Morris Minor Owners Club

I have decided to change the water pump on the a+ 1275 engine I have just purchased to make sure it doesn't leak after not been used for years, will a standard 1098 pump fit, looking at the correct replacement for an a+ the pulley mount looks different for the fan.

As far as I know - they are all the same. Older pumps had a smaller impeller - but the new bigger impeller can be fitted after a check for internal clearance. Some newer pumps have no bypass hose fitment. This is great if you fit a head with no bypass you have eliminated a regular source of trouble. As far as I know - the fan fitment is universal. But unless you have some reason to doubt the original pump - just use it ! the one thing they don't like is being run dry - with no water to lub the seal - otherwise they are very reliable.

As far as I know - they are all the same.

Apart from the last of the Ital ones with the Viscous fan which have a form of screw on fitting this may be the type you are looking at, just replace it with the ordinary type as they are far more readily available.

yes it was an A+ pump for an ital with a threaded top to the pulley mount I was shown for a replacement, I think I will take bmcecosse advice and use the original pump, as the engine has hardly been used since reconditioning.

Viscous fan on A series - something new learned by me today then !!

Yep, the highly neglected Marina/ Ital lump I flogged on here had a viscous fan fitted.

I'd go for getting a pattern Metro pump myself - the impeller on the last one I got was pressed steel so a bit lighter than the cast original one (and in terms of rotating/ reciprocating weight saving every little helps...), was larger and was chosen because it was a fiver cheaper than teh Minor one and had no outlet for the bypass hose. The bypass in the head was blanked off, and yay, no more potential for nasty little bypass hose failure

Though thinking about it, does your A+ have a bypass hose anyway? If not then you've little choice but to get an A+ 1275 pump unless you want to start trying to block off the outlet on an old A one.

The Metro water pumps had no bypass fitment. Bought one brand new in the summer at autojumble for £5 - along with a perfectly good starter for £1 !!

The bypass in the head was blanked off, and yay, no more potential for nasty little bypass hose failure

So what did you use to blank it off with.
I have often puzzled over the bypass hose issue, if it is blanked off this does not allow the water to circulate properly while the thermostat is closed, now I have heard that you can drill the thermostat to allow the water to circulate but does this affect warm up times, and does it have any other side effects, I know the later A series engines did away with it but didnt they have a different type of thermostat housing to allow for this, all I was wondering is what the advantages were apart from not having a bypass hose against the disadvantages.

main advantage - NO bypass hose!! If you think over the years of the breakdowns/missed appointments/ruined engines and just general money spent on repairs - the bypass hose has a lot to answer for. Without the bypass - provided you keep the heater valve open all the time, then warm up (as measured by warm air coming from the heater) and general heater performance are both improved using an 88 deg stat with no rim holes - in summer time I use a 74 deg thermostat with 2 x 1/8" holes drilled in the rim - just to let some water circulate to the radiator all the time.

I have often puzzled over the bypass hose issue, if it is blanked off this does not allow the water to circulate properly while the thermostat is closed,

Yes - you just need the heater circuit open. A simple way to do that is to use the marina style 'stub' outlet instead of the valve. Doing this you've eliminated 2 of the 3 most likely water leaks, and as the 3rd is the radiator you ca't really get rid of it ;-)

What is it about the bypass hose that makes it so unreliable compared to the other hoses in the system?

I don't think its any less reliable (unless you use the concertinaed?? one) Its just harder to change thats all. I use a piece of 1/2 inch hose and swap it every time I touch the head or waterpump. I never had one fail.

I'm going to wish I hadn't said that!

Exactly - it's just where it is - gets splattered in oil if there are any leaks at the front of the engine - and is just generally neglected.

The other unique problem with the bypass hose - if the stub on the head is very corroded you have not many options apart from trying to get the bypas hose to seal on the corroded stub
If the thermostat housing has corroded away under the top hose, you can just replace the housing.

rayofleamington wrote:if the stub on the head is very corroded you have not many options apart from trying to get the bypas hose to seal on the corroded stub

I bought an unleaded head with a totally rotten bypass hose stub (I thought it had been fully rebuilt but it had actually only had the exhaust valves and seats replaced - never mind). Getting the remains of the old stub out required the use of oxyacetylene and a hammer and chisel, but new stubs are easily available. I'm not entirely sure what to use to seal the threads when I screw it in - my dad says Loctite threadlock will do it, but I was wondering if PTFE tape might be more appropriate.

Something old fashioned like Bosswhite would do the job

Kevin wrote: So what did you use to blank it off with.

As teh dratted thing wouldn't unscrew, first a very tough bolt of the right diameter was used to cut a thread inside the stub (more effort and needs a more careful approach than using a tap, but was all there was to hand), then another bolt of the same diameter but correct length (approx the same length as the stub, so as not to interrupt coolant flow, not that it's probably critical) was wound in with a copper washer IIRC. There was also a bit of instant bodge smoothed over the threads to esnure it was well sealed. And sealed it indeed appears to be

I have often puzzled over the bypass hose issue, if it is blanked off this does not allow the water to circulate properly while the thermostat is closed, now I have heard that you can drill the thermostat to allow the water to circulate but does this affect warm up times, and does it have any other side effects,

bmc disagrees with my take on this, but I would drill a handful of 3/8 (or slightly smaller - Basically a nice size that fits in the groove in the stat) holes to allow some flow to prevent localising overheating.

I can't see that would cause a noticeable delay in warm up times as the flow will still be minimal, but enough for there to be a flow which is what's needed to try and keep the heat distribution fairly even in the head.

I know the later A series engines did away with it but didnt they have a different type of thermostat housing to allow for this, all I was wondering is what the advantages were apart from not having a bypass hose against the disadvantages.

The A+ engines I've seen without the bypass have a sandwich take off between head and stat housing. I'm desperately trying to remember where it takes off to other than the heater (or what the heater plumbing does to allow circulation when the valve is off). And I can't!

Yes - the later A-series ran the heater and the manifold pipework (if used) from another connecting block sandwiced under the thermostat housing. Either this was to help the water flow at the front of the head when not having the bypass hose, or it was just a cost issue to reduce having another water outlet machined in the head.

ALEX - if you have managed to get the stub out - seize the chance and plug the wretched hole. This is your golden opportunity to be by-pass free!! And ALL - believe me - if you want the best possible heater - drill NO holes in the stat. I have to say - there just is no room for 3/8" (???) holes in the stat - a couple of 1/8" holes are plenty in the summer

if you want the best possible heater - drill NO holes in the stat.

with a stub outlet (certainly not the unreliable cable type taps) for the heater I'd think that would be a good way of doing it.
Drilling holes in the stat also makes the car run cooler - not good unless you want to wear gloves in winter.