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6 cyl Bristol cars Type 400 to 406 - restoration, repair, maintenance etc

401 Cooling

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Old 01-12-19, 07:12 PM
Join Date: Dec 2019
Posts: 1
Default 401 Cooling

Good day everyone I am new to the thread. Have owned a 401 for a number of years and have been enjoying incremental improvement. My 401 has an early water pump (no thermostat), but is missing the shutter assembly on the radiator. So effectively it’s running without a thermostat. As the seasons change in uk, I have used different sizes of card to blank portions of the radiator. It works quite so the running temp sits in the range 75-85degC, but is not elegant. I have seen that a Renault 5 thermostat exists that could fit in the top hose, a relatively easy mod, and less that £10. So my question would be when that thermostat is shut effectively blocking the top hose is there a bypass water gallery where the pump mounts on the block that would effectively allow the water to circulate around the block e.g a bypass without going thro’ the radiator.
Any thoughts?
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Old 01-12-19, 11:51 PM
Join Date: Jul 2008
Location: Sydney, Australia
Posts: 330

most thermostats have a bleed hole drilled in them to allow some circulation of the water until the valve opens .

I fitted a similar thermostat in my 400 and found that in the hot weather it must have restricted the flow of water and tended to run too hot .
Once removed the temperature was not a problem .

At GBP10 give one a trial over winter & summer .
If there is no bleed hole , drill one about 1/8 inch in diameter

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Old 02-12-19, 12:15 AM
Join Date: Aug 2008
Posts: 10

Don't know about the Renault 5 thermostat but the three connection bottom hose type used on some Rover and Land Rover vehicles gives pretty much full flow bypass as they are effectively a change-over valve. For example part no PEM101021 is an 87° device listed for Rover 200, Rover 400, Rover 600, Rover 75, MG ZT, MG TF and 1.8 K series engined Freelanders. £40 for genuine from Rimmer Bros. Pattern probably rather cheaper. EuroCar Parts do a more generic Vernet branded one that lists for Honda, Land Rover Defender & Discovery too for under £30. There may be other vehicles that use similar devices.

My Range Rover P38 4.0 V8 has a similar but larger device with an extra stub for the heater which seems to work well.

As I understand matters you simply put a Tee connection in the top hose and run a hose down to the correct stub on the thermostat. The other two being for water pump and radiator. Cooling system diagram for the car it officially fits should make it clear how everything works but almost certainly two stubs up and oen stub down with the down one going to the bottom hose connector on the radiator.

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Old 02-12-19, 02:27 PM
Join Date: May 2013
Location: Hereford
Posts: 29

I see from the Workshop Manual that the 400 and early 401 both used a shutter arrangement in front of the radiator. You could re-instate the shutter to keep the originality of the car.
(I have dug around in my spares and I have one - pm me if interested. It is rather nicely engineered, with a sprung loaded mechanism operating with brass slats).

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