Water Pump/Viscous Fan

[C33]

To add to the list of to do's on my car I've got a rather important one...the water pump failed on Friday and is wobbling about all over the place. Replacement looks easy enough, undo the bolts screw a couple back in to ease out the pump.

However as the viscous fan has to come out to do the job, I'm thinking of replacing it with an electric one, I've a fan and shroud off a mid-90's Honda Accord that looks a perfect fit. Is there a coolant temperature switch anywhere in the engine bay that switches at about 90oC that I can tap a relay into, the temperature gauge sender is obviously no good as its an analogue signal to the dash. Does the dash have a temperature warning light? If so how does this operate?

Regards
Iain

[StuBeeDoo]

I recently fitted an RSTurdo fan to my Touring. I got a sensor kit from Demon Tweeks. Not the cheapest of places, I know. It's got a sensor which slides into the top hose. http://www.demon-tweeks.co.uk/products/ ... e=PCTCF305
What I should have done, with the benefit of hindsight, is got one of the ones where you cut the top hose.
See here....
http://www.demon-tweeks.co.uk/products/ ... e=GLOEFC25
HTH
Stuart.

[Brianmoooore]

Some radiators, (especially ones that have been replaced), have a boss about 2/3 of the way up on the right hand end. This is where the electric fan switch for aircon cars is fitted. there are also spare relay and fuse sockets in the standard fusebox for the purpose.
All E30 instrument clusters have a position for an excess temperature light behind the red of the temp gauge but I have never seen or heard of it being used.
There is also a position for an excess temp light in the overhead check panel, which is used in some markets. Have never been able to establish exactly what controls it, but I suspect there is a switch available that goes into one of the spare bosses on M20 thermostat elbows.

[StuBeeDoo]

Some radiators, (especially ones that have been replaced), have a boss about 2/3 of the way up on the right hand end. This is where the electric fan switch for aircon cars is fitted. there are also spare relay and fuse sockets in the standard fusebox for the purpose.

I think mine's got this boss. I seem to recall a blue bung somewhere. So Brian, all I need is the correct sensor for an air-con equipped car and preferably a scrapper with air-con that I can rape for the necessary loom etc? That correct??

[Brianmoooore]

You're more likely to find the bits on old 5 and 7 series Beemers than 3's.
You sire the blue bung is on the side? The drain at the bottom is blue!

[DanThe]

This is how ive mounted the fan switch for my M50 conversion

14mm fine thread nut welded into tubing dropped into the top hose

[Brianmoooore]

This is how ive mounted the fan switch for my M50 conversion

14mm fine thread nut welded into tubing dropped into the top hose

That's a good alternative if you don't have the radiator boss.

[C33]

My radiator has the blanked hole...it has a 99 date stamp. Is the thread in the radiator M14 fine as mentioned above?

Regards
Iain

[Brianmoooore]

My radiator has the blanked hole...it has a 99 date stamp. Is the thread in the radiator M14 fine as mentioned above?

Regards
Iain

Never measured it TBH, but it'll fit the standard BMW duel temp switch, which is what it looks like DanThe has in his pic.

[StuBeeDoo]

You sire the blue bung is on the side? The drain at the bottom is blue!

You're spot-on as ever Brian. Mine's got a blue bung in the bottom of the left-hand tank and a brass plug about 50mm from the top of the right-hand one.

[C33]

Right...so, I need one of these...
http://www.realoem.com/bmw/showparts.do ... g=17&fg=05
10 DOUBLE TEMPERATURE SWITCH 91/99CEL 1 61311378073

then plumb into the existing loom, the owners manual refers to fuse 3 - 91degC feeding relay k1 and fuse 18 - 99degC feeding relay K6 however my fusebox doesnt appear to have the full compliment of wires in there. Is it a case of finding a e30 scrapper and raiding the appropriate loom?

Trying to does this as tidily as possible!

Any chance of a wiring diagram or colours tracers?
Regards
Iain

[DanThe]

Thats the one, about £20 IIRC.
Ive robbed an E32 of the loom and small relay box that holds the fan relays, so in theory all I need to do is supply fused power to this box

[Brianmoooore]

You need two fuse pins and two relay pins for the fusebox from your friendly BMW dealer, and the appropriate part of the wiring loom from an E34 or a 7 series scrapper. feed the wiring from the fan across the front of the car and back the left hand inner wing.
On the side of the fusebox nearest the wing you will find an unused rubber nipple. Cut the end of this, and feed your wires into the fusebox. Fit the pins to the wires, snap them into place, and fit the relays and fuses.

[C33]

Friendly BMW dealer...do they exist? sorry I come from a world where every enquiry is met with indifference and the standard response of "they all do that sir"...T4DTS.

Right sorry, yes, I'll give that a go, do you know off hand which of the pins on the switch is the 91oC, 99oC and which is the common feed?

I'm thinking it will be easier and just as neat to buy the fuse/relay box connectors and the connector to the switch and use my own wiring, I've plenty of 25A cable which will be more than enough for a single fan, I've some thinner stuff too for the control side. Where are there any earth points in the engine bay to route back to.

Sorry for all the questions, this forum (and google) is the only reference I have, and I like doing things once...properly.

Regards
Iain

[Brianmoooore]

You can make up your own wiring, but if you get it from a scrapper the plug for the thermoswitch is already fitted and the colours are correct.
Earth point in the engine bay is on the inner wing just behind the LH headlamp.
Pin 1 (green/black) is common on the switch, pin 3 (black/red) is 99 degree, and pin 2 (black) is 91 degree.
Any "attitude" from BMW dealers, then contact BMW UK. They take customer service VERY seriously.

[C33]

Cheers, that makes a refreshing change from what I usually hear from both main dealers and indy's, which is why I do most of the work to my cars myself.

I'll call round the local yards and see whats in.

Regards
Iain

[Morat]

dumb question time: Whats the advantage of an electric fan over the standard one?

cheers...

[C33]

My main justification is that I wont have the standard fan sapping power from the engine at all times, only when cooling is needed, so less power sap and the car will warm up quicker, reaching its best fuel economy quicker. As such it will help fuel consumption and, although inperceivably as in maybe 1hp if that, increase power available to the drive the wheels.

Anything that will help fuel consumption, however small, is welcome to me as I do around 2k miles per month in the car. Say I average 30mpg, improving to 31mpg over those distances means I save a shade over 2gallons a month, or £120/year. Not much in the grand scheme of things but it all helps.

I'll also be fitting a manual overide, so say it's a hot summers day and I'm driving along the motorway both eyes on the speedo making sure I'm doing exactly 70mph, and I hit (but hopefully not literally) traffic, I can switch on the fan straight away instead of waiting for the coolant to reach 91oC.

There's other subtle advantages that will probably only be of interest to an engineer like me, such as the water pump wont have a fan dangling off the end of it which is a fairly unbalanced rotating mass. Removing the fan should increase the bearing life of the water pump, which afterall is the reason I've got started on all of this workin the first place. Another virtually inperceivabe advantage will be better throttle response (less mass to accellerate), but I really am clutching at straws now, there's no way on earth I'll notice that!

Regards
Iain

[StuBeeDoo]

My main justification is that I wont have the standard fan sapping power from the engine at all times, only when cooling is needed, so less power sap and the car will warm up quicker, reaching its best fuel economy quicker. As such it will help fuel consumption and, although inperceivably as in maybe 1hp if that, increase power available to the drive the wheels.

Anything that will help fuel consumption, however small, is welcome to me as I do around 2k miles per month in the car. Say I average 30mpg, improving to 31mpg over those distances means I save a shade over 2gallons a month, or £120/year. Not much in the grand scheme of things but it all helps.

I'll also be fitting a manual overide, so say it's a hot summers day and I'm driving along the motorway both eyes on the speedo making sure I'm doing exactly 70mph, and I hit (but hopefully not literally) traffic, I can switch on the fan straight away instead of waiting for the coolant to reach 91oC.

There's other subtle advantages that will probably only be of interest to an engineer like me, such as the water pump wont have a fan dangling off the end of it which is a fairly unbalanced rotating mass. Removing the fan should increase the bearing life of the water pump, which afterall is the reason I've got started on all of this workin the first place. Another virtually inperceivabe advantage will be better throttle response (less mass to accellerate), but I really am clutching at straws now, there's no way on earth I'll notice that!

Regards
Iain

Snap! Great minds etc.
That is virtually how I worded my rationale when I was asked why I did the mod.
......And it has the added bonus on an M20 engine of making it easier to remove the distributor cap.
Stuart.

[Brianmoooore]

Unfortunately most of your justifications are severely flawed. You don't get owt for n'owt.
The OE fan is driven by a viscous coupling, and most of the time just freewheels, probably actually being driven by the ram airflow at higher speeds.
An electric fan is driven by electricity, which is produced by the alternator, which is driven by the engine. This two stage process of turning rotational energy into and electricity and then back into rotational energy again is probably around 20% efficient. I.E. It takes five times the power from the engine to move the same amount of air as a fan driven directly.
An electric fan will also be an order of magnitude less reliable as well.

[C33]

While yes you have the losses of the alternator and the motor to contend with, as the fan isn't on all the time, infact hopfully for very little time as such there are still efficiencies to be had. A viscous coupling still has a significant amount of drag, and is not just for packaging reasons (eg transverse mounted engines) that the overwhelming majority of currently produced cars use electrically powered cooling fans.

In my previous job I was involved in a power study for a new range of military gensets, the AMMPS project for the DoD, and we concluded that the most efficient and reliable cooling method was using electric not viscous fans, and its that experience that leads me to fit an electric fan whenever possible.

As always pays your money takes your choice. BTW have you seen what the WRC boys do with their fans, set them in reverse on the snow rallies to heat the coolant using the heat radiated from the engine to speed up the engines getting up to temperature. Clever li'l buggers those rally boys.

Regards
Iain

[DanThe]

Finally got round to wiring my fan in today, couldnt use the E32 relay box because there isnt enough room in the engine bay
So fitted the relays to the fusebox, relay K6 needed a ground to pin 86, dont know why the ground wasnt allready provided though like it is for relay K1?
Any thoughts?

[Brianmoooore]

Finally got round to wiring my fan in today, couldnt use the E32 relay box because there isnt enough room in the engine bay
So fitted the relays to the fusebox, relay K6 needed a ground to pin 86, dont know why the ground wasnt allready provided though like it is for relay K1?
Any thoughts?

86 on K1 is earthed by a pin directly to the PCB, while K6 requires a brown piece of wire. Don't know why its designed like this though.