cooling fan

[subi_man]

Actually - does the hub have any electronic s,arts at all? OR is it purely 100% mechanical??

AFAIK there are no electrics associated with the viscous fan, it relies on bi-metallics (expand/contract with temp) and the fluid to engage/disengage - how it actually does this, in relation to temp, engine revs, a/c etc. I don't quite know but it would be interesting to know

[Jumma]

I thought the sensor you are talking about read the temperature of the air flowing through the radiator to it and engaged the clutch accordingly. Don't take my word on this. I am still not sure if there are other sensors involved.

This forms the segue to my logic that the fan should engage more often when the vehicle is stationary as the air flowing through the radiator is travelling at a lower speed and volume and more likely to be hotter. As opposed to when the radiator is being forced through the air at speed (say on the freeway) when the air flow is travelling at a much higher velocity and volume and would have to be cooler....

However - there must be some relationship between the clutch engagement/sensor and a/c unit demand. As if the air flow was too low and the air temp was accordingly too high then the compressor for the a/c would be placed under too much strain.....yes??

Perhaps there is another sensor again that picks up the air temperature around the vicinity of the engine bay/fan/a/c radiator ...?? but then this would mean there has to be another connection to the hub - yes?

UNLESS - unless the bimetal sensor on the hub simply engages the clutch to lock the fan in to spin at whatever the engine revs are wether the a/c is on or not. So it is purely temp dependant and the a/c cooling air supply is automatically catered for once the temperature reaches a particular level?

This does not sound very efficient however as the a/c requirements may be considerably different to the engine cooling requirements and that may mean that the VERY NOISY mechanical fan is on more often than may be required if say the a/c had a separate electric fan....

James

[Jumma]

Further to this - would a bi-metallic switch or thermostat need a power supply? i.e. the metal expands and closes a point through which a current can flow to then close/open a cicuit and activate a system..

Or is the switch also mechanical and based on the contact of the bi-metal component with an actual mechanical switch which then in turn releases a fluid that the existance off along with another recriprocating fluid creates in our case the shear plane than then drives or locks in the fan drive?

This second option would be the most likely or actually the only choice AFAIK if there is no power supply to this rotating hub.

Well - at least we are learning a lot or perhaps just theorising about these things but that is where ideas come from...... I wonder if the fan/radiator/coolant/system capacity of these models is perhaps insufficient for some driving conditions and may be a design fault....!

[subi_man]

From what I know the bi-metal "switch" alters the valving inside the fan's hub where the fluid is, purely by mechanical means, no power required. So basically the fluid is free to circulate when the fan isn't required, and when the fan is needed, the valving is changed when the bimetal switch expands and restricts the path of the fluid which causes the fan to engage.

I'm sure I haven't explained this clearly but hopefully you know what I mean... Your case is a strange one Jumma, because normally problems with viscous couplings see them NOT engage properly, whereas yours seems to engage too often

and I might add I'm happy to be proven wrong on any of this because I am, by any stretch of the imagination, NOT an expert

[sierra]

I'm beginning to doubt that any ML Tritons have an electric fan bolted in front of the A/C radiator and it might just be an assumption? Could someone with an 09 GLX-R actually have a look please?
I can tell you exactly how the fan works because it's the same as my 93 Ford Courier fan and I tweaked that to get it to come on more, not less. If you feel across the hub centre there's a flat bi-metallic strip. Under that strip is a button plunger that wants to come out but the strip holds it back. When the plunger is in, the drive is off, when it's out it's engaged and the fan gets driven. When it's cold the strip is flat, when it heats up in the hot air through the radiators, it lengthens and buckles out, allowing the button to move out and engage the drive.
Mine wasn't engaging until it was too hot so I got 2 small screwdrivers and tweaked the strip out a bit[bent it] and luckily got it right first time which was pure arse.

[Jumma]

I understand what you are saying....

Yes - I hope to find a solution some time soon .. hopefully!

James

[sierra]

Jumma,

The first obvious thing for you to check, now we know it's the same simple action as the Courier, is to feel the strip when it's stone cold and make sure it's flat and not already bulging out. It should be dead flat to the hub centre cold.

[Jumma]

I will check that out sierra... so if the strip is already bulging out or partially "activated" in stone cold conditions then it would likely come on more often than it should I. I guess this is the logic...I will have a look.

Though it has had a brand new hub put in only a month or so ago now (apparently).... Not sure how you tell if the hub is actually a new one without pulling the whole front end apart!!

I will investigate.

THansk

James

[destorman]

Hey Jumma ... or anyone else ... what was the outcome with your fan?

Reading this thread it sounds like I have the same issue you had ... fan coming on too much, too soon, too often!

[DanLawler]

Hi guys,

Recently joined the triton club, bought a 2009 ml glxr 3.2 auto, has 200k on it but well looked after and so far i'm loving it. Have noticed however the viscous fan seems to be engaged an awful lot especially with the a/c on. It's fine when cold but on a warm day a/c on it is virtually engaged all the time even on the highway doing over 100km/h. Even when a/c is off you can hear coming in and out at times, this is still on the highway. From what i understand anything over about 40km/h basically makes the fan redundant. Temp gauge never goes above about half. Does my fan operation sound normal?

Thanks,

Dan

[Thongsbot3000]

Giddy Dan, welcome to the forum. Lots of handy info here.
I too recently bought a ML 3.2, after shortly noticing the viscous fan frequently in and out. I replaced it with a dayco brand from eBay. Fixed the issue. Though I did wonder after if outside temp transitioning from spring into summer here in Cairns had played effect on temp spring..

Off topic- Further more I bought a replacement fan, but noticed how roaring the sound is through the gears. So I ripped the new fan off and carefully grinded down the old fan blades 15%, which reduced the roar mildly, the temp gauge remained the same. Today I was travelling in 3.0 patrol, and noted how quiet in comparison. So I'm looking into into configuration of blades and qty. Though the patrol Intercooler is on top, so the fan draw power is something I also need to consider

[NowForThe5th]

I haven't actually investigated this but the fan on the 3.2l Pajero is so quiet that I can honestly say that I've never noticed it in 2.5 years. Quite likely that it would fit on the Triton. I don't miss the roar when cold, or when hot and with the a/c on, at all.

Instead of hacking up the fan you may be able to achieve some reduction in noise by slightly changing the shape of the leading and trailing edges of the fan blades so that the air flow is smoothed out a bit and turbulence decreased. A little work with a file and some emery paper can go a long way.

[Thongsbot3000]

Thanks Chris, i will look into the pajero fan configuration.

[DanLawler]

I should have done a search lucky the mods moved my post here (thanks) Its still a bit hard to know whether it's an issue whether a hub will fix it or not. The pajero fan idea sounds interesting, maybe the radiator also as other have said the core is quite thin. Think Pajero have an electric condenser fan though? And the intercooler sounds right down low, not so much in front of the radiator/condenser. Drove it last night, was quite cool and i never heard it, but any hot day it's practically on all the time. I just worry it's sapping power and fuel economy. My parents have a V6 Jackaroo and in the 16years we've had it i've never heard the fan other than cold start.

[RHKTriton]

After about five years (ml) my disco also seemed to be on a lot.

I got rid of it all together and replaced with electric unit. The next step will be a wide row radiator (26mm v 16mm) to cap off the installation.

Also doesn't hurt to get all that mass off the water pump bearing.