Have I f***ed it?

[teecee90]

HELP

So, just left my bike ticking over in the garage for about 15 minutes. When I went back the temperature warning light was on and the gauge said 122 degrees. Turned it off straight away and could hear the coolant boiling. I assume the fan must have failed...


What are the chances I have f***ed it and what is the most likely outcome - head gasket?

[ogri48]

I reckon it will be fine mate. relatively modern engines have to cope with all sorts of extremes in other countries. aside from major mechanical issues they are pretty bulletproof (and thankfully for moi, fairly idiot proof too)

[teecee90]

Fingers crossed it won't have done any major damage.... was scary to hear the coolant boiling.


Have just tested the fan and it has definitely failed.


Anything I can do to check there is nothing seriously wrong?

[limax2]

Anything I can do to check there is nothing seriously wrong?

Not trying to be clever but I would say take it for a ride and if it runs o.k. then you will be fine.

[teecee90]

Anything I can do to check there is nothing seriously wrong?

Not trying to be clever but I would say take it for a ride and if it runs o.k. then you will be fine.

Well yes, but the fan has failed so don't really want to risk that until I get a replacement so was wondering if there are any other checks I could usefully do in the meantime. Fowlers want £378 for a new one..!

[Trebus]

Doubt the fan would come on in normal riding this time of year so ok to test. Is the thermostat stuck closed?

[celticbiker]

Have you tested the fan to be sure it's that and not something else causing it to not come on?

[His Dudeness]

The fan is probably ok. It's more likely that there is a leak somewhere in the cooling system so the cooling system is losing pressure and that caused the coolant to boil over at a lower temperature than it should. If there's a leak the coolant could boil over before the fan comes on. I'd dry the bike off, fill the cooling system back up and start it up and look for leaks. Look for any drips or wet areas. The o ring on thermostats can fail. Looking at the wiring diagram. You could test the fan by pushing a bit of wire into the green/black connection on the fan relay, then touch the other end of the wire to the negative of the battery or the frame of the bike, the fan should come on. That will test the fan fuse, relay and the fan

[robbo]

Could be the rad cap not maintaining sufficient pressure to stop the coolant boiling.

[VNA - BMW Wank]

When I went back the temperature warning light was on and the gauge said 122 degrees.

There's a temperature warning light - but a gauge?

[teecee90]

I have a multi gauge which shows the temperature.


Fan is definitely shagged. I disconnected the plug to the fan under the tank and used a power probe to send 12v direct to the fan and nothing.....

[His Dudeness]

did you ground the other pin at the same time?

[VNA - BMW Wank]

I have a multi gauge which shows the temperature.


Fan is definitely shagged. I disconnected the plug to the fan under the tank and used a power probe to send 12v direct to the fan and nothing.....

Ah, got you. 

Make sure you got a good clean connection with your probe etc etc.

Fowlers want £378 for a new one..!

If your fan has expired there are loads of used ones on e-bay.

[steve 10562cc]

EBAY  ITEM NUMBER 163799706299 £37

[teecee90]

I can sort the fan out. My main concern was the possibility of anything more serious. I guess the most likely thing would have been the head gasket, but there is no evidence of coolant in the oil so far, so hopefully ok and a change of fan is all that’s needed.


Anybody else ever had a fan go like this? Bike is a 2003 with 31,000 miles. I suppose I should have noticed as the fan usually kicks in quite early when the bike is idling stationary.

[celticbiker]

If it helps, the manual for my fz8 says if the temperature reaches 130 degrees pull over and stop.
If you only got to 122 I reckon you're OK.

[teecee90]

Ok, so something strange is going on. Started the bike this morning and it seems to run fine, but the fan didn't come on at all while the bike was idling. As soon as I revved it the fan came on, but not at full speed. As soon as I stopped revving it the fan stopped again and wouldn't run regardless of the rising temperature gauge. Revved it, and the fan started up but again not at full speed. Not sure what is going on here.....

[His Dudeness]

I think you have high resistance in the fan circuit and that's causing low voltage and low current at the fan. When you rev the engine it raises the voltage and current enough to start the fan turning but the voltage and current are still lower than they should be because of the high resistance so the fan is spinning slower than it should. I'd guess there's corrosion in a connector or wire.

To confirm it you could measure the voltage at the fan when the fan is spinning. The fan has to be spinning for the voltage test to be accurate because there has to be current flowing through the circuit. You should be seeing close to battery voltage on the fan connector when the fan is spinning but I think you'll see lower voltage because of high resistance. Basically in a good circuit all of the voltage should be dropped across the load which in this case is the fan but because there is added resistance in the circuit some of the voltage is dropped across the added resistance and what's left is dropped across the fan. If you find low voltage on the fan connector you can determine if the resistance is on the 12V wire or the ground wire by leaving one probe in the positive wire of the fan and touch the other probe to the positive of the battery. On a good circuit you should see close to 0V, if there's added resistance on the positive side of the circuit you will see some voltage on the meter so you know then that the problem is on the positive side. You can then do the same test on the ground side of the fan. One probe in the ground wire of the fan, touch the other probe to negative battery terminal. On a good circuit you should see close to 0V. If you see voltage, there's resistance on the ground side of the circuit. Again the fan has to be spinning for it to be a valid test.

[teecee90]

I think you have high resistance in the fan circuit and that's causing low voltage and low current at the fan. When you rev the engine it raises the voltage and current enough to start the fan turning but the voltage and current are still lower than they should be because of the high resistance so the fan is spinning slower than it should. I'd guess there's corrosion in a connector or wire.

To confirm it you could measure the voltage at the fan when the fan is spinning. The fan has to be spinning for the voltage test to be accurate because there has to be current flowing through the circuit. You should be seeing close to battery voltage on the fan connector when the fan is spinning but I think you'll see lower voltage because of high resistance. Basically in a good circuit all of the voltage should be dropped across the load which in this case is the fan but because there is added resistance in the circuit some of the voltage is dropped across the added resistance and what's left is dropped across the fan. If you find low voltage on the fan connector you can determine if the resistance is on the 12V wire or the ground wire by leaving one probe in the positive wire of the fan and touch the other probe to the positive of the battery. On a good circuit you should see close to 0V, if there's added resistance on the positive side of the circuit you will see some voltage on the meter so you know then that the problem is on the positive side. You can then do the same test on the ground side of the fan. One probe in the ground wire of the fan, touch the other probe to negative battery terminal. On a good circuit you should see close to 0V. If you see voltage, there's resistance on the ground side of the circuit. Again the fan has to be spinning for it to be a valid test.

Thanks for the advice - I've just ordered some back probes for my multi-meter and will give this tests a try. Cheers

[ogri48]

I think you have high resistance in the fan circuit and that's causing low voltage and low current at the fan. When you rev the engine it raises the voltage and current enough to start the fan turning but the voltage and current are still lower than they should be because of the high resistance so the fan is spinning slower than it should. I'd guess there's corrosion in a connector or wire.

To confirm it you could measure the voltage at the fan when the fan is spinning. The fan has to be spinning for the voltage test to be accurate because there has to be current flowing through the circuit. You should be seeing close to battery voltage on the fan connector when the fan is spinning but I think you'll see lower voltage because of high resistance. Basically in a good circuit all of the voltage should be dropped across the load which in this case is the fan but because there is added resistance in the circuit some of the voltage is dropped across the added resistance and what's left is dropped across the fan. If you find low voltage on the fan connector you can determine if the resistance is on the 12V wire or the ground wire by leaving one probe in the positive wire of the fan and touch the other probe to the positive of the battery. On a good circuit you should see close to 0V, if there's added resistance on the positive side of the circuit you will see some voltage on the meter so you know then that the problem is on the positive side. You can then do the same test on the ground side of the fan. One probe in the ground wire of the fan, touch the other probe to negative battery terminal. On a good circuit you should see close to 0V. If you see voltage, there's resistance on the ground side of the circuit. Again the fan has to be spinning for it to be a valid test.

thats a helluva helpful reply dude, respect. I do love learning summat too...

[His Dudeness]

I'm just guessing using a bit of basic circuit theory but hopefully it's correct info and he sorts his bike. Another possible cause would be high resistance in the fan itself. In that case you would be getting the full 12V at the fan connector when the fan is spinning but it would be turning slower than usual. To check that you would unplug the fan and put your meter to resistance. There should be a resistance spec for the fan in the manual.

[VNA - BMW Wank]

I think you have high resistance in the fan circuit and that's causing low voltage and low current at the fan.

Excellant post Dudeness.

Thanks for the advice - I've just ordered some back probes for my multi-meter and will give this tests a try. Cheers

Yup all the stuff, everything, His Dudeness says, all makes sense.  In the meantime while you are waiting for your probs clean all the connectors and make sure they are nice and tight.  Wouldn't be at all surpised if it's just a bit of corrosion on the fan connector.
Very much doubt you've cooked it by the way - fingers crossed.

[ogri48]

like VNA says, thats worth checking too. I had to rewire my '82 z1000 so that the coils got the full 12v direct via a relay, as they were down to 8- 9v feed through the ageing wiring loom/connectors.

[teecee90]

So, turns out that the wires attached directly to the fan had a fault, at the tight angle where they enter the fan motor at the bottom. I've had the fan apart and re-wired it and it seems to be working perfectly now.


Only issue at this stage is that I only had black cable of the right size and didn't take a note of which was positive and which negative (Doh).


Looking at the shape of the fan blades I assume that the fan runs anti-clockwise when looking at it from the back of the radiator - drawing air towards the engine. Would some kind person please check theirs and let me know if that's correct?


Thanks

[VNA - BMW Wank]

Looking at the shape of the fan blades I assume that the fan runs anti-clockwise when looking at it from the back of the radiator - drawing air towards the engine. Would some kind person please check theirs and let me know if that's correct?

When the fan runs it should suck cold air through the radiator.  You don't want it to blow hot air from around the engine through the radiator. 
I'd just check with a bit of paper.  Wait till the fan runs and it should suck a piece of paper onto the rad - or blow it towards the engine from the back of the fan.

I'd go oot tae the garage and double check for you bud, but I'm a bit sore tonight, my kidney stent is playing up again. Though I'm getting it out tomorrow - happy days .

Anyway looks like you've got it sorted.  I figure the bike will be fine - I doubt very much that you've cooked it.