Welcome to our Site for MG, Triumph and Austin-Healey Car Information.


MG parts spares and accessories are available for MG T Series (TA, MG TB, MG TC, MG TD, MG TF), Magnette, MGA, Twin cam, MGB, MGBGT, MGC, MGC GT, MG Midget, Sprite and other MG models from British car spares company LBCarCo.

MG MGB Technical - MGB water pump problem

Hi, I am having terrible trouble trying to replace a water pump on my 1968 MGB roadster. The pump GWP115 fits the engine block, and according to the engine number should be OK, but it's too long by about 1.5 cms. so the fan belt is out of line. I can't find a pump that is the right fit but is shorter. (the edge of the casting to front edge of the pump needs to be 11 cms. and the diameter of the impeller is 60.3mm) can anyone help with this?
Thanks in anticipation.
J Reckitt

Some info on the different pumps fitted on Paul Hunt's website

You may need to copy and paste, as I can't get the link to work.

For some reason, an 's' has been added to the 'http' when I clicked on the submit button.

Edit: when I edited the post, the 's' disappeared. Go figure.
Dave O'Neill 2

Thanks for this. I have looked and maybe GWP117 is the answer. I have asked for measurements.
J Reckitt

Jim the water pump you have part no GWP115, is for the 3 main brg engine, GWP 117 is for the 18V engine, if your engine is the original one you need a GWP114, what is your engine no, I put a post on in August/September, about badly fitting water pumps even when the correct one was obtained, you need to order a water pump by engine number, post your engine prefix and we can tell you which one to order
Andy Tilney

GWP 114 is the only one that has a 60mm impeller which is what my engine needs. The other two have impellers that won't fit into the block. However GWP114 is too long by a cm or so. My old pump is 11cms long from the edge of the casting to the front, which is shorter than GWP114 which other than that fits. The engine number doesn't help because I've spoken to MG Owners Club spares about this and they say I've got a non-standard pump and have suggested that the engine has been modified at some point with the original engine number fixed onto a non-standard block! To make matters worse, my local garage man who is a classic car enthusiast tried to get another pump, sent off my old one, and has now lost it. Great!!!
Anyway, the engine number is 18GB-V-H47376 Year 1966, Chassis no. GHN3 87624
J Reckitt

Jim I have just measured the length of a GWP114 water pump which was 106mm, I did this with the pump in my hand so this reading is exact, you say your original pump was 110mm, so we are talking of a 4mm difference, I also measured the water pump pulley height which was 61mm, when I changed my water pump (GWP114) the belt did not run inline by a mile, this was a pump I bought from Moss the problem was the front fixing lug was to thick, it needs to 18mm thick to get the belt to run inline, this pump was made in China, after ringing round 3 other retailers and asking them where there pumps came from, I was told either we don't know they come in a plain box or China/India, in the end I bought a pump made in Britain by Quinton Hazell and it fitted perfectly and the belt ran in line exactly as it should, your engine should run a GWP114 pump, I would be interested to know what you did when you get this finally sorted, best of luck A.T
Andy Tilney

It's all down to long-nose and short-nose pumps, as in that link.

Long nose need a deep pulley and no fan spacer, short-nose need a shallow pulley and the fan spacer. With no spacer the fan will hit the block unless it is turned over (and no that doesn't reverse air-flow direction). Technically the wrong way round as the blades are shaped and mounted in a particular way, but mine was like that for many years with no problems until I realised. Fitting a spacer and putting the fan the correct way round made no detectable difference to running.

Fitting a spacer to a long-nose will probably chew the rad.

Andy, thanks for your input. I will try a QH pump and see if it works.
J Reckitt

The part number of the QH pump is QCP556, that cross references to a GWP114,
Andy Tilney

I've got the same pulley arrangement as Paul describes ie an early pump, with a deep spacer on an 18GB block, but running an alternator in a '72 Roadster, but without a fan (got an electric pusher one). All works fine.
Peter Allen

Have a look at this website for the lengths of the 3 main pumps,GWP114,GWP115 and GWP130 that are used in the UK
GWP117 was a pump made for the US market with smog pumps,the only difference between this pump and GWP130 is the rib on the left is ground down so the smog bracket fits on the bolts,length is still the same.
s p brown

Jim how did you get on with sorting out your water pump problem. have you managed to resolve it yet.
Andy Tilney

I have finally found a pump that fits! The spec. is:Water Pump BMC1.5 60mm Impeller, 4 hole pulley boss
I found it on a site for boat engines which oddly are the same block as the MGB 1800. All put together and running well, no leaks. Thanks for your advice. Jim
J Reckitt

Not odd, the same basic block was also used for diesel engines in narrow boats :o)

This thread was discussed between 26/12/2017 and 10/01/2018

MG MGB Technical index

This thread is from the archives. Join the live MG MGB Technical BBS now