Leak at Thermostat

bjalphasud

bjalphasud

Joined
Jul 8, 2010
Messages
125
Location
Montgomery County, PA
Bike
05 ST-Candy Red
I was trying to trace my leak and assume it was the pipes near the thermostat. I even ordered the torque clamps but come to find out the leak was at the thermostat itself. My assumption is that the O ring (4 months old) was not properly sealing the connection. Anyone seen this before? Have to order new O ring. Powersports takes too long coz they have to order from Honda first..who gets OEM parts pronto?
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I'm thinking you need an new thermostat. It's a known issue. A few years ago I ordered a dozen aftermarket thermostats from California and they were all taken by local ST owners within 2 weeks. I think I cleaned out the store of all stock and word was they weren't going to stock them anymore. I just found the information and the order was in 2008 and I delt with Garry at Turbo City. I check the website and I couldn't find any mention of Thermostats. But that's been a while so maybe someone else may knows the current intel.

Good luck and Happy New Year.
 
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Thanks cpsseals. I changed the thermostat 1000 miles or so ago and it's fine. I will bench test it all the same. Pretty sure it's the ring but didn't know there're two types out there.
 
cpsseals said:
I'm thinking you need an new thermostat.
Click to expand...

There are no thermostat failures that would cause the housing to leak. Failed closed and the system is in bypass (and the engine overheats), failed open and it runs cold.

--Mark
 
Hi, I have the same problem (leak at thermostat) on my 2005 st1300..........will order a new thermostat and o ring from Partzilla....never heard of that site before...thanks for your (link) comments here..............a buddy who's a good mechanic did most of the work.......it is quite a job just removing the plastic...........also, saw Partzilla has 2 o rings to choose from depending on the bike's serial number...........

Mark









bjalphasud said:
Decided to order a new O ring and turns out Powersportsplus has 2 different O rings depending on the Engine Serial Number of your ST. The one I previously purchased was for the 'wrong' engine serial so now I got the right one. Still have the old one so I'll compare and see what the difference is (are).

http://www.partzilla.com/parts/search/Honda/Motorcycle/2005/ST1300A+A/WATER+PIPE/parts.html
Click to expand...
 
If you take a close look at the second picture you will see coolant leaking from the hose near the top. It's hard to see but the hose on the right might be leaking in the same spot. I doubt it is the O-ring.
 
Interesting. I don't remember seeing that last time I ordered a thermostat combo, but I ordered it from another online supplier.
 
It's a common O ring available from any good industrial supplier. No waiting.

At 22,000 miles I replaced the original thermostat and O ring. This O ring eventually leaked and I found this out at a major service at 86,000 miles. I replaced the OEM one with one about .5 mm thicker because that is what size was closest when i walked into said rubber and gasket distributor because I did not want to wait for an OEM one. It fits snugly in the housing recess and causes the housing retaining screws to take up earlier when compressing the O ring. The replacement OEM thermostat has been fine close to 95,000 miles. It was just a bad batch of them that we're installed in new bikes at that time. I think replacement Honda stats have been OK.
 
I replaced my O ring for the second time this past summer. You could see it was leaking from the housing and not from a hose. The leak would quit after the bike would warm up and the thermostat would open up. The first one was replaced when I replaced the thermostat as it was stuck open. I just started the bike after it sat in 30 degree temps and it was leaking coolant. Need to remove the bodywork and see where it is coming from now.
 
I know of two critical areas where you must use a torque wrench to have a 90% chance of no leaking. The thermostat housing and the valve covers. When I replaced my thermostat at 17K (stuck open) I didn't "bother" to torque it down. It started leaking around 30K. The O-ring was replaced but it continued to "drip". I replaced the housing and no more issues. Same with the valve covers, when I used the correct torque, no leaks. when I didn't (first time) leaks...:eek:4:

Make sure you use the correct value when you are torqueing them down.
 
Bout the only thing I could add is make sure the o-ring and the seat on both sides are squeaky clean.
Little dielectric grease film on the o-ring might help it seat?
 
thanks everyone for your input..........I'm ordering parts tonight and maybe in a week or so we'll have the thermostat and o ring changed. We will be sure to follow the torque specs for the thermostat cover....have a great weekend.......oh, by the way I'm an NHL hockey fan (Devils!!) and the shortened season starts Saturday :).....
 
I'm ready to order the o ring and I'm finding out there are 2 choices, depending on the engine serial number.......where can I find that???...appreciate any help...thought it was the number on the plate (JCxxxx) on the front frame....maybe I should just order both....they aren't expensive.....thanks
 
The engine SN is stamped on a machined spot on the right side of the engine block just behind the water pump cover and ahead of the #2 cylinder exhaust header. The best part is you don't have to remove the fairing or cowling to see it. Take a flashlight and peer between the lower front corner of the RH valve cover and the fairing and you can see it stamped on a ledge that sticks out about an inch from the block. You might have to take your fingers and pull the fairing out a bit to see better.
 
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Byron, I think you're right- the hose on the left in the picture does show a possible leak history. I tightened the clump. Thanks to Honda assemblers- you can tighten the interior clamps right through the thermostat housing with a long screw driver since the heads face the outside.

DDuelin-where did you get the thicker O-ring- Lowes or Home Depot type store?

Als0- just got the 'right' O-ring shipped and I compared it to the other one I had for different series of engine serial numbers. They look exactly identical. Go figure.
 
Looked around for a thicker O-ring and finally found one at a local hardware store. Used to an ACE store. Put it on and ran the engine for about 30 min. Will check in the morning and the next couple days to see if that fixed it.
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DeJa Vu.................almost a year later and the same problem is back...........a leak at the thermostat cover...........last year I replaced the o-ring.....torqued the cover to spec......any suggestions??.........are there other options (different o-ring or gasket, some type of sealant (form-a-gasket)...............thanks for any input..
 
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