New thermostat?

[VetteJim]

Hello group. I have been reading a lot of posts about the thermostat and it's issues (getting stuck open). Right now I am going over the bike and seeing what needs to be done. I bought it last summer and am going through it now (since it's winter and nothing else to do!). My question is, should I go ahead and just replace the thermostat while I have time and access to it? Is it one of those things you should just do? Mine is a 2008 with 53,000 miles on it. I don't have any idea what has been done to the bike. It looks clean so I think it has been taken care of but no idea about what has been replaced. It is not leaking any coolant and the temp gauge seems to be fine.

 

[dduelin]

Sticking OEM thermostats seemed to affect 2003-2005 models more than later ones. If you haven't seen coolant temperatures fluctuate at less than 3 bars when riding and the housing isn't showing signs of weeping or leaking I'd leave it alone.

 

[VetteJim]

Sticking OEM thermostats seemed to affect 2003-2005 models more than later ones. If you haven't seen coolant temperatures fluctuate at less than 3 bars when riding and the housing isn't showing signs of weeping or leaking I'd leave it alone.

Sounds good - I'll just go ahead with a flush then. Thanks

 

[Igofar]

Showing three bars is not always a good indicator of your t-stat working properly.
How long it takes you to reach the first bar is a better indicator.
You should reach the first bar in a minute or two at the most.
When the coolant reaches operating temperatures it will show three bars, despite being stuck open.
With that mileage, and never having replaced it, I’ll bet you a donut that you’re going to find yours stuck open.
Your mpg will also show if it needs replacing.
Don’t do it now, you’ll just need to do it all over again when you figure it out.

 

[dduelin]

The time is takes to reach one bar is dependent on the ambient temperature. In cold weather it takes longer then it does in warm weather, making time to one bar not so much a reliable indicator of t-stat failure.

A stuck one or one operating properly will always reach three bars when idling long enough. They both do this. The test is whether or not the gauge stays at three bars when riding the bike on the road. When riding on the road air is forced to pass through the radiator and thus cools the coolant and the thermostat reacts by closing enough to reduce flow through the radiator in order to hold the coolant temp to that which registers 3 bars - the normal operating temp of a ST1300 in 20F or 100F ambient. If the t-stat is stuck open, the usual mode of failure, it cannot regulate the coolant temperature and the gauge falls to 1 or 2 bars depending on ambient temperature. As soon as the bike is stopped and allowed to idle the gauge climbs back to three bars. As long as I've been around ST1300s this has held true.

The 1-2-3 bar dance......

https://www.st-owners.com/forums/search/197675/?q=1-2+bar+dance&o=date

 

[Rob20111]

My 2004 temp gauge was always normal at 3 bars, but after opening the thermostat housing to change a leaking o-ring I found the thermostat (cold) in the open position. It tested bad too.
You may want to test yours to be sure.
It should be closed when cold then open when placed into a pot of boiling water, then close again when cooled.
Access is pretty simple.
Drain coolant, radiator off, then cross member bracket and T stat housing.
After replacing, my engine now warms up quicker and fuel consumption is reduced.

 

[Igofar]

The time is takes to reach one bar is dependent on the ambient temperature. In cold weather it takes longer then it does in warm weather, making time to one bar not so much a reliable indicator of t-stat failure.

A stuck one or one operating properly will always reach three bars when idling long enough. They both do this. The test is whether or not the gauge stays at three bars when riding the bike on the road. When riding on the road air is forced to pass through the radiator and thus cools the coolant and the thermostat reacts by closing enough to reduce flow through the radiator in order to hold the coolant temp to that which registers 3 bars - the normal operating temp of a ST1300 in 20F or 100F ambient. If the t-stat is stuck open, the usual mode of failure, it cannot regulate the coolant temperature and the gauge falls to 1 or 2 bars depending on ambient temperature. As soon as the bike is stopped and allowed to idle the gauge climbs back to three bars. As long as I've been around ST1300s this has held true.

The 1-2-3 bar dance......

https://www.st-owners.com/forums/search/197675/?q=1-2+bar+dance&o=date

As always, we will have to agree to disagree.
I have a 5 gallon bucket full of stuck thermostat's, that NEVER did the two bar-three bar dance.
Its very rare for a bike to come into the garage and NOT find its thermostat stuck open, despite the owner stating its operating normally.
I'm just guessing here, but I'm thinking I may have inspected and/or replaced a few hundred of them in the past few years, and this is what I've commonly found.
How many have you replaced or inspected?
If our OP is in that deep, and doing the service, it makes sense to replace it and move on, rather than have to do it twice etc.

 

[VetteJim]

My 2004 temp gauge was always normal at 3 bars, but after opening the thermostat housing to change a leaking o-ring I found the thermostat (cold) in the open position. It tested bad too.
You may want to test yours to be sure.
It should be closed when cold then open when placed into a pot of boiling water, then close again when cooled.
Access is pretty simple.
Drain coolant, radiator off, then cross member bracket and T stat housing.
After replacing, my engine now warms up quicker and fuel consumption is reduced.

OK - I was reading the service manual (I know - who does that!) and it said you have to remove the tank, air box and a bunch of other stuff to replace the thermostat which was leading me to skip it. But what you are saying sounds much easier. I don't think I found any articles here on replacing the thermostat.

EDIT - just remembered dduelin sent me a couple yesterday.

 

[Igofar]

You don’t have to remove the tank, airbox, or throttle bodies, as the dealers will try and tell you.
Just the Tupperware, three bolts from the radiator, and two bolts from the cross brace.
The funny thing is the dealers will tell you you must remove the stuff and go in from the top to replace it because it is more work, more money, and even if you tried to go in from the top and removed all that stuff, you still would not be able to remove the t stat because the cross brace would prevent it, and you have to go in from the front to remove that out of the way.
While you’re in there, you’ll want to gently snug up all the loose clamps anyway.
But do not over tighten the two clamps on the radiator or you’ll crush the pipes.
Search the articles.

 

[maddog13]

The thermostat housing is more or less "floating" on the hoses. So before you remove the bolts put a piece of wood or a socket between the thermostat body and the engine block so there is something solid to press against to loosen the bolts.

 

[Sadlsor]

This is all curious to me, or at least one question comes to mind after reading all the posts here...
Do we ever see the 1300 (at least 2006 and later) in-dash temp gauge show OVER 3 bars?
And as an aside, seeing a couple references to fuel mileage... @Igofar has frequently posted his ~50mpg as I recall, whereas my best was 45 mostly at low speeds, but usually 40-42 without the trailer. Would a thermostat replacement actually improve my gas mileage? At 34K miles, I have no indication of t-stat problems.

 

[SMSW]

Since you have an uncertain maintenance history for your bike, you might read this:

Article - Maintenance Items Needed for a New (old) Bike | Articles

This article is the result of collaboration by Andrew Shadow, CYYJ, jfheath, Max Pete, SMSW, and SupraSabre. Igofar’s list was copied from the first link listed above. Click on the attached file. This one is V.11; in the future, any changes will be noted in the title on the first page as the...

www.st-owners.com

I tend to be a proponent for doing the maintenance when I have time - I really don't like the bike telling me something is wrong - usually just before a trip or when riding for hours a day ON a trip. I've been known to replace tires w/ a couple of thousand miles left, and brake pads for the same reason - because I have enough things going on that adding doing these things to a normal schedule makes for some scrambling and adjusting my schedule. There are enough other things in life that cause these interruptions that I want to remove the potential irritants if I can. YMMV - its a personal choice.

If you do go for the thermostat replacement, after removing the lower radiator bolts, tilt the radiator forward from the bottom and lift it off the top hangers. If you don't tilt it, something will have to bend. I replaced some hoses when I was in there for my 'stat and I replaced the clamps that I could reach with constant tension clamps.

 

[SMSW]

This is all curious to me, or at least one question comes to mind after reading all the posts here...
Do we ever see the 1300 (at least 2006 and later) in-dash temp gauge show OVER 3 bars?
And as an aside, seeing a couple references to fuel mileage... @Igofar has frequently posted his ~50mpg as I recall, whereas my best was 45 mostly at low speeds, but usually 40-42 without the trailer. Would a thermostat replacement actually improve my gas mileage? At 34K miles, I have no indication of t-stat problems.

Yes, to the 3 bars q. When my stat was exhibiting sticking symptoms (long time to warm up) I took the 1300 for a club ride. On the way home from lunch, the stat stuck in the closed position and I got up to 4+ bars. I pulled over, let it cool down and tried the stop and go construction traffic again. Repeat the cool down. Then I discovered if I maintained a steady 50 mph, the bike maintained 3 bars for the rest of the trip home.

If your stat sticks open, in cold weather (yeah, I know that is a foreign concept in southern Alabama) you will get lower gas mileage because the bike is running a richer mixture based on what the ECU sees for the coolant temp. For five years, I averaged 41 mpg (saved every gas receipt and put them on a spreadsheet). The bike returned that mileage consistently from year to year that I owned it - for roughly half slabbing and half surface riding. Much of the slabbing was at supra legal speeds (nothing outlandish) with a slightly larger than OEM windshield in the up position.

 

[RobbieAG]

I had a bad thermostat when I got my 2005 (8 years ago at 61k miles). The temp gauge would immediately go to 3 bars and the mpgs were around 35. I tested the thermostat per the procedure in the FSM and it proved bad. After replacing it, it behaved normally taking a couple minutes to go to 1 bar and reaching 3 bars at full operating temperature. The average mpgs went up to 42 - 43. Recently I had the radiator out for some other work so I preemptively replaced it while I was in there even though it was functioning normally. I'd say if you already have the radiator out, go ahead and replace it (and the o-ring).

 

[VetteJim]

yep, it's already on order with the O ring and some coolant.

 

[SupraSabre]

And remember to use a (1/4") torque wrench to torque the bolts that hold the thermostat cover in place.

That cover will leak, if not torqued down correctly!

 

[Igofar]

And remember to use a (1/4") torque wrench to torque the bolts that hold the thermostat cover in place.

That cover will leak, if not torqued down correctly!

The thermostat housing is more or less "floating" on the hoses. So before you remove the bolts put a piece of wood or a socket between the thermostat body and the engine block so there is something solid to press against to loosen the bolts.

A Hockey puck works great for supporting it, and very useful for knocking in bearings too, as they are hard and don't scratch things.