I have some queries about the GTM Coupe cooling set-up and just wanted to ask a couple of questions to the more knowledgeable.

Last night I was stuck in a bad traffic jam on the M3 from London heading back to Bournemouth. In around 2.5-3hrs we did 5 miles until we finally got moving again. All the time I was thinking I am glad I am not in a coupe right now as I saw at least 6 people at the side of the road many with overheating issues (in much newer cars obviously)

Now I know a traffic jam like that is rare and an extreme case but having looked at many pictures of the cooling set-up in the Coupe it doesn't seem surprising that the car struggles to stay cool.

So

Does anyone know how many Litres Per Minute the A-Series Mechanical Water Pump can shift?

My thought was fitting 1 or even 2 auxiliary electric water pumps inline with the cooling system (one on the 'hot' pipe from the block and one on the cooler 'return' pipe from the rad)

The plan is simply to match the pumping speed of the mechanical pump further down the system helping maintain a constant flow rate and get up the sharp rise back into the top of the cylinder head.

I realise electric failure would be a real issue if using auxiliary pumps (unless they were pass through when not being used but I am not sure if they are)

Now maybe this isn't possible for a number of reasons but just wanted to ask.

I did think about an additional radiator somewhere but space is obviously limited and it would mean the mechanical pump working the water through yet another radiator matrix.

Thanks

Rob

Hi Rob,
I used to run a big bore 1430 S engine in a Cox coupe yonks ago with standard big impellor water pump without over heating problems using a front mounted Renault R16 radiator, stuck in traffic jams I used to get vapour locks in the fuel system untill I went from 2x1-1/2 SU to a 45 Webber.
From racing experiance electric pumps are fine and have some advantages, but not in addition to a mechanicaly driven pump with its speed varying with engine speed, this will cause the mechanical pump to cavitate, if you want electric, you need to remove the drive to the mechanical pump and must only fit one pump, if electric or mechanical.
Good luck
john

Hi

Thanks for the reply. Yes I was hoping that by matching the mechanical pump rate with any auxiliary pumps it would negate any cavitation but of course forgot that is variable based on engine speeds. i know you could completely lose the mechanical pump and go fully electric but that is concern in case of electrical failure.

It's interesting that some people seem to have no problems with cooling at all and others are plagued by it even after extensive work to eradicate it. Maybe just a high capacity pump combined with a properly cowled, good quality radiator should be enough. I am sure heat soak from the exhaust into the head is also a factor so better ventilation in the bay may also help. The addition of an extra switchable rad fan would also probably be a good idea!

Static traffic will always be a problem as it usually is on standard Minis although (touch wood) mine has never boiled over! but I do use the heater a lot in traffic just to blow a little extra heat out of the system

Rob

Agree totally with what John said, I too use to ran one on my Miglia it was a Craig and Davies unit. I removed the old mechanical pump and made up a new housing intake and ran it directly from the pump. It worked very very well, too well actually. We found it actually circulated the water too quickly and thus did not get time to cool through the rad, we resolved this by installing a resistor on the pump feed wire and ran the pump at 6 volts instead of 12, at that speed/voltage I could race all day long at 8000 rpm + and sit for ages at a stand still without overheating.

If you can find one of the early cast iron impeller waterpumps use it, these were the best mechanical pump BMC produced, the tin ones cavitate at anything above 3500 rpm and at low rpm don't shift enough water. Cooling also comes down to rad size and tube volume, for a long time it was all about the number of cooling rows a rad had but now it is believed that its best to have fewer larger ones. In my Coupe I ran a Golf GTI (V5) rad and a single high flow electric rad. This had no issues cooling my very warm (race spec) 1430. Oh but I was running a cast impeller water pump.

My experience is quite different. I ran a Davies Craig electric pump along with the standard Mini mechanical pump and had no problems at all. It worked so well that I was even able to run a Laminova oil/water intercooler and it still didn't overheat. If you keep the thermostat make sure you wire the pump through a temperature switch so it stays off till the thermostat opens.

This is interesting,

I don't suppose you have any drawings floating around of your set-up? (or maybe skecth one down if you are feeling generous ) whereabouts did you mount the electric pump?

Rob

I'll see what I've got at home. I'm in Prague airport at the moment.

I mounted the pump low on the NS of the engine bay. I can't remember how I plumbed it but I've got a schematic somewhere.

Be carefull mounting those C&D pumps in the engine bay, they are only nylon and I've seen more than a few melt with engine heat. Make sure they are no where near the exhaust and if possible somewhere where there is a good air flow.

Yes I was concerned about fitting in the engine bay so thought I would mount it after the rad on the return to the cylinder head. So fix it under the bonnet area somewhere less heat and more room? However if GTMDriver has his mounted in the bay with no problems then I am sure it would be okay as long as sensibly positioned.

Right I'm home now.



You can just see the outlet of the pump on the photo.

I plumbed it into the return hose from the radiator so it took the cooled water coming back from the rad and pumped it into the inlet pipe of the standard water pump.

There was no indication of any heat damage from the exhaust although that was wrapped as you can see.

Also on the photo you can see the Laminova oil/water intercooler (the square alloy block) and (in the top left) the controller for the thermostatic switch which operates the electric pump.

All in all it was well worth doing on my car. It was particularly good at preventing heat soak problems when the engine was switched off. I wired it independently of the ignition so it would continue to circulate the water for a couple of minutes after the engine stopped.

So you just run it on or off with the temp? I and two others in the Mini club (one with a Rossa and another Coupe) have been looking at the possibilities of speed control with a PWM speed controller varying the speed of the pump with temperature (very early stages and largely just conversation over a pint so-far).

Do you keep the thermostat itself with this setup or ditch it? I'm thinking that with the control set correctly the thermostat is redundant and becomes just an obstruction to flow and an additional potential point of failure.

One of our bug-bears is heat soak when you switch the engine off so we too were planning to have them running after the ignition was switched off. My Coupe used to vaporise the fuel in the lines whilst standing and always took loads of turning to re-start because there was no fuel in the lines any more - hopefully sorted as it's going injection with the engine swap. The Rossa is turbo-charged so has even more trouble because of the hot turbo in the engine bay.

Iain

If you remove the thermostat also remove the bypass hose between head and the block and fit a thermostat blanking plate, or number 3 and 4 cylinders get starved of cooling water
John

Yes, I just turned it on or off with a thermostatic switch. No speed controller. And yes I kept the standard thermostat.

As long as the stat is open before the pump turns on there is no problem.

To ensure this I fitted the switch sensor in the top hose so the hot water didn't touch it till the stat opened.

I have raced mini's off road in sprint type events here in Nigeria and driven the same car on the road without overheating with temperatures from 26c to over 40c, the last car I built a Twinny mini with 1380 engine in front and 1400 engine in the back, in both engines the thermostat and bypass were removed and a blanking sleeve fitted, never had overheating with big impellor mechanical pumps, I used an S rad with the heater core as an auxilliary rad in front and a 1.8 golf rad across the back with holes cut in the boot lid to let the hot air out, I always used oil coolers on both engines.
Keep it simple if it works
John