Thread: Will a bonnet scoop reduce heat in the engine bay?

Hood Louvers - Fender Louvre in Steel & Aluminum - from 928 Motorsports(R)

found this place. probably equivalent one in australia (which gets their parts from US)

Louvres.jpg
i kinda like the look of that. would look better on a deefer or disco though rather than a sports car like shown. if you live in the blue mountains it would boost your window defrosting abilities as well. after the 6 hours it would take your engine to warm up.

me again. i've gone one better and actually found this. looks pretty good IMO

car23.jpg

Pffft - Jeremy Clarkson has already shown us what works during the Bolivia special years ago..

snapshot20091228181306.jpg

Radiator cooling depends on the pressure differential between the front and the rear of the radiator.

By fitting a rearward facing hood scoop with entry near the screen you are reducing the pressure differential.

Actually Clarkson's scoops are pretty good . They are in somewhat the correct position anyway.

A similar effect can be made by opening up the grille and maybe fitting mesh with a high void/solid ratio as Land Rover did with the Saudi grille. They do know something and I have done this on my D2.

Also sealing all leaks past the radiator like missing rubber seals, ensuring no spotties in front of the grille, and if a bullbar is fitted . making up a new scoop that replicates the factory scoop behind the bumper bar.
If you must fit scoops I think the bonnet side ones would be effective and not let too much water in. BUT LR didn't feel they needed them even in Saudi.

And yet they overheated from new all over the world.

A workmate had one brand new - in Scotland in 1982 - it overheated the first Summer - in Glasgow!!!! In laws had a meticulously maintained 86 model bought just out of warranty that overheated if used hard - like towing a 1.3 tonne caravan - on hot days. Never failed to get them home but had to baby it. How many other stories are there like this and why are there so many threads on so many forums about how to keep RRC’s and early Discos cool?

I don’t buy for a minute that the factory cooling system is adequate - it never has been, its only ever been ‘just enough’ to get them out the door IMO

How many other Marques have such consistent issues over so many years?

What are we talking about here?

Increasing the cooling of the radiator or reducing engine compartment temperature? They are not the same thing.

Here's a pic of the P38A that had the bonnet scoup.
P38AirScoup.JPG

The owner told me it was successful. It reduced engine bay temperature.

Had the scoup been reversed, it would have increased the airflow through the radiator but done bugger all for the engine bay temperature. That is where the extra heat lost by the radiator would have gone.

Quick story:
About '92-ish I went for a drive up to Ayers Rock(that's what it was known as back then, but Uluru if that's less offensive to some) .. in my '79 RRC.
Drive up was uneventful, but long.
Stopped and had a sleep at the camp ground near the rock.
Next day, started off ok, had brekky at about 7AM, ambient was about 15-20-ish, but got to about 30+ by late morning.
From that point onwards the needle on temp gauge shot up to the start of the red zone and stayed there no matter how fast or slow I went. Tried everything from 40k/h in 3rd, 4th and 5th, to 110 in 4th and 5th .. no difference, needle in the red zone all the time.
I had Hella spotties, so removed them .. no difference!
Cooling system never actually felt overly hot tho, or over pressured, but I was spooked none the less.
Before lunch I pulled up into a car park, and changed the thermostat from the 88° it had then, to a 72° I had as a spare.
No difference. Pulled the thermostat out and as I suspected, made no difference, put the 72 back in.
Checked coolant level regularly, and it was fine .. no loss.

Being 2500klm from home I had no choice but to try to press on as far as I could.
Pulled into another rest stop on the Lasseter Hwy and by chance there was a solid looking box dumped in the bin .. perfect!
I placed it under the bonnet, for the bonnet to rest on, wired the bonnet down with some coat hanger wire so it didn't fling up and over the roof, and drive off.
At first at about 60k/h, then 80, then settled at 90.

temp needle dropped immediately down to the start of the normal section(I think on those gauges at the mark where the white cold area meets the black normal area) with all that cool air going straight to the engine area, but with a massive box still blocking a lot of that gap.
I'd reckon the gap was about 4" high, and the box about half the total width of the bonnet .. so air came in from over the headlights more so that from over the radiator area.

I reckon I got to about Coober Pedy or Glendambo(whatever distance that was, and it started to rain so I pulled up again and removed it(kept the box in the back just in case).

Assessment, in terms of forced air in via a forward facing scoop, I reckon you can't go wrong. On a 300 Tdi, over the turbo area makes about the most sense too.

Heating issue turned out (2 years later!!) to be a stuffed radiator .. so the overheating showed on the temp gauge was real, just didn't feel like it under the bonnet.

Originally Posted by PhilipA

Radiator cooling depends on the pressure differential between the front and the rear of the radiator.

By fitting a rearward facing hood scoop with entry near the screen you are reducing the pressure differential.

Actually Clarkson's scoops are pretty good . They are in somewhat the correct position anyway.

A similar effect can be made by opening up the grille and maybe fitting mesh with a high void/solid ratio as Land Rover did with the Saudi grille. They do know something and I have done this on my D2.

Any pics, was it easy to do?

Mark