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Les Henson

300TDi belt tensioner.

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A bit of tech stuff for you people with shiny motors :P

I had a couple of jobs to do on a 300TDi Disco today, so I thought a couple of Tech threads might be in order.

This is the fan belt tensioner bearing replacement.

Not a very difficult job to do really, a bit fiddly, and you need to have a vice or similar means of gripping.

Wear of the bearing is identified by a hissing noise coming from the tensioner whilst the engine is running. Removal of the belt will allow you to spin the tensioner wheel and any wear will be obvious. A small amount of movement forwards and backwards is ok, but a dry rushing noise, uneven feel, or other play, means the bearing has to be replaced. While engine damage will not happen if the bearing fails - the worn wheel will throw the belt off in the end, and you'll be stuck at the side of the road.

Normally you would need to buy the whole wheel, and it's £43 from Bearmach, and god knows how much from the main dealer. As in a lot of things, there's a trick to removing the bearing, which is a lot cheaper.

This is the tensioner in place and doing it's job.

med_gallery_2_67_618243.jpg

The bolt that holds the wheel on the tensioner body is opposite thread, so 15mm socket and lever in an anti-clockwise direction to release tension from the belt and lift it off the wheel. The tensioner will move anti-clockwise until it comes to it's own stop.

med_gallery_2_67_617856.jpg

Now click the rachet in the opposite direction and undo the centre bolt (clockwise) The wheel will then lift off easily. This is the removed wheel with centre bearing clearly shown.

med_gallery_2_67_344272.jpg

Now the bit that isn't recommended, but I don't see why there's a problem doing this.

The bearing is a pressed fit in the centre of the wheel and then retained by a snap ring. These things are almost impossible to remove - hence the need to buy the whole wheel.

I file a notch as shown, far enough down to be able to apply side pressure to the snap ring, which then is easily removed.

med_gallery_2_67_801673.jpg

The old bearing is easily pressed out using a suitable drift. The wheel is made out of cast iron, so take care not to fracture it. I used an old socket and a nylon mallet to knock it out.

I took the old bearing to Thamesdown Bearings where they matched it up. The new bearing is made by SKF, and as a reference, the part number is 6203-2RSH.

Don't bash the new bearing in, it's very small and can be easily damaged. I used a 30mm socket (same diameter as the bearing), and pressed it in.

med_gallery_2_67_357752.jpg

Replace the snap ring, and the wheel is ready to be put back on. Use a small amount of thread lock on the bolt.

Quite an easy and cheap job to do.

Edited to add information from forum member Rejo.:-

This same bearing will replace the one in the air con belt tensioner.

Les. :)

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Eurgh, a diesel in one's Discovery, horror of horrors :P:ph34r:

Good thread Les, tech archive in due course I think as it comes up lots :)

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Weel done, Les..... this is a job that's on my 'to-do' list..... I was gonna go the expensive route and replace the whole thing, but if an extra hour, with a bit of blood, sweat and tears can save me 30-odd quid, then I'm all for it!!

Dunk

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I have done three now and with a sharp edged screwdriver I managed to removed the circlip on all of them, it got easier after the first one.

push the screwdriver into the clip and lever away from the edge then a scribe between the clip and pulleylevering it up and out, then exactly the same as above.

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Another thing worth mentioning is replacing the snap ring with a proper circlip in case it ever needs doing again. Particularly if removed in the way Tony suggests.

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I tried levering the snap ring out with a sharp screwdriver, but the damn thing kept moving round in it's groove. The circlip idea is good, but I didn't know if the tabs would foul on the alloy casting of the tensioner.

Les. :)

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we tried to go down that route when i did mine, but the 'snap ring' is thiner than any available circlip, was going to get my mates engineering firm to put a circlip on a surface grinder with a magnetic table and grind a couple of microns off it, but in the end we put the original clip back. :huh:

its an easy job except for removing the snap ring. good idea about filing a bit out of the wheel though Les.... :)

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From Hobson a new bearing ID:

the code for it is: 6203-2RSH-C3

can be found here on SKF bearings website

full bearing spec --

6203-2RSH C3 SKF RUBBER SEALED BEARING

(also known as 6203RSC3)

C3 BEARINGS HAVE EXTRA INTERNAL CLEARANCE TO ALLOW

EXPANSION IN HIGH SPEED/TEMPERATURE ENVIRONMENTS

Rubber sealed to keep moisture and dirt from entering the bearing

BORE17mm

O.D 40mm

WIDTH 12mm

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I modded the snap ring by cutting a corner of it:

large.IMG_1714.JPG.5ad9e023cbcf553d269a208edddd1276.JPG

 

This will make it much easier next time, as you can just remove it with a screwdriver.

large.IMG_1715.JPG.650e34c6b46ed41cfcf52ba42639ed7d.JPG

 

Daan

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