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Thermostat switches on GEMS 4.6


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If you are using an electric water pump, how are you doing this with a thermostat in place ?

I would cut the top hose and put a small tube in between with the senders in place. I made mine and can have 3 sender in it.

like x engineerings :


How did you get a normal thermostat housing to fit a gems 4.6. I'm sure i tried that and it touched the alternator ? I run the normal gems housing, but no thermostat and no heater circuit.

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I'm keeping the normal pump. The electrical will be an additional pump since I'm moving the rad to the back. Once water temp reaches 68 deg, the elec water pump will start.

My thermostat is in the housing where the top hose attaches to, so, if I'm not wrong, coolant will only pass one the thermostat opens.

The bypass hose (No 4 in pic) is blanked off. Can i place the switches there?

How did you get a normal thermostat housing to fit a gems 4.6. I'm sure i tried that and it touched the alternator ? I run the normal gems housing, but no thermostat and no heater circuit.

I don't really know since when I bought the engine it was already like that :lol:. I'll take a picture and post it.

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Why run an extra pump ? We have never had a problem with rear mounted radiators and standard v8 water pumps.

If you have no bypass hose and no p38 thermostat housing how will the water circulate before the stat opens ?

An electric water pump normally goes on the bottom hose of the radiator, if you have this switching on at 68 and are running a stat i think you are making things difficult. Do you have a heater matrix circuit - if so where does this return to ?

Where are you planning on plumbing the electric pump into ? See hybrid from hells recent thread about them.


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There are some inlet top housing that have a thread for I think A/C but change this to rad one and bingo ?


Nige, you got it. I remember now.

I tried to fit a housing that takes the A/C switch, but that is what fouled on the alternator - the actual switch.

Here is my engine mid-fit, you can see the blank where a sender would go in - but doesn't fit.


Then made this to use instead :



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More flow does not necessarily equate to more cooling - see Nige's thread on electric water pumps.

Also, putting one pump in line with another will probably end up with them fighting each other, the EWP instructions advise you to take the impeller off the original pump. Otherwise, what happens to the flow for example when the EWP is stopped but the engine water pump is running?

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From what I got from this post bu Team Idris, more flow will be better...


Some interesting stuff on the other thread there. The faster the water flow the higher the Reynolds number, so less boundary layer and better water to metal heat transfer.

But also, watts = mass-flow-rate * heat-capacity-fluid * temp difference. If the watts are fixed and the mass flow rate doubled, the temp difference halves. So 100 over 90 deg.c becomes 100 over 95. (assuming engine makes 100 deg.c and rad exits 90 deg.c). 95 is further from the ambient cooling air than 90, so the rad works better. So you get a double helping from a faster water flow. But the back pressure is the square of the velocity, so twice the flow could take a lot more shaft power?

Sure is a tricky one :)

See question 7 on this link from Craig Davis website...http://www.daviescraig.com.au/Electric_Water_Pumps__EWP-content.aspx
They put in two Elec WP inline for better cooling
I tested flow on a switched off EWP and water passes through the pump normally.
I got the idea from some guys here in Malta who run this setup, and had no issues with cooling even in Croatia.
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  • 2 weeks later...
The diagram I uploaded before is wrong.


The box on top is the radiator. The electric pump will be placed in between the bottom of the rad and the water pump.

The thermostat will be removed to have constant flow.

Now I figured out I'll place the thermostatic switches on the bottom hose in between the rad and the electric water pump with a housing similar to the one Zim posted


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