Radiator bleed with EWP

Hi all. I want to connect up a bleed from the top of my radiator to the header tank to aid bleeding. However im using a Davies Craig EWP 130 remote pump to pump coolant up through the tunnel up to the engine then returning back. The bleed point I have in my radiator is obviously in a lower pressure area than if the coolant was being pumped from the engine.
An engineering friend of mine has suggested if a connect up the bleed, the pressure may be too low and I could risk sucking in air from the header tank.
If this is the case , I could potentially move the pump over to the return leg so it effectively pumps toward the top rad inlet, and therefore the pressure in the bleed area would be higher. However I would prefer not to do this if can help it.

Any thoughts on the effectiveness of the rad bleed in these circumstances ?
 

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Hi Jason,
It sounds to me that your engineering friend is right. Have a look at my response to the earlier post 'Overheating'. I have found that the radiator to header tank bleed doesn't flow on my GT40, and I have installed a static bleed to the radiator. Bottom line, just try it and see. There are about 40 different owner solutions to keeping the radiator air-free and I have no idea who has the best scheme. Make sure that all the air which hits the front of the car is directed into the radiator, you may need to add some baffles and seal some gaps. Incidentally, I took out my Davis Craig pump and returned to the good ol' Ford mechanical one.
Tony.
 

Bill Kearley

GT40s Supporter
I'm not sure about a system using a pump like that, what do you use for a thermostat bypass? I installed a bleed valve at the top of my rad and a short bit of hose down the side of the rad to the ground. Open valve when filling and shut of when coolant starts to flow out. A second bleed done the same way at the highest point on the engine. End of problem and works great.
 
Hi Jason,
It sounds to me that your engineering friend is right. Have a look at my response to the earlier post 'Overheating'. I have found that the radiator to header tank bleed doesn't flow on my GT40, and I have installed a static bleed to the radiator. Bottom line, just try it and see. There are about 40 different owner solutions to keeping the radiator air-free and I have no idea who has the best scheme. Make sure that all the air which hits the front of the car is directed into the radiator, you may need to add some baffles and seal some gaps. Incidentally, I took out my Davis Craig pump and returned to the good ol' Ford mechanical one.
Tony.
Thanks Tony. Did you ever try putting the DC pump on the other flow side, ie pushing toward the top hose of the radiator? At the moment I have taken off the inlet manifold to tap the rear water passages to see if that helps. On my last EWP installation I had the pump mounted on the front of the engine and the set up worked great. Not an option on the SPF as the engine is too close to the bulkhead, hence going with a front mounted pump.

Funny , I emailed Davies Craig and there engineer said it should work.
 
I'm not sure about a system using a pump like that, what do you use for a thermostat bypass? I installed a bleed valve at the top of my rad and a short bit of hose down the side of the rad to the ground. Open valve when filling and shut of when coolant starts to flow out. A second bleed done the same way at the highest point on the engine. End of problem and works great.
Hi Bill. With a front mounted EWP there is no bypass hose, Davies Craig recommended drilling two small 5mm holes in the thermostat, and that's it.
Really trying to understand the effects of the positive and negative of the pump. Maybe I just pipe into a bucket of water see if air bubbles come out,. That way I know that the pump pressure is forcing excess air out of the bleed line.
 
Hi Jason,
I’ve got a similar layout to what you propose – see attached (vent line is upper left on rad). The vent line back to the header head does flow in the right direction (I use a clear hard nylon pipe) and I’ve had no issues with my system in temperatures over 35 deg C. I agree in theory where the vent line is in a lower pressure area, feeding the inlet to the pump, but it does work.
A few other points to consider. My thermostat is at the front with a bypass, as this allows the main coolant pipes to run at engine temperature. This minimises thermal shock on the engine as the thermostat opens, but means there is no need to run a separate heater feed & return to the engine.
Regarding the electric pump, I’d recommend replacing the Davis Craig unit with a Pierburg CWA200 unit. These are used by the mainstream OEM’s (BMW, Volvo etc) and far more robust and durable than the aftermarket ones. Their quoted flow figures are against a head of pressure, unlike the DC ones! The downside is that they need a PWM controller, but most ECU’s now have this function, enabling flow rate to be matched coolant temperature.
Hope this helps,
Regards,
Andy

IMG_20190812_222848864.jpg
 

Bill Kearley

GT40s Supporter
IMHO I think it's possible to draw air from your header tank withe that setup. An air bleed to let air out as the system is filled and then shut is a better option. Also, your system can only blend cooled rad flow with hot engine outflow when the thermostat opens. Some inline thermostats come with a built in bypass that will modulate temp and give much better control.
 
Bill,
Well it MAY be possible to draw air from the header tank, it practice it doesn't happen! I've run this system for over 10,000 miles in ambient temperatures over 35 deg C. with any issues
The design of the thermostat housing closes off the bypass route when it opens, so any blending only happens as the thermostat's transitional opening period.
Andy
 
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