After getting back from the 2016 MTC and removing my leaking Davies Craig booster water pump, I also wanted to confirm I had a thermostat and what temperature rating it was.
 
I had been taking it easy and monitoring my coolant temp throughout MTC, which was in the 80s range day 1, with a peak of 91 at one stage. When idle on the track and waiting for a run it would reach higher 80s, but was lower 80s when actually driving. I could use my radiator waterspray for 5 seconds which would then drop it 10 degrees in about 10 seconds. I also stopped racing for half the day while I changed to another set of wheels due to too much understeer.
 
On day 2, I topped up a little coolant in the morning and the day started off the same, but then after coming in to pits after a run, I left the car running and went for a walk for 5-10 minutes to get some water and when I returned noticed a puddle of coolant under the car which I traced back to coming out the overflow hose (and maybe radiator cap). Temps were still ok, low 80s, so kept it running longer and turned off car.
Next session I went out and came back and noticed the same thing, and not wanting to risk anything decided I would rebleed the cooling system like many others were doing, thinking I had air in the system too. Thanks to some advice and help from Paul Brell and Geoff Fear I got this done, and my next session felt great, car seemed to be going much better, temps were even lower..in 70s, but then I came in after doing a full lap cool down. My temperatures started rising and got over 100, I finally found a working hose and sprayed the radiator while the engine was still running, and cleaned coolant off my exhaust too. Still concerned I took it on the road to get some flow into the radiator, but didn’t get 500m before having to turn around and roll back as the car wouldn’t go over 60kmh. I got back to my garage to see my Davies Craig pump had split and was leaking coolant out the seam. I then decided that was the end of racing for me. 
 
So after the essay, my questions.
I found I didn’t have a thermostat, so assume my booster Davies Craig  water pump runs constantly (otherwise it would be pushing against the thermostat). Should I replace my booster pump and thermostat? What are advantages and disadvantages of doing so, such as taking a long time to warm up and staying that way, bad fuel economy? Anyone else running a booster water pump?

I just run a standard toyota water pump and a trd thermostat. I drilled a small hole in it just in case it does block so I will have some flow. I also have the large Mishimoto radiator. Everything else is standard and it doesn't overheat. My advice is to stay with standard parts unless you really have to change. The most reliable solution is always standard toyota.

After talking to some of the guys at MTC (who have much more power than me, and are more track cars) I was leaning towards just replacing with a standard thermostat and be done with it. But after reading the benefits of an electric water pump, I'm thinking it will keep my engine under control better mainly due to point 1 below.'
The Good

• With the right ECU water can be circulated in direct proportion to a set temperature, even when only idling or switched off. The hotter the water then the faster it is pumped round the engine and this will assist with cooling. It also means that the pump is only running when it is actually required allowing the engine to warm up quickly and maintain an optimum operating temperature.

The Bad

• Electric water pump will not last as long as a mechanical one.
• I think failure of an electric one can be more serious than a mechanical one.
• Should remove the existing water pump impeller and the thermostat.

I believe I still have the impeller as the car has always been listed with a "booster pump", but then again I thought wrong about the thermostat. I like the idea of a temperature controlled booster pump which also runs when idling or engine off, but it will be pushing against the impeller and thermostat. If I remove both of those then I risk the electric water pump failing without warning and cooking my engine.

I would have to assume you still either have a full, or ground down impellor on your mechanical water pump, as a booster pump cannot flow enough to maintain any kind of engine temps.

If you want to maintain the elec water pump idea, get a davis craig speed controller. They are designed to run one of their pumps with no thermostat, and run the pumps slowly/pulsed just enough to slowly circulate the water until it starts getting up to temp. These allow the engine to get up to temp quite quickly.

Booster pumps dont handle coolant pressure too well. I would personally recommend you jump on davis craigs website, as they rate their pumps in horsepower. You may find stepping up to an ewp 80 or ewp110 is what you need.

The best thing about this combination of pump and controller, is they can circulated the water for a bit after you turn the engine off to prevent boiling.

What other good brands are there besides Davies Craig?
 
I have been on their website, looking for a pump for a Frozen Boost W2A system.
I've read the forum posts where many people have had their Davies Craig pumps fail, which makes me think maybe the alloy version might be better. Perhaps their quality has since improved, or all these people didn't mount it in the best spot to be primed or high heat.  I would hate to pay for the alloy one and still have it fail in a similar way.
It turns out my booster pump was an EWP.
Is it possible to setup a warning light to detect when the pump has stopped working, what could you measure? 

I have davies craig ewp on W2A and no dramas for a couple of years, very robust pump. I dont understand your booster system well, and assuming that the pump was throttled in some way leading to the pump housing split, the fact that the pump discharge pipe split rather than the impeller/motor giving up first is probaly a good sign for the quality of the rotating parts. with an alloy housing it should be better. purely my opnion of course!

I had one ewp80 pump leak out of the back seal, i havent split one yet. I have several high powered cars running the alloy bodied units. I think mounting needs to be considered carefully to ensure they last.

They are rated for 5 or 8000 hours of use, which is nowhere near rhe life of a mechanical pump, but im on my second pump in 6 years.

As for alternatives, i never really looked, as davis crai are made locally, and you can eaily pick them up at repco, bursons etc.

 
https://www.youtube.com/watch?v=akz9YYWjSK0

I should clarify what I mean by split. In the picture I have a garden hose pushing water through the pump (not that much pressure) but you can see where the water is coming out at a join which goes around the whole pump. Not sure if this is just a seal, can't see how you would replace it.

I have read EWPs should be replaced every 5-7 years, so maybe it's time was up. After further investigation I can confirm I don't have an impeller!!!, or its definitely been clipped (I can't see it but can definitely feel it, compared to another pump I have sitting around) so I will have to stick another EWP in there.
 
Thanks Admin for that video, really showed me I need to test flow as you have done. I might even look for a something OEM out of another car, any idea what your big silver one is from? 
 
In terms of making sure it's primed, would you say putting it where the standard intercooler goes would be lower enough? That's where it was pumping straight into the engine, but I'm starting to think this isn't an ideal position for priming. I like where B24 has put his in the frunk, nice and low but you lose the spare wheel.
 
 

So the pump has been replaced with an alloy EWP130 and custom bracket made to sit it even lower in the system.
Car drove great after replacement, although during the coolant top up process I noticed the following, and it has been sitting in garage for months and I would love to get it ready for MTC2017.
 
1. If taken for a 10 minute drive with some boost, then left sitting for 5 days and the coolant cap taken off to top up coolant, it overflows. You can hear the pressure just before the cap is fully released. The same 10 minute drive with no (very little) boost and 5 days, produces no coolant overflow from cap.
 
2. After some weeks, I also found milky substance under the oil cap. It was some time ago now in autumn/winter, but I think I cleaned it out and went for another boosted 10min drive and found the same milkiness. 
 
3. Based on the above I then assumed I have a blown head gasket, my worst fear. It would seem my combustion chamber is leaking into my cooling system causing pressure to remain after boosted driving, and coolant is also entering my oil system, although the dipstick oil shows no milkiness. Could it be possible the milkiness is just condensation?
A compression test (engine cold) shows 130,124,125,129. It also has a 110kpa coolant cap.
 
I’m about to drop the engine, shave the head and install a new head gasket, but was curious to hear any opinions. Anyone think it’s not a head gasket, that’s the only way I can explain the coolant pressure build up.