Water pump reconditioning?

Well it was apparent as I stripped both motors that the water pumps on each were different.

The motor in the car was fitted with a large format pump- apparently identical to the pre 85 pump illustrated in the parts list.

The pump that came with the spare motor was smaller and resembled the post 86 pump, but it wasn't by any means identical; the main differences were some variations in the pipe moulding patterns and a lack of stub pipe to thermostat housing and the blocking off of the heater return stub pipe opening on the front of the  pump body.
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Although I had believed this was a post 86 pump, I have since discovered that it is in fact an earlier model as fitted to the Eclat or Excel 907 motors and which was  superceded by the larger pump used on the Excel (and for Elites/Eclats with aircon) and which was fitted to the motor in the car.

The pump that came with the spare engine is in worse condition with a bent shaft, but since I had intended to renovate one of them anyway, I still do have a choice as to which I use. The pump selected then dictates the fitting of other components such as the hoses required and possibly brackets for other ancillary equipment as well.

Parts diagram-later pump on left, pre-86 pump (larger) on right

Pre 85 style on right, pump from spare motor and subsequently identified as Eclat/Elite on left. The heater recirculation pipe inlet wasn't an original feature of this pump but one has been added and subsequently blocked off 

Block mating surfaces of both pumps- both need cleaning but hole patterns are the same and both fit nicely onto the block.  Note that the temp sender mounting hole is also blocked in the Elite/eclat pump. 

According to the parts lists, the pre 85 style pump is fixed to the block by 4 25mm bolts around the edge and a single 75mm that passes through the deeper hole right through the pump body. However in my case I had found that the lower two bolts also passed through the PAS pump bracket which is positioned outside the water pump and these are 35mm long.

Note mounting hole bottom right (in this view) of the thermostat housing in this pump which goes right through the thickness of the pump body and is filled by the 75mm bolt....

and in this one (Elite/Eclat)where the thickness of the casting is reduced.

I am also told that Lotus generally over-drilled the block holes and used bolts that were shorter than the full length of thread available. If so then longer bolts might be accommodated relatively simply. I think its probably best to use the longest that will still screw up to the relatively low torque specified for this position; 7-8 lb ft. I ordered an Allen button cap bolt M6 25mm to use under the auxiliary pulley where my own bolt was missing.

Given that the pre 86 pump I have is in better condition (shaft not bent), it appears to be correct for the year of car and that I have most mounting bolts, hoses and a matching alternator bracket, it seems wisest to go with this pump. However, since I cannot be sure of its condition and  as it has been sitting unused for many years (albeit surprisingly with water in it!) I think I will still send it away for renovation.

Block mating surface, the pattern of 5 bolt holes fits with either pump.

Having looked around I decided to order a rebuilt pump (exchange) from PNM engineering  who appear to offer the best price. I sent them the pictures above to confirm the price and the suitability of their kit. Interestingly, they didn't recognise the second (smaller) pump as a Lotus pump at all- which at least confirmed my decision to use the bigger one. However, I know that this pump was fitted to the block of my second motor and that its bolt pattern matches. Further this pump has the numbers 907E and 02196 stamped on it so I think it must mean its a Lotus pump. I checked the parts list for earlier cars also using the 907 block, and although I couldn't find this number, I did see that this pump looks very much like an earlier pump fitted to the Elites or Eclats w/o air con. The same parts list also revealed that Elites/Eclats with air con were fitted with a different pump (C907E0878J) that resembles closely that used later on Excels - including my car, although this pump has acquired a different number (A912E0878J). These two numbers don't seem a great distance apart but presumably there is some difference to the pumps to warrant a number change? If I find out what it is I will post it here.

Elite Eclat parts list, note resemblance to the two pumps I have. The second motor's pump looks like that on the left whilst the one fitted to the car when I got it is very like that on the right. Note the pump on left has no heater return hose stub and apparently no temperature sender drilling either. Image reproduced from RD enterprises.

It therefore seems that the more chunky pump is right for my car.

I also ordered some new hoses from SJS- I suspected attempting reuse of my hardened hoses is just a way of booking a second strip-down in pretty short order so best to use new. I did notice a bit of a mystery regarding the inlet manifold to pump hose though; in the diagram (above) it's shown as a simple, straight hose- and indeed that's what I found had been fitted when I took it apart (see removing the head... although I did have to cut the hose to remove it). However, the replacement sold by SJS for this position has a slight kink in it, a straight hose being sold for the HC engine only. I am not therefore sure which is best for this car. Also given the evidence of attention by the LBPO, I can't be sure that the wrong hose hasn't been fitted in the past. Overall, I think that I will follow the parts list  and will order the straight HC motor hose - its about half the price anyway and so the cheapest to start with. I can always order the kinked hose later if needed.

OOOps...The Best laid plans....
I had to clean the nasty old RTV gunk from the pump before mailing it to PNM- and having done this I could then see that the bolt holes are in a bad state- 2 are very enlarged and distorted and 2, although still round, look rather larger than the M6 bolt that should go through them! I am therefore worried that it won't sit firmly and could move on the block in service. This might explain why it was fitted with RTV gunk rather than the gasket which is correct for this year. I therefore need to reconsider my selection of pump to use for my resto; or get an age-appropriate used one to recondition.

Note two distorted bolt holes bottom and Right revealed once the RTV has been cleaned off. All holes are intended to accept an M6 bolt but even the two top and left look rather bigger than the deeper and undistorted hole shown top right at app 2 O' clock