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I guess they could leak?

Mine doesn't, but it is really eager to lock up and drive the fan an awful lot. I'm wondering if this is a trait of cheaper viscous couplings - both the Britpart one I put on my first P38 and whatever unit is on my new one do the same thing. It drowns out the V8 completely :(

Firstly, the engine isn't overheating, building any excessive pressure or really doing anything out of the ordinary (then again, it is a Rover V8, maybe that isn't normal). It can sit for a couple of hours at "70" and behave itself, and I can sit in traffic for ages barely moving without any issue.

My commute is say 20 miles on the motorway and then 8 miles or so minor roads through town etc. As soon as I come off the motorway, the fan will lock up, and then never shut up at low speeds. I get that is sort of the point - but its 5c outside, I wouldn't have thought it would take long to appease things and let go again. It will do the same from cold if I'm driving around town for long enough.

The red P38 we have doesn't do this... the fan will lock up from the heat soak in the engine bay if you stop and restart it a little while later, and then cool off fairly quickly and go quiet again. Otherwise it remains quiet - even after a run on the motorway.

What's your experience?

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In all honesty I've never taken much notice of it and don't really hear any increase in noise but it must be working. On Monday I did about 600 miles at 80 mph with a couple of tonnes on a trailer on the back and then immediately stopped in stationary traffic in Paris. With the heat soak I would have thought that would be the time when things would start to get a bit warm but nothing seemed to change.

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You can't miss mine. From inside the car you can't hear anything else drivetrain related unless you give it some and it eventually loosens at higher engine speeds.

It is really annoying. I might see if I can swap it over with the red one and see how that goes, keeping the one from my breaker in the boot just in case.

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diesel, but in this regard no difference:

the fan is "locked" in the morning and hows with engine revvs for the first kilometer or so, then it quiets down and I don't really hear it for the rest of the trip.

Had two times after one another a fan (aftermarket) from Bearmach, in the end I sent both back as they would not come free, the "morning howl" was permanently present.... zo I put back the genuine one (Swapped after headgaskett failure to be certain the initial overheat was not caused by the fan)

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Mmmm mine does that too in the morning, and does loosen off after a short distance when cold, which I don't mind. Weirdly, my BMW doesn't do this at all when cold... in fact the viscous fan on that only ever locks up when ambient is over 25c and it has been driven hard. When it comes to summer I'm always worried it might have failed since the last hot weather and might not lock up at all :)

I was considering getting a Bearmach... maybe not. There is a local place up the road from my work that probably has some used fan/coupling assemblies - they've probably got some known good ones. Might pop in some time.

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I did think about setting up a bench test rig for checking the fan viscous unit.
Clamp the unit in a heated water bath and try to measure the shaft torque at a fixed speed of say 1000 rpm. Maybe by using a variable speed electric drill and measuring the amps for various temps? It should spin freely then virtually lockup. Anyone know what temp they kick in?

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Sounds like an interesting idea - though don't the couplings need to be vertically orientated to work properly?

I was underneath the car on the weekend doing some unrelated investigating....

I noticed the bottom of the radiator is covered in a mixture of ATF and coolant. The coolant is coming from the hose between the thermostat and the pump, and the ATF seems to be coming from the gearbox cooler. Took the slam panel off and the front of the radiator looks to be wet from the cooler down, and the front of the cooler that I could see was about the same. So I guess over time, the radiator has had a layer of filth building up and is probably now choking it somewhat. Need to take the condenser out to be sure but I guess I'm looking for a new cooler next!

Any suggestions on what I might use to clean off the radiator?

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Sloth Wrote:

Sounds like an interesting idea - though don't the couplings need to be vertically orientated to work properly?

Don't know much about them. I think it is fluid inside that gels at a certain temp.

Any suggestions on what I might use to clean off the radiator?

Probably Gunk spray. Don't use a pressure washer, you can damage the fins.

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Definitely counts as oily now:

Not entirely sure whether it is the gearbox cooler leaking, or a leak from the bottom of the oil cooler yet. This probably explains the fan running excessively.

enter image description here

And now...

enter image description here

Oddly satisfying cleaning it all up. I've left the A/C condenser off now to drive it a bit and hopefully see where this leak is coming from, keeping an eye on things.

Bonus pic of my other other car... this little 323F V6 is the most reliable car I've had and know... unfortunately, its a Mazda. So most of it has now been swept up and is in the bin. One problem P38s don't have at least!

enter image description here

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Just a minor update, had to drive the P38 to work and back today as my daily diesel is spending some quality time with a local indie.

The fan barely tightened up at all - massive improvement. Pleased to have noticed this, given come summer (if we get one...), I'm sure it would have lead to things getting a bit toasty. Next up is finding the leak that caused it.

Now I need to find £1k for injectors for the daily... that came as a bit of a shock this morning :( arse.

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And people say that P38's are expensive to run!!

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Sloth: are you talking about replacing all the diesel injectors for £1k? There is nothing much to them apart from no.4, just a simple pintle valve. You are being ripped off I think.

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It's a 530D, common rail M57 engine. The indie isn't cheap but I'd rather they had it than anyone else around here, and I don't fancy my luck pulling those injectors out myself. It's getting two brand new injectors, plus thermostat as that's stuck open. One new injector on my parents old common rail C Class diesel came in at £450 elsewhere, so I don't think this is far off the mark.

I can't really complain too much, bar an injector loom (~£30 from a breaker) it hasn't cost me anything in repairs in the 2 years I've had it doing 300 miles a week, pretty much neglecting it otherwise and driving it like any typical BMW driver. The only thing I wish it had were lighter steering - its always so odd going between it and the P38. That said on the motorway it stays straight and true all day long.

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Hi

In looking over the engine I noticed that it has twin [I presume] electric fans just behind the front grill. Having looked at RAVE there is no mention of them. The car runs perfectly, gets up to temp & then the gauge never moves. I have never noticed the sound of these fans engaging [I once fitted a Kenlowe fan to a Capri 3.0 & a manual switch in the car, when operated you could hear it start up.

So is this an after market fit, or did some car get the twin fans?
How do i find out if they work as the car never gets hot [it has the normal viscous fan fitted]?
Would I be better doing what i did with the Capri & just fitting a manual switch with an in line fuse?

Thanks John 4.0 Westminster 2002 model on LPG

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The are in RAVE but you are looking in the wrong part, they are the AC condenser fans so listed under the Heating and Ventilation section, not the cooling system. Whenever the compressor kicks in they run connected in series so run slowly and run in parallel, so at high speed, if the engine temperature gets too high. I heard mine start up for the first time in the 10 years I've owned it while checking the EAS calibration and having the engine idling for about 30 minutes.

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Thanks for that, much appreciated.

John

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Jump the relevant relays and you can see the electric fans working

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Also, the viscous fan should be making a noise like a plane taking off for about 10 to 20 seconds and the go noticeably quieter.
It's worth checking the metallic coil on the viscous unit to make sure it's not crudded up with crap.
Having changed mine a couple of years ago it's only ever come on fully when we have had really hot days and been climbing steep hills.

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Seeing as it has been a mere 4 years, spose I better respond - and just as an FYI:

The fans will only run at slow speed if either the A/C is on AND the single pressure switch has been tripped (I think this is 15 bar or so) requiring additional condenser cooling OR the engine ECU has determined the engine is melting, and wishes for a smidge of cooling assist (which will do shit all pushing through the condenser, auto and engine oil coolers and THEN the engine rad on low speed anyway).

It is perfectly normal to never see these fans running if your viscous fan is operating correctly - even spinning freely it pulls enough air over the whole cooling pack to keep the pressure in the AC high side low enough to not trip the single pressure switch. On an extremely hot day with a hot interior, you might get it to trip and bring them on at low speed for a while. But they're so quiet running in series that you probably won't notice.

In my case, my viscous fan went in the bin in favour of my custom setup with a Volvo two speed beast of a fan and a custom shroud. So I have bypassed the single pressure switch so the two front fans always run in low speed while my AC is switched on, and with another relay and a small wiring adjustment, they kick up to high speed when the compressor clutch pulls in. This was to aid my AC on hot days with a cold engine, as I have no constant draw of air over the condenser while stationary with no viscous fan. As a result on really hot days the high side of my AC was tripping the high (but not quite the 'OH S### she's gunna blow!' safety cut out thankfully) pressure switch and bringing them on at high speed - which you will really notice.

I digress - none of this is required if you have a working viscous fan - so I'm not going to post up what I've done (I'd also have to check the specifics..) as doing it to a car without a beast of an electric fan should not be needed unless you're trying to hide a cooling problem. I'm not hiding any problems - I just dislike viscous fans. Some may see this as more complicated, but I'm happy with it and even at 35c my AC has been good, and the Volvo fan has never had to come on at high speed.

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I noticed that the viscous fan on the car I've put the new engine in locks up a lot more then the fan does on the other VSE. I swapped them around and the behaviour follows the fan rather then the car so I'm going to swap the fan out at some point over the next couple of weeks when I've decided if I'm going new aftermarket or second hand original.

David.