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[andy_driver]

hi there does any one know if the electric aux water pump should been running all the time when engine running reason for asking is mines doesnt work at all well the pump works as i tested but no power going to the plug its the pump that sits on the radiator at the battery side 2.5 v6 manual anyone good with electrics  . 

[doz]

Isn't it only used if you put the heater on without the engine running?

[Andy B]

Isn't it only used if you put the heater on without the engine running?

That a different electric pump 
The aux pump on the rad should only run after the engine is switch off to circulate coolant to prevent localised over heating. Not sure of the criteria  ie temps etc it should run at, because it won't always run if the engine /ambient temps are lower.

[andy_driver]

thank for the reply i have run the engine to full running temp as soon as cooling fan comes on i switch off engine and still no joy from aux pump running and still no power getting to plug .

[2woody]

There are two electric water pumps - one on the radiator shroud and one on the inner wheel-house panel.

the radiator shroud pump is to prevent "afterboil", which is exactly as it sounds. energised only after shutdown if coolant exceeds a certain temperature.

the wheelhouse mounted pump is to draw hot coolant more effectively through the heater. energised when the ignition is on and when the heater is used after shutdown for a short length of time.

[Andy B]

There are two electric water pumps - one on the radiator shroud and one on the inner wheel-house panel......

As said many times before ....... not all cars have two electric pumps 

Mine has a cruise box of trick on the offside inner wing and an electric pump just on the radiator.

The answer we need .....is what actually switches the rad pump? 

[Simon.rose1]

Never heard of these before where are they what should I be looking for all I get is a fan behind the front fog going for few min on start up what is that for

[Kevin Wood]

The answer we need .....is what actually switches the rad pump? 

The radiator thermoswitch, via a confusing system of relays. If the coolant is above the first or second stage fan temperatures AND the engine is stopped, the pump runs.

[andy_driver]

thanks for the info i will probley try a new switch 

[Andy B]

Never heard of these before where are they what should I be looking for all I get is a fan behind the front fog going for few min on start up what is that for

There's a small pump at the top of the rad on the nearside 1 ¹/₂"  x 5" or 6" and on some cars there's a similar pump on the driver's side inner wing.
The 'fan' you can hear on start up is the Secondary Air Injection Pump, and is to appease the Tree Huggers 

[2woody]

yes of course, not all cars have the flitch-mounted pump.

I am doubting if the ambient temperature here in the UK is ever enough for afterboil to be a problem.

[Andy B]

.......
I am doubting if the ambient temperature here in the UK is ever enough for afterboil to be a problem.

The aux electric coolant pump has often run in the few hot summer days we've had on my Omega 

[Entwood]

It's run on mine in France a few times ... hot day after a long tow, there's a fair bit of heat still to disperse  

IME the little pump only runs if the ignition is off BUT the cooling fans are still running, which makes sense as the coolant then needs to circulate more than a thermal syphon would cause

[Andy B]

It's run on mine in France a few times ... hot day after a long tow, there's a fair bit of heat still to disperse  

IME the little pump only runs if the ignition is off BUT the cooling fans are still running, which makes sense as the coolant then needs to circulate more than a thermal syphon would cause

Like wise 

  I wonder if my Merc will do the same this year? 

[andy_driver]

as av mentioned before the pump doesnt work at high temp after fans av came on and went off and engine off still cant here the pump working av checked no power getting to pump does anyone know were there is a relay or a fuse for it .