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OK, now my fingers have thawed out from a day of spraying water in all directions, here's where I'm at!

Jury rigged the auxiliary pump from the battery connection under the bonnet.
Ran the car and had the pump running too.
Still no joy.
(Am now accepting that a simple ignition live feed to the pump will solve that part of the equation)

Suspecting air locks, I pull off each cooling hose one at a time and slowly chased the air round the system.
I got to the point of getting hot water into the heater matrix, but only lukewarm coming out. So seems there may be a blockage in the matrix.
Flushed it back and forth many times and got the water flowing out of it clear and a good rate of flow.
However, during all that I somehow introduced air somewhere else.
This could be my own fault as I had lifted the pump up onto the wing, making it the highest point. Maybe it's been pumping air around the system.

By this time it had started raining again and I was stinking of anti-freeze and completely fed up!
I've left the car overnight with the expansion tank cap and vent screw off and the front end raised on ramps, making the tank the highest point.
All I need is some kind of Rumplestiltskin character to sneak in and bleed it while I'm asleep.

So, in summary, I've bypassed the electrical problem but there is a chance that because that pump hasn't been working then the heater matrix has irretrievably silted up. Just because water flows through it doesn't mean its not missing out most of the capillary tubes.
Tomorrow is either fix it or try to source some Semtex!

Did the water look nasty when it first came out? I haven't seen manky coolant outside of Discoverys in anything half looked after for many a long year.

I suppose if there was a leak and someone repeatedly topped it up in a hard water area then maybe there'd be blockages.

smorris_12 wrote: ↑Wed Nov 23, 2022 8:12 pm Did the water look nasty when it first came out? I haven't seen manky coolant outside of Discoverys in anything half looked after for many a long year.

I suppose if there was a leak and someone repeatedly topped it up in a hard water area then maybe there'd be blockages.

This car had a new head gasket apparently, about 3 years ago.
I'm wondering if an interim fix involved rad-weld or something similar.
There have been a few lumps of powdery debris making their way through.
As you can see, I've circumvented the electrical issue and now it seems I'm just down to potential blockages and air locks.
Progress of a kind.

Ah, radweld. Yes, that could well be it. I wonder how ball achingly awful a matrix swap is? The X5 I run was a distress purchase to replace a Disco that burst its heater matrix in a snowy February as it seemed a job too much.

I suppose things that eat radweld will eat anything on site too!

smorris_12 wrote: ↑Wed Nov 23, 2022 8:44 pm Ah, radweld. Yes, that could well be it. I wonder how ball achingly awful a matrix swap is? The X5 I run was a distress purchase to replace a Disco that burst its heater matrix in a snowy February as it seemed a job too much.

I suppose things that eat radweld will eat anything on site too!

You basically have to remove the dash, remove the heater assembly, split it in half, swap the matrix and put it all back together.
Hence my considering breaking the damn thing. It was only intended as a runabout and by the time the heater is out the car is 50% dismantled anyway.

Same as every other car then; bloody awful job!

Paraffin stove in the footwell instead?

smorris_12 wrote: ↑Wed Nov 23, 2022 11:01 pm Same as every other car then; bloody awful job!

Paraffin stove in the footwell instead?

Funnily enough, was just saying to bigwinn that I’ll put it back together tomorrow with the pump wired to an ignition live. Live in hope that the fact the pump is running now may help shift the crud. Then leave a woolly hat and gloves in the car and use it anyway

Another little step forwards this morning.
Gave the heater matrix another ten minutes of back and forth flushing, then with the front end on ramps I refilled with properly mixed coolant, whilst having the auxiliary pump connected to the battery terminals to try to help shift any potential air pockets.
Fired it all up and whilst not exactly toasting, it is definitely pushing warm air out. I am still living in hope that this may improve now the pump is circulating water through the matrix.
Only thing left to do now is wire the pump properly to an ignition live and learn to live with it.
Not exactly fixed the initial fault, but bypassed it.

colb wrote: ↑Thu Nov 10, 2022 4:58 pm Got to be an impeller inside the pump to force the water through it, the fact that you can hear the motor working makes me wonder if the impeller is not being turned by the motor spindle hence no flow or maybe the heater matrix is blocked preventing flow.

colb, I dismantled the original pump and found that the impeller is mounted solidly on a magnetic cylinder. The motor is sealed away from the water, the hollow cylinder sits over the sealed section and it spins through an induction principle.
So without a physical link to the motor it is quite possible that the impeller was being stopped by the blocked matrix not allowing any water to flow?
With all the vibration in the engine bay and the smooth running of the pump design it is very difficult to tell if the pump is now running when plugged back in properly. When I get someone to help me I'm going to get them to start the engine while I'm holding the pump, to see if in fact it starts up. I can feel it stop and start, but simply putting my hand on it when it is already running (or not) it is impossible to tell.

Don't suppose a stethascope will be any good at picking up sound from that impeller then, just the noise from the motor. Might be an idea to temp fix a see through plastic pipe on the outlet and see if you can see a flow, now you have warm air from the heater at least some hot water must be getting through. Leak sealant is all good and well as an emergency fix but best avoided as a long time fix always best to replace the leaking part, easier said than done when its the heater matrix.

colb wrote: ↑Thu Nov 24, 2022 7:22 pm Don't suppose a stethascope will be any good at picking up sound from that impeller then, just the noise from the motor. Might be an idea to temp fix a see through plastic pipe on the outlet and see if you can see a flow, now you have warm air from the heater at least some hot water must be getting through. Leak sealant is all good and well as an emergency fix but best avoided as a long time fix always best to replace the leaking part, easier said than done when its the heater matrix.

I know from connecting it with jumper leads under the bonnet that I can feel it kick in. So all I need to do is be holding it when someone else starts the car. I can't run fast enough to do it on my own.

When it comes to refilling and getting air out I use a Vaccum Filler like this
https://www.ebay.co.uk/itm/393420043034 ... BMxpbBr5Vh
Have done a couple of Z3's with this kit and had no problems with trapped air in the system, it worked really well just needed a second pair of hands to hold the plug secure over the filler on the Rad and maintain the seal. You do need an airline with this kit, suck all the air and coolant residue out so it creates a vaccum in the systen and collapses the hoses. Close the valve on it and check the system maintains the vaccum, if it dosn't then there will be a leak somewhere for you to find. With a good vaccum maintained pick up pipe is dropped into the pre mixed coolant and the intake valve is opened that allows the coolant to be sucked into the system displacving air as it travels into the system. Once full, run the car to temp and have the bleed screw open and monitor for bubbles as any air left is expelled. Tighten the bleed screw when no more air is seen and check the temp guage is steady at 12 o'clock. Test Drive keeping an eye on the guage.

I must say I've never had any great problems bleeding BMWs.

OTOH, I did once go up a muddy 45deg slope in a 300tdi Disco as the last, and successful, attempt at bleeding the ruddy thing!