Auxiliary Drive Belt Tensioner
According to Land Rover the auxiliary drive belt tensioner used on the 300Tdi engines isn't a serviceable item and when a problem occurs the whole unit has to be replaced. The genuine part typically costs over £80 (or over £40 for a pattern component) but most problems are down to wear of the bearing in the rotating wheel which pushes on the drive belt to correctly tension it. Rumbling and squeaking noises from the tensioner are the normal symptoms.
This bearing is fairly simple and cheap to replace, with the whole job taking me about 30 minutes to complete.
I would also recommend the following
- Put the NEW bearing in the freezer well before you start and don't take it out until the LAST possible moment. Applying a little heat to the tensioner wheel will also ease fitting of the new bearing.
- Try to have a new circlip available. The snap spring ring holding the bearing in place isn't designed to be a serviceable part. The new circlip would need to be for internal fitting and suitable for retaining the 40mm bearing.
I got my replacement bearing from a motorcycle shop for £6 (it's also commonly used on motorbike wheels) though any bearing supplier should have it in stock. The bearing itself is a 6203-2RS and is fitted with two synthetic rubber seals to prevent leakage of lubricant as well as entry of dust, water and other harmful material. Dimensions are detailed in the diagram below.
Changing The Bearing
After disconnecting the battery remove the viscous coupling and fan to
give access to the tensioner.
Using a 15mm ring spanner on the tensioner pulley retaining bolt ( B ),
rotate the tensioner anti-clockwise to release the pulley tension from
the belt. Detach the belt from the pulley and release the tensioner.
Undo nut ( A ) with a 15mm socket and the complete tensioner assembly
can now be removed from the vehicle.
Clamp the tensioner body securely (above), using some packing if necessary
to ensure it isn't damaged by the vice. With a 15mm socket and breaker bar
the tensioner pulley retaining bolt ( C ) is removed by rotating
clockwise (left hand thread). Bearing retaining plate ( D ) is removed
with the bolt and tensioner wheel.
With the bolt and retaining plate removed the bearing and circlip can be
seen.
The circlip doesn't have the usual "eyes" at the ends so
standard circlip pliers can't be used for removal. Ensure you wear suitable
eye protection incase it springs out when being removed. If you're reusing the
old circlip also make sure it can't fly away never to be seen again, a clear
plastic bag and a bit of imagination can take care of this. I used a small
pointed tool and carefully levered it from its retaining slot ( E ).
The circlip and removal tool.
Turn the wheel over and remove the old bearing using a hammer with a suitably
sized socket as a drift - 11/16 A/F was a perfect fit in my case. Clean the
bearing housing and circlip slot before putting the new bearing in - again I
found a 5/8" W socket ensured the new bearing went in squarely without any
damage. If it's a bit of a tight fit then cooling the new bearing in a freezer
and warming the wheel can help.
Carefully refit the ciclip and the tensioner is ready to be put back together.
Reassemble the tensioner remembering the bolt is left hand thread so will
need turning anticlockwise to tighten.
Refit the tensioner assembly onto its engine auxiliary bracket stud and
tighten the nut to 45 Nm. Using the ring spanner on the tensioner pulley retaining bolt,
rotate the tensioner anti-clockwise to release the pulley tensioner and allow the
drive belt to be refitted. Removing the ring spanner will automatically tension
the drive belt. Refit the viscous coupling and fan and reconnect the battery.
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