91 ST1100 coolant hose change tips???

I appear to have blown a coolant hose the other day. I had just passed a few vehicles and was going about 90. When I slowed down, I suddenly had steam trailing me. When I got home (only a few miles), there was steam rolling out from under the fairing and seat. The obvious conclusion is that I blew a coolant hose. I will be taking the plastic off tomorrow to verify that is the problem and change the hoses. Are there any tips, advice, etc. for doing this? Can I find the right size hose at NAPA, and what kind of antifreeze should I put in (I assume it's an aluminum radiator, right)? Is there anything else I should be aware of?

Thanks,
Tom

I've read a few threads on replacing radiator hoses on the st1100.org site.
Jamie Z has a thread over there called 'the big job' (i think). He has done a through R&R and describes replacing the radiator hoses in detail.

You might go over and read about what he did and send him a PM (he's a member here too).

Mark

I replaced the coolant hoses on my 98 this winter. The 2 main hoses that run from the thermostat housing to hte heads are pre-shaped and I doubt you'd get one from NAPA to bend that way - unless you knew someone there and they let you behind the counter to play match-up all day - and then *if* you can't match one, you end up having to order them from Honda anyway. I took the safe route and ordered all my parts from Zanotti Motors (best prices I could find).

While you are changing the hoses, you should go ahead and change all the cooling system parts while you are in there. Also it'd be a good idea to go ahead and remove the PAIR system too. Also, go ahead and replace the carb boots (carb isolators) as well - they get old and hard and make putting the carbs back on a BEAR. The new ones are soft and putting the carbs back on is MUCH easier with new boots and a light smear of vasoline on the inside lip of them.

Easiest coolant to use is the Honda HP coolant. Already mixed 50/50 and comes in 1-liter bottles. Buy 3 and pour them in - no fuss. http://www.wingworx.com/browseproducts/Pro-Honda-HP-Coolant-Premix.html

Here is the parts list I worked from but my 98 was a *little* different because I don't have the oil cooler.

http://home.insightbb.com/~mmartin36/Hose.htm

Here are all the links I saved while scouring the forums for info before diving into this project....

http://inturace.com/shopsite_sc/store/html/product7.html
http://inturace.com/shopsite_sc/store/html/page19.html
http://koczarski.com/Motorcycles/ST1100/Carbs&Cooling/CarbsCooling.htm
http://koczarski.com/Motorcycles/ST1100/PAIRremoval/PAIR.htm
http://community.webshots.com/album/56797755XfYwTD
http://community.webshots.com/album/111247119dEOHDD

If you need anything else, let me know - this is still fairly fresh in my mind.

Mark said:

Jamie Z has a thread over there called 'the big job' (i think). He has done a through R&R and describes replacing the radiator hoses in detail.

Click to expand...

Here I am. Kinda freaky to read your name in a thread you've never seen before.

Yes, I've got a (very long) continuing thread over on my-mc detailing my extensive maintenance and upgrade job on my own '91. I feel it would be a stretch to say that I described the hose replacement "in detail." Rather, the links given by #9 are what I used, and describe the procedure very well. All I did was upload a couple of pics of my finished work.

I used all Honda hoses, except for the right side hose under the carbs. The Honda part was on backorder at the time, and since it's just a simple 90-degree bend, I got a thicker equivalent from the Napa bulk hose roll. While there, I also found a pretty good match for the left side, but I ended up not using it and used the Honda part instead.

Be sure to get the O-rings you'll need also. Heck, I even have a bunch of left over "bulk hose" if you need a length. PM me your address.

You'll need to remove the carburetors, which seemed intimidating, even to me, but it turns out to be a fairly simple job. Oh.. as long as you're pulling the carbs, probably a good idea to replace the four carb boots, too. They'll get hard and brittle after a while and you'll reduce the risk of vacuum leaks by putting new ones in.

Really, all you need is the links given by #9, a space to work, a couple days labor, and a couple hundred bucks. You'll be back on the road and good to go for another 15 years.

Jamie

I tore the plastic off and let it idle to find the leak. There is no obvious leak, but I found a wet spot under the left side head toward the back. There is enough liquid so I can watch it drip, but I don't think it's enough to account for all of the steam I was seeing. Anyway, it appears that the leak is somewhere in the back of the engine, but since it butts up against the frame, I can't see exactly where it's leaking. I'm kind of stumped on how to proceed at this point since I can't see much less reach any leaks back there.

Tom

TomInOregon said:

Anyway, it appears that the leak is somewhere in the back of the engine, but since it butts up against the frame, I can't see exactly where it's leaking. I'm kind of stumped on how to proceed at this point since I can't see much less reach any leaks back there.

Click to expand...

There aren't any coolant lines on the back of the engine. The most rearward are the two hoses which come from the thermostat housing under the carburetors and go into the heads. I strongly suspect that's where the leak is. In my reading about the ST1100, more than a few people have had their under-carb coolant hoses blow. Lots of people (me included) change out the hoses even before something bad happens.

I think what has happened is one of the under-carb hoses has split or otherwise developped a leak. The coolant drips down on the top of the engine and flows backward until you can see it. Even a small leak can cause lots of steam. When the engine is hot, the cooling system is under pressure. Just a small leak can compromise that pressure, which allows the liquid to boil, and water vapor can escape a small leak much faster than liquid water.

If you've got the plastic off, removing the carbs really isn't a big deal. It's a major bonus if another ST owner near you can drop by for some advice. That's what I did, and after the guy showed me how to do it, I almost felt silly that I'd asked for his help, but it was very helpful.

Do you have a shop manual of some sort? Many people don't like the Haynes, but I like it for it's down-to-earth style suited for non-professionals. My Honda manual is thorough, but I'm often left wondering how to go about procedures. The Haynes does a good job of explaining how to remove stuff. I've not had any experience with the Clymer, but many recommend it.

As long as the plastic is off, removing the carbs is about a 1 to 2 hour job for someone who hasn't done it. Take out the fuel tank (four bolts and 4 wires), remove the air cleaner housing (six bolts and a fuel line), and you'll be staring at the carbs. to get them out is only a couple of cables and four screw clamps.

With the carbs off, you can look directly at the coolant hoses which have most likely failed. Those links provided by #9 will give you all the part numbers you need to do a full coolant system R&R.

Jamie

I figured a picture would be more useful than all that blabber:



This is after I replace my lines (and took out the PAIR system). The hose which has failed is one of the two large black or red hose (the red hose is a Napa non-Honda part).

The four stuffed holes are the intakes where the carbs attach with only hose clamps. Easy to remove, unless your boots are old and stiff.

Jamie

Jamie, thanks. The pictures are a big help. I had about given up on getting to those hoses. I removed the airbox, but still couldn't see where they go. Now that I know what's there, it's not as intimidating. I'll try removing the carbs and see what I can see. Removing the carbs shouldn't do anything to mess with the synchronization, right? I don't see how it would, but just checking before tearing in.

Thanks,
Tom

Tom - the carbs can be a bit finnicky, so its probably a good idea to re-synch them after you get them back in....it wouldn't need much adjustment, but sometimes that 1/2 turn is what gets you into the sweet spot.

Good tips there, guys. I've gotten the carburetors off now (nearly broke a shovel handle prying them up) and finally pulled off the 2 big coolant hoses going into the block. One has expanded to twice its' normal size and has a deep split in it which doesn't quite go through. The other is really spongy and loose and was seeping coolant when I wiggled it. I am going to try to find replacement hoses at NAPA today along with a thermostat. Is there any tips for putting the carburetors back on? As much force as I had to use to get them off, I am worried about getting them back on.

Thanks,
Tom

If the plastic/rubber boots are really dry you might want to replace them...
Silicone spray will make the carbs slip in a little bit easier (well that is the theory anyway! ).

Mark

Mark said:

If the plastic/rubber boots are really dry you might want to replace them...
Silicone spray will make the carbs slip in a little bit easier (well that is the theory anyway! ).

Mark

Click to expand...

Do I need to get them from Honda, or can I just use some Heater hose with the same Inner Diameter?

Using a substitute for the Honda carb boots?
There are a lot of *thrifty* people who have replaced the boots and I have never heard of anyone using anything but the Honda carb boots as replacements. Doesn't mean it can't be done; but, you might be back in there working on them when you could be riding if they fail...

Mark

Ick! I live ~45 miles away from the closest Honda Dealer, so I was hoping to save a trip. I'm working on a limited time budget. I'm doing all of this in my yard since I don't have a garage and I suspect it will rain some time today.

Tom

OOPS! I didn't note which hose goes to which port on the thermostat housing. I think the left side hose (the longer one and the black one in the above photo) goes on the top port and the right side hose (the shorter one and the red one in the above photo) goes to the lower port. I don't think it realistically matters, but I'd like to keep it the way it came from the factory. Can anyone verify this before I get the carbs back on (or cuss up a mean streak trying)?

Tom

FYI, I just got a 2 foot length of NAPA 19.0MM (7/8 inch) heater hose and it works for both hoses without kinking. It's slightly thicker than the OEM hose, too.

Is there any tips for putting the carburetors back on? As much force as I had to use to get them off, I am worried about getting them back on.

Click to expand...

New carb boots are the key (about $6 each) - they are soft where the ones on your bike will be old and hardened. Even with new boots you need some heat and lube. Sit the new boots in front of a heater or get them warm with a heat gun, then smear some vasaline around the tops and just a bit inside - smear it, don't goop it. Tighen down the lower clamps first, then put on the upper clamps as loose as they will go without the nuts falling off. Sit the carbs down on the boots and push them on - into the boots. I found that getting the fronts started a little helps - kinda the reverse they came out when you popped them out with the shovel handle. You can look around at all the boots and confirm the carbs are starting into them good as you go. A long T-handle 4mm ball-end allen wrench makes tightening the clamps mush easier.

I managed to get them back on with a bit of effort. What ended up working for me was to seat the right side carbs first, then push the carbs to the right to get them lined up with the left side boots. I then took a long breaker bar and placed it across the whole assembly and pressed the whole thing down. It took me 20 minutes to figure out this technique, but it went in easily. Oh yeah, I used Silicone spray as well. I started it up and initially, a few of the cylinders weren't firing, but it settled down and is running fine now. I still need to adjust the throttle cables (the return isn't pulling the throttle closed when I let off of the throttle) and I have a massive leak around the thermostat housing, but it runs and the hoses appear to be leak-free. I will hopefully finish up tomorrow when my wife can work on the thermostat housing (her smaller hands and infinite patience should do the trick there).

Tom

When you replace the hoses the T-stat housing needs to be removed and the hose knecks cleaned really well as they will have corrosion build up on them (atleast my '98 did with 18,000 miles) which doesn't provide the best chance at getting a good seal. You should replace the T-stat when you do the hoses anyway so you'd have the housing already off. Did you clean the knecks off? If you had to force & fight the hoses back on the kneck, you could have possibly cracked it.

The T-stat housing wasn't badly corroded. There was a small amount of corrosion on the outer edge (outside the O-ring) that cleaned off pretty easily. I can see that the bottom portion of the housing isn't seated properly and that is where the leak is coming from. I suspect the thermostat slipped down and is preventing the 2 halves from mating together properly.

Tom

It's hard to tell at this point, but it looks like my wife got the T-stat housing to stop leaking. Now the problem is a leak where the lower hose goes onto the T-stat housing. It is leaking where the hose goes on. I have just about given up. I will most likely have to pull the carbs yet again. I don't really have the will to do it either, since I've already replaced the hose. The only thing I know to do with a leaking hose is to replace it. I've done that and tightened it as much as possible and it still leaks. I have little patience for crappy design and this was designed to give as little access as possible for working on it. The bike itself is great as long as it runs, but normal wear items are inaccessible. Looks like I'll miss my trip to California this week. Sorry for venting, but it's frustrating when it's something as simple as a damn hose. Cooling systems suck!

Tom