408: A lot of heat coming through the firewall.

[Nick Challacombe]

When I first bought my 407 the heat in the passenger footwell was horrendous, so much so my wife hated it! I then spent quite a bit on heatproofing the firewall and floor, it made a difference but not much. I flushed the radiator, a little more difference. Boiling in traffic was also a problem, the name kettle suited it well. I upped the % of antifreeze, this at least reduced the boiling but not the temperature . I read that the cabin cooing was only effective if the rear windows were open, that also helped. The fans were ok. I then, through another member, had the radiator exchanged for a rebuilt one which was thicker than mine by about 1/2 inch. Bingo, no more overheating, temperature remains 85 degrees whilst motor is running and I have just completed a 1,200 mile trip to Cornwall and 3 days tulip rally then back to Suffolk via Bristol staying in the Hotel Bristol! No problems at all, cruising on motorway at around 75mph at which the Bristol feels at home.
I have owned it for 23 years now and having fitted power steering a couple of years ago find it the the ideal car for a 78 year old one legged old git to be driving. Happy motoring!

[AndrewA]

Brilliant!!

[dwomby]

The 408 has a water valve to shut off the hot coolant going to the heater but, even though the valve is in the closed position, both the input and output hoses for the heater are the same temperature of approximately 140F after a run. Am I right in thinking that means the heater valve is not fully closing and letting hot coolant circulate through the heater?

David
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[AndrewA]

Yes...you could try just connecting the two together - bypassing the heater matrix and going for another drive....I checked with my fellow he felt the main problem with mine was cable related but I did put on a new valve as well. The old one was not great.

[Barrie]

I had the same problem with a Jensen CV8 with a 6.3 engine. Apart from fitting heat insulators under the carpet I also had the exhaust wrapped in heatproof tape. (You can do the manifolds as well) This keeps down the air temperature in the engine bay.
Also I installed a Delta fan controller which prevents the engine from getting too hot in the first place. Auto Cooling Additionally it dealt with the occasional fuel vaporisation problem on really hot days and must help to provide desirable cooler air to the carb intake.
Try Summit for parts and advice https://www.summitracing.com/
Let us know how you get on.

[dwomby]

Does anybody happen to know the internal diameter of the heater hose? I'd like to buy the fittings to bypass it temporarily before I drain the coolant and pull the hoses off the heater matrix.

Thanks

David

[AndrewA]

On mine it's 13mm int diameter, 20mm external.