408: A lot of heat coming through the firewall.
 

I get a lot of heat from the firewall. The last owner added insulation inside the car but I am wondering what else I might do to cool the engine compartment. The car left the factory with no valance under the front end as shown in the first photo.

A previous owner fitted a metal tray to mine to hide the visible suspension and smooth airflow, I suppose. Might it help cool the engine bay if I take it off?

Also, did the car leave the factory with a rubber seal along the rear edge of the bonnet opening? Mine has a nice new aftermarket seal fitted and I wondered about removing it to let air leak out from the engine compartment there?

Thanks for any thoughts.

David

I guess if it's not too difficult to remove the tray it's got to be worth a try..will have a look and see what I've got on rear edge of bonnet opening but the more you can do to let heat out the better. How bad is it? I had a '62 Thunderbird that had heat soak problems and it made life very uncomfortable in all but the coldest weather ...never really got a completely satisfactory solution..

Andrew

How bad? Well, I can live with it as I don't drive it in summers here in Florida (no AC installed) but it's very noticeably a source of heat in the cabin by your legs.

I wondered about maybe cutting some holes in the panels between the engine compartment and the wheel wells but I don't know enough about the aerodynamics of the car to be sure it wouldn't make things worse. Aston Martins of that vintage had louvred panels there.

David

Just a thought and not trying to send you off on a wild goose chase but I thought I had heat soak issues early on in my ownership of this car but sorting out which vents were open - and what heater controls were doing what has made the problem vanish - I didn't do the work myself but I can ask the fellow that did. The control knobs were swapped over and when it said everything was off - it wasn't!
I've still got a bit too much fresh air on drivers side - but I can live with that.

I will check the heater controls.

David

Yes, to jump on a bandwagon - I had this too and the heater was constantly on. Drove from England to France in July and it was a bit of sauna.

If it's coming out from the heater, I'd check that the heater valve is working (not constantly on) and that the heater flaps are opening and closing.

You can also take the heater apart and check that the seals on it do close properly. If you are refurbishing it, the heater core is I think the same as one of the sprites.

Yes - forgotten I'd done that as well - had little matrix in heater refurbished and getting the valve to work properly - and seal correctly took a bit of time.
Good luck - but I still can't see that removing your sump guard is going to do any harm.

Was just at the car (didn't check the heater controls yet) and noticed something glaring! It has a gorgeous, new aftermarket aluminium radiator and a big new single electric fan. However, I suspect the radiator is not as wide as the original because down one side there's a 1" gap and on the other side a 2.5-3" gap!!!!!

I don't think it will affect the under bonnet heat but I'll be blocking those off tomorrow!

David

Aren't gaps good?

I think the idea is to get as much air as possible flowing through the radiator not around it. This is to benefit engine temperature, of course. As to what effect the gaps or lack of them has on engine COMPARTMENT temperature - I have no clue.

David

Hot Firewall and legs!
 

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!

Brilliant!!

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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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.

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.

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

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

Thanks, Andrew. I thought it looked a skinny one!

Looking around the web, I think the heater valve is the same as the Jaguar MK2 C.16559. So that's what I ordered. Time will tell if I got it right.

David

More money but probably worth getting a radiator guy to flush out/pressure test the little matrix as well - it wasn't much money in the scheme of things - about £70 from memory...or perhaps one thing at a time!

I haven't tried it but ceramic coating the headers is supposed to help keep down under bonnet temperature. Anyone any experience of this?