3 bars on coolant temperature from cold

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Aug 12, 2014
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2004 ST1300
For the past few weeks my temperature has flicked between three and two and it's using more fuel, so I've got a new thermostat and seal to fit this weekend. For the last couple of days, when I've turned the ignition on from cold its' shown three bars, and it stays there for the whole journey. I'm wondering if I've got another problem as well as the thermostat, maybe the temperature sender? Has anyone had this problem before?

The bike is a 2004 ST1300 with 73,000 miles showing.
 

ibike2havefun

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For the past few weeks my temperature has flicked between three and two and it's using more fuel, so I've got a new thermostat and seal to fit this weekend. For the last couple of days, when I've turned the ignition on from cold its' shown three bars, and it stays there for the whole journey. I'm wondering if I've got another problem as well as the thermostat, maybe the temperature sender? Has anyone had this problem before?

The bike is a 2004 ST1300 with 73,000 miles showing.
I'd start by addressing a known issue, which you are already planning to do, before going to look for other troubles. The symptoms you describe are all known to be associated with a failing / failed thermostat. If the issue persists, then it's time to dig deeper. But I'll wager $0.02 that the thermostat change will make the symptoms disappear.
 

dduelin

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It's not normal for the temp to show 3 bars from at engine-off cold. It shouldn't show any bars when cold.

When you take the thermostat housing apart look closely for corrosion in the connector for the green ground wire. Resistance in this circuit will cause the temperature gauge to read high or show excessive heat.
 
OP
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Hmm, I searched for three bars when cold and got nothing. That's a great help guys, I'll take the easy step first and hope it's a ground problem. The bike is permanently wet at the moment with all the rain we are having, I do 104 miles a day in all weathers, so a corroded lead is quite likely.
 

T_C

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Yep... you may or may not have a thermostat problem. Yes they are known trouble spots on the ST1300. First jobs on both of my bikes was replacing it because they wouldn't hold temperature. But I do also know of an ST1300 with over 125k on the original unit.

I would first dig into your false reading before replacing the unit. If the ECU is not getting the proper reading it would be enriching the gas mixture thinking the engine is still cold.

Of copurse how do you know if you really fixed the electrical half if your mechanical half is still questionable??

But yes, 3 bars from key-on is a definite pointer in the issue and in no way shape or form could be caused by a stuck open thermostat.
 
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You may have a corroded connector and bad thermostat as well. When my thermostat was stuck open my temp gauge would flicker between two and three bars, stay on two bars if the temp was around 35 F (2C) and my fuel mileage dropped from in the mid 40's to 30-32 mpg.
 
OP
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Update: The thermostat was stuck in the open position, so I've changed it and replaced the coolant. I haven't managed to do anything under the tank yet. The bike now runs better, with the fuel consumption rising to near normal levels, but the temperature display is still wrong.
 
OP
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Update to the update, I finally got around to replacing the temperature sender, not a nice job. I bought a set of JIS screwdrivers, but quite a few fasteners had already been chewed up. I had to drill a few out, it would have been easier with the main tank removed but I kept it propped up. I got a replacement airbox off eBay, I was too enthusiastic with the drill, and made a good one up from the two, and I have spares in case the problem happens again. I didn't want to remove the throttle bodies so I had to skin my knuckles to remove the electric connector and unscrew the sensor. The old one was clearly past its best, all corroded apart from the tip. Anyway, I've put it all back together, I have no bars from cold, and my fuel consumption is back to normal. I had to sit in traffic today and it went up to four bars, but down to three once I started to move, so it seems the problem is solved now.

I don't know if one problem led to the next, but if you are repairing one problem then it's best to be prepared to do them both, after several years immersed in coolant the sensor will probably show signs of corrosion.
 

dduelin

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Too late now but the thermostat housing and sending unit connections are easily accessed by removing the radiator. The service manual says to remove the airbox and throttle bodies and come from the top down but the easiest way to get at it is to come at it from the front.

Still, someone reading this thread later may benefit.
 

wjbertrand

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If the ECU is not getting the proper reading it would be enriching the gas mixture thinking the engine is still cold.

Of course how do you know if you really fixed the electrical half if your mechanical half is still questionable??

But yes, 3 bars from key-on is a definite pointer in the issue and in no way shape or form could be caused by a stuck open thermostat.
There are two problems here. The 2-3 bar flicker and excess fuel consumption is a known issue caused by a stuck open t-stat. There may also be a problem with the sensor or one of the lead wires. Getting at the engine coolant temp sensor is a bit of a PITA as is screwed into the back of the t-stat housing and projects backward under the throttle bodies. It can be changed without removing the TBs but plan on leaving a little blood behind (BTDT). The ECT has three leads, ground, one lead for the gauge and a third for the ECM.
 
OP
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Too late now but the thermostat housing and sending unit connections are easily accessed by removing the radiator. The service manual says to remove the airbox and throttle bodies and come from the top down but the easiest way to get at it is to come at it from the front.

Still, someone reading this thread later may benefit.
I wouldn't say easy, I had the radiator out to do the thermostat and chose to go in the other way for the temperature sender. That rusty piece of metal that holds the rubber at the front would need to come out, or you risk cutting an artery. I had to change the sensor, which would have been impossible from behind the radiator as there's no spanner room, the airbox needs to be off the bike.
 

dduelin

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I wouldn't say easy, I had the radiator out to do the thermostat and chose to go in the other way for the temperature sender. That rusty piece of metal that holds the rubber at the front would need to come out, or you risk cutting an artery. I had to change the sensor, which would have been impossible from behind the radiator as there's no spanner room, the airbox needs to be off the bike.
With 161,690 miles on my older ST1300 I've been in the vee several times and removed the thermostat housing twice. For me, it's easier to come at it from the front by removing the radiator. Remove a few hoses and you can take the housing in the house and change out the sensor while enjoying the air conditioning.
 
OP
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Ah, I was changing it on the bike. I replaced the thermostat first, together with a coolant change, the thermostat was stuck open so I left the sensor replacement for another day. Although it would have been easier to do it your way, in this instance I've saved my self further grief, for balancing throttles etc by replacing all the faulty fasteners. As an example, the bike has obviously been dropped off the stand at some stage, the right-hand mirror was held on with a wood screw! I had to retap the thread and fit the correct bolt, so you can imagine what I found under the tank of a 12 year old bike :)
 

RobbieAG

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When I bought my 05 1300 last November (with 62k miles) the temperature gauge displayed 3 bars from key on. The fuel mileage was in the 30s also. As part of my ?new bike maintenance?, I decided to replace the thermostat. I removed the radiator and replaced it from the front (as Dduelin stated). Since I replaced it, the temperature gauge is behaving normally and the fuel mileage is in the normal range too. So far no issues with the sensor.
 
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