Do I need a new Thermostat?

[carpevita]

Went for a ride in the cold afew days ago. Noticed that when the outside temp is about 45, the engine temp varies between 2 and 3 bars. 2 when moving and 3 when stopped at a light. When the outside temp is around 35, it varies between 1 and 2.. Ive read about guys getting thermostats replaced and wondered if its my turn. I ask the question here first because Im real leary bringing my bike to a dealer for the work after reading the horror stories about dealer mechanics.

Anyone have info on riding their bike in the cold temps? Thanks Dan

 

[Drew]

My '05 is always 3 bars even at 30 deg. I'd keep an eye on it, but it sure sounds like the T-stat is starting to fail.

Drew

 

[carpevita]

The gauge appears fine..It self tests fine when I turn the key on and the fans dont turn on unless the bike has been sitting for several minutes..The gauge has never gone above 3 bars..The cold (35-45) ram air when Im riding appears to cool the gauge down to 1 or 2 bars...Im assuming that would indicate a thermostat stuck open... My guess anyway.. Dan

 

[carpevita]

One more thing ..Its an 04 with 13000miles and I never changed the coolant...I thought that isnt done until much higher mileage...

 

[Mellow]

Note:

If the temp is 100 degrees, the bike should warm up to 3 bars and stay there since the fans will cool it off before it hits 4 bars..

If the temp is below or around 40s the bike should warm up to 3 bars and stay there since the thermostat will close and let the engine warm itself up..

Bottom line - if the thermostat doesn't stay at 3 bars especially when moving.. odds are your thermostat is failing - Cold weather situations have typically been the problem since the therm will fail open and not closed.

 

[nm6r]

My failed thermostat was stuck open. There was no need to conduct further testing as it was open at room temperature. That is plenty enough test.

The new thermostat (closed at room temperature) lets the bike warm up to 3 bars and stay there.

Ray

 

[carpevita]

Excellant!!!! The above article is exactly what I needed!...Looks like I have a day project once the weather warms up a little. I think I might be smelling a little antifreeze so whille Im in there, I could tighten up some hose clamps as well..Dan

 

[ALANT]

Went for a ride in the cold afew days ago. Noticed that when the outside temp is about 45, the engine temp varies between 2 and 3 bars. 2 when moving and 3 when stopped at a light. When the outside temp is around 35, it varies between 1 and 2.. Ive read about guys getting thermostats replaced and wondered if its my turn. I ask the question here first because Im real leary bringing my bike to a dealer for the work after reading the horror stories about dealer mechanics.

Anyone have info on riding their bike in the cold temps? Thanks Dan

Sounds just like the problem I had back at Thanksgiving with my '04 and at about the same mileage too. My stat was stuck open causing my temp gauge to indicate 1 or 2 bars and my gas mileage dropped 6 to 8 mpg as well. I replace the thermostat myself (not too difficult) and flushed and refilled the system. Been running 3 bars since then and gas mileage returned to normal. Cost for thermostat, o-ring, and coolant was about $35 plus shipping from Service Honda.

Hope this helps...Alan

 

[nm6r]

One thing to be sure to do when flushing the system is to clean the overflow bottle. I had some dark residue left in mine that I didn't want going back into the system. Someone suggested cleaning it with BB's. That with a little soapy water cleaned it right up. Of course, I rinsed it out well. Not only did I get all the residue, I now have a good view of the coolant.

Ray

 

[carpevita]

OK!

I'm going to give it a try. Going to try to remove the radiator and drain and flush out the coolant, remove inspect and replace (if necessary) the thermostat. Couple of questions for those that have done it..The shop manual talks about removing the drain bolt/sealing washer to drain coolant from the cylinder. Is this really necessary? The link posted a few replies back talks about connecting a garden hose to the input into the engine and flushing it that way....Secondly, the manual mentions several different o-rings to replace...Is it enough to only replace the thermostat o-ring? Thanks Dan

 

[Gug]

I just had my bike in for the 16K service and noted to service about my temp guage running between 1-3 bars in the colder (cooler) weather. I had no loss of mileage though that I have heard of on the board. There was 1-3 mpg loss but that would be normal in colder weather with additional windshield being used and fluid viscosities being thicker. Anyhow when all said and done they said they called Honda and said this is normal. The manual states the same thing as they quoted. That is the the normal operating range is between the H and C marks. I haven't had any problems with it, so I'll just ride it. It is documented on my invoice from the original service write up.

 

[nm6r]

I pulled the drain plug last and was surprised how much coolant came out. I would highly recommend pulling the plug and definitely replace the sealing washer.

BTW, who was the brain child at Honda that put the drain plug there? I think mother Honda dropped that kid on it's head.

Ray

 

[isbarense]

My '05 is 11 months old with 14.5k miles. Since it was new I always got 3 bars on the water temp guage once warmed. When the outside air temp is 40 to 90 degF -- 3 bars.

Now the water temp guage mostly it reads 2 bars, sometimes 3 bars on my 90 mile daily commute rt at 55 to 75 deg outside air temperature. I think the milage is less (3-5 mpg) than when the bike was consistantly at 3 bars. I can't be certain because so much depends on the speed you drive.

I've seen the dealer but have not left the bike there yet. The mechanic says he has not seen this issue w/ any ST1300. I get the feeling he does not consider this to be abnormal. The mechanic agreeed to call Honda factory for advice before preceeding and leaving the bike. This is happening on Tuesday. Can the mechanic tell what the problem is by connecting to a service computer?

From your experience - is the issue more likely a stuck open thermostat; a bad ECT sensor; bad harness connection, a bad water temp gauge, or no issue at all? Perhaps something else? What are typical costs (or hours) if the mechanic has to pull the throttle body to get to the sensor or the thermostat and the warrenty does not cover it?

Thanks,
Ian

 

[Txrebel]

Question. I sorta suspect my stat is going , but it does always get to three bars , just takes a while to get there. So was wondering. In 40-50 deg F temps how many miles do you have to ride to show three bars ????

If it always gets to 3 bars, just slow to get there maybe it is not stuck open very wide. IF you are ready to change the fluid anyways I would go ahead and pull the T-stat for inspection. It should be closed.

 

[Txrebel]

My '05 is 11 months old with 14.5k miles. Since it was new I always got 3 bars on the water temp guage once warmed. When the outside air temp is 40 to 90 degF -- 3 bars.

Now the water temp guage mostly it reads 2 bars, sometimes 3 bars on my 90 mile daily commute rt at 55 to 75 deg outside air temperature. I think the milage is less (3-5 mpg) than when the bike was consistantly at 3 bars. I can't be certain because so much depends on the speed you drive.

I've seen the dealer but have not left the bike there yet. The mechanic says he has not seen this issue w/ any ST1300. I get the feeling he does not consider this to be abnormal. The mechanic agreeed to call Honda factory for advice before preceeding and leaving the bike. This is happening on Tuesday. Can the mechanic tell what the problem is by connecting to a service computer?

From your experience - is the issue more likely a stuck open thermostat; a bad ECT sensor; bad harness connection, a bad water temp gauge, or no issue at all? Perhaps something else? What are typical costs (or hours) if the mechanic has to pull the throttle body to get to the sensor or the thermostat and the warrenty does not cover it?

Thanks,
Ian

This one sounds like it is stuck open to me. I did the work myself but some have had luck getting the dealer to agree to do the work on your dime unless the t-stat proves to be stuck open once it is removed.

 

[isbarense]

Txrebel,

How long did it take you to do the work yourself - to remove the thermostat and reassemble the bike? Tomorrow the dealer will call Honda for advice and see if the work is covered under warranty. I'm looking forward to finding out the details.

Ian

 

[Txrebel]

It took several hours. But was not very difficult. Very straight forward details and step by step procedures are available on this site.

 

[isbarense]

Thanks for the information.

I thought I'd share this information with anyone who wants to read it. My dealer called the Honda hotline for mechanics. They indicated that a way to check if the themostat is stuck open is to:
1) let the bike cool overnight
2) remove the radiator cap
3) start the bike and observe if the radiator water/glycol mixture is flowing. If it flows, then the thermostat is stuck open.

I'll try it this weekend and see what happens.