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MG Midget and Sprite Technical - Any tips on changing the waterpump

Changing water pump on the Frogeye tomortow.1275 block and I'm praying it's the correct one as I know there are differences. Any tips or things to look out for/avoid?
G Lazarus

Never found this to be a particularly difficult job, and have found minispares units to be the way to go I also see that Swiftune do an electric pump, should you be interested in modding the system.
As for the period correct unit, i am not sure which one suits.
Did the A series guru, viazrd talk about removing metal from the block to aid punmp efficiency ??

P Bentley

Apologies if I'm 'teaching granny to suck eggs'...

Change the bypass hose at the same time as a precaution, and use a 'proper' length of plain hose rather than the relatively weak convoluted item. Make sure the screws for the clips are orientated so that, if need be, you can access them easily at a later date.

Plenty of anti-seize on the fasteners to prevent any corrosion between them and the aluminium alloy pump housing.
Jonathan Severn

AFAIK there are three key points:

some [presumable 'early' style] pumps have a spigot for the bypass hose

the depth of the pump [distance from engine face to the impeller]. Early blocks had a shallower recess than later blocks so a pump with a deeper impeller will / may foul the bottom of the recess.

the impeller size / design evolved to improve circulation

I stand to be corrected,

Doug Plumb

AFAIK all the 1275 blocks had clearance for the larger impeller.

Good tip from Jonathan about the bypass hose - assuming you have one fitted.
Dave O'Neill 2

No bypass hose fitted. Peter May fast riad head. It's been blanked and I have holes drilled in the thermostat. All other hoses are silicone with mikalor clips.
G Lazarus

The none bypass pump should be the one with the larger impeller anyway. The cast impeller is apparently superior to the pressed metal variety. Its a straight swap with the original.

Bob Beaumont

Sorry I was getting confused with the hose between the head and the block. A bit of brain fade there!
G Lazarus

Note the different length of screws/bolts and their locations.

If required change the drive belt whilst you're at it.

BTW the larger (exhaust size) Mikalor clips can go at the welds so instead consider the Norma GBS type "Mechanically locked design for exceptional band tensile force".

Check your rotor arm.
Nigel Atkins

Or Stainless Steel Jubilee clips (which are recommended for my silicone hoses).

Standard practice on marine engines is double-clipping because, as Nigel remarked, hose clips can fail. I tend to follow the same practice where I have physical space for two clips.
Okay a fractured clip on a car won't cause it to sink at its mooring like a boat, but neither will it strand you with no coolant if there's another sharing the duty.
Just a thought....

A completely successful days efforts. The old water pump came out like dream, the only problem being one of the captive nuts on the radiator refused to stay captive. The new pump went in without any trouble, the sun shone. One of those jobs that just went completely to plan.
G Lazarus

This thread was discussed between 18/05/2018 and 19/05/2018

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