Keeping it cool

[dangerous doug]

So after a few outings Offroad in my defender I have found that it gets really F'IN hot under the bonnet. There is not enough airflow when stopped/stuck so I've started looking at what people are doing to keep them cool

Pretty safe place to start are the bonnet holes;

Before you read on I don't recommend doing it this way, my truck is not a looker so I wasn't perticulary fussed on the overall look.

Quick little Google search showed that not all bonnets are the same, mine is an early one(200tdi) so the webbing underneath is fairly modest compaied to newer moddles

I started by marking a line 2" from the bottom bonnet lip

Then from the rear of the bonnet mark 5.5" down that line. This is the centre of the first hole allowing clearance for the webbing at the back of the bonnet, it now also acts as a datum point as The next holes are simply 3" apart starting from This point

Gently tickling the holes with the hole saw (2") made a fairly neat job considering I diddnt use masking tape(not advisable)

I then cleaned the holes with a de burring tool which Finished them nicely

The only thing I don't like is it now exposes my xcess bonnet ram brackets but after hanging my hand out of the windw while driving I can feel hot air coming from them so half hours work seems to Have done something. This isn't the solution to my problems but it's a start. If anyone else wants to share what they have done please do because I could cook an egg on the bonnet at the moment lol

[Mo Murphy]

IIRC Doug, Nigel (HfH) did a lot of testing to reduce underbonnet temperatures, might be worth a search to get more ideas.

Mo

[Bowie69]

Nige ended up with bonnet louvres stamped into his 90 bonnet, like an old Morgan/MG T, three strips I believe, one long one in the middle, almost the length of the bonnet, and two either side, towards the rear, and not so long.

Your speed holes will certainly help though, plus N9ge is running about 50% more BHP than you... so more heat is expected.

How hot is "F'IN hot", cos up to about 105C I wouldn't be worrying THAT much...

[Team Idris]

I went with a blowing fan directed at the carbs for winch challenge. The duct is a later add-on to take cool air to the alternator.

I believed that the exhaust manifolds could generate so much heat that I could never remove it fast enough, but I could blow their heat away. The problem is much worse for me because it is rear-rad.

[dangerous doug]

Nige ended up with bonnet louvres stamped into his 90 bonnet, like an old Morgan/MG T, three strips I believe, one long one in the middle, almost the length of the bonnet, and two either side, towards the rear, and not so long.

Your speed holes will certainly help though, plus N9ge is running about 50% more BHP than you... so more heat is expected.

How hot is "F'IN hot", cos up to about 105C I wouldn't be worrying THAT much...

The temp gauge shoots to the red. 200tdi sensor and 200rdi gauge. I don't think I've seen his truck in one piece, last time I saw it the front end was missing just showing the massive rad

I understand the manifolds are part of the problem, I've wrapped the down pipes but the mud and crack has nicely stuck to them. I thought about ceramic coating the manifolds but I don't know how that would fair up when dunked in water.

However part of the issue might be its getting warm because of the retarded timing it was set up with from the tuner

[Bowie69]

Get a proper gauge in there, or plug your MS in

You not swapped the timing map I sent you?

[dangerous doug]

Nigh was very nice and flashed the ecu with the Thor map. It was the alignment at the trigger wheel

[Bowie69]

Ah