K11 Owners Group

Dagger · Joined: 11 Apr 2013 Posts: 8 Location: de Troit, MI - USA

According to my temp gauge my '93 K1100Lt is running dangerously hot. My local BMW certified mechanic at my dealership has gone through my cooling system and has found everything to be acceptable.

The bike doesn't lose any coolant. The radiator is clean both inside and out. The cooling fan comes on when the needle is into the red part of the gauge. My mechanic says that the temp sensors are reading properly, especially the one for the ECU. The light on the instrument cluster has not come on. I haven't noticed a lack of power.

This all started just this year after having the spring service at the dealership. The bike always ran a bit over mid gauge unless it wasn't moving. Now the temp runs at the edge of the red on the gauge while rolling at 70mph.

Could it be the water pump impeller? I have had to replace the impellers on my E36 BMW automobile because the plastic fins on the impeller fail.

Any suggestions?
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1993 K1100Lt Pine Green Metallic

rbm · Posted: Thu Jul 30, 2015 6:01 pm Post subject:

Temp sensor for the gauge is located in the pump housing and the one for the ECU/temp relay is in the stand pipe off the block. Two different sensors. Could be the gauge or the sensor that is acting up and displaying an incorrect temperature. If the fan cycles properly when operating the bike, then look at the temp gauge sensor.
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- Robert
1987 K75 @k75retro.blogspot.ca
2011 Moto Guzzi V7 Racer

N41EF · Posted: Thu Jul 30, 2015 8:30 pm Post subject:

Do you have an infrared thermometer? Easy to see if it is really that hot or just a gage issue.

I'd replace the thermostat or install a low temp thermostat like I did. Mine runs below mid scale, just above the left mark on the gage, and slowly rises sitting in traffic til the fan comes on.
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2014 R1200RT Water Cooled
2001 R1100S Light
1993 K1100LT. Nissan Ice Blue.(Gone)

Flying Duck · Posted: Thu Jul 30, 2015 8:42 pm Post subject:

I'd just ride and not worry about. It could be that the gauge sensor or gauge itself is out of whack a bit but that shouldn't do any harm.

If the fan is kicking in and your tech has verified the resistance on the temp sensor for the Motronic then you should be good.

It will be very hard to damage the bike unless you are really trying.

Here's what happens as the bike heats up:

1 - 185 degrees - Thermostat opens up (mechanical)

2 - 221 degrees - Motroninc kicks in fan (electrical)

3 - 239 degrees - Idiot light comes on (electrical)

4 - 248 degrees - Radiator cap blows (mechanical, like a car)

I've heard that once the bike hits 248 that the Motronic will also shut down but I've had a radiator cap blow without that happening so I'm not 100% sure if that's true.

Ride it and if the idiot light ever comes on then pull over and have a burger or whatever to give the bike a little time to cool down.
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Dagger · Joined: 11 Apr 2013 Posts: 8 Location: de Troit, MI - USA

Thank you all for the responses. I'm just going to ride and see what happens. I'm heading into the wilds of Michigan's Upper Peninsula. Air temps will be a lot cooler so my beemer should run cooler.
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1993 K1100Lt Pine Green Metallic

Jim · Posted: Mon Aug 03, 2015 2:20 am Post subject:

Dagger - yes, it could be the impeller.
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Jim
1997 K1100LTSE 94,000 - still has gremlins!
1995 R100RT Classic 16,650 crashed - repaired!
1992 K75RTP 46,000

"We shall not all die, but we shall all be changed."