ST1100 Running very hot at low speeds

barto

barto

Joined
May 26, 2010
Messages
282
Location
Nashville
Bike
99 ST1100
New owner of a '99 ST1100 - I've noticed a lower speeds - 25 to 30 mph or even less the bike tends to run pretty hot - temp gauge not into the red but pretty close. The temperature disipates fairly quickly once I'm running at speed - anything from 40 or 45 mph on up.

Today I got stuck in a traffic jam, had to creep along for 10 or 15 minutes. YIKES - the temp gauge went all the way into the RED for a while. Just when I was ready to stop and shut 'er down traffic opened up and temperature came back down.

I know there is an electric fan that's supposed to kick on at some point - I'm not sure but I don't believe it did.

Two questions really:

1) How can I tell for sure if the fan is or isn't working?

2) Given that heat seems excessive even when moving (at LOW speeds) is the fan likely to be the culprit or is there something else (even worse) I should be looking for?

Thanks for any help...I'm definitely concerned about this issue doing real harm to my "new" bike.

PS: If it is "just" the fan, what should I expect to pay to have it replaced or repaired?
 
Get off the bike and listen on the left side (fan is closer to the left). You'll hear it if it's on. Also you'll get a blast of heat. It should come on when you get to about 2/3 on the gauge.
 
Somethings wrong - the temp gauge usually shouldn't get past the 1/2 way pont without the fan kicking on.

To check, start it up and just let it idle - keep and eye on the temp gauge. You should definitley hear the fan turn on around the 1/2 way point, it it gets much hotter than that and is still hasn't turned on, shut it down and report back
 
I had the same problem before. The res hose was cracked and would not bring fluid to the radiator. Make sure to take a good look at the radiator not the overflow container. Coolant leaks will leave a salty looking slime on the right side mostly........if it's from the hose off the thermostat cap or over flow. Might puddle if it's under the carbs.
Might be worth it to take the right side fairing off and have a good snoop around.
Good luck!!!
 
Several reasons for overheating or appearing to overheat.....

1. Fan either not working or jammed.

2. Sensor, left side of radiator, faulty.

3. Sensor, same one, not getting immersed in coolant inside the rad.

4. Sensor, same one again, incorrectly fitted, or wiring incorrectly done.

For;

1. Attempt to turn fan blade manually, with bike cold and ignition off of course, if it doesn't or is very stiff... strip and investigate, not you the bike....

2. Disconnect sensor connector and with ignition on. short sensor wire to ground, not sensor itself mind, the wire that goes to it. If the fan runs, it isn't the fan itself causing the problem.

3. Check fluid levels in both header tank and radiator. IF the radiator isn't full to the brim, or at least visible in the filler neck, this may cause the issue. Fill system with appropriate coolant.

4. The sensor for the fan is fitted to the radiator which itself isolated from ground. What the sensor does when it closes is completes the ground circuit by grounding the fan through the radiator, through the sensor switch closing making the ground circuit complete. Fan should run.
If the bike has been stripped down and the radiator removed, the fan ground cable may inadvertently have been placed in the wrong sequence on the mounting point, effectively isolating it permanently.

I would suspect it is more likely to be 1, 2 or 3 though.

Personally I would start with 2 in the fault finding process as it is the easiest.


Of course there are other options, the radiator is clogged externally or internally..... externally is obvious, internally not so obvious.... hope it's not though, clogged...., or as previously mentioned, split hoses....
 
Last edited:
STranger said:
I had the same problem before. The res hose was cracked and would not bring fluid to the radiator. Make sure to take a good look at the radiator not the overflow container. Coolant leaks will leave a salty looking slime on the right side mostly........if it's from the hose off the thermostat cap or over flow. Might puddle if it's under the carbs.
Might be worth it to take the right side fairing off and have a good snoop around.
Good luck!!!
Click to expand...

+1 on the cracked hose.

A quick check of the reservoir can give lots of info. If the reservoir is very full then you have a cracked hose. When the bike cools remove the plastics to get to the radiator and then check the coolant level to verifiy. The crack is usually right at the end where it connects to the radiator. You can just trim off a little and re-attach if the crack is not very long. I had the same problem last year. Re-fill the radiator, I used what was in the reservoir and then a little extra.

What happens is when the bike gets hot it pushes fluid into the overflow tank, but when it cools and usually sucks it back into the radiator. However, if there is a crack air sucks easier than fluid so it doesn't bring any fluid back. It just keeps pushing it out.
 
Another possibility is a stuck thermostat. All the above are good things to check, if the bike has any significant miles, any/all these could be present. I need to do the same to lipSTick before taking off east next week, she's been showing high (never in the red) heat levels for several weeks.

Who has the Stant after-market thermostat number at the tip of their finger?
 
Thanks for the great feedback.

While I still suspect the fan is the primary culprit, the idea of a crack in the hose sounds like another likely issue. When the dealer checked out the bike for initial service after I bought it he said the coolant reservoir was over full and drained off the excess.

I'll check all this out and go from there. Thanks again...as a brand new owner this forum has been a great way to get up to speed quickly!
 
Thanks once again for all the great info. My ST's in the shop now for the repairs. (And I miss it...)

1) Sending unit/switch bad, needs replacement (Fan was not coming on at all)
2) There IS a crack in the hose from the radiator to the overflow tank
3) Also replacing the radiator cap, too.

Pretty minor stuff, all in all. Parts and labor should be less than $2OO bucks. Whew! Feared much worse...
 
I have mine in the shop for the same thing. It will overheat when sitting idle but if you get out on the highway it will come down to the 1/2 way point. Overflow was about a 1/4 quart low and fan was working. I had a hard time telling if the fan was running or not and if you hit the jill switch it will kill the fan also, I found the best way to see if fan was running was to put kickstand down while in gear and it would kill the bike but fan would still run.

This is the first repair I have had to do in almost 21,000 miles and 2.5 years. It is still under my 3 year unlimited mileage warranty so it should be a free repair to the taxpayers.

I will update whenI find out what was wrong with it.
 
tnman said:
I have mine in the shop for the same thing. It will overheat when sitting idle but if you get out on the highway it will come down to the 1/2 way point. Overflow was about a 1/4 quart low and fan was working. I had a hard time telling if the fan was running or not and if you hit the jill switch it will kill the fan also, I found the best way to see if fan was running was to put kickstand down while in gear and it would kill the bike but fan would still run.

This is the first repair I have had to do in almost 21,000 miles and 2.5 years. It is still under my 3 year unlimited mileage warranty so it should be a free repair to the taxpayers.

I will update whenI find out what was wrong with it.
Click to expand...

They have it done, said a hose was pinched, they repaired that and it did not fix the issue so they put a new T-stat in it. Guess we wil find out if that fixes it.
 
Exactly the same slow speed overheating just happened to me. In my case its a faulty sensor. When cruising at high speed the air keeps it all col, but as soon as I slowed in traffic, up she went and blew steam. No fan operation - pulled the wire off the sensor and shortied to ground and fan came on and cooled it all down pretty quick. I have ordered an replacement sensor ( Australian $100.00 ) and while I'm waiting I'm also currently putting in a manual override switch and a flashing red light so if the thing still overheats I can flick the switch, turn on the fan and with the red light flashing - wont forget to turn it off again >>>
 
You may also check the fuse to the fan, I had a the same problem and found a bad fuse for the fan.
 
One thing not mentioned here is also very important... The cleanliness of your rad and I'm not talking about the rad's interior.

I have found that the 1100 picks up a lot of debris that gets lodged in the fins. To help with that I've cut window screen and placed it between the rad and the plastic grill cover. It helps me deal with cleaning bug debris much more easily but it doesn't fix everything.

I've had my rad off twice in a 3 year interval, (timing belt in /07 when I bought it and coolant pump this year). I always have a look at it and every time I've had to backwash then blow out the rad with compressed air to clear it of a surprising amount of fine sand. It gets really stuck in there. I'm almost always driving on pavement too. After doing it I notice a reduction in the cooling fan's run time when it kicks in. My bike has never even come close to getting hot. Obviously, having a clear rad in extreme temperatures is essential in preventing over heating. If you have your rad off sometime, I suggest that you give it a good wash and inspection. You may be surprised what you find.

Now, if I could only find something that would keep ME cool when that fan cuts in!

Ross
 
update:
11233 is the radiator cap;
13868 is the "new" Stant number for the 180 degree thermostat.

Auto Zone 'puter cross checks the old number 35868 to a thermo switch for a fan, tho on-line references still show a thermostat.

Headed back there now to get the "correct" new number part.

Oh, yeah, the "old" 'stat was stuck closed, which was causing temp. to rise and fan to kick on all weekend at CreSTOC.
 
George said:
Oh, yeah, the "old" 'stat was stuck closed, which was causing temp. to rise and fan to kick on all weekend at CreSTOC.
Click to expand...

Hmmm.. the ST1300 stats stick open.... another reason to.... nah, I can't do it.. wait, I just did. oops.
 
Usually the ST11 thermostat sticks open as well. Only a few cases of overheating from a stuck shut thermostat. At least the St13 stuck open syndrome is consistent as they all seem to do it :) With the ST11 is is just old age...
 
You must log in or register to reply here.
Back
Top Bottom