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300Tdi timing belt modifications
Around 1997, Land Rover dealers started to report that some 300Tdi engined Defenders, Discoveries and Range Rovers were suffering premature timing belt failure. The belt was rubbing against the flanged edge of the tensioner, getting worn away and eventually breaking long before the scheduled change interval. The cause was misalignment of the pulleys , tensioner and roller, due to a combination of an inadequately strong timing case, poorly designed injection pump bracket and incorrect assembly methods. Not all vehicles were affected, and no official recall program was ever put in place, but Land Rover issued a series of technical bulletins to dealers, changed the design of tensioner, idler and bottom pulley, and produced two modification kits for affected vehicles.
The first modification kit STC4095K, for earlier vehicles, included a new timing case, injection pump bracket and sundry other hardware. The second kit STC4096K was less comprehensive, comprising a new belt, later type tensioner, idler, lower pulley, bolts and studs. Dealers were instructed to paint a yellow square on the upper left end of the timing cover on vehicles which had been fitted with a modification kit. However, as not all vehicles were affected by the problem, not all were modified. This can lead to problems when trying to work out which components to order.
In theory, if your vehicle has a chassis number lower than VA117353 (Defender) or VA560897 (Discovery) it should have the early type tensioner and idler, with a flanged lip on the tensioner and no lip on the bottom pulley. However, if it has been modified, or if the chassis number is higher than those quoted above, it will need the later type tensioner and idler. The only way you can confirm for sure which type you need is to remove the timing cover and have a look. This isn’t quite as bad as it sounds since on a 300Tdi you don’t have to disturb the water pump to remove the cover, but you will need to remove the crankshaft vibration damper and belt pulley.
On removing the timing cover, if the edge of the belt is heavily shredded and the timing cover is full of something that looks like black candyfloss, then you have a problem. Land Rover advise that the modification kits should be fitted as follows:
Discovery to VA711273 (except VA542371-VA558898), Defender to VA101256, Range Rover Classic (all) require kit STC4095K.
Discovery VA542371-VA558898 and VA711274-WA748935, Defender VA101257-VA129096 require kit STC4096K.
Discovery from WA748936 and Defender from VA129097 should not require any modification.
In addition, when fitting kit STC4096K you will need to replace the front outer timing cover seal with part ERR7143, if your vehicle’s VIN number is in the following ranges:
Discovery VA548520-VA558898 and VA716897-WA748935, Defender VA107351-VA129096.
