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1Back to top Go down    Underheating cooling system on Tue Mar 04, 2014 5:42 am

jayseabea

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Sorry if this topic has been covered before.
 I have an '85 K100 RT and last summer I took the fairing lowers off to aid leg coooling while riding in France during the summer. I've left them off as I like the look but also to ease cleaning and servicing.
 The bike was left standing for a couple of months over winter and since then the engine's temperature gauge hardly gets above the two blue lines and when I stop at traffic lights or whatever the fan cuts in. The gauge used to sit steadily at near half way and only occaisonally have the fan cut-in in hot weather, whilst riding in central London for instance. The engine shows no sign of overheating or being in distress.
 Has anybody else had this phenomena and is there a cure?

    

2Back to top Go down    Re: Underheating cooling system on Tue Mar 04, 2014 5:50 am

charlie99

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yes indeed ...change the thermostat in the first instance

next is to clean up the air paths through the core of the radiator ...that can accumulate a lot of spray and dirt between the fins of the core of the radiator cooling path ...go steady you don't need to use a high pressure water sprayer,,,just something that degreases and lifts the gunk  out .

hope that helps ..!


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cheezy grin whilst riding, kinda bloke ....oh the joy !!!! ...... ( brick aviator )

'86 K100 RT..#0090401 ..."Gerty" ( Gertrude Von Clickandshift ) --------O%O
    

3Back to top Go down    Re: Underheating cooling system on Tue Mar 04, 2014 7:57 am

japuentes

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Hi there, if the fan is cutting in, under the right conditions, and the needle is still on the cool zone, then I would think the problem is the thermometer. Check the temp gauge system, this is a separate circuit from the temp control and has nothing to do with the engine management.
If the fan is cutting in and out and there are no sign of overheating, then I would think that your cooling system is ok and would not work with it until clearing the temp gauge circuit.
Hope this helps
Best regards
JAP


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1988 K100RS SE/ABS
    

4Back to top Go down    Re: Underheating cooling system on Tue Mar 04, 2014 8:21 am

jayseabea

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Thank you both for your replies. I've just ordered a new temp.sensor from Motorworks.
 My thinking is that it's not the thermostat as it's default position is open so that if that was faulty and closed permanently,then the bike would over heat rather than the reverse. Similarly the blocked with dirt radiator idea.
 This leaves the temp. switch relay or the sensor in the water system. As the switch is still working, i.e. making the fan come on, all be it at a lower temp. then I think it must be the sensor, which is most likely to be corroded after 97k miles and probably 30 years of service in hot,cold,hot water conditions. Is it a bi-metallic strip system?
 Anyway a new one is only £35, so I'll let you know how it goes on when I put it on.
Cheers, Chris.

    

5Back to top Go down    Re: Underheating cooling system on Tue Mar 04, 2014 10:12 am

TacKler

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Along with Charlie's thinking, looking at the age and mileage, I would be cleaning the external surface of the radiator and also giving it a good flush out. You would be amazed at the difference a new/clean radiator makes. 

I have not heard much here about sensors failing, so perhaps these are one of those rare failures?


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Red 1991 K75S
    

6Back to top Go down    Re: Underheating cooling system on Tue Mar 04, 2014 12:47 pm

klamityboy

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@japuentes wrote:Hi there, if the fan is cutting in, under the right conditions, and the needle is still on the cool zone, then I would think the problem is the thermometer. Check the temp gauge system, this is a separate circuit from the temp control and has nothing to do with the engine management.
If the fan is cutting in and out and there are no sign of overheating, then I would think that your cooling system is ok and would not work with it until clearing the temp gauge circuit.
Hope this helps
Best regards
JAP
To second this. I recently cleaned up the ground area under the tank on my bike. Afterwards I noticed that the temp gauge was going higher. Initially, I thought that something else was causing the bike to overheat. Now I realize that the gauge is probably working more in spec. Luckily for the health of the bike, the temp gauge does not control when the fan comes on or off. I would check the gauge.


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Klamityboy
1991 K75RT-P

Model Description: K 75RT
Market: Europe
Type: 0565
E-Code: K569
Engine: 3_ZYL - 0,70l (55kW)
Transmission: Manual
Body Color: Polizeiweiss
Production Date: 30.08.1990
    

7Back to top Go down    Re: Underheating cooling system on Tue Mar 04, 2014 8:14 pm

RicK G

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If you have access to an infrared thermometer check the actual engine temperatures and the coolant temps going into and out of the radiator. Let it stand idling till the fan cuts in and do the checks again.  I think you will find the temp gauge system is at fault.
As for cleaning the radiator, If you have a leaking fork seal the oil will often spray back into the radiator fins and then collect all sorts of road grime and block the air flow.
I spent almost a full day getting rid of oil and dirt and a heap of grass seeds that had collected over the years and it made an amazing difference (it worked like new or maybe even better).


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If everything seems under control then you aint goin fast enough:- Mario Andretti
Bikes 1986 K100RT, 1993 K1100 LT, 1994 K1100 LT, 1993 K75 RT, 1996 K75RT, 1986 K75 GS, 1979 Z1300 Kawasaki X 2 & 1976 SR 500 Yamaha for now
    

8Back to top Go down    Re: Underheating cooling system on Wed Mar 05, 2014 6:25 am

charlie99

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@klamityboy wrote:
@japuentes wrote:Hi there, if the fan is cutting in, under the right conditions, and the needle is still on the cool zone, then I would think the problem is the thermometer. Check the temp gauge system, this is a separate circuit from the temp control and has nothing to do with the engine management.
If the fan is cutting in and out and there are no sign of overheating, then I would think that your cooling system is ok and would not work with it until clearing the temp gauge circuit.
Hope this helps
Best regards
JAP
To second this. I recently cleaned up the ground area under the tank on my bike. Afterwards I noticed that the temp gauge was going higher. Initially, I thought that something else was causing the bike to overheat. Now I realize that the gauge is probably working more in spec. Luckily for the health of the bike, the temp gauge does not control when the fan comes on or off. I would check the gauge.

to add to this ...it is always a good policy to clean up the main battery earth connection to that gearbox stud .
there are cable upgrades as well for this and the main battery power to the starter relay ...amongst other things
if perhaps you do find corrosion amongst any of the connectors ...might be a good idea to attend to some of the multi pin connections that feed the instruments ...likewise the spade connections that connect to the temperature sensor for the gauge and the oil pressure sensor ...right next door ...on the water-oil pump assembly ..
we have found a product called "deoxit " works very well (lots of posts throughout the forum about this amazing product ....just use the search feature )

good luck !


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cheezy grin whilst riding, kinda bloke ....oh the joy !!!! ...... ( brick aviator )

'86 K100 RT..#0090401 ..."Gerty" ( Gertrude Von Clickandshift ) --------O%O
    

9Back to top Go down    Re: Underheating cooling system on Thu Mar 06, 2014 11:46 am

jayseabea

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The sensor arrived this morning, so having nothing better to do I decided to buckle down and do the replacement.
 After doing all the removals I came to the coolant drain plug and found that that was a sensor too, and it was corroded; intact, but still needed a good scraping on both the plug and connector.
 Anyway, the old sensor came out easily and the new one went in. All the pipe work and connectors refitted, the worst bit being the rubber bar on top of the radiator. Coolant replaced, tank back on, the engine was started.
 One pipe had a slight leak, luckily it was one on the right hand side so easily accessible and only needed the clip rearranging.
 I left it to tick over and the needle went passed the first white line ( where the problem fan starting was) and it carried on all the way to the third white line and past for a few millimetres and then the fan cut in, took the temp. back down past the white line and then stopped. Hurrah!!
 Right, on with the riding gear and go and have a bacon sarnie at Cranfield airfield cafe. On arrival the gauge was as it should be, just under the second white line and no sign of dripping water.
 Now back home and all seems well....fingers crossed; but the problem could still have been the sensor OR the corroded connector. Rolling Eyes 
 Either way, I'm happy and many thanks for the input from all of you.

    

10Back to top Go down    Re: Underheating cooling system on Thu Mar 06, 2014 1:11 pm

klamityboy

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The sensor in the drain plug is the one for the temp gauge.


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Klamityboy
1991 K75RT-P

Model Description: K 75RT
Market: Europe
Type: 0565
E-Code: K569
Engine: 3_ZYL - 0,70l (55kW)
Transmission: Manual
Body Color: Polizeiweiss
Production Date: 30.08.1990
    

11Back to top Go down    Re: Underheating cooling system on Thu Mar 06, 2014 1:20 pm

jayseabea

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Ok. 
 Then what does the sensor above the engine sense? Does that one turn the fan on and the one as a drain plug drive the temp.gauge?
 Why does my Haynes manual only show the drain plug sensor as a drain plug undone by an allen key?
 I'm going to disconnect the drain sensor lead and see what happens... 🇳🇴 Don't wait up, I might be sometime.

    

12Back to top Go down    Re: Underheating cooling system on Thu Mar 06, 2014 1:30 pm

klamityboy

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@jayseabea wrote:Ok. 
 Then what does the sensor above the engine sense? Does that one turn the fan on and the one as a drain plug drive the temp.gauge?
 Why does my Haynes manual only show the drain plug sensor as a drain plug undone by an allen key?
 I'm going to disconnect the drain sensor lead and see what happens... 🇳🇴 Don't wait up, I might be sometime.
The upper sensor tells the computer the temperature of the coolant and turns the fan on and off. I think it also might also have something to do with feeding info to the computer for the fuel injection. 

On k-bikes without temp gauges (which are apparently most of them according to the manual publishers) there is just a drain plug that uses an allen key to remove. Thus since such a small percentage of bikes have the temp sensor at the drain location there is absolutely no reason to mention it at all.  Very Happy


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Klamityboy
1991 K75RT-P

Model Description: K 75RT
Market: Europe
Type: 0565
E-Code: K569
Engine: 3_ZYL - 0,70l (55kW)
Transmission: Manual
Body Color: Polizeiweiss
Production Date: 30.08.1990
    

13Back to top Go down    Re: Underheating cooling system on Thu Mar 06, 2014 2:30 pm

jayseabea

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Yes, I've just come to that conclusion about the different functions. Good insight into the drain plug conundrum though.
 So the conclusion, to my mind, is that the corrosion on the lower sensor hindered the function of the temp gauge and the fan coming on early might/might not have been an upper sensor fault or was only responding to the poor connection on the lower.... 
 Isn't life wonderful. Shocked

    

14Back to top Go down    Re: Underheating cooling system on Thu Mar 06, 2014 7:26 pm

RicK G

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The sensor on the water riser behind the radiator has 2 sensors in one housing.
One connects to the ECU which controls mixture and the temp light the other the fan on and off the sensor on the pump only works the temp gauge and has nothing to do with the ECU at all.


__________________________________________________
If everything seems under control then you aint goin fast enough:- Mario Andretti
Bikes 1986 K100RT, 1993 K1100 LT, 1994 K1100 LT, 1993 K75 RT, 1996 K75RT, 1986 K75 GS, 1979 Z1300 Kawasaki X 2 & 1976 SR 500 Yamaha for now
    

JediGirl

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Dear All, 

My bike does a strange thing (woman speaking about mechanics, this is embarassing) Very Happy However, I decided to be able to fix my own bike with time and I have to start at some point. I have one Kexpert at home, but I would like to have my own opinion on the subject.

When I get it started and go for a ride, after riding for some time on a motorway and going into regular traffic it often goes off. 

I wonder what can be the reason for that. From what I have already read it can have something to do with the thermostat (please pardon my 'ignorant woman talking about serious matters'syntax). I will ride again tomorrow, so if you have any hints to what I should pay special attention - please write.


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"There is a theory which states that if ever anyone discovers exactly what the Universe is for and why it is here, it will instantly disappear and be replaced by something even more bizarre and inexplicable.There is another theory which states that this has already happened." (Douglas Adams)
    

16Back to top Go down    Re: Underheating cooling system on Fri Dec 05, 2014 4:33 pm

92KK 84WW Olaf

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Hi Magda,

How do you mean goes off? Do you mean bike stops or fan comes on?

Was good to meet up last week too!


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1992 K100LT 0193214 101,000 miles
1984 K100RT 0022575 Baja Red bought 36,000 now 89,150 miles
1997 K1100LT 58,645 now 60,500 miles
    

17Back to top Go down    Re: Underheating cooling system on Fri Dec 05, 2014 7:10 pm

charlie99

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hi magda

if the fluid levels were low this could well happen
poor circulation could mean that you get  a overheat situation as the cooling function would seriously be hindered,
once air gets in there the pressure can be exteeme as air expands far quicker than fluid  

but it may be something else ..just offering some where to start looking

by the way having fuel hoses about and inch and a half extra length (main one being the verticle hose to the injector rail ) will allow you to swivel the tank and get to the fluid filler cap without disconnecting the fuel hoses .

just a tip

good luck


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cheezy grin whilst riding, kinda bloke ....oh the joy !!!! ...... ( brick aviator )

'86 K100 RT..#0090401 ..."Gerty" ( Gertrude Von Clickandshift ) --------O%O
    

18Back to top Go down    Re: Underheating cooling system on Sun Dec 07, 2014 1:06 pm

JediGirl

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Thanks for the hints! 

Olaf, it was good to meet you indeed. By goes off I meant engine stops working'. 

The indicator of the temperature never crosses the half of the range.


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"There is a theory which states that if ever anyone discovers exactly what the Universe is for and why it is here, it will instantly disappear and be replaced by something even more bizarre and inexplicable.There is another theory which states that this has already happened." (Douglas Adams)
    

19Back to top Go down    Thermostats on Sun Dec 14, 2014 7:06 am

WandererK1

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Hi all,

Has anyone found a substitute new thermostat or are we locked into the expensive BMW job.?

Cheers Jeremy

    

20Back to top Go down    Re: Underheating cooling system on Sun Dec 14, 2014 7:27 am

Inge K.

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I think Charlie have used a thermostat from a Corolla......search the forum.


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Inge K.
K100RS -86. (first owner), K1100LTSE -94.
    

21Back to top Go down    Re: Underheating cooling system on Sun Dec 14, 2014 11:44 am

charlie99

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your right inge ...yet again ...!!


try here for the modified thermostat

  http://www.k100-forum.com/t1833p650-85-rt-resto-my-attempt-hey-im-not-into-making-a-show-bike#88242


__________________________________________________
cheezy grin whilst riding, kinda bloke ....oh the joy !!!! ...... ( brick aviator )

'86 K100 RT..#0090401 ..."Gerty" ( Gertrude Von Clickandshift ) --------O%O
    

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