Coolant leaking from front of engine, behind clutch cover

[millenium7]

Firstly could this just be overflow and too much coolant in radiator and overflow bottle? Doubtful but worth asking. Bike leaked some coolant before I stripped it down to carbs but then stopped. Coolant was not up to the rad cap so I topped that off

I've ran the bike in the garage for 5-10 minutes syncing carbs and noticed a pool of coolant, running the engine it's quite a fast leak. Looks to be coming behind the front cover on the engine where the clutch slave mounts to. What are the likely candidates? And what's involved?

 

[Oldbikefixr]

Likely the water pump needs some attention if there's not a split hose. While you have the bike down for the carb sync, inspect ALL the hoses underneath them especially those under the rubber heat blanket, your upper radiator hose, cap and seal, and the long overflow tube that runs from the thermostat housing back to the overflow tank. Check your fuel and vent tubes as well.

 

[millenium7]

Bugger, just want this thing assembled
So the water pump requires removing the timing belt right?

And I see a lot of mention on forums about replacing the entire pump. Bugger that if I can get away with it. It looks like just a rubber o-ring gasket. Surely just that can be replaced if it otherwise feels smooth

 

[Erdoc48]

Before you get too involved with this, follow the steps above- the hoses can split depending on the mileage your bike has and can start leaking. Go from least to most complicated and if it is the WP, you’re taking the carb bank off anyway, so you can better inspect the hoses, O rings, and metal elbows under the carbs and under the rubber sheet. If it is the WP, you’re in there anyway, so you could swap that out with the timing belt (I would not get that far in and not swap out the belt)- if the WP is not an issue and it’s smooth in operation, swap out the hoses, O rings and elbows while you’re in there, do the timing belt (now you’d have full access), put it all together, and ride on. How many miles on your ST? It is time consuming no doubt, but can be done in a pretty straightforward fashion (I have some limited mechanical skills and I’ve done this work minus the WP swap twice so far, so if I can do this, anyone can).

 

[ST1100Y]

A "fast leak" in that area seems like #13 ...

TUBE 5.5X380MM, P/N 950055538020

Internal bypass, sitting way front, directly behind the t/belt housing, connecting the chrome pipe to the t/stat housing...
often overlooked/neglected, no airflow there, rubber drying out, turning brittle...

Issues at the internal passages (#1, #3, #8/11) cause seepage at the aft of the engine, below alternator/main-stand shaft...

Anyway, carbs off, rubber mat out, inspect all and everything...
Only if that all is cleared I'd focus on the w/pump...

 

[millenium7]

Hmm alright i'll give it a look, i'm suspecting its the water pump seal due to the location of the leak but i'll not jump to conclusions yet. It's not too difficult to pull the carbs again, but I obviously can't run the engine without them and see it actually leaking

Assuming its not the water pump, are all hoses and o-rings readily available? and is there a kit or just have to order individual honda part numbers?
I'm getting very over working on this bike, its supposed to be a cheap buy that I use occasionally, so far its sucked so much of my time and gone beyond well cheap, should have bought a different one. Can't work out if the PO was just incompetent or a very good scammer with the amount of shoddy work i've seen once the curtain was pulled back

 

[Sunday Rider]

You have it now, don’t look back. Once you get it sorted it will be easy and cheap to maintain. A great group here to help you out when needed. You’ve got the right bike and you’ve come to the right place. It’s too bad you are getting into it sooner than later.

 

[millenium7]

You guys have been fantastic and I can see that from trawling threads over the past few weeks. It's just disheartening buying a 'known reliable' bike that had no apparent issues on first inspection/ride other than a few simple tune up and tweak jobs, and then it all goes to ***** very fast and requires a tonne of labor to bring it up to scratch. Only so much that could be inspected when all the fairings are on
I've had 2 rides on it and it's turned into an unrideable project bike

Especially this job which looks like an enormous PITA if it is the water pump. I dont have time this morning but I started it again and within 60 seconds it leaks a lot of coolant, it's cold so it's not a passage that relies on the thermostat opening (unless it's locked open)
Bike is on its centre stand and coolant dripping on both sides of the timing belt cover where it meets the clutch housing, nothing in the rear of the engine

Is it still possible to be anything other than the water pump? I'm so much not looking forward to the labor involved let alone the prospect of throwing $500+ more at the bike that I am strongly considering just cutting my losses and listing it as a parts bike. It's been nothing but a kick in the nuts so far.

 

[millenium7]

Well I grit my teeth and got into it
Under the carbs is clean, actually surprisingly decent condition for the most part. Can see hose #13 has already been replaced with something different, but its not leaking from there

I tore into the front of the engine and yep its an absolute mess of coolant behind the covers, loosened off the tensioner and removed the belt and I can feel some small amount of play in the water pump so it is definitely toast
I attempted to remove the water pump housing to inspect anyway, but how the heck do you actually get it out? I can manage to slide it out halfway at the bottom, but the bikes frame is in the way, there's just no clearance to fully slide it out. I can't see how to go any further?

 

[ST1100Y]

I attempted to remove the water pump housing to inspect anyway, but how the heck do you actually get it out? I can manage to slide it out halfway at the bottom, but the bikes frame is in the way, there's just no clearance to fully slide it out.

Remove LHS cam pulley and housing (new paper gasket required though...)

depending on skill level and/or motivation:

HONDA ST1100/A PAN EUROPEAN WATER PUMP SEAL AND BEARING KIT 90-02 B103:F952 | eBay

HONDA ST1100/A PAN EUROPEAN WATER PUMP SEAL AND BEARING KIT 90-02 B103:F952 | Vehicle Parts & Accessories, Motorcycle & Scooter Parts & Accessories, Engine Cooling | eBay!

www.ebay.ie

 

[Erdoc48]

OK, I have a potentially stupid question here- when a WP fails, is it just typically the bearing that fails (assuming the impeller is still in decent shape) and just swapping the parts (the seal and bearing kit) basically renews the pump? Change those parts and a new gasket and you’re good to go?

 

[dwalby]

OK, I have a potentially stupid question here- when a WP fails, is it just typically the bearing that fails (assuming the impeller is still in decent shape) and just swapping the parts (the seal and bearing kit) basically renews the pump? Change those parts and a new gasket and you’re good to go?

There were a few reports here of people doing a rebuild rather than buying a new pump, so it is an option. I seem to recall it requires significant force to remove the bearing, and cracking the housing in the process is a possibility, depending on how you have it braced. I think Jim Van might have been the first to do it, but he doesn't post very often these days. Martin's post contains one source for the replacement parts, and I think there was a post here a few years ago on how to do the parts swap, maybe a search might find it.

 

[Uncle Phil]

One thing is for sure - when the water pump fails at speed, you can kiss the engine goodbye - BTDTGTS!
So unless you have a lot of confidence in your rebuilding abilities, I'd go with new if they can be had.

 

[millenium7]

Ok pulled the LHS rear housing off then got the water pump out. The bearing is quite rough so it definitely needs replacement

I now need to weigh up what I can do
I've rang all the wreckers yards and can't source a pump, I don't have a press so I would need an engineering shop to refit parts anyway, investigated this avenue and inclusive of labor it's getting around the $350ish mark which at that point it's not worthwhile as a new housing is $400-500 landed from webikes.net
Honda hasn't yet returned my call but I'm expecting $600ish

First question is what does the OEM part number include? All seals or just the housing? Essentially what other parts would I need?
What about the idler is that included or an extra part?

Is there a better/cheaper source of parts? This is in $AUD so prices would also have to include shipping to Australia which almost always rules out USA which likes to charge an arm and a dick for shipping here

Considering I should probably also be doing the timing belt and tensioner, and I already don't want to spend this much time or money on it (as who knows what else might go wrong) I'm very half-half between fix and scrap. If anyone has any miracles around this conundrum I'm all ears

 

[Erdoc48]

OK, I’ll ask…mileage (and year) of your ST, overall condition (was a near running basket case or actually pretty good condition ST with most other cosmetics and running gear intact). How bad did you want to get it back on the road and would you rather give it up for scrap (meaning you didn‘t pay too much for it and don’t want to put a lot of $$$ into it which we all understand) and get another bike? These are tough questions to ask, but it better helps with your decisions to fix it vs ‘quit while you’re ahead‘. Part number is 19200-MAJ-G20 and it looks like it’s been discontinued (I just checked for sites in the US that would have the part), so your only option would be to change the bearing and seal with one of the kits as higher up in the thread (and maybe have a machine shop carefully press the bearing in). It’s a tough call- might be a nice bike once all corrected or a royal PIA and something else goes south driving you nuts.

I did come across this in the UK (but a used part):

~~~ HONDA ST1100 PAN EUROPEAN WATER PUMP NR17 ~~~ | eBay

Find many great new & used options and get the best deals for ~~~ HONDA ST1100 PAN EUROPEAN WATER PUMP NR17 ~~~ at the best online prices at eBay! Free shipping for many products!

www.ebay.com

EDIT: I suspect the part above is for a post 95 ST- I think the other part number you specified is for the earlier bikes. I guess your only real choice if you choose to go ahead is change the bearing and seal of the pump.

 

[millenium7]

1995 approx 140,000km off the top of my head
Condition is good for the most part, but with some bodging. Ride fine just needed jetting put back to stock (had 130 mains and carbs needed a good clean), resync and then some adjustments and TLC. That's all I thought I had to do and ive done all that

Honda got back to me and said part number 19200-MY3-000 and 19200-MY3-010 are completely unattainable, as did webikes, so new isn't even an option that I can find

Of course id like it rideable but the intention with this was just to buy it as a cheap comfy road thing that was nothing like any bike I've owned, ride it for a few months and see how I go. Other bike is a KTM 990SMT, but I do like the comfort and ease of riding of the ST as a nice contrast to the insane arm wrenching brutality of the 990

 

[raygks]

1995 approx 140,000km off the top of my head

Honda got back to me and said part number 19200-MY3-000 and 19200-MY3-010 are completely unattainable, as did webikes, so new isn't even an option that I can find

Where I'm located, there's a bike shop that still has "NOS" water pump p/n: 19200-MAJ-G20, it's applicable for my 2000 Y model, not sure if it'll fit your model exactly without any minor mods.
I don't know if they'll do the overseas shipping, you can try contacting them on this portion.

https://www.carousell.sg/p/honda-st1100-water-pump-283773032/?t-id=5075226_1700635729337&t-referrer=%2Flikes%2F&t-referrer_page_type=like_page&t-tap_index=47

 

[ST1100Y]

Where I'm located, there's a bike shop that still has "NOS" water pump p/n: 19200-MAJ-G20, it's applicable for my 2000 Y model, not sure if it'll fit your model exactly without any minor mods.

Pre '96 ST's have an oil cooler, hence the 19200-MAJ-G20 won't do...

Financially a rebuild seems reasonable...
Tool-wise a drill-press and a heat-gun seem sufficient...

some reading:

Rebuilding the Water Pump ( ST1100 ) *

Rebuilding the Water Pump ( ST1100 ) *

www.st-riders.net

 

[John OoSTerhuis]

If your ST1100 has an oil cooler (donut fitting between the oil filter and engine case, with two coolant hoses connected to it), you can use the water pump for later models by capping the nipple on the Water Pipe, removing the cooler, and then replacing the short ‘pipe’ that the oil filter screws onto with the part the later models use (shorter… IIRC it’s called a ‘boss’**). FWIW

**edit: BOSS, OIL FILTER/90019-MB0-000 [#12, oil pump fiche]

Personally, I’d do that and get my ST running, then repair the old pump and sell it to some poor fellow STrider in need (or donate it as-is to a DIYer). Also FWIW

Good Luck, John

 

[John OoSTerhuis]

capping the nipple on the Water Pipe*

* PIPE, WATER/19510-MT3-000

Or replace with the later model years’: PIPE, WATER/19510-MAJ-G20 [#4, Water Pipe fiche]