Detailed questions on removing and replacing the chain tensioner on a 560SL

[dmorrison]

Ok did a search and could not find the specific item I needed.
Need to replace the timming chain tensioner. I have a new one and have a couple of questions.
The 560SL manual talkes about replacing the unit. It give 2 torque settings.

Screws for chain tensioner on cylinder head 25Nm
Coupling nut for chain tensioner 90Nm.

No where in the diagram is the coupling nut pointed out.

Also the manual says

1. Remove fastening screws and remove tensioner.

2. Mount chain tensioner with a new gasket and tighten screws uniformily.

Ok heres the question. Removing and replacing the tensioner. Do I in anyway loosen the large bolt in the center to remove the tension. And once the 2 mounting bolts are tight , do I then tighten down on the large center bolt. Or does it just come off and installing it only requires a little force?? Is there enough bolt length in the 2 mounting bolts to catch the treads and then tighten the unit. If so then I NEVER touch the large center bolt.
I guess I need specifics on Just the R+R of the tensioner.

Thanks guys

Dave

[ctaylor738]

I think it's like the 380 - you take out the old and put in the new with the two screws. You may need to push on it to get the screws started but I don't remember it being a big deal

If you bought a Febi replacment tensioner, the center bolt should come pre-set at 90 nm. I checked mine with a torque wrench and it was on the money.

Due to the increased tension from the new tensioner, the 8M x 1.25 fasteners for the tensioner may be too short to begin threading. Start with a longer fastener on one end to bring the tensioner closer. Then use the stock fastener on the opposite end, and finally replace the longer fastener with the other stock fastener.

Rich Mayer
82 500 SL

[Strife]

I'm worried about this more than anything on changing my timing stuff (chain, tensioner, upper rails+arm). I have also read that "pre-tensioning" it or somehow filling it with oil is required (?). Is this true? I have a feeling that this is one of those fixes that if it works in the first three seconds, it will be fine for 150K.

The following SEEMS logical (but COULD be and MAY BE WRONG!!!, I don't know)

1. Loosen or remove the center bolt/cap

2. Install the unit with proper tension on perimiter bolts

3. Tighten the center bolt/cap to proper touque

Maybe this will become obvious when I recv it (a Febi).

[dmorrison]

A followup on this post.

First of all thanks to all who posted a reply. It helped me "get" to the job.

Starting the car, I would get a 1 second timming chain noise that quickly disappeared. My service rep at the dealer pointed to the tensioner as the problem. However when I started it to move it in the garage, I heard no chain noise. Once I installed the new tensioner (without filling it with oil or doing anything to the new tensioner) starting the car produced no noise. I will be pulling the valve covers to examine the chain rails and to measure my chain stretch. 90,000 miles with Mobil 1.

Removing the large nut (36MM) on the tensioner does not do anything as far as the spring tension. So removing it is of no consequence.

The following is a job for a 1988 560SL.

1. Remove the windshield washer tank. by removing the one mounting screw.
2. Disconnect the the fluid level connector and the pump motor connector.
3. Pullout the pump from the tank OR disconnect the hose to the pump. If you pull the pump the fluid will come out the hole. Now is the time to replace the washer pump grommet if it was leaking or old.
4. Remove the tank completely from the car.
5. The grease covered large nut, actually a cap (36MM) is the tensioner. I cleaned mine with brake cleaning fluid. Don't do this on a hot engine
6. One mounting bolt is on the top and the other is under the 36MM cap.
7. Work the mounting bolts out evenly. A sidewinder ratchet really helps in this position.

http://www.jcwhitney.com/webapp/wcs/stores/servlet/Product?storeId=10101&Pr=p_Product.CATENTRY_ID%3A2007892&TID=100&TID=100&productId=2007892&catalogId=10101

8. Remove the tensioner.
9. Install the gasket on the new tensioner. Mine came with a light oil coating which helps the gasket stick.
10. Place the tensioner in the hole and make sure it is entering the hole perpendicular to the block face. I had the top bolt installed while positioning the tensioner. Press the tensioner into the hole to allow the mounting bolt to catch some threads. Then do the same for the bottom bolt. the force of the spring is very small.
11. Draw the 2 mounting bolts into their hole evenly so the tensioner is pushing centered on the tension rail.
12. Torque the mounting bolts to 25NM, this is very lite. Most of my torque wrenches range from 35-200FtLB or my small unit goes from 20InLb to 200In Lb. 25Nm = 221 Inlb. Since the bolts are steel and the block is steel I set it at 35Ftlb (18Ftlb = 25Nm) so I'm a little tight.

Picture #1
Locating the beast.
Picture #2
Dis-connecting the washer tank electrical connections
Picture #3
Washer tank mounting bolt.
Picture #4
Mounting bolt location.
Picture #5
The large cap removed. Again it does not effect the spring tension.

Dave

[Walrus]

Thanks for an excellent post (with pics!!! ). Great info!