Is this the original water pump

[Sparkrite]

whist underneath my tcs I noticed a blue toothed pulley possibly anodised aluminium which seems non original. This might be an aftermarket pulley for the water pump. Is this better/worse or no different to the original, and could this mean the whole water pump had been replaced.

[BDA]

It’s hard to tell without a picture but it sounds like a gilmer belt pulley. Is there a similar one on the crank?

If so, mod is not unusual and to my mind, desirable.

[Sparkrite]

Yes,there is a similar one on the crank with obviously a toothed belt.

[BDA]

I don’t think it means that the water pump has necessarily been replaced.

I consider it an advantage since there should be minimal pressure on the water pump bearing. The original v-belt should put little pressure on the bearing too, but the length of the belts can vary so if you used a shorter one you could get added pressure. Since a v-belt uses friction, there is some pressure on the bearing. Properly sized, it should not be a problem. Since a gilmer belt drives from the cogs, rather than friction it should impart no pressure on the bearing.

Is the cost of a gilmer belt kit for your water pump worth the price (which is not unsubstantial)? Practically speaking, probably not, especially if you fit the best fitting belt. But then you already have yours so I would be happy! Besides, gilmer belts are cooler than v-belts! 

[Footer]

BDA regarding your comment about the best fitting belt.  What are your criteria for "the best fitting belt"?  I have what I believe to be the original, factory fitted belt since the motor only has 22,000 miles on it.  I am rebuilding the original pump and intended to get a match for the belt I have.  I don't think stretching of the old belt is a significant factor.
I'd appreciate your thoughts. Thanks.

[BDA]

I don't have any firsthand knowledge about this because I have a different motor and my water pump uses a gilmer belt, it is apparent (and not that surprising) that the same size belt from one manufacturer will differ with a belt from another. This was brought home in EuropaTCs post about changing his water pump (http://www.lotuseuropa.org/LotusForum/index.php?topic=4128.0 he discusses different belts at the bottom of the text). His post is very worthwhile if you're changing or considering changing your water pump on your TC.

Since changing the water pump on a TC is such a big job, one would want to make sure it lasts as long as possible and that implies a bet that is no tighter than it needs to be. A gilmer belt is ideal for that since it doesn't require friction (i.e. tightness) to work so if properly sized, a gilmer belt will supply no stress on the bearing but as I say, the functional difference between a gilmer belt and a properly sized v-belt may not be enough to justify the cost.

To check the fit, I would take the loosest belt that when installed will not slip on the crank pulley when trying to turn the pump pulley. Even that may be tighter than you absolutely need. Maybe EuropaTC could chime in and describe how he determined the belt that fit the best.

[EuropaTC]

To check the fit, I would take the loosest belt that when installed will not slip on the crank pulley when trying to turn the pump pulley. Even that may be tighter than you absolutely need. Maybe EuropaTC could chime in and describe how he determined the belt that fit the best.

That's pretty much what I did only I was turning the crank pulley with a spanner. 

With the same engine in a Ford or Elan, the belt also drives the alternator/dynamo and a clunky lump of steel pretending to cool the radiator as well  and the description is for 1/2" play between the pump/dynamo.  (pic below)   

IIRC it was Mike Walters during one of his talks at Club Lotus weekends who said you could run it much looser, especially if you had removed the fan blade on the water pump pulley. He also said that running with the belt too tight was a big cause of failures and the Europa was better because you couldn't adjust it !

With that in mind I reduced tension on my Elan belt and was surprised how low it could go and not slip. On the Europa it's even better because the load on the pump must be approaching zilch;  it's only circulating water, it shouldn't be thrashing it about or pumping to a great head.

The replacement belt bought years ago from a Lotus specialist was very, very hard to fit. I reckon when you have to lever the pulley into place with a sacrificial  screwdriver and the belt won't move sideways at all, it's too tight. There's been loads of discussion about belts on the Yahoo Knowledgebase and it seems I wasn't alone on this. Talk of folks shaving belts to fit, etc.

I bought 5 belts with a range of diameters but similar angles and it's surprising how little change makes the belt too tight or too loose. My final selection is probably around 1/2" slack with finger pressure, maybe a touch less but it doesn't feel tight to touch. It won't slip and moves instantly turning the crank by hand with a spanner. Ironically, the belt that fitted the best was the cheapest of the lot - obviously Colin Chapman had a hand in selecting it back in the day   

Brian