K75 engine temp/cooling matters

For the past several days the radiator fan has been coming on intermittently. Sometimes it comes on and then immediately switches off in a fraction of a second - like my two year old and a light switch. Other times it will come on and stay on for a couple or ten seconds before shutting off again. This seemingly bizarre behavior is independent of it coming on when it's supposed to - which I think it does.

Also, for the first time this morning, the engine temp light came on just after I exited the freeway. For a while the engine temp light flashed in conjunction with my turn signals, but then it "settled down" and, like the radiator fan, stayed on until I turned the corner into a cool headwind. Then all was normal for the remaining two blocks to my parking garage. No temp light, no bizarre engine fan behavior.

The bike is a '92 K75S, 33K miles. The wiring harness was replaced a year ago.

Electrical issues? Thermostat issues? Any ideas?

Don't mean to sound stupid, but did you check your coolant level? And if the overflow bottle is full, did you check the radiator itself? DAMIK.

I'm stupid for posting my problem before checking the coolant levels, but the problem manifested itself after I had been riding for 45 minutes so I thought I'd wait for a cold engine before this afternoon's ride home before I pop the cork on the cooling system.

I will be checking the coolant level - but even if I had a low coolant level, would that explain the weird behavior of the radiator fan and the temp light?

Any time I've had multiple unrelated light blinking at the instrument panel, it was battery related. Is your bike starting ok?

The quick on-off of the cooling fan could be related to the fan relay. There is a procedure at ibmwr.org showing how to test such things.

Make sure the fan spins nice and freely with your fingertips. Reach in there after the bike has cooled off.

Hopefully its just low coolant level.

Ah didn't I say DAMHIK?

That is Zacky what mine did when I had a leaking water pump. It was fine as long as I was moving. Once I slowed down or stopped, the fan, then the light came on. Yours sounds alot more touchy than mine, but that sure sounds like it.

See, I took a long ride to Canada a couple years ago. I started noticing a couple, three drops of coolant under my bike every once in a while. Finally I checked the overflow bottle and lo! and behold! It was low. That got my attention. So at every gas stop, I would add water trying to nurse her home. On the final leg, she quit asking for more water. "Strange" Godzilla thought. "Oh well" Godzilla said.

About 40 miles form home after a long interstate slab run and after dark the temp light came on at a stop sign. "Uh-Oh" Godzilla said.

I got her home and up to Wilbur, my mechanic. He explained ( Godzilla said) that once the coolant level in the radiator gets too low, it won't siphon out of the overflow bottle.

You asked, sort of.

godzilla said:

Ah didn't I say DAMHIK?

That is Zacky what mine did when I had a leaking water pump. It was fine as long as I was moving. Once I slowed down or stopped, the fan, then the light came on. Yours sounds alot more touchy than mine, but that sure sounds like it.

See, I took a long ride to Canada a couple years ago. I started noticing a couple, three drops of coolant under my bike every once in a while. Finally I checked the overflow bottle and lo! and behold! It was low. That got my attention. So at every gas stop, I would add water trying to nurse her home. On the final leg, she quit asking for more water. "Strange" Godzilla thought. "Oh well" Godzilla said.

About 40 miles form home after a long interstate slab run and after dark the temp light came on at a stop sign. "Uh-Oh" Godzilla said.

I got her home and up to Wilbur, my mechanic. He explained ( Godzilla said) that once the coolant level in the radiator gets too low, it won't siphon out of the overflow bottle.

You asked, sort of.

Click to expand...

Wow. An awful lot of coolant has to come out that hole to drain the radiator!! The underside of the engine would be completely white.

You'd think it would have been obvious, but not so! The drips were actually coming from the TRANSMISSION area! The coolant was being blown back around the engine somehow and dripping to the ground from there! Godzilla isn't lying!

The problem was the seal in the water pump.

Guess I'll take a couple of extra water bottles to the garage after work

I park inside - both at home and here at work - and I've never seen a drop under the bike. Of course, with the belly pan, how would I know if fluids were slowly dripping out from the bottom of the bike!

Thanks for the hints - I'll be very happy if this can be fixed with a quart of water instead of a new wiring harness!

Okay - just went and eyeballed the bike. The level of coolant in the overflow tank was just a tiny bit below halfway between the min and max lines. I added about six ounces of water to take it to the "max" line, under the theory that the level was too low to siphon from the tank and into the rest of the cooling system.

I noticed my oil level is just a tiny bit low, so that might contribute to a boost of a couple degrees in the engine temp, but I can't imagine that would be enough to upset my cooling system - especially since temps here have been in the 35-55 degree range the past six months.

I'm interested to see how she performs on her way home. I'll be adding some oil once she cools down tonight. I'll keep you posted should the problems continue...

I didn't realize new pumps were available. My dealer told me they weren't for my 85 K100RT. I had them rebuild mine which was a nightmare I care not to go into, but eventualy, they figured out how to make it work- and yes, that's about my level of satisfaction I have with them. But I digress... Glad to hear they are available.

By the way, did you see your oil pressure sending unit wire in there? I'm trying to figure out how to snake mine through to replace it.

Update

Before the ride home from work last night, I added about a cup of water to the coolant overflow reservoir, brining the level to the "max" line on the tank.

Last night, after the bike had cooled down for a couple of hours, I added about a cup of oil to the engine. Engine oil now covers roughly the lower two-thirds of the sight glass with the bike on the center stand.

The ride home was uneventful. The engine fan operated almost continuously once I exited the highway and while I rode the approx. 4 miles of surface streets home.

I was tempted to leave the engine running with the bike on the center stand to see if/when the fan ever shut off on its own, but I also didn't want to fill my garage with CO.

On the ride in this morning, all was fine until I exited the freeway and rode the approx. 10 blocks to the parking garage. After the equivalent of about 8 blocks of stop and go driving on downtown city streets, the temp light began to flicker intermittently for about a minute. Then it stopped completely once I began riding through the parking garage and remained off until I stopped the bike.

Is this all normal, or is the recent appearance of the temp light indicative of something wrong?

dvandkq said:

Is this all normal, or is the recent appearance of the temp light indicative of something wrong?

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In almost 18 years of owning one K75, the temp light has come on twice. Both episodes were related to a dead cooling fan.

Does your horn work? If the horn fuse is blown, then the cooling fan is probably dead.

jdiaz said:

In almost 18 years of owning one K75, the temp light has come on twice. Both episodes were related to a dead cooling fan.

Does your horn work? If the horn fuse is blown, then the cooling fan is probably dead.

Click to expand...

Horn works fine. In fact, I just added two huge Fiamm horns. Fan works - sometimes it comes on and off, on and off - for a second or for a minute. Other times it comes on and stays on until I shut the bike down.

You gotta get in there and see how easy the fan spins. Maybe its on the verge of seizing up?

Just pull that small black decorative cover on the bottom of the RH fairing panel, then the airbox intake tube. Then you can reach in and check the fan.

I know the fan is an expensive part to replace - how easy is the task?

dvandkq said:

I know the fan is an expensive part to replace - how easy is the task?

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Two hours if you are familiar with taking the fairing off.. And the fan isn't expensive.....$138 from BeemerBoneyard.

But let's make sure that's it. If you find the fan is fine, then its time to check the fan relay and the coolant temp sensor next.

jdiaz said:

Two hours if you are familiar with taking the fairing off.. And the fan isn't expensive.....$138 from BeemerBoneyard.

But let's make sure that's it. If you find the fan is fine, then its time to check the fan relay and the coolant temp sensor next.

Click to expand...

Baby steps!

Thanks for the suggestions - I'm sure the wife will be excited that tonight means another night of me laying on the floor of the garage, taking apart the bike

dvandkq said:

Thanks for the suggestions - I'm sure the wife will be excited that tonight means another night of me laying on the floor of the garage, taking apart the bike

Click to expand...

Just check the fan during your lunch hour. It will take five minutes to get in there.

The other jobs might take longer.

dvandkq said:

....Is this all normal, or is the recent appearance of the temp light indicative of something wrong?

Click to expand...

In 118,000 miles, the temp light on my K75 has never come on. The only time the fan came on was after slowing down to "in-town" speeds after a long high-speed run thru the desert in 100+ degree weather.

My normal daily commute is thru LA city stop and slow traffic. Even in summer, neither the fan nor the light comes on.

I think you definitely have a cooling problem.

I know it is a pain to do, but check the coolant level in the radiator itself. Seems to me that I have to loosen the radiator cowling to get at the radiator cap. I don't THINK I had to loosen the gas tank, but maybe. Of course my K is nekkid, so there is no fairing to deal with. If the radiator gets too low, it will not siphon out of the bottle. I think if the level in the radiator is physically lower than the bottom of the bottle, it can't suck in the needed boost of coolant. That is what happen to mine...