K11 Owners Group

ross_rl · Joined: 06 Jun 2009 Posts: 7

Hello,

I am new to this forum so I just wanted to say thanks for having me first.

My question relates to the normal engine operating temperature on the K1100RS. Recently I noticed that my bike is running with the needle on the temperature gauge at just under the first white line (about 1/3) when i'm cruising.

I am sure that it used to sit just under the 1/2 way line before and the owners handbook confirms this is correct.

So, I have assumed that there is something wrong and in an attempt to fix it I have carried out the following tasks:-

1) Replaced temperature gauge sensor
2) Tried a replacement gauge (a good used example)
3) Cleaned all electrical connections and checked for good continuity
4) Checked thermostat - it is working correctly
5) Replaced thermostat 'U' seal and thermostat cover seal
5) Replaced coolant

After all of this the damn temperature gauge is still reading 1/3 at cruising speed!!!

I found another related post on here where it was suggested that the thermostat can move sideways allowing more coolant to flow through the radiator? I thought that the protrusions on the rear of the thermostat cover are there to hold the thermostat in place? If not maybe I should check my thermostat is installed correctly.

I can't think of any other reason why the engine should be running cold - can anyone offer any suggestions please?

How does the temperature gauge read on your bikes?

Or am I just being over sensitive? It is a bit cool here in the UK at the moment so maybe the engine and temperature gauge are working perfectly fine and it is just the fact that the ambient temperature is low?

Its just bugging me because i'm sure it always used to sit just under the centre when cruising.

Thank you,

Ross
_________________
1994 BMW K1100RS
2002 Ducati 748
1961 Triumph T100
1959 BSA Bantam
1977 Honda XL250

Off the grid · Posted: Sun Jun 07, 2009 7:14 am Post subject:

Considering how hot these bikes tend to run, I wouldn't worry about it too much.

Welcome to the site.
_________________
Bane of your existence since July 2006
2007 Triumph Tiger ABS. "Sabertooth"
2009 Husqvarna TE610. "The dirty Italian mistress"

Scott_Anderson · Posted: Sun Jun 07, 2009 8:47 am Post subject:

Yes, welcome as well.

As far as the temp goes, is the cooling fan staying on all the time?
If it's only at crusing speed, like Dave said I wouldn't worry about it too much.

You might also track your fuel consumption. Most of the RS bikes should be in the area of 45-50 MPG U.S. Gallon.
Check your spark plugs for burn pattern, lean or rich.
If your engine is in fact running cold, not just low guage reading, the fuel injection controller will run richer mixture of fuel.
_________________
Ride safe.

1995 K1100LT 0302044
2017 FLHTK Ultra Limited
Garmin StreetPilot 2820
Garmin Zumo 550
Garmin Zumo XT
"One who does not ask questions is ashamed to learn" Danish proverb
1997 K1100LT 0302488(R.I.P.)
1997 R1100RT ZC62149(sold)

ross_rl · Joined: 06 Jun 2009 Posts: 7

Thanks for your replies.

I checked the fan and it is not running continuosly, I will have to monitor the fuel consumption and check the spark plugs when I have more time however the bike is running very well so I don't expect to find anything wrong.

I did notice however that the fan kicks in at 2/3 on the temperature gauge. This has also changed because it used to kick in at just before the red zone, so I guess this confirms that the engine is probably running correctly (as the fan is controlled by the other temperature sensor for the ECU) and my gauge has started reading low for some reason?

I wonder if the BMW ECU diagnostics machine will give an engine temperature readout which I can use to confirm that the engine is running correctly and put my mind at rest. Does anyone know if this is possible?

Thanks again
_________________
1994 BMW K1100RS
2002 Ducati 748
1961 Triumph T100
1959 BSA Bantam
1977 Honda XL250

Flying Duck · Posted: Sun Jun 07, 2009 5:24 pm Post subject:

I suspect it's a temp sensor issue. Note that the gauge has it's own temp sensor at the bottom of the water pump and the temp sensor for the Motronic engine computer reads a temp sensor at the top of the cylide rhead where coolant exits.

To test the temp sensor:

Remove the belly pan. You'll see two sensors on the water/oil pump. The front lower one is the temp sensor. Pull the lead off and ground it to the engine. That should make the gauge needle peg all of the way to the right.

It could just be that the temp sensor lead connection is dirty/loose - either at that plug or where it connects under the tank - (single wire blue connector)
_________________
93 LT (x2)
94 RS
86-97 K75F(K75/100/1100 Frankenbrick)
86 K75C w/paralever, hi perf cams,TURBO!
91 & 92 K75Ss
91 K1
86 custom K100
14 WR250R
IBA #17739 (SS1K, BBG, 50CC)
Buy parts HERE

ross_rl · Joined: 06 Jun 2009 Posts: 7

Hi,

Thanks for your response.

When I ground the temp gauge sensor wire I get full defelection on the temp gauge indicating that it is working correctly.

I have tried 2 new sensors and I get the same result - 1/3 deflection on the temperature gauge at normal operating temp.

For everyones interest (or cure for insomnia) I wired the temperature gauge up on the bench at work with the sensor in some hot water and a separate (calibrated) thermometer. At 85 Degrees C (according to the BMW manual this is the normal operating temperature) the temperature gauge needle sits at 1/3 marker - which is where it sits in operation on the bike at cruising speed. At 91 degrees C the sensor sits where it should i.e. just under halfway marker.

And if your not asleep yet - the sensor resistance at 85 degrees C is 75 ohms and it is 50 ohms at 91 degress C.

If 85 degrees C is the correct operating temperature then I can definately rule out that my engine has a fault and it must be the instrument making it read low (I guess a high resistance somewhere).

Correct me if I am wrong but the K1100RS owners handbook does state that at normal operating temparature the needle on the temperature gauge should sit just under the middle marker?

Thanks,

Ross
_________________
1994 BMW K1100RS
2002 Ducati 748
1961 Triumph T100
1959 BSA Bantam
1977 Honda XL250

Phil Marvin · Posted: Sun Jun 07, 2009 8:04 pm Post subject:

Hi, Ross,
Yes, your temperature gauge should be near the center of the gauge when running normally and, yes, you can change the sensor and it still won't do that and, yes, you may even change the gauge and it may not make a difference. My first K1100LT ran "normally", running with the temp gauge registering about 1/3 the way up the gauge and the fan coming on a little before the red zone. It never overheated and I ran the bike that way until I sold it with 124k miles. It's probably still running that way with nearly 150k miles.
I don't know how to fix the problem; I did all you have done or are suggesting you might do. It did me no good! My advice is, "Shut up and ride!" That's what I did for about 90k miles and 7 years after my gauge went slightly wonky. Then I bought another K1100LT, sold the first one, and a year later hit a deer. But that's another story.
_________________
Ride Safe,
Phil Marvin in El Paso, TX
'94 K75A/3
'95 K75RTP

carp · Posted: Sun Jun 07, 2009 9:35 pm Post subject:

My temp gauge runs just under half. I test rode a k1100lt 5 years ago that hugged just under the red zone. I wasn't impressed. I was wondering if mine was running cold, but now I know its normal - thanks to your post.
_________________
93 K1100LT
07 Bandit 1250S

Scott_Anderson · Posted: Mon Jun 08, 2009 7:19 am Post subject:

Neither of my 2 LT's run the same temp.
My '97 runs just a needle width above the 1/3 mark at cruising and the '95 runs at the 1/2 line.
Both fans come on just before the red line and run down to about the 1/2 mark.
_________________
Ride safe.

1995 K1100LT 0302044
2017 FLHTK Ultra Limited
Garmin StreetPilot 2820
Garmin Zumo 550
Garmin Zumo XT
"One who does not ask questions is ashamed to learn" Danish proverb
1997 K1100LT 0302488(R.I.P.)
1997 R1100RT ZC62149(sold)

ross_rl · Joined: 06 Jun 2009 Posts: 7

Hi,

Its interesting that there seems to be this variation between temperature gauge readings. There must be something that causes it - in my case I have experienced a change from reading 1/2 way at cruising speed to 1/3 seemingly overnight.

I think the fault has to be either with the internal temperature gauge wiring or with the wiring loom somewhere (perhaps current leaking away somewhere on a wire indirectly linked to the temperature gauge).

Its not going to stop me riding the bike, indeed I am going on a 1500 mile trip around Scotland next month, however it would be nice to know what's causing it.

If I find out I will let you know.

Thanks - Ross
_________________
1994 BMW K1100RS
2002 Ducati 748
1961 Triumph T100
1959 BSA Bantam
1977 Honda XL250

Flying Duck · Posted: Mon Jun 08, 2009 3:36 pm Post subject:

FYI: There's no intermediate wiring. The temp sensor lead goes straight from the temp sensor to the gauge with one connector under the tank..
_________________
93 LT (x2)
94 RS
86-97 K75F(K75/100/1100 Frankenbrick)
86 K75C w/paralever, hi perf cams,TURBO!
91 & 92 K75Ss
91 K1
86 custom K100
14 WR250R
IBA #17739 (SS1K, BBG, 50CC)
Buy parts HERE

ross_rl · Joined: 06 Jun 2009 Posts: 7

That's true, I checked the wire to the sensor and it measured practically no resistance so good continuity. Also the power supply to the instrument measured 12 ish Volts so perhaps I can rule out the wiring loom?

I wondered if there is some kind of damping circuit inside the temperature gauge that has failed.

To explain my thinking - I once owned an MGF sports car and the temperature gauge in that never moved from the centre in use, even when the fan came on. It only moved up the scale when the engine started to get seriously hot (as I found out when the head gasket failed!!!).

I made some enquires at the time about this and apparently the temperature gauge was wired like that on purpose by the factory because they found that if the gauge displays the actual temperature then paranoid owners (like me) keep taking the car back saying there is something wrong i.e. it was running slightly hotter than normal or cooler etc. So to stop this they designed the circuit so only significant changes in temperature are displayed on the gauge.

If the BMW instrument is wired like this and that part of the circuit has failed and susequently changed resistance, then I guess that could cause the instrument to read low?

Or am I clutching at sraws????

Sorry to keep on with this subject - I know I worry to much.

Thanks.
_________________
1994 BMW K1100RS
2002 Ducati 748
1961 Triumph T100
1959 BSA Bantam
1977 Honda XL250

Jim · Posted: Mon Jun 08, 2009 7:20 pm Post subject: temp gauge

I think you're clutching at straws - or something - AND worrying too much.

Before I installed a 3 core radiator, the temp gauge pretty much ran between the 1/3 mark and the half mark - depending on ambient temperature - mostly a bit below the 1/2 mark. It now runs a little lower, but not much. The fan turns on at the 2/3 mark, off when it drops to 1/2.

I think as long as it's between the 1/3 and 2/3 marks it's very likely OK. Seems like there is usually an operating range - not an operating point - anything within the range is normal.

Ride it and enjoy it - if it's not in the red, the fan isn't running constantly, or the engine didn't shut down for over heat, you're good to go.
_________________
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."

ross_rl · Joined: 06 Jun 2009 Posts: 7

Thanks for that Jim,

You are right - after reading your post I have realised that I am trying to fix something that isn't broken. My bike is running better than ever at the moment so there is obviously nothing wrong with it and I should leave it alone.

I intend to take your advice and just enjoy it.

I do think these K bikes are absolutely brilliant - I have had mine for just over 3 years now and have covered over 20,000 miles. That's probably not that much compared with some of you fellow BMW owners but with 5 other bikes that get used as often as possible, I guess that's not too bad.

Even my precious Ducati stays at home a lot more now, as in all honesty, I enjoy riding my Beamer more.

Cheers,

Ross
_________________
1994 BMW K1100RS
2002 Ducati 748
1961 Triumph T100
1959 BSA Bantam
1977 Honda XL250

carp · Posted: Mon Jun 22, 2009 9:18 pm Post subject:

My gauge went from running at 1/2 to running at 2/3 to 3/4. It stays under the red zone, but just barely sometimes. I haven't heard the fan run like I do on my k75. What are your suggestions. The outside temps have warmed up plus I put my side covers back on. Would that make a difference?
_________________
93 K1100LT
07 Bandit 1250S

Scott_Anderson · Posted: Mon Jun 22, 2009 9:41 pm Post subject:

ross_rl · Joined: 06 Jun 2009 Posts: 7

To close this thread - I have fixed the problem.

I replaced the thermostat and now my temperature gauge is back to normal i.e. the needle sitting just under the middle at cruising speed, fan kicking in at approx 3/4 of the temperature scale.

SO THERE WAS A FAULT AND IT WASN'T ME BEING OVERSENSITIVE.

Just to note - I did test my old thermostat in a pan of boiling water with a thermometer and it does open at around 85 degrees, however it was obviously faulty in some way (maybe openening fully at 85 degrees and staying open rather than adjusting for a given coolant temperatue - who knows!!).

Whilst my bike had this fault it was running a significantly rich mixture (as confirmed by a black exhaust, slightly sooty plugs and flames coming out of the exhaust on the overun!). So it needed fixing in my opinion.

The thermostat seal also needed replacing as the original was quite deteriorated on removal (possible that someone has used the wrong kind of coolant at some point?)

Just a final thing - and this is from my experience and not something I can say is definately true - there is a difference between the 8V and 16V temperature gauge sensors. The only visible difference is that the 8V sensor has a blue plastic ring and the 16V has a green plastic ring. The actual temperature instruments are identical on both bikes.

Both sensors will work, howvever if you have an 8V sensor fitted to a 16V bike the temperature gauge will read very close to the red before the fan kicks in. As everyone knows, the fan on the 16V bikes is actually controlled by the ECU via the other coolant sensor and therefore it is not a problem - I guess it is just that the resistance characteristics of the 8V temperature gauge sensor are different to the 16V sensor hence making the gauge record a higher temp?

With the correct sensor on the 16V bikes the fan should kick in at approx 3/4 of the temperature scale.

So anyone with a 16V bike complaining that the fan doesn't kick in until the red then check that you have the correct temperature gauge sensor fitted!!!

At normal operating temperature the gauge should read aout the same with either sensor fitted i.e just under the middle.

I thought I would post everything I have learned whilst fixing this fault incase it helps someone else in the future.

Thanks for all your help and suggestions.

Ross
_________________
1994 BMW K1100RS
2002 Ducati 748
1961 Triumph T100
1959 BSA Bantam
1977 Honda XL250