Thermostat failing?

Joined
Sep 4, 2013
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2010 ST1300
This summer I had planned to change the stat and all associated hoses. This was preventative maintenance and I wanted to change the hose clamps to stop the ubiquitous slow leak. Pulled the radiator and when I saw how cramped the thermostat housing is and how difficult it was going to be to change all the hoses, I just put the rad back and buttoned everything up after tightening all the clamps. I've had not a whisper of trouble with the stat to date (37k miles on the 2010 bike).

Today was 41 deg F. Bike is stored in my garage that is heated to 40 (water pipes in house/garage wall had frozen before it was heated). Started the bike up per usual, donned my gear and once I had two bars, I rode off. Down the drive, rode about 200 yards and noticed that I still did not have 3 bars. All summer and fall (yes, much warmer temps) would get me 3 bars by the turn around. Today, nope. Made the turn to go back down the boulevard and drove about a mile to my next turn. In that distance, I got my 3 bars, then it went back to two, then up to 3, and back to two. I'd never noticed this behavior before - always got 3 bars and it held steady today once it hit 3 again by the end of that 1st mile, but to be honest, I don't monitor the temp gage very actively once it hits the third bar. (Speed on the boulevard was about 40).

Rode about 75 miles to our greasy spoon for today's lunch and not a flicker on the gage - steady 3 bars. On the way home I stopped at a friend's house and chatted for about an hour and a half. The bike went from 3 bars to zero in that time and I let it warm to two before I left (temp was now 50 deg F). As I rode away, it seemed to take a while to hit that 3rd bar, then back to 2, then 3 and it held steady w/o a flicker for the rest of the trip home. (Speed after leaving friends house was 50 to 60 - mostly 55). To be honest, I was watching the temp gage like a hawk for the entire ride today.

Does this sound like a failing stat or normal behavior in comparatively cold weather?
 

ibike2havefun

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Exactly what I saw, before replacing mine. It would also drop at longer stoplights on cold days.

Changed it two years ago. No more issue.

Easy work if you go in from front. Why Honda says go from top is beyond me.
 
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When I purchased my 2007 ST in June 2011 I did not see any issues with the thermostat until I rode it in cold temperatures, i.e., less than 50 degrees, during the winter. Then I would get two bars, but not three. I changed the thermostat that spring. I haven't seen less than three bars since. When it's cold outside it can take a while to get three bars, though.

I think a new thermostat is in your future. :)
 

dduelin

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The two bar two step is definitive. It's time to replace the thermostat and the O-ring that seals the housing. Send me an email address for a little how-to help on this job.
 
Joined
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My 2006 is in the beginning stages of this "two bar two step."
I will pm my email to you. Could you send me this help also? Thanks!
 

motofisch

(Scott)
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... Send me an email address for a little how-to help on this job.
My '06 has been presenting the same symptoms for a couple of years. Also, there is a significant drop in fuel mileage (and thus, range) when three bars of temperature is not maintained. Please Dave, send me copy of those how-to instructions at scott.fischer@pa.metrocast.net and I'll finally take care of this issue. Thanks in advance, Scott.
 
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Arizona
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The body of the T-stat housing is starting to corrode, and the spring is starting to, or has stuck completely in the open position.
When you remove and inspect it, you'll probably find the body is dark brown or grey, and it may have a couple shiny wear spots where it has been dragging or catching, in an attempt to open.
After removing the radiator, the only thing you'll need to move is the cross bar brace (2 bolts), then remove the (2) 8 mm head bolts, being careful not to damage the ground wire on the cover.
Make sure you clean any black paint trash you may find in there (from the radiator pipe over spray).
When replacing the T-stat, make sure the vent (little rivet looking thing) is positioned at 12 o-clock, and make sure the unit is in the key type slots at three and nine, so it cannot rotate clockwise.
Replace the o-ring, and put her back together, then burp the air out of the system.
 

dduelin

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Scott and Steve,

Done. It really as as simple as Larry posted but a step by step tutorial with pictures never hurts.
 

SupraSabre

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The body of the T-stat housing is starting to corrode, and the spring is starting to, or has stuck completely in the open position.
When you remove and inspect it, you'll probably find the body is dark brown or grey, and it may have a couple shiny wear spots where it has been dragging or catching, in an attempt to open.
After removing the radiator, the only thing you'll need to move is the cross bar brace (2 bolts), then remove the (2) 8 mm head bolts, being careful not to damage the ground wire on the cover.
Make sure you clean any black paint trash you may find in there (from the radiator pipe over spray).
When replacing the T-stat, make sure the vent (little rivet looking thing) is positioned at 12 o-clock, and make sure the unit is in the key type slots at three and nine, so it cannot rotate clockwise.
Replace the o-ring, and put her back together, then burp the air out of the system.
Use a torque wrench to tighten down those two bolts on the thermostat housing. If you over-tighten them, it will create a leak! DAMHIK!
 

DavidR8

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If I can offer one tip from recently doing this job.
I didn't want a big mess of coolant so I siphoned it from radiator before I disconnected any hoses. In retrospect I wish I had managed to siphon out the return hose also as I spilled some removing the hose from the rad. Other wise not a drop it the floor.
 

SupraSabre

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If I can offer one tip from recently doing this job.
I didn't want a big mess of coolant so I siphoned it from radiator before I disconnected any hoses. In retrospect I wish I had managed to siphon out the return hose also as I spilled some removing the hose from the rad. Other wise not a drop it the floor.
It's a messy job, no matter how you do it! :eek:4:
 

dduelin

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I only needed a couple of paper towels to wipe up the 1/4 cup that spilled from the hose. Had I siphoned the hose no coolant would have hit the floor.
Yes, I siphon the radiator out and barely dampen a paper towel for the drip or two on the floor.
 
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Take a plastic gallon water jug, cut the bottom out, turn it upside down, hold it by the handle, and slip it up underneath the hose and the spout, this will direct both the spout (towards you) and the hose (away from you) directly down into your catch pan.
Not a drop will touch the floor (pet friendly method).
Also, when loosening the (2) t-stat cover bolts, I find it easier to take a wooden wedge (doorstop) and place it underneath the housing to keep it from twisting too much.
 
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91 ST1100/06 ST1300
Newbie to ST1300's here. I got a really pristine looking 2006 on the 26th of October. Rode it home, some 265 miles. Drove it around town for two weeks just to assess it for any obvious issues...and found nothing that concerned me. Then I pulled the plastic and started fluid changes. Air filter was very old and the seal had deteriorated, so I looked closer at everything....nothing else.

I began my coolant change/flush. Refilled the radiator with fresh coolant and started it up (cold)...it immediately began circulating fluid.

Over the course of the 400 miles or so I have ridden it, this 2006 (just over 15,000 miles) never went above three bars, even at lights. Our local temps maxed out around 80F at this time.

I suspect the thermostat is stuck open, but thought I should ask you more experienced 1300 guys. Thermostat or normal for the 1300?
 

DavidR8

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Three bars is the normal temp level on the gauge. If the thermostat was stuck open you see fluctuating readings of two to three bars.


Sent from my iPhone using Tapatalk
 
OP
OP
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My bike has always warmed up to 3 bars and stayed there all day (well, as long as I was riding) regardless of the ambient temperature. No fluctuations at all (until now).
 
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Thanks for all the input everyone.
I suppose my concern was water immediately circulating from first start of the day. In all my other vehicles there was no circulation until the thermostat opened, at which coolant circulation began.
 
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