ENGINE COOLING PROBLEM STILL PERSISTS!!!

[johnnycactus]

ok, almost tearing my hair out now, especially with a spell of good weather taunting my inability to ride!!!! argh!!!

bike is still overheating- at least i know the warning light works!!!

thought i'd traced it to the temp sender unit or fan switch. -wrong!

i bought and replaced fan switch, thermostat, and temp sender unit. figured as i was draining the coolant i'd just say **** it and put in all new parts.

(add to the wallet draining mix, a nail in my rear 275 mile old rear tyre...grrr :evil: )

last time i checked the fan motor came on when i disconnected it and connected it to a battery. same when i jumped the fan switch wires. fan came on.

anyone got any suggestions!?

getting desperate- nuts and bolts i can manage, but electrics tie my head in knots. i am assuming its wiring based.

so if theres anyone out there with some pointers (idiot terms) it would be greatly appreciated!!!! :???:

[pendraig]

Hi, Johnnie;
Does the fan come on as it starts to get hot? Mine gets pretty far up the dial before the fan kicks in. If the fan isn't coming on;
a) The engine isn't really hot enough or,
b) The sensor-switch is defective or,
c) There isn't any coolant in the radiator for the sensor-switch to "sense" or,
d) The fan only works intermittantly (since you checked that it does operate) or you have an open circuit caused by a bad wire or loose coonection.
I've never seen a temp warning light on my instrument panel, and I pegged the gauge once, coming through the Holland Tunnel in NYC. (Caution, if your fan doesn't work, stay out of long tunnels. The air moves at the same speed as traffic, so you're sitting in "dead air" with no apparent wind passing through the radiator---and you can't pull over and shut down without being squashed like a bug.)

Cactus:

Not to insult you, but, have you checked the oil? After rebuilding my engine and driving it 100 miles my temp light started coming on. I sort of expected this since I didn't 'burp' the cooling system but when I pulled the radiator cover off and found it full I about shat myself! I checked the oil and the stick was dry.

You're probably well aware of your oil level... it's just a thought...

Good luck!

[johnnycactus]

thanks for posting guys-
spragclutch- i will double check the oil, although recently it seemed fine (fresh oil with chain and sprockets). At the moment i'll double check anything! especially as the shop can't fit me in until the 26th of this month!

pendraig-
fan isn't coming on at all- warning light comes on, engine is v.v.hot and coolant can be heard bubbling away. so engine seems to be hot enough.

coolant levels are fine, so there is enough to 'sense'.

old sensor switches were replaced with new, still no joy

guessing it has to be a bad wire somewhere. i'm rubbish with electrics, wouldn't know where to start!

-also all fuses are good!

funniest thing.. After a successful spragclutch replacement project, my temp sensor light is coming on. First I checked coolant: full. Then oil: low. I fill it, go for a good ride today, no problems. Tonight the temp light comes on again. I, feeling pretty gxdxmn good about myself for having been successful with the last project, decide to pop off the radiator cap again (the bike is warm, the light is on yet the pipes aren't that hot). Radiator spews a little coolant out, no big deal. Now I want a look at the thermostat. I pop the hose that houses it, knowing coolant will spew out but still feeling like a baddxss. About a cup full comes pouring out all over my right hand and here I am with skin peeling off of my knuckles hunting and pecking about the keyboard with my left hand trying to write this shxt. Needless to say, I no longer feel like a badxss.

The first thing I did the first time I started the bike after the sprgcltch job was let the bike run till the fan came on. It worked! Now that the light is on, however, I'm a little skeptical of the 'heat her up till the fan comes on' technique.

Whatever... My f-ing knuckles hurt...

[Speed3]

Have you replaced your thermostat? Does it just spew coolant after running hard, or does it really overheat? I switched to Evans waterless coolant after my bike would spew, and it hasn't done it since. It has a boiling point of 375 F, so won't boil over. but you have to have your system in good working order. Here is a link. Good Luck!
Evans

[crogger]

if the fan starts when you jump the fan switch wires with another wire, it would seem there cant be anything wrong with the wiring. Other wise it would not come on when you take the switch out of the cicuit. i know it seems unlikely but could the new fan switch be faulty? when you jump the fan switch with another wire you are just making the circuit without the switch so if fan starts then circuit must be fine.then its gotgot to be switch, thats the way i understand it in the workshop manual. i am having probs when i noticed my fan didnt come on in the recent hot spell, the fan works with a remote 12 v battery connected direct but when i jumped the switch wire ,nothing i think it must be a wiring fault in my case.

[sprinter900]

Don't really know if this is possible but any ideas worth a try I feel. Is there a chance that the pump has air in it therefore not pumping the water around so result is hot engine and the water in the radiator is cooler? depends if your light is a sensor on the engine or in the water as the fan is only driven from the radiator switch normally, guages from a sensor. Otherwise any possibility of corrosion between fan switch and water as this could act as an insulator to heat - normally these are something like a bimetallic switch and when they get to a designed temp they switch over thus driving the fan. (just like the old room thermostats) your fan circuit should just be +12 - fuse - switch - fan - 0v thats it!

cheers 4 now

[johnnycactus]

i had considered the pump not working- but the coolant in the radiator can be heard boiling away after a good ride.
i'm going to run it into work today- straight roads with no hold ups- should keep cool enough- and re test all wiring for continuity.
i guess there is a chance the replacement fan switch is defective.

really is stumping me now....

[sailfish]

Regarding the pump, it is driven by the oil pump shaft. It will probably leak before it will out right fail. The sending unit in the head runs only the gauge and maybe a warning light. The fan circuit is a simple circuit so it's easy to troubleshoot. There appear to be no relay in the circuit. Jump the wires past the fan switch was previously suggested. At this point don't assume that your new parts are actually working, sometimes they don't. I would seem that our British brothers ride in weather conditions that are hard on bikes. You may have a corrosion problem. Does the fan have a good ground? Lastly, I don't like electrical troubleshooting either but 2 things that help tremendously are a manual with a wiring diagram and a volt/ohm meter.