Bit of a long post, but it might be of interest... I know this is a bit of a controversial topic, and I get why. The viscous fan when working correctly, is hard to beat.

Mine however, did not. Well it did - far too much. The fan is/was fully locked up I'd say 90-95% of the time, and resulting in a loss of power, MPG and the engine never got above 85-7c. Those of you that have seen/heard my car know it isn't that quiet. No centre silencer improves the V8 rumble no end, but its no fun when your viscous fan drowns it out entirely!

The ideal electric replacement fan would, by all accounts, be the 18" Lincoln Mk VIII fan found on various vehicles across the pond. Alledgedly rated at 4000CFM or so. Getting one over there is simple, getting it over here would be £200-250... err... no.

Looking at generic aftermarket options, Spal do a 16" 'HO' high output fan, that does about 3000CFM. I couldn't even find a price on that, so declared it unobtainium. All others I've looked at seem to top out around 2000CFM. And current draw on those topped out at about 10amps, which seemed a bit too good to be true.

A bit more googling looking at OEM fans pointed me at a pretty readily available Volvo 850/940/S70 fan... the internet suggests on low speed, its around 2500CFM, and on high its around 3300CFM. Best bit is, its about £30 on ebay, and another £15 for the Volvo relay module, which is a handy box that a) handles the current of the fan on high (about 30 amps running), and you just ground either the low or high speed selection to start the fan. A handy feature is high speed always takes priority - so if you hook low speed up to say, come on with air conditioning, and then have a thermostat for engine cooling on the high speed, the high always comes on regardless of what the low speed is doing.

It's a bit smaller than the mahoosive viscous fan, but not overly so:

I wanted a cowling/shroud that would get the fan pulling air across the whole radiator surface. Take one 600x600 network cabinet lid, and a bit of steel from one of the doors, and you're left with this:

And some fettling later. Sadly I didn't remember to take any pictures of the cowling with the fan in place, and the pegs on the bottom that fit into the standard radiator cowling mounts. The ears on the top are used to bolt the cowling to the radiator mount brackets - so the weight is hanging off the mounts holding the radiator, rather than the radiator itself. It isn't actually that heavy anyway.

Plenty of room!

The relay module can be wired up using 10mm spade crimps for the positive feed - the fan plugs straight in. The ground goes to the fan directly, again a 10mm spade fits nicely. The only problem is the speed selection that has round pins. I soldered some wires onto some red bullets, crimped them a bit smaller, pushed onto the pins in the module socket, and then filled with resin. Don't want them falling off!

Currently I don't have a thermostat - so I'm grounding the low speed before I set off and leaving it running. It's in the post...

Today it has been 17-18c all day, and I've had the fan running on low while driving around town, hooning it a bit, and letting it idle. At idle, it will keep the coolant temp down at 87c, with the A/C on too. Once I get the thermostat and can set the on/off points, it should cycle and keep the thing running proper temperature.

Best bit... I can hear my V8 again! And I no longer sound like a Nissan Navara pulling away...

I love it when it comes to DIY engineering, great solution!
Do you know the temp settings of the thermostat/sensor, are they close to maintain correct operating temp and where do you place it?
There are 3-stage electronic sensors, or even adjustable ones that feed your fan by relays (I think from Kenlowe).

Oh, and what when the owner finds his cabinet in that state tomorrow?

Ferryman wrote:

Oh, and what when the owner finds his cabinet in that state tomorrow?

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I was wondering about that. Are you going to put your old viscous fan onto the cabinet to hide the evidence?

I'm going to use (or try, anyway) a generic 12v digital thermostat board, with the probe in the fins of the radiator. That way, I can set the on and off points separately. Most actual fan thermostats for cars seem to have quite a wide hysteresis, many of which have the 'off' point below that of the thermostat closing, resulting in the fan never turning off on a petrol P38...

Will take some tinkering to get the actual temperature of the radiator to match the coolant, but I think I want it to come on when the coolant temp is around 95c, and off at 90. That way the stat is still partially open, and it will actually cycle on/off.

The cabinet is one I've been keeping at work for such things :) It's pretty much useless to me, and worth nothing to sell - very tall, but not deep enough for rack mounted servers. Already have similar network cabinets in places I need them, and this one was actually removed and replaced with a small one.

I missed a picture... this is the cowling before the mounting pegs, fan hole and fan were added. Bit of paint on the bottom half as we were running out of time to stop it rusting, and in it went!

Most afterfit electric fans that I've seen put the sensor in the top hose coolant flow, rather than on the rad itself. The thinking behind that is that you're measuring the actual liquid coolant temperature rather than somewhere where airflow over the sensor and the reliance on surface contact can skew the figures.
I used one of these on the V8 Hybrid (it had a twin fan electric setup). It did what it said on the tin! Shiny shiny too :)

Yeah, I have been looking at options like that, but there isn't much space in the top hose to fit one that I'd be all that happy with. That said, I'm considing a custom silicone top hose anyway, and now that I have no fan, I can actually lower the high point of the top hose to make it level with the top of the rad too. It does mean you'd have to remove the top hose to change the belt, but I've changed coolant more times than I've changed belts so far, so... pros and cons!

I'll be sticking the probe to the thermostat into the fits of the rad with thermal adhesive - both to make sure it stays put, and to improve the conductivity. I see merits of both options, and there are a lot of good reports to the 'probe in the rad fins' approach as well as the top hose method.

If it doesn't work, its only £4 worth of probe/thermostat.

I'll second the stick it in the top hose method too, at least then you will be taking a reading from the actual coolant temperature. If you are going for silicon coolant hoses then you must have pretty looking anodised bits too, it's just not done to have silicon hoses without.

Your network cabinet reminds me of when I had a car that needed some serious welding doing to the underside and required large sheets of steel. I used an ex-Civil Service issue filing cabinet......

While looking around for steel, I did come across a large (full) filing cabinet in a store room... it was very tempting. Spin it round so it faced the wall and I'm sure no one would have ever noticed...

The fan has been performing well over the last few days, including a 120 mile round trip this afternoon. Nanocom has been on throughout and all is good.

A bit too good today... down to 75c while underway good... thermostat has started to stick open it would seem. Looks like that nice genuine one sitting waiting for the red car might need to go walkies...

That's good news. Just another cooling system drain/ fill/ bleed to go then. Do you use a vacuum filler or just pour coolant in when refilling?

I just pour in and occasionally use a pressure heater to force air out of high points with the clamps etc loosened and hose partially off. Seems to work okay. That said I'd like to try a vacuum filler at some point.

Engine off and fan still running - when you walk behind the car you can really feel the heat!

My vacuum filler failed me big time today (first time ever!). Got the mother of all air locks in the VSE.
Not sure if it's because I drained both sides of the block, despite the dire warnings in RAVE, as had to get all the crap out of the waterways after the heads swap.
Are you going to put a timer in the ignition off fan circuit?

That's annoying :/ I haven't seen these warnings in rave - surely an empty block is an empty block? I shall have a perusal.

I'm thinking about it. For now, I'm going to wire the thermostat into an ignition switched source. I figure the viscous fan stops when the engine is stopped, so clearly there isn't a worry about the latent heat. On the other hand, a timer probably wouldn't be all that difficult to at least cool the rad off.

Orangebean wrote:

Not sure if it's because I drained both sides of the block, despite the dire warnings in RAVE,

When I got my block back from the linerjob it sure was empty, both plugs have been out and refilled as per Rave (partially).
I have seen this warning too but don't get the point.
Refilling a Rover V8 is patience, patience, patience. Initial run until tophose becomes warm (stat still closed) and stop engine for full cool down.
Repeat.

To add to prev. post, when tophose becomes warm, or level in expansiontank rises whichever comes first, I stop the engine for cooling down, but also close the cap of expansiontank to prevent sucking air back throug the radiator overflow pipe. Don't know if this is the trick but after 2-3 exercises most air has gone.

Well the good news (I think?) is my coolant thermostat is behaving itself again now...

I had a play around with the probe-in-radiator fan thermostat earlier today, and I think I'm going to scrap that idea already. It doesn't react quickly enough for my liking.

Next idea is a 32mm adapter to fit an M22 fan switch that has two sets of contacts, one switching on at 95-90c, and the other at 100-95c. That way I can connect it to both low and high speeds. It's a Ford part - Intermotor 50018. That will fit between some nice silicone top hose bits.

Did you see the X-Eng data sheets for the Intermotor sensors Sloth?
I used the one they supply with the shiny shiny for the Hybrid (had a tuned Vitesse efi 3.5 in it with twin electric fans) which had the cooler 88-83/ 92-87 switch. Worked fine for me with no conflict between fans and thermostat and never had to resort to the manual over-ride. I did run a lower temp thermostat (82C IIRC) in the Hybrid though.

I've rebuilt a few engines now, and never have a problem with air locks, I fill the engine from the top hose, then connect that to rad, I then lift the expansion bottle up as much as I can and crack the heater hoses, lpg regulator, then start the sucker up, might take another litre after that when the stat opens.
Any top up after that is minimal , and usually nothing needs bleeding again.

Thanks for the bleeding stuff Tony and Chris. Never had a problem before using my vacuum filler (and I've used it lots of times on the GEMS and the Thor). I will refill and bleed using the traditional method (as above ish, only using the reducer temp sensor-highest point- to bleed heater/ lpg lines) after I've replaced the coolant temperature sender, which will hopefully arrive with Mr Postie this morning. I'd better hand his fan thread back to Sloth now :)