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Davo

RRC Bonnet Vents (Yes, I Know It's Been Covered Before!)

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I've been doing my searches - as I like to do before posting questions, it being the polite thing to do and all - but haven't found out all that much. Though it sounds like this is a very common problem.

Having had my SIIA for the last 21 years, recently I made the inevitable next step and bought an '83 Rangie. Now that we're at the hottest time of the year over here, that is, like 45c, it's behaving like a Rangie and getting very hot under the bonnet when you park it. Of course I put in a new radiator and coolant and all that, but the engine running temperature isn't the problem, it's when you stop and ten minutes later it won't start. (And I haven't rebuilt the carbies yet but they're on the list.)

Holes are definitely going into the bonnet as there just isn't any other way to get that enormous heat build-up out of there, but the question is what has been done and what's been proven to work? I don't want to get out the holesaws only to find that whatever I'm doing has been tried and didn't go too well. Oh, and as I'm in the middle of nowhere, buying fancy gear . . . well, buying anything for that matter . . . is out of the question. (This includes diesel engines!)

Anyone got pictures as well?

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Common practice over here when tricking up the Range Rover is to cut two or three holes along the side of bonnet with a little bit of mesh stuck to the inside.

I have seen vents on the top and quite frankly they look horrendous.

Side vents do at least look okay.

Whether it will actually reduce engine bay temperature noticeably I do not know.

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Hi Davo,

just an idea, may be silly, but why not get some circulation under the bonnet, instead of making large holes? You could mount a small kenlowe fan or the like behind the rad, and set a timing relay to let it run say 20 mins. after you have turned the engine off. Should cure your hot start problems with the carbs (air locks).

Regards

Bo - with 20 cm´s of snow outside the windows.

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Anyone got pictures as well?

Hi Davo

I cut three 3inch holes and bolted stainless wire mesh on the inside of the bonnet, its quick and simple. Even when stopped it chucks out loadsa heat with the engine running and the viscous fan turning.

post-11055-052745500 1290809887_thumb.jpg

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LR realised this was a problem, the EFi engines are supposed to turn on the airconn fans if the fuel temp exceeds (can't remember exactly) a preset temp with the ignition off.

Putting holes in the side as above will stop the build up of heat with the engine running and help your problem, and allow some of the heat to escape when the engine is turned off.

It's an accepted fact that under bonnet temperatures can peak as much as 30 minutes after the engine has been turned off.

I have to agree that holes in the top face of the bonnet look pretty naff. Do you have any way of cutting louvres in there? like on (amongst others) the E type bonnet.

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Overfinch and Carmichael (6x4 Fire Engines) also added grilles in the side of the bonnet or scuttle panel. However, Carmichael used them to cool the underbonnet when the vehicle was stationary whilst the engine was running the generators or fire pump!

Even the fan on my lowly Golf Country runs on after the vehicle has been switched off, so the problem is not limited to Range Rovers! I would suggest poping over to your nearest neighbour and whipping the electric fan out of his motor ;) and connecting it up as Bo suggests.

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Hi, living in Cyprus my S1 can get hot under the hood when standing in the sun, I have got round the problem by fitting some stainless steel woven tube over the fuel pipe which on it's S3 engine runs over the thermostat housing to add to the heat gain. The tube is the cheap pipe that you get to connect water taps under the sink at home, cut off the ends slip it over and tidy the ends up with a bit of coloured insulating tape.

Another thought would be to put a computer fan next to each carburettor.

I have had to resort to tipping a bottle of water over the carb which does the trick instantly, so windscreen washer jet strategically placed might fix the job elegantly.

Once when the engine stopped and wouldn't restart on our local boat launching slipway I was holding up a queue of other boaters. I lifted the bonnet, poured a plastic bottle of water over the carb and restarted .... much to the astonishment of a German tourist. "You pour water in ze engine, she start how does zis work?

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Soooo . . . I read all these wonderfully helpful posts, and like a big fool, I think, "Okay, I'll just reply when I've sorted it out." And here we are, a year later on.

I did cut four holes in the sides of the bonnet, at the back end, and put some expanded mesh in, just like in the photo above. Looks quite groovy. The holes are 54mm because that's the size I had - for installing door knobs - and the expanded mesh is what I found at the tip!

I also wired up the aircon fans with a separate switch, and when they're running with the engine off the amount of hot air that comes through the bonnet holes is pretty decent. This also cut down the waiting time when the car wouldn't start.

But what really helped were two new carbies. Once these things are old, there's no getting around it - they just won't work so well any more.

So thanks very much for your help and for pointing me in the right direction.

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LR realised this was a problem, the EFi engines are supposed to turn on the airconn fans if the fuel temp exceeds (can't remember exactly) a preset temp with the ignition off.

I thought I was fairly well 'clued up' on RRC's but you learn something new each day! My '87 does'nt have AC but can't say I've ever noticed a problem with underbonnet temp.

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