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MG Midget and Sprite Technical - 1275 Water pumps

Just thought I'd throw this one into the pot! My 1275 was making a rather unpleasant "clanking" noise today which seemed to be coming from the timing chain cover.... seemed noisier at tick over than when driving. On switching off and having a closer look - coolant dribbling out of the water pump and a rather slack feel to the bearing when wiggling the plastic fan blades!..... conclusion...knacked water pump. Got a new one on order - is it a radiator out job or can they be changed with the rad in place? The Haynes manual seems to suggest rad out ....Cheers - Neal
N Broadbent

When i did mine it was a rad out job. it makes it much easer to get at everything and get it all torqued up correctly. Getting at the bypass hose is a real pain otherwise anyway.

As a bonus you can lubricate the steering rack while you have the rad out of the way :)

I'm in agreement with you there - as you say it's worth getting good access for torquing up and the mating face can be cleaned up too - cheers
N Broadbent

You CAN do it with the rad in place, but it's a hell of a lot easier to take the rad out... Gives you chance to flush the rad and clean the core....

M T Boldry

I'd get a Metro water pump with no by-pass outlet and blank off the cylinder head pipe. I did this some years ago and recommend it. The by-pass serves no real purpose and without the need to fit the by-pass hose life is a lot easier. The Metro pump also has a deeper impeller.
Chris H (1970 Midget 1275)

I have never got the cooling system working properly without the bypass.
It always resulted in verry long warmup times and general cold running.

I have tryed all options thermostat, blanking sleve, thermostat with smal holes in it (several sizes)

Finaly i have retuned to the bypass setup and replaced the hose with a piece of silicone hose so i never have to worry about it again.
Onno Könemann

The BMC1300 pumps also had the deeper impeller, and the by-pass as well.

If you use a solid bit of 1/2" heater hose rather than the bellows type of bypass hose you'll get much better life out of it. Disadvantage is you need to remove the pump or the head to fit one - but that's where you are at present.
Paul Walbran

There are 18 different water pumps + pattern pumps so which of those is the BMC 1300 pump? I don't have a firm list of which of those 18 Pumps were for the Metro. So - part numbers anyone?

Yep, no bypass and no thermostat does increase warm up times and the engine runs cooler. Maybe the Netherlands has generally cooler weather than the UK?
Daniel Thirteen-Twelve

1300 - GWP132 or 134 changed at July '68
midget - ditto
Metro - GWP154 or 187 change points many and varied, by engine number.
David Smith

I agree that 1/2" heater hose for the by-pass is definitely better than the thin bellows hoses. I find that by cutting the hose the proper length and by placing the clamps with the screws facing the left front tip of the car, it is easy enough to slip on the hose and tighten clamps down. It isn't necessary to remove the water pump or the head to change the hose.
Glenn Mallory

Neal, just in case you've not done the job yet -

Rad out and take the oppitunity the thoroughly forward flush, shake up, back flush, shake up, forward flush it again

You could also do the same to the heater matrix and flush thorough the engine block

When you've fully reassembled you could if necessary use a cleaning flushing agent on the whole system (don't forget to open heater tap) and then thoroughly flush through with water

I'd also fully drain down and fill with 4-LIFE engine coolant (if your engine has fairly recently been reconned) - - an additional benefit is that it shows up the source of leaks well (clips to nip up, gaskets not bedded, I always use gasket sealant as well as gasket)

My last 'Bypass Hose kit' (off-cut of silicone hose and two turned edged clips) went at the NEC or I'd stick one in the post to you

Leave the clips with their heads where you can still get at them after the rad is refitted

Apparently some other countries are now involved in manufacturing some parts and the quality is much better (a very small upside to global recession) so much so that I was able to buy a standard waterpump (from MGOC) instead of a more expensive uprated version
Nigel Atkins

This thread was discussed between 23/11/2010 and 02/12/2010

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