Evening guys, another question coming, but first off little back story, truck started over heating (not into red!) On uphills, took it into garage, they find the rad is blocked/damaged basically not doing a fat lot, water temp out was the same as in, so they replace it with an updated one. I get it back then find I have the opposite problem, engine is running far too cool, took it back in today, they found that somebody had taken apart the stat, and just left the frame of the stat, we are guessing a quick bodge to 'fix' it without finding the true problem. Now some of you may remember I had an odd noise a couple months back when it was warmed up a noise was there that rose with the engine note, since it started over heating the engine started to roar, I'm guessing it's the fan as it's only when it's warmed up that it really roars. My question is, is the roar normal? Or is the viscous fan on its way out, or already gone? Mechanic doesn't seem too concerned about it, but I find it odd it never did it before, there is some resistance when it's not running, it will spin probably half a turn? Is that ok or too much resistance?
It's a 2010 btw

Cheers Ash

My guess is it's normal as it's shifting more air...certainly in cars I've had with two speed fans the Faster fan has been louder BUT Ive never owned a series 4. I know @krutly is online and does own a series 4 so may be able to help

I can go out and spin mine and see how much it turns if that helps ?

just gave mine a spin (on a stone cold engine) and it'll spin about a quarter of a turn , there is obvious resistance there
dont know if this helps you are all ?
I dont get any kind of roar from mine

very suspicious that someone has previously messed with the thermostat though , that would concern me
mine takes quite a while to get to normal temp (halfway on the gauge) , probably a good 4 or 5 miles unlike my old truck that would be at temp within a mile or so

Cheers, sounds the same resistance then, but strange mines roaring then, it's very loud, no way of missing it. As said I'm guessing the stat bodge was to solve the rad issue, it has bothered me, but I'm hoping it's what we think, if not and still have an issue it's onto the next thing, I'm too far into this truck to give up on it lol

Krutly you're right about the difference in the k74 and b40 warm up times. My k74 takes a mile, my boss's b40 which i now drive quite alot takes a good couple of miles to get to operating temp. Thought something was wrong with the b40 lol

maybe your roaring is a bearing shot in the alternator or the like ? strange it only happens when hot though ....... could it be the EGR valve staying open when it shouldn't (I'm only guessing here)
@FoxyChris sells a gizmo that keeps the egr shut that may be worth a try ....... can't see it helping your overheating / underheating (is that a real word?) issues though
when mine's running the exhaust is louder than the engine (although mine has a slightly different exhaust from yours)

Yeah I've got one of those fitted 😁
Will see when I take it for a proper run to see if it still overheats, it will be straight back in if it does, and suppose pump next, before anybody says anything, no sign of the dreaded HG, water is good, oil is good, no bubbling, no blowback etc etc

yeah, HG failure is much less prolific on the later trucks although it was not unheard of on earlier 2006/7 models
Hope you get it sorted bud

Cheers and thanks for your help, hopefully we will get it sorted and I can enjoy it again without worrying it's going to go wrong lol

My fan makes a very loud noise when towing in hot weather, needle stays bang in the middle so always thought it was normal.

Yeah I've given it a blast now, and it's all working fine, temps are bang on, just same as you, makes a right roar once it kicks in. I've heard other 4x4's doing it in the past, but never heard an l200 doing it, and then never owning a car with a viscous fan, is why I'd thought I'd ask, don't want to go out spend yet more money on a new fan when it's potentially perfectly fine.