Anti-Freeze leak

PmodelinUS

PmodelinUS

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Joined
Jul 22, 2021
Messages
272
Age
56
Location
Gages Lakes, IL
Bike
1993 Honda ST1100
2024 Miles
000200
I am trying to track down an antifreeze leak and I'm hoping someone can at least give me an idea of where to look or a likely culprit. I got a 93 ST 1100 about a year ago with just under 55k. I have been chasing an occasional antifreeze leak. Yesterday as I was getting ready for a ride it it started to leak more then just a wiff or small drip. I have antifreeze dripping down the back of the motor. Looks to be located more on the right side. Only leaks when bike is running so assuming its not a gasket. So before I go tearing everything off any suggestions would be nice. Thanks.
 
The hose clamps that fasten the hoses that go to the rear of the cylinder heads, under the carbs, have been one source of those types of leak, but it is usually only seen when the bike has been sitting in a cold environment, where the hoses shrink to a degree and allow some seepage past the clamps.

If those hoses are still original, they may be leaking under pressure if their inner structure has been compromised and creating a leak through the threads that reinforce the hose internally.
 
Assuming no holes in the hoses, there are something like six potential spots for leaks furthest rear and they are all fairly inaccessible if you don't take things apart. I agree with Bush, if you think the hoses are on the old side, it's not going to get any better. I have seen threads where guys have been able to get in and tighten up a clamp that solved things, but that seems iffy. If you look at a parts diagram, you can see how many parts are involved: http://www.adeptpowersports.com/oem-parts/1993-honda-st1100-water-pipe-assembly.html
And actually, maybe it's more than six potential spots to leak. I'm not familiar with the coolant lines that run to the oil filter on the older bikes.
 
Take the fuel tank out for a better view of the under carb. hose fasteners. Don't forget to disconnect a connector on the left side of the tank that's easily missed.
 
Just to give you a bit more motivation, the hoses under the carbs that are being discussed will typically fail by bursting along the length of the hose and dump all your coolant at once, leaving you stranded on the side of the road. If you're lucky and they're just leaking a little bit now, then you got a better advance warning than most. Those are the typical source of coolant leaks to the rear of the engine, so that's the first place to start looking.

There's a standard list of things to replace while in there:

- the two hoses
- the two metal elbows the hoses attach to (they get brittle and need to be replaced) and their O-rings (there will be a rubbery goo in there now)
- the 4 carb boots
 
Would this be the hose leaking antifreeze?
 

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Ummmmm . . . I don't even recognize that hose, but it isn't either of the two that we are talking about.
 
Did the '93 have the PAIR system? Maybe that's why it looks foreign to me. Never had PAIR myself.
 
PmodelinUS said:
Would this be the hose leaking antifreeze?
Click to expand...
no, the ones we're talking about go from the inside part of the cylinder head forward and up to the T-stat housing, which is on the upper right side of the engine compartment.Capture.JPG
 
PmodelinUS said:
Would this be the hose leaking antifreeze?
Click to expand...


Your photo is of the underside of the carbs. There arn't any coolant hoses there .You have to dig deeper ! The hoses and "elbows" you want to change are under that rubber matt -under the carbs. You have to take the carbs off , I didn't take the gas tank out , and was OK. The hoses with tape (1+2) have flimsy "elbows"(2) were they connect to the heads. You must change them also. A photo of mine - It didn't leak yet ,but you can see one is getting a little green . There is one more small dia hose there too , the one that runs paralel to hose 1. it goes to the thermostat house -change that also.
DSC_0243.JPG
 
dwalby said:
no, the ones we're talking about go from the inside part of the cylinder head forward and up to the T-stat housing, which is on the upper right side of the engine compartment.View attachment 289434
Click to expand...
Thank you. So carbs need to come
JJames said:
Your photo is of the underside of the carbs. There arn't any coolant hoses there .You have to dig deeper ! The hoses and "elbows" you want to change are under that rubber matt -under the carbs. You have to take the carbs off , I didn't take the gas tank out , and was OK. The hoses with tape (1+2) have flimsy "elbows"(2) were they connect to the heads. You must change them also. A photo of mine - It didn't leak yet ,but you can see one is getting a little green . There is one more small dia hose there too , the one that runs paralel to hose 1. it goes to the thermostat house -change that also.
View attachment 289444
Click to expand...
 
Ok thanks for all the information so far. Next question? I have loosened the clamps securing the carbs to the cylinder head. I expect to have to tug a bit but that sucker ain't moving. What did I miss. Disconnected all the cables and hoses I'm supposed to? I used to work on my bikes years ago so keep it simple please. This pig is way different than any other bike I dealt with. And my dad was around then.
 
The carb boots tend to get hard with age. You can apply some heat with a hair dryer. Don't go overboard and set them on fire, just heat them to soften them a bit. Be careful with the carbs. When you put the new ones on, a tiny dab of silicone grease will make them slide on more easily.
 
PmodelinUS said:
Ok thanks for all the information so far. Next question? I have loosened the clamps securing the carbs to the cylinder head. I expect to have to tug a bit but that sucker ain't moving. What did I miss. Disconnected all the cables and hoses I'm supposed to? I used to work on my bikes years ago so keep it simple please. This pig is way different than any other bike I dealt with. And my dad was around then.
Click to expand...
Join the other ST forum...

http://www.st-riders.net/

Check the ST1100 archive of wisdom .. there is information to help you get your carb bank out and get it back in again.....
 
PmodelinUS said:
Ok thanks for all the information so far. Next question? I have loosened the clamps securing the carbs to the cylinder head. I expect to have to tug a bit but that sucker ain't moving. What did I miss. Disconnected all the cables and hoses I'm supposed to? I used to work on my bikes years ago so keep it simple please. This pig is way different than any other bike I dealt with. And my dad was around then.
Click to expand...

Use a wooden broom handle to gently pry between the frame on each side of the carb assembly, taking care not to be prying on any linkages. It will pop right off.
 
PmodelinUS said:
Ok thanks for all the information so far. Next question? I have loosened the clamps securing the carbs to the cylinder head. I expect to have to tug a bit but that sucker ain't moving. What did I miss. Disconnected all the cables and hoses I'm supposed to? I used to work on my bikes years ago so keep it simple please. This pig is way different than any other bike I dealt with. And my dad was around then.
Click to expand...
I have a long, flat crowbar that doubles as a carb remover. I cover the flat end with several layers of tape, duct tape or blue painter's tape, so it will not scratch anything. Insert between the frame side tubes and bottom end of the carbs and push gently. Once carbs begin to pop out, move to the other side of the bike and repeat. The carbs will pop out of the boots. Consider replacing all the hoses under there, including the carb boots. If thy are still pliable and there are no cracks, you can likely get some more miles out of them.
 
For the record, the hardest part of this operation with hose removal and replacement isn’t the hoses or the elbows. It is the carb boots. As others have said, get new ones before you put the carbs back on - the carb replacement can be quite frustrating to line them up properly. Use a little silicone spray or silicone grease to get them to pop back in the boots. Also, when tightening the bolts for the metal elbows (get new ones if possible with new O-rings), the torque spec is quite low- those bolts will easily snap if you’re not careful.
 
Got the carbs off. Pretty easy with a broom stick. Thanks to everyone for your advice. I'd feel better if I had any clue what I was doing. Lol
 
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