Coolant Leak right in the middle of my ST1100

Winfried

Winfried

Joined
Jan 15, 2016
Messages
75
Location
Moorpark, CA
Bike
2002 Honda ST1100
My 2002 ST1100. While riding I felt my left leg was feeling more heat then normal. Decided it was time to flush and replace the coolant and the thermostat while I was add it. After flushing and replacing the coolant I found coolant coming out right in the middle, like where my center stand is. It is not easy to see what is leaking where as you can imagine.

So what and how do I have to remove to find and fix or replace what is leaking? I saw on YouTube
where he removed the fuel tank and carburetors just to be able to get to see what was what. Anybody has better instructions? He is working on a 1998 ST1100 and the overflow container is at a different location then the 2002.
 
I think the overflow container location varies between the ABS2 and non-ABS versions, not necessarily the model year.

Regarding the coolant hoses. You need to remove the carbs as you stated. To make that easier it makes sense to remove the fuel tank to the rear of the engine so you can pry the carbs up and out of their boots after loosening the carb boot screws. Folks have used something like a wooden broom handle to do the prying, using the frame crossmember for leverage.

You can keep the throttle cables attached and just swing the carbs to the side, but you'll need to remove the choke cable. When I did mine I also ended up mangling the hose that attaches to the front of the carbs because it was really stuck onto its fitting, so be careful with that hose or else have a new one on hand.

For parts you'll need two hoses, two elbows, two O-rings for the elbows, four carb boots, and the bulk hose that runs from the "water pipe" to the T-stat housing. You'll find all the parts here, but shop a few different sites to check the prices. The O-ring inside the water pipe housing is a judgement call, some replace it, some don't because getting access is a bit tricky.

Honda Motorcycle 1997 OEM Parts Diagram for Water Pipe | Partzilla.com

Buy OEM Parts for Honda Motorcycle 1997 Water Pipe Diagram
www.partzilla.com www.partzilla.com
 
The video is good. I did the same two years ago this month and posted a short tale with photos and highlighted what I found. Search on '1991 ST1100 refurbishment'. There are LOTS of fasteners. I put them in ziplock baggies by assembly and labeled with a marker and kept everything organized by assembly. I also made frequent use of the Honda manual and part breakdowns on line (Partzilla, Revzilla, and such).
Replaced ALL the water hoses, fuel hoses, vacuum hoses and inspected for other surprises while was at it. At some point in a bike's lifetime, this is necessary.....doesn't make much sense to me to tear into a bike, replace a leaky hose, reassemble, repeat.
 
When I did this in 2012 on my 2002 ST I also used labeled baggies to keep the parts / fasteners organized + I took a lot of photos during the disassembly.

In my case the carbs came off easy and gas tank removal was not necessary. I disconnected all carb cables, it only take an extra minute or so to do this, just to get the whole assembly out of the way.

Be especially careful to cover the 4 inlet manifolds as soon as you can as you don't want anything dropping in there.
 
I had this same thing happen to my 1998 ST1100 within a week after buying it from a Suzuki dealer. Coolant was dripping down the rear side of the engine. I took it back to them to fix since it was less than a month after purchase and they didn't know how to find the problem. I did a little online searching and took a picture of the top of the engine "V" area and pointed out the evidence of the leak by looking through the inspection hole on the left side with a flashlight. The leak was due to degraded O rings at the elbows where the coolant hoses enter the block in the V. Turns out that is a common issue after time. Only one was leaking but they replaced both while in there.

Unfortunately I didn't do that work so can't help with the disassembly or assembly there.
 
It's a task that I have had to do on two of my st1100's. I removed the Pair system while in there and am not really sure there is a benefit to removing this other than the rubber hoses are gone along with the small chrome pipes. There are also a couple of good videos on the other St forum St-riders. I think they are listed as carb removal and pair removal.

I did take a full set of photos from start to finish, on my bike, so when I put it all back together, I just played the photos in reverse.

The big hose split on my 97 st1100 and I replaced everything and hope it's another 100K miles before going back in.
 

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I had this issue on my 01 1100 shortly after I got it (private party). At the time it had 41k miles. One of the large hoses in the V of the engine split on the way home from work. I replaced all the hoses and o-rings under there as I wanted to only have to do it once. Removing the carbs wasn't easy and I ended up using a long screwdriver to gently leverage them off. I also replaced the carb boots. You may want to consider that as they may be difficult to get going forward. IIRC I didn't have to remove the fuel tank.
 
Well worth the couple extra minutes to pull the fuel tank to remove the carbs. Easy job. Just make sure it doesn't have a lot of gas in it. 60 pound vs. a whole lot less to lift.
 
So much wrong with the YT video…. wonder if after he reversed the #1 boot clamp the throttle didn’t hang up on it… I doubt he had a service manual. Certainly wasn’t on an Internet forum.

You don’t need to remove the tank but it’s worth it, if just to inspect and clean. I found a long term oil seep from the pulse generator my first time. As mentioned, to just access the area under the carbs the carbs don’t have to be separated, nor the throttle and choke cables detached/removed… just release the idle adjust cable from the rubber gas splash surround if the tank’s still in, place a towel on the left frame rail, pry the carbs up and swing them over onto the towel. BTDT

Coolant Hoses and Timing Belt R&R

Coolant Hoses & Timing Belt ( ST1100 ) *

Coolant Hoses & Timing Belt ( ST1100 ) *
www.st-riders.net

John
 
Replace the cylinder head elbows for good measure: JOINT, WATER 19523-MT3-000 [item 8 or 10 on the fiche, depending on the site]
 
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I'm glad for all the responses. I figured I was doing a flush and replacing the thermostat. At first I didn't think much of leakage as it was happening while filling the radiator so I assumed I was being messy. But when I watched the video again, I went back to see about burping air out. After trying to fill radiator up, and the more I filled, the more ended on the garage floor. That's when I woke up to see what was really happening.

Anyway, after getting all your advice, I'm going to do a full job including removing the tank as it only has about a gallon in it. But I'm doing it over a couple of weekends. My garage is so full so I'm going to have to leave my 2006 VTX1800C2 in the driveway under its motorcycle cover for awhile so I can have room to work.
 
John OoSTerhuis said:
So much wrong with the YT video…. wonder if after he reversed the #1 boot clamp the throttle didn’t hang up on it… I doubt he had a service manual. Certainly wasn’t on an Internet forum.

You don’t need to remove the tank but it’s worth it, if just to inspect and clean. I found a long term oil seep from the pulse generator my first time. As mentioned, to just access the area under the carbs the carbs don’t have to be separated, nor the throttle and choke cables detached/removed… just release the idle adjust cable from the rubber gas splash surround if the tank’s still in, place a towel on the left frame rail, pry the carbs up and swing them over onto the towel. BTDT

Coolant Hoses and Timing Belt R&R

Coolant Hoses & Timing Belt ( ST1100 ) *

Coolant Hoses & Timing Belt ( ST1100 ) *
www.st-riders.net

John
Click to expand...
That single boot clamp is the most frequently found loose. I'm suspecting the location error was discovered after carb reinstallation. Rather than remove the carbs again and do a proper install, it just gets moved out of the way, hoping the joint won't leak.
 
dwalby said:
The O-ring inside the water pipe housing is a judgement call, some replace it, some don't because getting access is a bit tricky.
Click to expand...

I did two bikes and neither presented a problem with this part, so I'd personally include it. There is a trick with loosening a bolt on the front of the engine that make space needed to get in there, but I forgot the details. It's noted in the how-to articles. I'd also replace the carb insulators if they are old as pointed out.
I would suggest you buy the parts before tearing into it unless you just can't use it as is. Some of them were hard to find last year when I did the job last. Maybe supply chains have recovered, I don't know. I found eBay and CMSNL are good options if you can't get parts from the usual sources.
 
What parts, such as hoses, etc. should I order and what are the part numbers and who is carrying the parts?
 
I went on Partzilla and it doesn't show all the hoses, it goes by part number. Do I have to take the hoses out to find the hose to fit online? I saw in the responses to replace all the hoses since I am in there now, but how do I find the right hoses online? Or do I have to go to the Honda dealer's parts department to get the part numbers?
 
Winfried said:
Okay, finally I got to see the diagram on Partzilla, https://www.partzilla.com/catalog/honda/motorcycle/2002/st1100-a/water-pipe
Let me know which parts on this diagram I should order, and anything else I might need.
Click to expand...
that question has already been answered.
dwalby said:
For parts you'll need two hoses, two elbows, two O-rings for the elbows, four carb boots, and the bulk hose that runs from the "water pipe" to the T-stat housing. You'll find all the parts here, but shop a few different sites to check the prices. The O-ring inside the water pipe housing is a judgement call, some replace it, some don't because getting access is a bit tricky.
Click to expand...
the carb boots are on the cylinder head fiche, they're called "insulators" rather than boots
 
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