Thread: Max. engine revs.

Originally Posted by disco 3 door

Hi All,
More to report, Engine only flight reving to 3500 on mine & 4600 on nieghbours. Have to drop 1 gear to retain same speed as nieghbours on certain hill running out of Melbourne. Also empty trailer (6X4) knocks top end performance about. Arthur, would mesuring Alternator pulleys do the same as the vibration test as I am running the longer (1595)of the 2 different belts as the short one (1585) would squeal after a short period.
Regards Shane.

Aside from your power issue, the alternators over the life of those Discovery motors do get replaced and there can be mixups with what is correct diameter pulley to use.

The tacho is calibrated to a particular size pulley, with the early Discovery 300TDi motors there was a change from a larger diameter alternator pulley to a smaller, current, pulley.

Without changing the tacho, it is best to determine which size pulley to use and fit the one that is correct for the tacho reading and it's matching belt. The longer (1595) belt goes with the larger pulley and the shorter (1585) belt is for the smaller and later pulley size.

You touched on the squealing belt issue, there has been some postings to threads on this forum that can, confuse a lump of concrete !
Get your pulley size sorted first, then with a new belt if it squeals, I would make these following checks.

Check the alignment of the serpentine belt idler, the idler has a bush in it's pivot that can wear off to side, after dismantling one of these, I say that once worn, they are beyond economical repair, so replace with a new one easily done but before the idler is replaced take the stud out of the cover put some thread lock on the thread, (cover end only) and then fit it back onto the cover.

Try the all the bearings for being tight or noisy when turned by hand.
The fan hub bearing in the timing belt housing cover can be replaced, most important is to get the measurement precise from the cover, to the face of where that pulley sits, when changing this bearing over, some Jag water pump bearings can be brought cheaply and modified by cutting the unneeded part of the shaft off --- don't get the shaft hot while doing this as it will wreck the seal and you will need a good press while doing this work, to push the old bearing out and the new one back in.

The Timing belt housing can distort in time, this allows the water pump and the steering pump to run the belt off a little, this is another cause of the belt canary's, not a common fault this one. I found another distortion caused where someone has dressed the surface on the back of the timing belt housing, it's where the 'P' gasket has caused corrosion and this surface was been filed smooth but missed the other points of contact to the block. This botch up has since been fixed by me, taking the housing to a engineering shop and then milled ( removed 0.016" ) so that the surfaces of the two sides are now parallel, this does mean that the pulley's that use this housing as their mount, are now back by that amount in respect to the bottom crankshaft pulley, another likely source of belt canary's, a painful fix for that is shimming the other pulley back to their original positions. Or just buy a new housing $$$$.
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Originally Posted by disco 3 door

Hi Arthur,
The engine in mine was an 18L originly. Was changed by previous owner to a 20L fron later model. I think this maybe where the problem lies.
Regards Shane.

Hi Shane

All you need is a new longer belt and the large pulley, or borrow that to try the idea that the alternator is running too fast.

Or change the Tacho over from a later D1, not hard to do either.
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