ST1300 overheating

I noticed it last week when it went to 4 bars up a pass in Montana last weekend, then it was fine until yesterday headed across Wyoming, I have to stop to keep it out of the 6th bar. Coolant is full, fan is working overtime, 75K on bike. I did a search but only came up with stuck open thermostats, never stuck closed. If I run at 40mph below 80 degrees I can keep it at 5 bars, sometimes to 4. I'm going home to Colorado tomorrow and don't really wanna nurse it home in the heat like this.
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Sounds to me like a weak water pump or a thermostat that is stuck only slightly open and wont open any farther.

I figured a water pump would gradually fail, only overheating when being pushed, and maintaining temp when being ridden easily. I hope it's the thermostat, but have never heard of one sticking closed.
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I'm going to assume that you've made sure that nothing is blocking the radiator and that you've visually checked the coolant level in the radiator itself...not just the overflow bottle....

If the radiator is good I'm going to vote for the failed water pump or stuck closed thermostat....

I think that I would start with the thermostat and take a good look at it. If that is not the problem it could be the water pump. Good luck on fixing this problem.

If it is stuck open it could overheat, it never gets a chance to set in the radiator to cool. You have less than a gallon of coolant. I bet it's stuck open, any takers? :smile:

A failing water pump usually leaks or makes a bunch of noise and is not usually characterized by engine overheating, exceptions exist of course. Second the suggestion to check the actual fluid level in the radiator and not depend on the reservoir level. I would guess a bad cap or t-stat.

If your water pump is not leaking or making noise then it should be good. (I just repaired my leaking pump.) Bike temps were fine. The pump (impeller) is driven by a chain turning a gear with a spline that the impeller shaft slips into. I vote for a bad stat or a bad radiator cap, or lack of fluid in the radiator. Also make sure your over flow bottle cap is making a good seal. Check the hoses going to the bottle from the radiator. Make sure you don't have too many radiator fins bent from rock, bugs etc. If I remember correctly, the book say no more than 20% of the fins should be bent. If so straighten them out. Time consuming yes, cheaper than a radiator. When was the last time you changed the coolant? Good luck and give us a follow up on what you find.

PS: just an added thought, could the temp sensor be failing?

I vote the stat is stuck ... barely open!
At least its an easy to fix/check before ripping open the pump.

Yup. And if you're sufficiently sneaky about it, you can do it without draining the cooling system and losing only a small amount of coolant.

--Mark

I'm also in the T-stat stuck closed or nearly closed, and/or lack of fluid in the radiator, and/or bad radiator cap.

An actual pump (impeller) failure doesn't seem likely. The impeller would have to seize, or the splines on the end of the impeller would have to be rounded off, or the chain would have to snap or come off the gear ... and if that were to happen you would definitely know it.

TMUS2122 said:

If it is stuck open it could overheat, it never gets a chance to set in the radiator to cool. You have less than a gallon of coolant. I bet it's stuck open, any takers? :smile:

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LOL.

I vote stuck closed thermostat for it to get that hot ! Good luck !


MIKE

Don't know...have ridden in FL and now NV heat, always at 3 bars...no matter the temp. Only time it went over was stopped in traffic at 90+ day, idling with no air flow...simple solution to turn off the bike until moving again. But curious to know what you find!

Installed the Motorad thermostat this morning, much easier than expected. Actually, one could do it only removing the right side fairing, loosening the lower left side, and using the radiator hinge on the top mount to get enough clearance to access it from the right side only.

Rode it around town today in warm temps, fans were cycling on and off, whereas they stayed on constantly before under those conditions as the temp climbed.

Never saw more than three bars. There is a bypass hole in the new thermostat, the old one had none.

Mission accomplished! Thanks for all the input, boys. So now we know they can also stick closed (or almost so) as mine did.

Glad you got it fixed and thanks for the feedback in confirming the stuck stat !


MIKE

It seems to take longer to reach operating temperature than it used to, I'm guessing it's the little bypass hole in the new thermostat that the original did not have, but it's working well, no overheating whatsoever.

khanawalt said:

It seems to take longer to reach operating temperature than it used to, I'm guessing it's the little bypass hole in the new thermostat that the original did not have, but it's working well, no overheating whatsoever.

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Glad to hear it's resolved.