Electric Water Pump - 3 300 (when does it actually work?)

[Northnoble]

All,

Help please....

Over the last couple of weeks I (when I say I...I really mean my mechanic mate) has had the engine out to replace the clutch and also check out the gearbox.

Everything went back together as expected and having now done about 100 miles everything feels spot on.

So, the question, my mechanic wasn't sure that the small electric water pump was working, although the car came up to temperature fine and stayed at the normal temperature with no signs of over heating. All the pipes were warm (eventually...we were surprised how long that actually took) so there was evidence of circulation.

Having done a number of searches I am more confused than ever....

Is the electrical water pump running all the time or is it temp controlled?...living in Scotland we probably never get warm enough!!

What triggers it to come on? (So we can test it is working)

Does it run when the engine is on (or just when the engine is off...as a cool down aid)?

Which fuses / relays should I check?

Thanks for any help / advice....just want to stop worrying!

[Yorkshire]

Hi Hamish

When i have filled my radiator system recently and run it to remove any air the electric pump only seems to kick in once the engine reaches approx 90 degrees.

Up to that point the water is circulating round the engine and header tank but the pipes to the front radiator are stone cold. Once it hits 90 they warm up and the circulation becomes faster.

I have to run to over 90 then bleed the front radiator with the brass bleed valve on top then all seems ok

I assume it is triggered by the ECU but not 100% on that one.

Cheers

Stuart

[smokin]

I suspect that the electric pump only engages when the engine is off and the fan is on. When the engine's running the internal water pump is providing the circulation. If you turn off the engine hot then the fan continues to run and the electric pump circulates the fluid.

I've never checked the electric pump is actually working but assume it is as the temp wouldn't drop as quick as it does with engine off, fan running and no circulation. I think the trigger is from the water temp sender in the T piece in the cooling pipe.

Water pump relay on mine is the lower of the two on the right. The fuse is top one of the three vertical but is shared by both fan and water pump. So if fan runs then fuse to pump is good

[John Scherrer]

My understanding ..

On the 245, if the water temp is high enough, the fan runs but cuts out when the ignition is switched to OFF.

On the 300, the fan is wired in parallel with the electric water pump and if the water temp is high enough, the fan will stay on with the electric water pump running even though the ignition is switched off until the water temp reduces.

If a 245 goes back to the factory for a charger upgrade post-build, on ignition switch off, some cars run the water pump and the fan, some just run the water pump. Not sure what dictates this ... ease of wiring, access to the loom ?

Some 245s may also get the electric water pump added (along with the additional radiator) if the car is being exported to a hot country.

Link to technical details for the EWP - Click on Installation Instructions for more detailed info

http://www.daviescraig.com.au/Electric_Water_Pumps-EWP80__12V__ELECTRIC_WATER_PUMP___PART_No__8005-details.aspx


Here's a pic of the electric water pump ..

 

[Northnoble]

Thanks guys...makes sense.

On the basis we couldn't get the water temp above 78 on Sunday, no surprise the EWP didnt kick in.

To be honest the highest temp I have seen was 94.....and that was stuck in traffic on a hot "Scottish" day.....i.e. About 20 degrees! Even track days seems to hover around the low 90's