It will have the procedure, special tools and torque specs.

Give our parts specialists a call at 1-888-280-7799. - Nick at Pelican Parts
 
MrMorninwood Comments: I want to try the WD40 trick on my C4S, to pinpoint the noise.
Can I run the car with the airbox off?
August 18, 2015
  Followup from the Pelican Staff: As long as the mass air flow sensor remains connected. - Nick at Pelican Parts  
ryan Comments: IIRC on my '05 carrera C2 motor its a rebuild the bolt on the back of the tensioner pulley is 16mm.
May 15, 2015
  Followup from the Pelican Staff: Ahhh yes. I remember that too. 9x7 cars use 16mm head bolt on rear of tensioning pulley. Thank you for that reminder. - Casey at Pelican Parts  
Jordan Comments: I am having trouble removing the spring loaded tensioner. I can't seem to get a 15mm wrench on the back of it, how did you do it?
February 1, 2015
  Followup from the Pelican Staff: Not sure what vehicle you are working on, but on a 996, I recall the front of the tensioner being 24mm. - Nick at Pelican Parts  
jhhaas Comments: DO NOT buy the kit unless you intend to replace the actual tensioner which is not covered by this article. I bought the kit and spent ~$90.00 I did not need to. Makes a nice expensive paperweight though.
October 14, 2014
  Followup from the Pelican Staff: The idler pulleys can fail, in the case you need the tensioner, the bracket has to be replaced. - Nick at Pelican Parts  
Itchy Comments: I wish there was a guide for the actual tensioner replacement. It's on the backside of the bracket that holds the power steering pump. I think the ps pump and throttle body might need to come off to gain access to the bolts tha secure the tensioner unit. Is there a write up on this that I'm not aware of?
October 5, 2014
  Followup from the Pelican Staff: The tensioner is built into the power steering bracket. You will have to remove the power steering pump and the bracket to replace it. - Nick at Pelican Parts  
Ric Comments: Just would like to know if the part numbers I listed are the ones as described in the article:
Replace Belt Tensioners - Porsche 911 Carrera
Wayne R. Dempsey
July 15, 2014
  Followup from the Pelican Staff: The parts are here: http://www.pelicanparts.com/catalog/shopcart/996J/POR_996J_ENGmis_pg1.htm


and here:

http://www.pelicanparts.com/catalog/shopcart/996J/POR_996J_ENGmis_pg1.htm
- Nick at Pelican Parts
 
Ric Comments: I have part numbers 99710211900 & 99710211800 , when I look up both these number they both come up with a set of 3 pulleys. Are these both the same or is there a difference?
July 8, 2014
  Followup from the Pelican Staff: Give our parts specialists a call at 1-888-280-7799. They can help you find the right part.
- Nick at Pelican Parts
 

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