mk1-forum.net

After a longish run at about 70mph the alloy water pump on my '66 S has loud sounding bearings. I'm considering fitting an original cast type. According to the details on the Somerford page (http://www.somerfordmini.co.uk/eshop/in ... page&id=96) there doesn't seem to be a distinction between pumps for the different engine sizes available in the mid 60's. Is this true? Or was there something different about the S pumps?

Related to this, since I've had it my car has never been up to the N mark on the temp gauge. Could it be that the modern alloy pump it has fitted is too efficient and the temp will be normal if I switch back to a cast one?

Any thoughts appreciated.

I use a cast water pump on my S and its allways running a little bit on the hotter side. In between I changed to a newer alloy water without any changes temperaturwise. So now I'm back on the original cast pump. Due to this experiance I can say it won't bring any changes on your S.

So long
the doc

The S's were fitted with a higher capacity pump, but (I think) in the late 60's they standardised across the range to the S design pump.

These days, not all pumps are the same. If you compare impellers between pump brands not many are the same as the originals, sme are better and some, well,,,,,,, It shouldn't matter one bit if the pump body is cast iron or alloy as far as how well the pump works and in turn how hot the engine runs.

I have found, with just about all pumps, if they ever run dry, it usually does ruin the seal, though not always right away.

Thanks for the replies so far.

My thinking around the cast vs alloy partly has to do with the original appearance of the cast one and partly with the fact that I have a spare cast one that looks usable (from a '63 Morris 850). But if the one used on the 850 is not up to the job on a 1275 S, it obviously makes sense to rather go with a modern alloy one that is.

So are we sure there were originally two different cast pump options, one used on S's and the other on the rest?

Big bore and small bore pumps were different in the olde days based on the depth of the impeller. The big bore block could take an impeller that fitted deeper into the block. That same impeller would not clear the internal block casting on a small bore block. Looking at it the other way, you could fit your small bore pump into your S engine, but you'd be using a small, less effective impeller.

cheleker wrote:Big bore and small bore pumps were different in the olde days based on the depth of the impeller. The big bore block could take an impeller that fitted deeper into the block. That same impeller would not clear the internal block casting on a small bore block. Looking at it the other way, you could fit your small bore pump into your S engine, but you'd be using a small, less effective impeller.

Early S-engines had the smaller impeller, the same as the 850.

Gareth, with early S, do you mean Mk1 S as opposed to Mk2 & 3 or do you mean really early? Any ideas of a change over date?

Has you say the early Cooper 'S' was fitted with the small bore and small impeller water pumps (2A776), a bit later they were fitted with new 'S' water pump( a new iron casting was made for this pump 12G1771) this had big bore inlet and a deep impeller,a bigger bore bottom hose was needed 12A1550 because of the inlet bore size.

Len.

Thanks. I just checked the bible ...it says there was a pump upgrade in Feb '68, so I'll assume that was the change from narrow impeller to wide. This is supported by Somerford's parts list.

If anyone can disprove this, please let me know.

abri wrote:Gareth, with early S, do you mean Mk1 S as opposed to Mk2 & 3 or do you mean really early? Any ideas of a change over date?

Really early Mk 1s had the "smaller" one. Change date I'm not sure off.

Point being, watch out for the impeller length and use the bigger one, if it will fit.