Water pump size

[Pascal]

Hi,

I have a water pump stamped 12H3255 on my 1974 MGB GT that I need to replace.

The 12H3255 is about 80 mm long between the base and the front of the pulley plate:



Could anybody tell me this measurement on the following pumps ?

GWP117
GWP123
GWP130

Many thanks !

[Vic Butler]

The standard replacement water pump for an engine with the number starting 18V, is GWP.130. . Your car should have an 18V engine as that was what the original fitment was unless it's been changed at some time.

[Peter Cresswell]

I must admit I thought there were only two type - for chrome bumper cars and rubber bumper. The dimension shown is shorter on CB cars than RB cars because of the location of the radiator. I have found that this distance is somewhat variable and the face for the pulley needs to be adjusted to make the fan belt run true.

[Peter Cresswell]

Having just looked them up in the B&G catalogue on line and they thoughtfully provide pictures with a vernier measurement. The distances are GWP 115 is for 3 bearing engines 18G and 18GA and is 105.55mm; GWP 114 is 5 bearing engines 18GB to 18GG and is 106.01; GWP 130 is for 18V engines and is 83.06mm. I would assume the GWP 115 has an impeller of 59.39mm and GWP 114 impeller is 68.43mm and GWP 130 is 69.19mm. So the CB cars have the longer body water pump and RB cars the shorter on.
I live and learn!
Pete

[KRG113]

Hi,

I have a water pump stamped 12H3255 on my 1974 MGB GT that I need to replace.

The 12H3255 is about 80 mm long between the base and the front of the pulley plate:



Could anybody tell me this measurement on the following pumps ?

GWP117
GWP123
GWP130

Many thanks !

Pascal hi, did you manage to source this pump if so could you kindly supply a link?

I too have a shot 12H3255 pump but its on a BMC 1.5 diesel the odd thing is mine has different dimensions to yours from the gasket flange to the top of the pulley mount is 95mm whereas yours looks to be 80mm. The closest I have found to mine so far is for an AUSTIN A60 WATER PUMP (** From 1967- 71 **). but some dimensions are a little off.
https://www.ebay.co.uk/itm/222333131800 ... OON.R1.TR4

[KRG113]

Having just looked them up in the B&G catalogue on line and they thoughtfully provide pictures with a vernier measurement. The distances are GWP 115 is for 3 bearing engines 18G and 18GA and is 105.55mm; GWP 114 is 5 bearing engines 18GB to 18GG and is 106.01; GWP 130 is for 18V engines and is 83.06mm. I would assume the GWP 115 has an impeller of 59.39mm and GWP 114 impeller is 68.43mm and GWP 130 is 69.19mm. So the CB cars have the longer body water pump and RB cars the shorter on.
I live and learn!
Pete

Hi Peter, that's some good information there thank you but still does not meet the criteria of my pump. I searched for the B&G catalogue you mentioned but was unable to find it do you have a link?
I have spend hours researching this pump (which led me here) it seems BMC/Leyland/Thornycroft used dozens of different water pumps I have also called many suppliers but still have no replacement pump as yet.
I found the following site with measurements but they are different again

http://mgparts.co.nz/b-series-water-pumps-which-one/

Any help from members would be much appreciated! I will upload pictures with dimensions shortly but I don't seem to have that option as yet must be as I'm a noob

[Paul Scott]

https://www.google.com/url?sa=i&url=htt ... AdAAAAABAD

[Paul Scott]

https://www.ebay.co.uk/itm/163742882405 ... olid=10001

Water Pump

For BMC 1.5 Diesel Engine

Multiple types of water pump were used in these engines, please compare photo to your old pump
If this isn't correct for you then please search our eBay store as we do have the other pumps
If you would like any help please send in a photo of your old one

Used in Marine Applications:

BMC Newage Tempest & Captain
Thornycrof 90 & 90/2
Westerbeke Four-90 & W30
Mermaid Marine, Lancing Marine, CT Marine Watermota and G & M Powerplant

Used in Tractors:

Nuffield 4/25 & 154
Leyland 154

Used in Cars:

Austin A60
Morris Oxford, Ital & Marina
Austin/Morris JB, J2, J4 & JU-250

& Many Many More Applications

Manufacturer Part Number 131090
Brand Entek


might be worth contacting seller to check measurements

[KRG113]

https://www.ebay.co.uk/itm/163742882405 ... olid=10001

Water Pump

For BMC 1.5 Diesel Engine

Multiple types of water pump were used in these engines, please compare photo to your old pump
If this isn't correct for you then please search our eBay store as we do have the other pumps
If you would like any help please send in a photo of your old one

Used in Marine Applications:

BMC Newage Tempest & Captain
Thornycrof 90 & 90/2
Westerbeke Four-90 & W30
Mermaid Marine, Lancing Marine, CT Marine Watermota and G & M Powerplant

Used in Tractors:

Nuffield 4/25 & 154
Leyland 154

Used in Cars:

Austin A60
Morris Oxford, Ital & Marina
Austin/Morris JB, J2, J4 & JU-250

& Many Many More Applications

Manufacturer Part Number 131090
Brand Entek


might be worth contacting seller to check measurements

Thanks Paul, yes I found that one too. I think pictures and many emails to sellers is the way as on the phone it seems much too much trouble from who I'v tried so far. I have some pictures i will upload here (if i can) but they're pretty naff will do better ones when I get time. The impeller is about 71mm diameter

[Peter Cresswell]

You can adjust the distance in question by using a puller to increase it or a press to decrease it. I had to do this with the new pump I got, to make the 3 pulleys line up for the fan belt. You have a few mm each way to play with, but not cm!
I too have searched against the part number you quoted and it came up with a 1622cc Morris J4 Van, so your car might have had an incorrect water pump fitted at some time in the past. Have you tried ordering the correct one from one of the main suppliers - and not one with Z suffix to the part number! Those with the Z suffix tend to have a pressed steel impeller, which tends to corrode quickly and becomes lose on the spindle so it stops pumping!
BTW - Although your engine should be fitted with a GWP130 water pump (18V engine), my GWP114 water pump (5 bearing engines to 1971) came from B&G and other than the slight adjustment noted above it fitted and has performed fine.