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Zetec And Electric Water Pump Still Overcooling


speedtripledan

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It sounds like you have a thermo syphon going with the new rad & the electro-pump providing very little resistance to flow when stopped. Have you tried a run with the pump sensor dis-connected & if pump motor will take 12 volts direct atemp switch in the cockpit to switch on & off as you motor?

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Going back to basics, with a properly designed system, the radiator should have excess cooling capacity to manage the hottest day and crawling traffic. Yet it is still able to maintain the correct running temperature in mid winter. So too big a radiator should not be a problem. The stat works by reacting to the temperature of water leaving the engine and by variably obstructing it continuously changes the flow rate to maintain the exiting water within the required temperature limits.

 

As I understand it the DC system is the opposite to this. The pump runs continuously but has a variable flow rate. It electrically monitors the temperature of the water leaving the engine and responds by varying the speed of the pump to change the flow rate.

 

So by that reasoning it's running too fast. Each cooling system is unique. Viscosity, obstructions, pipe sizes, rad cores restriction, etc. I take it you set software or switches or whatever to maintain a temperature. Possibly 85-90C but its maintaining 75C

What would happen if you told it to maintain 100C? Might it run at 85C?

The other way you could try would be to artificially slow the flow by introducing a fixed restriction. (But this rather negates the whole point of having electric pump and sensor.)

 

Nigel

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From our texts yesterday and Nigel's post above (which is spot on and the same as I was explaining yesterday) I'm starting to think the ewp115 pump is too big for your engine? So even at the slowest speed on the pump via the controller, this is still too fast for your engine?

I have the ewp115 on the v8 and it maintains temp perfectly.

They sell a smaller pump, the ewp80 which will have a lower water flow rate at its slowest speed than the ewp115.


Thinking back, I'm sure I rear somewhere when buying my pump that the ewp80 was advised for 4 cylinder engines and the ewp115 is for 6 and 8 pots.

Edited by steamer
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If the pump runs continuously but at variable rates why not try putting an over-ride switch in circuit to cut all power to the pump -- if that cures the problem fit another electrical 'stat in series with the present electrics.; pump will then be able to run from zero up to max.

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Bob, the way my controller works (assuming the newer ones are the same);

 

below 75degC, the pump just pulses on/off (0v, 6v)

 

Between 75degC and the set temp, (80,85,90,95) the controller varys the speed of the pump by increasing the voltage to it from 6v up to 12v

 

If you get above the set point, the controller sends a voltage (via a relay) to the electric fan.

 

 

To be overcooling, the ewp115 pump is pumping more water, even at 6v, than the engine needs.

 

The possible solutions I can see are to add the stat back into the system (which still has a question mark hanging over it because of what I've read about the raceline water rails also causing overcooling issues), a smaller pump (ewp80) so that it moves less water at 6v.........

 

or (and I'm not sure how this would be achieved), find a way of making the pump go even slower by reducing the voltage to it, say 4v-10v varying?

Edited by steamer
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So if the pump pulses on /off below 75*C then a permanent OFF via a second switch ( manual or controlled by temp ) should make the water temp rise. From this far south it seems that the added value of the extra cooling due to forward motion of the car & the pulsing pump ( never actually off ) keeps the water temp down.

 

Other than that ---- stick a lump of cardboard in the grill.

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As a test i.m going to run a 15mm hose from the rail to the bottom hose

I don't think that's a goer. If you join the bottom hose on the inlet side of the pump you just make an uncontrolled rad bypass. If you join on the outlet side of the pump you may get reverse flow from bottom hose to rail and possibly very reduced flow through the engine. Either way will run hotter, probably much hotter but no longer controlled.

You need to introduce something to reduce flow rate below the current minimum. C.D. suggest this by refitting the stat but a stat is a variable flow reducer complicating things for the pump controller. i.e. as the coolant gets too hot the pump will speed up and the stat will open. Both increase flow and you are likely to get wild fluctuations in temp. I think introducing a fixed obstruction might be the way to go. You could make up some plates to fit in place of the stat in your water rail that have different sized central holes. I would start with a 20mm diameter hole. That would slow flow some but leave the pump in command of temp control. Then trial it and go up or down by small increments. Cheap, easyish to fiddle with on the road. Probably don't need jumps of more than 2mm at a time.

 

Nigel

Edited by Longboarder
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