Temperature gauge reading

[Huntly]

Hello one and all
My 13 is showing six bars when I'm not moving but 3 when on the move I've done as the manual says and checked the level in the expansion bottle what do I check next
Thanks in advance
Richard

 

[TerryS]

When you are at 6 bars is the fan running? It really should be. If not you may have a blown fuse or wiring damage that is stopping it from running. At a standstill the fan is the only thing that can keep air moving through the radiator and keeping the engine cool. 3 bars is the normal running temperature for the ST.
With the motor cold, remove the radiator cap and make sure it is full to the brim with coolant. If there is low coolant or no coolant, you could have a radiator or hose leak.

 

[Igofar]

Are you sure your bike is even overheating?
Any other signs? Heat? Noise? Etc.
Sounds to me like you have an electrical issue or ground wire issue.
Find the cause, don’t chase the symptoms.

 

[NobodySpecial]

Definitely start with the fan. My fan will cycle on and off before it gets to 4 bars. My experience - irrespective of ambient temperatures or how hard I'm riding or how long it idles, etc. - is that from startup I see a progression from zero to three bars and then it doesn't change again until the bike has cooled while shut off. I have never seen 4 bars.

 

[Huntly]

When you are at 6 bars is the fan running? It really should be. If not you may have a blown fuse or wiring damage that is stopping it from running. At a standstill the fan is the only thing that can keep air moving through the radiator and keeping the engine cool. 3 bars is the normal running temperature for the ST.
With the motor cold, remove the radiator cap and make sure it is full to the brim with coolant. If there is low coolant or no coolant, you could have a radiator or hose leak.

The fan is kicking in like normal but when it's showing six bars the fan hasn't been on which is odd I will check the coolant in the rad pity it's such a pain to do

 

[Huntly]

Are you sure your bike is even overheating?
Any other signs? Heat? Noise? Etc.
Sounds to me like you have an electrical issue or ground wire issue.
Find the cause, don’t chase the symptoms.

Normally when bikes start to over heat the engine revs pick up not in this case so might be right about the electrical issue Igofar

 

[JohnK]

Richard

What model year? Any mods involving electronics on the bike? Did this just happen one day or progressively hotter readings over time? Mileage and last service of cooling system? Is the cooling fluid relatively clean or clear? What level of mechanical experience do you have or available to you?

I’m with IGOFAR. Get the plastic off the bike and start inspecting your wiring and connections among other things whilst in there - not uncommon to find lose, rodent bites, pinched or burnt connections. Once you eliminate that, start looking at temp sensors or fans and relay - temp sensor could be the issue but check the obvious first.

 

[Mikedo]

Other than when my thermostat was stuck open I've never seen anything but three bars for heat, once warmed up. When it was stuck it would get colder when riding in the fall/winter.

 

[Huntly]

Richard

What model year? Any mods involving electronics on the bike? Did this just happen one day or progressively hotter readings over time? Mileage and last service of cooling system? Is the cooling fluid relatively clean or clear? What level of mechanical experience do you have or available to you?

I’m with IGOFAR. Get the plastic off the bike and start inspecting your wiring and connections among other things whilst in there - not uncommon to find lose, rodent bites, pinched or burnt connections. Once you eliminate that, start looking at temp sensors or fans and relay - temp sensor could be the issue but check the obvious first.

Shes a 2003 no mods to the wireing type of girl I'm an engineer by trade and been spinning spanners on my bikes for 40 odd years so I will have a look under the plastics so I've got a better idea of what's going on

 

[Kevcules]

You can use an infrared gun to determine if your engine temp is actually as hot as the bike thinks it is when showing 6 bars. Sounds like a false alarm and an electrical issue for sure.

Lots of grounding issues at two main sources on these bikes. On the right side there's a yellow plastic bus/ground location in behind the headlights that is prone to corrosion. On the left side just in front of the valve cover, the ground wire in a large connector usally gets corroded as well. They can cause all kinds of weird things to happen like what you're seeing.

Good Luck

 

[Scooter]

The Engine Coolant Temperature sensor contains two internal thermistors. The one providing a signal to the the ECM uses the Green/Orange wire as the circuit common (this wire also provides a reference level for the map sensor, throttle position sensor, IAT sensor and others. The Yellow/Blue (called Pink in the 2003 manual; don't know if the wire colors are different for you Brits) wire is the signal wire running to the ECM.

The second thermistor controls the indicator on the dashboard. The signal wire is Green/Blue (part of the three wire connector that plugs into the ECT sensor) and the ground connection is made by the separate ground connector that attaches to the tab that is held in place by one of the two screws that secure the thermostat housing together.

I'd be looking at that ground connector first especially if it seems like the engine itself has been running normally. It seems likely that you have an intermittent connection at this point...

 

[JohnK]

Shes a 2003 no mods to the wireing type of girl I'm an engineer by trade and been spinning spanners on my bikes for 40 odd years so I will have a look under the plastics so I've got a better idea of what's going on

Best of luck sir, with your experience she’s going to find wellness again. Let us know what you find.

 

[Al Gully]

Sounds like when there's no air flow around your wiring, things go wonky due to thermal expansion.
Be careful as the wiring insulation may be brittle when you are wiggling your wiring around under the plastic tuperware.

 

[Huntly]

When you are at 6 bars is the fan running? It really should be. If not you may have a blown fuse or wiring damage that is stopping it from running. At a standstill the fan is the only thing that can keep air moving through the radiator and keeping the engine cool. 3 bars is the normal running temperature for the ST.
With the motor cold, remove the radiator cap and make sure it is full to the brim with coolant. If there is low coolant or no coolant, you could have a radiator or hose leak.

So I popped the cap off the rad and it was full so I fired her up and let her run and the fan kicked in a couple of times so I know that's working what was odd was the coolant level whent up in the rad and started to dribble out then came some bubbles and then it settled down the temp gauge stayed at 3 bars for ages then it shot up to six then back down to 3 if she was running hot she would have stayed at 6 and the fans would be on all the time so I think the temperature sensor switch is playing up so I've ordered a new one just got to find where it goes

 

[Huntly]

The Engine Coolant Temperature sensor contains two internal thermistors. The one providing a signal to the the ECM uses the Green/Orange wire as the circuit common (this wire also provides a reference level for the map sensor, throttle position sensor, IAT sensor and others. The Yellow/Blue (called Pink in the 2003 manual; don't know if the wire colors are different for you Brits) wire is the signal wire running to the ECM.

The second thermistor controls the indicator on the dashboard. The signal wire is Green/Blue (part of the three wire connector that plugs into the ECT sensor) and the ground connection is made by the separate ground connector that attaches to the tab that is held in place by one of the two screws that secure the thermostat housing together.

I'd be looking at that ground connector first especially if it seems like the engine itself has been running normally. It seems likely that you have an intermittent connection at this point...

Scotter

The Engine Coolant Temperature sensor contains two internal thermistors. The one providing a signal to the the ECM uses the Green/Orange wire as the circuit common (this wire also provides a reference level for the map sensor, throttle position sensor, IAT sensor and others. The Yellow/Blue (called Pink in the 2003 manual; don't know if the wire colors are different for you Brits) wire is the signal wire running to the ECM.

The second thermistor controls the indicator on the dashboard. The signal wire is Green/Blue (part of the three wire connector that plugs into the ECT sensor) and the ground connection is made by the separate ground connector that attaches to the tab that is held in place by one of the two screws that secure the thermostat housing together.

I'd be looking at that ground connector first especially if it seems like the engine itself has been running normally. It seems likely that you have an intermittent connection at this point...

Scooter I have ordered a new ECT to check the ground wire is it at the front of the engine

 

[TerryS]

Good diagnostics. Certainly sounds like the cooling system is in decent health, just a dodgy readout on the dash.

The service manual says if you jumper the blue/green wire on the temperature sensor plug to ground, you should get 6 bars on the gauge. That sounds like your issue which suggests to me you have chafing of that wire somewhere between the sensor and the gauge that is earthing to the chassis causing the high readings.

 

[Huntly]

Good diagnostics. Certainly sounds like the cooling system is in decent health, just a dodgy readout on the dash.

The service manual says if you jumper the blue/green wire on the temperature sensor plug to ground, you should get 6 bars on the gauge. That sounds like your issue which suggests to me you have chafing of that wire somewhere between the sensor and the gauge that is earthing to the chassis causing the high readings.

TerryS to get to these wires what needs to come off as I'm not to sure where the ECT is even located

 

[Josh_ST]

Yikes! Tank and TB off it appears

 

[Josh_ST]

SYSTEM INSPECTION
Drain the coolant (page 6-6).
Remove the throttle body (page 5-64),
Disconnect the ECT sensor wire connector from the sensor, Ground the Green/blue terminal of the 3P connector with a jumper wire.
Turn the ignition switch to "ON" and check the coolant temperature gauge. The coolant temperature gauge should indicate "H"
If the coolant temperature gauge does not indicate "H", check the wire harness for an open or short circuit. If the wire harness is normal,
replace the combination meter (page 22-11 ). If the coolant temperature gauge indicates "H", check the ECT sensor (page 22-15).

REMOVAL
Drain the coolant (page 6-6}.
Remove the throttle body (page 5-64).
Disconnect the ECT sensor wire connector from the sensor.
Remove the ECT sensor and sealing washer from the thermostat housing.

ECT SENSOR UNIT INSPECTION
Suspend the ECT sensor in a pan of coolant {50 - 50 mixture) an electric heating element and measure the resistance through the sensor as the coolant
heats up.
• Soak the ECT sensor in coolant up to its threads with at least 40 mm (1.6 in) from the bottom of the pan to the bottom of the sensor.
• Keep the temperature constant for 3 minutes before testing. A sudden change of temperature will result in incorrect readings. Do not let the
thermometer or ECT sensor touch the pan.

ECT SENSOR
The ECT sensor terminal is shown in the illustration. Replace the sensor if it is out of specification by more than 10% at any temperature listed.
Temperature 80°C (68°F) 120°c (248°F)
Resistance 2.1- 2.6 kohm 0.65- 0.73 kohm

 

[Igofar]

The ECT sensor wiring is one of the more commonly found damaged wires on these bikes.
Either by Heat (wires get crispy and the coating crumbles off exposing the wires to short out) or by folks trying to remove the T-stat, or tighten all the leaking clamps and twisting the T-stat housing to get at the clamps, thus causing the wire coating to crumble off etc.
Another sure fire way to damage these three wires is by trying to remove the T-stat cover WITHOUT propping a socket or piece of wood underneath the T-stat housing for support, and twisting the housing and hoses.
Problem is nobody ever looks behind the T-stat housing to check for damage in this area.
In the past 14 years or so, I've never found a damaged/bad ECT sensor terminal or switch, but I have found damaged wires, shorting out by touching each other more often than I'd care to admit.
I'm guessing your gonna find something like this behind the terminal connector....