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Heat Removal from Engine Bay


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So, LHD Series III with a Rover 3.5 block and 3.9 top end running on a 14 CUX with retained engine fan. The water temp is fine, never tops 178 F. However, it gets unbelievably hot under the bonnet. So hot that touching the wings, especially the driver's side, is painful. At road speeds, all is well. There's enough air flowing in under the bonnet (slightly larger than usual gap between bonnet and catch) and around the engine bay to help transfer heat out. On trail however, moving at slow speeds for extended periods of time, while the water temp remains fine, the idle will become lumpy/diesely, power will diminish, and eventually idle stalling will occur.

I think that the coil getting extremely hot is a factor, as may be the lack of cold air intake. Previously, before treating it to new wings, I had cut side vents at the rear of the engine bay on both sides (picture below):

P62206111.jpg

I don't believe that these vents made any real difference, probably being too small.

So, other than cutting large holes in the bonnet or wings (passenger side has the heater vent hole about six inches from the trumpet of the air intake under the bonnet)doesn anyone have good ideas and examples of less obtrusive ways to shift heat out of the engine bay.Liquid nitrogen mist would be great, but I'm shooting for less exotic and, preferably, something very discrete.

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that series is such a nice truck!

i will be watching this with interest as i am also having problems with under bonnet temperature. (lightweight with 3.5 efi)

in fact im having major issues with temperature all together. i know the temperature gauge i havent isnt the best as a tap on the front will cause it to drop slightly but its still reading at 90 degrees C at a 'normal' running temperature.

other problem with engine is hunting at tickover sometimes (could it be hot air in air intake or hot coil (mounted on inside wing lh side)?)

i also dont want to alter the look of the vehicle so dont really want any vents in the bonnet but think i may have to. question is what vents can i put in that wont let water in?

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Thanks to you both for the positive comments. I think the bonnet venting holes may work well. It has certainly been a solution for the RRC crowd and it looks quite good on that very smart 90, but I just think that it would look sort of 'boy-racer' on my S3. I didn't really like the wing vents on it previously for much the same reason.

I had thought about mounting one of those slim line electric fans to the bonnet, but that's just going to push hot air around in the bay unless there is venting to pull cooler air from outside in or vice-versa. And the only thing naffer than wing vents would be some kind of Hummer-like bonnet grill :o

What rad are you running in the Ltwt with the 3.5? I have a narrowed RRC rad with the integral oil cooler and, as I said, water temp is always good. With the Ltwt, if you aren't ready for a different radiator solution, I'd consider the following lower cost approaches (which I used effectively to cool the 2.25 when living in Dubai): an 8 blade military fan, really effective shrouding (often overlooked but critical), run a military oil cooler (not sure that it has the capacity for the 3.5? - I got mine from a Sharjah scrappy for about 15 quid), and possibly install an auxiliary pusher fan on a switch (I believe Ford Taurus scrapyard fans are popular in the UK). I ran the ACR 2.25 at 40+ C in Dubai without issue, and the oil cooler seemed to make the biggest single difference. I only ever needed the pusher fan when things got seriously hot and we were in the big dunes. Granted, that was the 2.25, but they are all bolt-on potential solutions to consider for the Ltwt...

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currently thinking about 3 fine mesh grills in between and either side of the bonnet hinges as i think they'd look ok if painted the same colour.

my biggest problem is lack of space. the engine is sat sort of where the original 2.25 was, except its higher. i have about an inch clearance between top of plenum and bonnet, and if i cut the threaded part off the waterpump will just about have an inch between that and the radiator.

the radiator is a 4 core series radiator which was bought new just over a year ago. it has a 16inch pacet mounted on the front of the radiator and is as big as i can squeeze in the standard area.

as regard to oil cooler, i am currently thinking about this option as i could run it along with a remote filter set up which would give me plenty of clearance between the front diff and what is currently bottom of oil filter.

another thought running through my mind is whether i could get a custom radiator made to fit above the steering relay and run full width, mount it further forward and get 2 big puller cooling fans behind it. i would then have room below for a nice oil cooler.

i have done a bit of reading about running temperatures of v8s but theres so much contradiction i dont know what the maximum permisable temperature is. last thing i want to do is damage the engine due to it running too hot.

also read a bit about drilling a hole in top of thermostat to help prevent steam build up causing thermostat to open and shut and create fluctuation of temperatures.

my biggest problem is cost of all of this. fitting a nice new radiator and such, is all very well and good, but when the vehicles stuck up to chassis in a muddy hole powering to try and get out, it doesnt matter what cooling there is if theres no where for the air to go so maybe some massive vents are the only realistic option.

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been thinking a bit more about possible solutions.

how does the following sound? (all thoughts welcome)

-big mesh grilles across the back of the bonnet (to let hot air out) how can i avoid water running in all over the engine and air intake when it rains?

-small cooling fan (ideally 6inch) mounted in the lh side of bonnet near the back to pull cool air in onto my air filter

-would cutting extra holes in the front panel (above the existing ones) help? or would it mean no air would go through the radiator?

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been thinking a bit more about possible solutions.

how does the following sound? (all thoughts welcome)

-big mesh grilles across the back of the bonnet (to let hot air out) how can i avoid water running in all over the engine and air intake when it rains?

-small cooling fan (ideally 6inch) mounted in the lh side of bonnet near the back to pull cool air in onto my air filter

-would cutting extra holes in the front panel (above the existing ones) help? or would it mean no air would go through the radiator?

This what we used

200432447359.jpg

To avoid water ingress we made a sort of baffle with a drain, spaced below the louvers, on the principle that hot air rises.

Now this was on a series 3, now in your case a lwt is easier, just cut and vent the sides of your bonnet.

If you put a fan use it as an extractor not a blower, if you want fresh air to the engine intake put a snorkle.

G

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An old volvo of mine had vents in the footwells that let fresh air in around your feet. My BMW has vents that draw cool air over the brakes to help keep them from getting too hot. These systems got me thinking the other day about putting a similar vent system into the wheel arches in the landy to ventilate the engine bay and help keep things cool. With some kind of flap mechanism, you could always close them in the winter to keep the bay warmer or if offroading/wading to keep the crud out.

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These are pretty good ideas. Zoltan - good call on the header wrap, I've got some coming. Trying to avoid any cutting into the wings or bonnet, but that may end up being the best/only solution. I wouldn't worry too much about vents and rain. It's not like it's dry in there when it rains anyway ;)

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The two problems with engine bay cooling with the V8 in a landrover,

1. getting the hot air out

2. getting enough airflow (unheated) in

Just boosting flow in or trying will not work, as usually this is limited by flow restriction in engine bay, and by the time its gone thru radiator its hotter anyway.

Oil cooler, and a good fan with cowling will keep coolant temp under control, but engine bay temps rocket esp in high ambient.

It depends on type of landrover series or coil what you can do on getting more cool air in , with coil type getting air in thru vents in front of wings ala td5 and wing top vents ala earlier defenders let heat out, but at speed these wing top ones dont work as wing tops are positive pressure areas. The reason I fit a blanking plate on heater intake in hot weather, as you cant turn the airflow off.

The airflow on bonnet top is greatly affected by having a spare wheel on bonnet. with spare wheel low pressure just in front of bulhead with out high pressure area.

I cut holes in lower inner wing and found this to help with reducing footwell heat build up.

My coil is on underside of front wing and never had any probs , even in dunes in 45C . HTSH

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So this afternoon my daughter came out while I was fiddling with various and sundry bits on the truck and I solicited her ideas on the subject. I thought her approach quite sensible:

"Cover those rusty pipes (exhaust manifold) with rubber or something to keep everything cooler"

"Put in a 'pipe-thingy' to bring in air from outside to under the bonnet" (Sounded like a snorkel concept to me)

"Put a fan in the side (inner wing) to pull the hot air out".

So, from now on, I'm not going to bother seeking the admittedly excellent advice from experienced folks on the Forum, I shall instead rely entirely on the sound advice of my 8 yo daughter :lol:

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Jethot/other ceramic coating on the exhaust manifold will also help. Grab/borrow an IR thermometer and drive/stop and scan the engine bay to see where it's coming from. Then you have a baseline for any changes that you make, getting the heat to hold in the exhaust is probably your best option.

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I can sympathise with your heat retention issues at low speed. I find my Ninety gets very hot inside in these situations

I think your idea with the side wing vents will help. Nige HfH on here has done this on his V8 Ninety as part of his ongoing quest for more cooling. He tells me they do make a worthwhile difference, more so than holes in the edge of the bonnet.

When travelling at low speed I expect the engine is not running that fast, therefore the belt driven fan won't be going particularly fast either. Maybe an electric auxilliary fan could be used to good effect in this situation.

Another gadget I remember seeing in the magazines a few years back was a bonnet top extractor fan. It looked like a wide and flat mushroom sat on the bonnet. I think it was made by Kenlowe.

Wrapping the exhaust manifolds and headers will help too.

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A friend of mine has a bonnet top mounted extractor fan, just a small one, for his V8 90, thing is, after wading all it does it eject steam right onto the windscreen.... great for cleaning it, but not for visibility -and with the wipers being 'not that great' like all LR, it takes a while to clear properly....

I would go with side fan/vents TBH.

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Step 1 - stop the the heat getting in, wrapping and coating etc, as above.

step 2 - lots of airflow through the bay to shift the heat out. If you don't want blingy vents I'd look at lifting the bonnet slightly, esp at the rear. You'll end up with a large narrow vent with a very large area, but a near-standard look. Otherwise, look at moving air downwards or into the wheel arches?

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There's a company called Caswell both in the states and over here, who sell ceramic manifold paint that is, as far as I can ascertain, almost identical to what the boy-racers pay about £400 to have their manifolds coated with. It cost about £30 for an obscenely small pot, but that should be enough to do a V8's manifolds with a little left over. I've just gotten some, but won't have the time to do anything with it for a week or three.

Youu need to blast the manifolds with ally-oxide grit first, but that's not too taxing.

Wrapping the manifolds will have the same effect, but if you're getting it wet, it can have undesirable side-effects on your exhaust's life span.

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Heath,

Thanks very much. Found it here Caswell Exhaust Coatings. $19.95 for a 4 oz pot which they say is enough for a set of small V8 headers or cast iron manifolds. That's the ticket. I'm also looking at raising the rear of the bonnet (acts as a defroster in the winter too? :D ) I think diminishing heat from the manifolds will be the big win.

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Going with larger diameter header and exhaust might also work wonders, but is obviously a more expensive option although would take much better to being wrapped up without cracking as cast iron is prone to. Though you might end up with a moderate horsepower gain. :)

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With the weather getting warmer i decided to take to the bonnet with a 24mm hole saw. got 10holes in the middle and with the engine running and fan on there is definetely warm air coming out. im going to put some into the lh side at the back as theres heat trying to come under the bonnet edge.

Im going to make up some aluminium plates to screw over the holes to keep the rain out when it comes back (probably end of week bank holiday!) The covers will also serve to return the engine bay to a confined space to pass scrutineering at trials.

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Hi Guys

I've got a little experience with this as well, from my former 90 V8.

On my new build, LW-body on RR frame and drivetrain, I'm planning to make the gearbow-tunnel oversize to get some of this hot air flowing through the vehicle this way.

Think the idea of cooling the headers is a must.

Cheers

Morten

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