Going back to the Drawing Board for a re-think.

 

Reread your post. I'd say you run the car with the hoses off for a week and take temps and record temperatures, length of driving, etc.


See if you can really graph out more data points to see if you're on to something here...

 

And hope that you don't get an oil leak otherwise you will get a very grubby windscreen!

 

Hi Vee

That is what I am planning to do and also see how it performs with the Car in Motion, when hopefully even more Hot Air, will be displaced by Cold Air coming in.

 

and engine fumes in the cabin as this is were the internal cabin air intake is located


god forbid any leaking exhaust gets in there as well

BB

 

Hi BB

Now that is something that I never thought of, so it looks like its back to the drawing board on that one.

But can you see a way round it?

Maybe I could put some Pipes through the Metal Stubs and then curve them up towards the Grid so it doesn't get into the Cabin?

 

OB, I am not doubting pics etc. however, engine temp is a function of the thermostats and the AAV runs it's own thermo bulb. I don't see how increased airflow in or out can lower your engine temperature if they are working as they should.
Even with bonnet open and refrigerated airflow through radiator and engine bay, the engine temp should still settle on that set by the thermostats.
The question of whether the base of windsceen is a high or low pressure area with the car moving should be investigated also. Since that is where the ventilation system gets it's air I quess it is not sucking on the drain tubes anyway.

 

Hi Baxtor

While I don't doubt that you are correct, it was mentioned in someone’s post, that if you got stuck in a Traffic Jam and were in danger of 'Boiling Up' unlatching the Bonnet/Hood, might save the situation.

So that is where my thinking was going on that, although after what BB was saying, it is beginning to look like a 'Non Starter'

So I am going to re-connect the Pipes and go back to the drawing board, where hopefully someone else will be able to find a better Solution.

 

this works out great! pix.

most vehicles develop a high pressure area at the windshield base(as mentioned), as speed increases , it can slow air out and some times build enough pressure to stop air flow and build underhood stagnation!

thats why Nascar use a nice large ducted air inlet around the carburator(EFI nowadays), as pressure builds it forces COOL air in the ducting area! ( mini supercharging).
also why old muscle cars had the reversed hood inlet, Cowl induction!

car pictured moved them forward out of hi/press. area.

just old fashioned yankee hotrodder stuff!

 

Hi Ron

It looks as though my idea just wasn't so great after all and seems like 'Louvres' are the way to go.

Is that your Red XJS She looks a beaut!

 

Why wouldn't you just replace the radiator instead of speculating about increased airflow this and that?

You could have a cooling system capable of over-cooling the engine, and the thermostat keeps the engine at optimum operating temps. If the cooling system is working properly, you don't need to worry about sitting around at lights or anything.

I get that it is common with the XJS to worry about the cooling system, but that just means you should fix it. Replacing anything worn out with something modern will certainly bring it back beyond spec.

So much more cooling can be accomplished with a better radiator and electric cooling fans than extracting some air from the engine bay. This isn't an air cooled engine, and you shouldn't be treating it as if it is. You are trying to grill you chicken hotter by turning the thermostat up in your home rather than just turning the stove to a higher setting.

I have been there, opening my hood after getting home to let the cat cool down. The way to "fix" this isn't to come up with new ways to introduce air, it is simply to fix the cooling system so it is in proper working order.

 

I think OB was trying to reduce the ' engine bay ' temperature by allowing more airflow through front to back

we know the engine regulates its own temp , but the bay does get hot due to being tightly packed and no vented outlets towards the rear , a previous poster heavily modified his engine bay side walls to allow air to escape towards the side of the car , about six months back if I recall

I have also done the ' pop the bonnet ' in slow traffic to allow the engine bay to breathe a little easier, but this is only good if you have a passenger to operate the lever , lol

a little thought and some engineering could pay off in the long run

BB

 

BB Explained it so much better than I did.

There is nothing wrong with my Radiator or the Fan and She always runs cool.

As BB has mentioned, I was trying to cool the Engine Compartment itself, with a variation of the Bonnet/Hood 'Pop up' idea but although it seemed to work quite well, there was a bit of a downside and so it needs more work.

To vent the Hot Air from the Engine Bay from a different part of the Car, without the need to make modifications to the bodywork.

 

IMOP the louvers are the way to , just another irresponsible move by Jaguar by not incorporating them in 1976. With said the cost of getting the hood louvers stamped & the cost of repainting isn't worth it, unless your a body man.
Lawrence

 

I'd get those hood louvers in a heart beat if there wasn't so much involved like cost of getting the hood painted & matching the color. I really think this is the only practical way to release hot under hood air.
Lawrence

 

Hi Laurence

They seem to have nailed it on my Merc, as where the Bonnet/Hood, meets the Windscreen.

The edge of the Bonnet/Hood is 'Swept Up' to allow 'Some' Hot Air, to get out.

 

The air is designed to go out the bottom of the car, past the exhaust, so taking the hottest air out last. That's part of the reason air dams were added to cars, it was to create an area of low pressure in the engine bay and suck the air out.

It's also the reason there is a piece of weatherstripping on the rear of the engine bay to seal the bonnet to the body, it keeps the high pressure air at the base of the windscreen out of the engine bay when moving. If that wasn't there, then you would reduce the airflow through the radiator as the windscreen air would flow into the engine bay to fill the vacuum created by the air dam, bypassing the radiator.

Yes, things are different when parked, and I do often pop the bonnet after getting home to let the heat out, but when moving it's a different story. Unless you have a wind tunnel and the ability to measure the static air pressure at various points around the car I would not want to mess around with what the factory did - the engineers at Jaguar were quite competent!

 

Cheers!

I never knew any of that, you learn something new every day (or at least try to)

 

Good points, and of course that brings us full circle back to perhaps the best 'mod', in adding electric fans that create your own airflow...

Also wondered about doing this?
https://www.jaguarforums.com/forum/a...64241483_n.jpg

https://www.jaguarforums.com/forum/a...06731883_n.jpg

The original thread here: Does a great job on his bonnet!
https://www.jaguarforums.com/forum/x...6/#post1393946

 

Here's the video... its the centre section I'm referring to.