water pump conversion

[turbineman]

worringly discovered water pump failure equals thrased engine if a mere water pump fails.
anyway thinking of belt driven pump only to take away parnoia of something else to worry about!!!!
anyway does anyone have any thoughts on this any opions greatly considered,
regards john

[DJT]

Hi There. Stop panicking. Water pump failure, per se, does not mean a trashed engine. But it does depend on what has failed.
The water pump, as you probably know, sits high in the vee and is driven by a jackshaft which, in turn is driven by one of the timing chains. This jackshaft also drives the distributor and, by another shaft attached to the distributor, the oil pump. This the same system employed in the Dolomite, TR7 and SAAB slant four engines.
There were some poorly hardened water pump shafts around a few years ago and the gear teeth failed very quickly. Although these should now have filtered out of the system, it is much better to rebuild a known good pump than fit a new one of dubious origin.
There has been a few examples of failed jackshaft/water pump gears in recent years (I had one myself). Also jackshaft front bearings seizing. It hasn't yet been established which leads to which. Bit of a chicken and egg situation. I was lucky in that the jackshaft bearing was fine and I fitted a known good jackshaft and rebuilt a known good pump. The failed pump had been in service for several thousand miles so wasn't one of the dodgy ones.
Due to the above, there has been a move in Triumph and SAAB circles to do away with the standard water pump by fitting a blanking plug and a Davies-Craig electric water pump. This has both advantages and disadvantages. One of the disadvantage being that you need another auxilliary pump to supply the cabin heater.
However, one of the Stag Owners Club members has recently developed another system with an externally mounted, belt driven, pump. This is so far proving totally reliable, even in this Summer's heat, and doesn't need another pump for the heater. In the unlikely event I get water pump problems with my current Stag, I shall be going down this route.

[Richard B]

You can fit the EWP without the auxillary pump.

The return from the heater matrix needs to be moved down to the feed for the EWP and the top return banked off.

This then circulates water through the heater.