Tensioner pulley replacement by chumneywarner

Hi all,

Here's a cheaper & easier fix to replacing your M47 engine ancillary drive belt tensioner pulley.

Normally, replacing the tensioner pulley, supplied with 'L' mount, would require the removal of the timing chain casing, but as long as your tensioner spring mechanism is OK, which is inside the casing, then this isn't necessary.

The cost of a new pulley starts at about £70 for a pattern part, up to £150 for an original. I have a cheaper repair to the pulley, if you have the confidence/knowledge/facilities to undertake a repair to your original pulley, but more on that later.

Jack up the right side of the car & support on axle stands. Remove the right front wheel, wheel arch inner liner & engine under tray & support the engine on the right side with a trolley jack (don't forget to put a block of wood on top of the jack to distribute the load to avoid cracking the sump). Remove all the right hand engine mountings & lower the engine until you can see as much of the pulley as possible. Remove the ancillary belt. Using a 15mm ring spanner, hold the bolt at the back of the pulley mounting. Using a 24mm socket on the pulleys' tension adjuster 'nut', undo the nut, holding the 15mm bolt steady. This is a left hand thread, so turns in the opposite direction to normal to loosen. You cannot remove the bolt, as there is not enough clearance between the adjuster 'L' mount & the timing case, but the adjuster nut & protective washer will come away with the pulley, along with a spacer that is between the back of the pulley & the adjuster mount. Rebuild in reverse order, discarding the new 'L' shaped mount & bolt that came with the new pulley, using just the new pulley, adjuster nut, protective washer & spacer.

You can repair the original pulley instead of buying a new one, if you have the confidence, for under £20, as it's usually only the bearing that wears & not the pulley face. You will need to purchase a good quality bearing, I used the following:

SKF 62202RS1 Rubber Sealed Deep Groove Ball Bearing 15x35x14mm
You will need a hydraulic press (or garage that has one & get them to press out & in the bearings) or good heafty engineers vice. Find a socket that will fit snuggly in the front hole of the pulley & another that sits on the back bearing housing part of the pulley, with a large enough hole for the bearing to slide inside of. Place the smaller socket in the hole in the front of the pulley & clamp the socket & pulley in the vice, with the back face of the pulley toward you. There are peened crimps around the back edge of the bearing, remove them if you can, its not strictly necessary, but can make life easier. Now tighten the vice to push the bearing out, it takes a LOT of effort. It is sometimes necessary to heat the pulleys' bearing housing just to get it initially moving, a good blow torch does the trick. Once the bearing is out far enough to touch the vice, get the larger socket around the bearing back face, to allow the bearing room to push all the way out to the inside of the socket (remember you heated it, so cool it off 1st to save burning yourself). Clean up the pulley & file off the crimps & get ready to press in the new bearing. You will need to find a socket that fits just inside the pulleys' bearing housing, that will push on the OUTER race of the bearing, for use a bit later. Clamp the pulley & bearing in the vice & tighten the vice to press home the bearing. Move small amounts at a time, checking that the bearing is entering the housing squarely. If it starts to push in unevenly, stop, take the whole lot out of the vice & adjust position to push on the side that is protruding out more until level again. Once you have the bearing level with the back edge of the pulley, remove from the vice & place the socket onto the outer race of the bearing, put back in the vice & push fully home. Now peen over the housing at the back edge of the bearing race, as added protection to stop the bearing coming out. This bearing is 1mm narrower than the original. Bearings quote sizes in the following way: Inside diameter (ID) 1st, outside diameter (OD) 2nd, then width (W) 3rd. The original bearing is 15mm wide, but I have been unable to source one. If you are also unable to find the correct width bearing & are using the (better quality) bearing quoted here, find a washer about 1 to 1.5mm thick, that will fit snuggly over the adjuster nut shaft & place it between the back face of the head of the adjuster nut & the protector washer. This will take up the slack caused by the slightly thinner bearing. I used a copper sealing washer, but aluminium sealing washers of the same size are available. Normal steel washers with this size inside diameter, usually have a large outer diameter, too large to fit into the pulley, but any metal washer of the correct size will do. Don't use plastic/nylon/fibre etc.

Job done, now refit to the car.

Posted 16 Aug 2013, 21:42 #1 

I have a revolving tensioner hex head- from the post this appears to be a bolt through the pulley with a left hand thread and with a 15mm nut on the engine side- making it difficult to get a purchase on the hex to rotate the offset or "L" shape shaft. I would like to know if anyone has identified what goes wrong so as to allow the bolt to rotate?
I have the special tool to detention the auxiliary belt. I applied it to the tensioner hex on the tensioner pulley & rotated it anticlockwise. I was able to get the belt off. Then after repairing the alternator ( it had a defective rotor) I used the tool to rotate the hex bolt anti-clockwise to allow me to put the auxiliary belt back on the car. I achieved this but then noticed 3 things:
1) the tool , still in its fully anti-clockwise position, did not readily snap back clockwise. It did seem to move back slowly at last, but I only witnessed it in its returned position. I was not there when it moved.
2) if I then rotated the hex anti-clockwise, it seemed to be rotating within the pulley, rather than moving the pulley towards the front of the car & take pressure off the belt
3) I then noticed I could rotate the hex clockwise - yes clockwise - although it was hard work. Not knowing of the nut or left hand thread, but thinking the hex simply screwed into a threaded hole. If I did this a little and then rotated the hex anti-clockwise, I was able to move the pulley forward to relieve pressure on the belt.
From the "How- to" it seems that the 15mm nut may have loosened. What does this signify please?

Posted 15 Jul 2017, 22:22 #2