Coolant leak around water pump cover?

Joined
Apr 8, 2011
Messages
58
Location
Plano, TX
Bike
2004 ST1300
STOC #
8598
In the last week I noticed a coolant trail at the bottom part of the water pump cover. It evaporates so no coolant on the driveway yet.

The area has been cleaned once to get a better idea of what's happening, however the gasket is getting dark again. The coolant at the bottom of the oil pan is heavy and slippery so is there potential oil mixed in? Before I remove tupperware and radiator, is there an idea of what I'm looking at?
 

Attachments

Joined
Aug 6, 2007
Messages
4,216
Age
49
Location
Grant, MN (aka Stillwater)
Bike
ST1100 & ST1300
STOC #
6145
The square hole is coolant coming from the V of the engine. One of the coolant lines up by the T-Stat, block, throttle body are is leaking.

How far can you ride before you have to top off?

I had a hole in one of the lines up there that goes from the right valve cover area to the T-Stat. The leak looked just like that but it was coming out really fast.
 
Joined
Jan 8, 2011
Messages
7,066
Location
Arizona
Bike
2007 Honda ST1300A
Loose clamps on the coolant hoses (waterpipes), and maybe an o-ring on the t-stat.
If your comfortable taking the plastic off, the radiator is held on by 3 small bolts.
Drain it, remove it, soak and flush it, replace a new T-stat while your there, and tighten all the hoseclamps.
Normally its just the two small hoses that come off the T-stat housing.
.02
 
OP
OP
nikonhonda
Joined
Apr 8, 2011
Messages
58
Location
Plano, TX
Bike
2004 ST1300
STOC #
8598
Sennister, when you say top off, do you mean the radiator itself or the overflow bottle? If the bottle, it is still at the upper mark when I changed the coolant out at 57,000 miles. The bike currently has 60,300 miles.

Igofar, taking the plastic and radiator off is no problem for me. I'm just a bit worried why the coolant has the feeling of oil mixed in.
 
Last edited:
Joined
Jan 8, 2011
Messages
7,066
Location
Arizona
Bike
2007 Honda ST1300A
Sennister, when you say top off, do you mean the radiator itself or the overflow bottle? If the bottle, it is still at the upper mark when I changed the coolant out at 57,000 miles. The bike currently has 60,300 miles.

Igofar, taking the plastic and radiator off is no problem for me. I'm just a bit worried why the coolant has the feeling of oil mixed in.
You'll have folks tell you its the mechanical water pump seal, road grime mixed with coolant that just looks like oil, etc.
My money is on the "mystery plug". Search my threads.
Very simple fix.
 
Joined
Aug 6, 2007
Messages
4,216
Age
49
Location
Grant, MN (aka Stillwater)
Bike
ST1100 & ST1300
STOC #
6145
Odds are you are fine as in there is no oil in it. If there was the bike wouldn't be running right at all. I was mainly talking about how much you are adding to the overflow bottle. Sounds like you rode 3K miles since the last work. Have you had to add any coolant? If not I find that a bit odd. It has to be coming from somewhere.

I know on the 1100 there is an issue where you can have a coolant leak on the hose that goes from the radiator overflow to the bottle. I guess it is possible that it is coming from that hose but it isn't common on the 1300. In the case of the 1100 as it heats up it pushes coolant out of the radiator where it leaks out. Then when it cools it should suck coolant back into the radiator from the overflow. However the crack in the line means it just sucks air so the level in the tank really doesn't change much. That is what happened to my 1100 and is very common on that bike.
 

dduelin

Tune my heart to sing Thy grace
Site Supporter
Joined
Feb 11, 2006
Messages
9,633
Location
Jacksonville
Bike
GL1800 R1200RT NC700
2024 Miles
006739
STOC #
6651
I strongly believe it is a simple coolant leak and is not oil.

A couple times in 7 years I found black oily mess in the same places many ST1300 owners find it, mainly in the vee between the cylinder heads under the thermostat housing, at the top front of the water pump cover, around the square and round weep holes, and running down and back the right side of the engine block. Both times I fixed the coolant leaks and the "oil leak" went away. I am talking about over 60,000 miles between "oil leaks". Not exactly a double blind test but good enough for me as empirically the oily black stuff strongly correlated to active coolant leaks.

When I removed the throttle bodies to access the alternator during its replacement 1,000 miles ago long dried oily black stuff was down in places I had been unable to access from the front and clean after fixing the prior hose clamp leaks. The top of the engine block between the cylinders is essentially flat with few raised areas, the galley plug being one, and liquid stuff can't run out and down the back of the engine because the alternator drive gear forms a dam with the cylinders and this gear drive forming three sides. Anything that spills or leaks out from the cylinder heads, coolant hoses, or engine block is contained in the vee with only the front open to draining. Now, to a reasonable inquiring mind if a engine started weeping, seeping, or leaking oil from the plug on top of the block it would continue to leak until fixed, thus the nature of oil leaks. However, I could not find any oily black stuff except what probably formed with the coolant leak that I fixed at 22,000 miles and the other leak discovered and fixed at 86,000 miles. 31,000 miles later when I was looking at the top of the engine with everything removed there was a layer of old dried oily black stuff on the flat upper surface of the block, but only where it had not been cleaned 31,000 miles prior because it was impossible to get to and clean and this includes the mystery plug and around it. If the source of the oily black stuff was an oil leak it would have continued leaking for over thirty thousand miles but obviously it did not as the stuff was dried like old oily surfaces get when caked with dust or dirt. To me, the link between coolant leaks and oily black stuff is even stronger after what I found during the alternator replacement. We know that minor leaks that make their presence known appear at first to be an oil leak. Countless threads start at this point...... It will be wet, black, and oily to the touch. It's because the water in the coolant evaporated leaving the glycol behind for road dirt and grime to stick to.
 
OP
OP
nikonhonda
Joined
Apr 8, 2011
Messages
58
Location
Plano, TX
Bike
2004 ST1300
STOC #
8598
Hello everyone, thanks for all the advice. As the weather is getting warmer the coolant trail has tapered off. I will keep monitering it and the overflow tank. When the time comes again to remove the plastic I will tackle the mystery location, mystery plug, replace T-stat, and tighten the clamps. Too bad this didn't show up when Mellow helped me with the valve clearance and brake bleed a couple of months ago.
 
Joined
Jan 8, 2011
Messages
7,066
Location
Arizona
Bike
2007 Honda ST1300A
Hello everyone, thanks for all the advice. As the weather is getting warmer the coolant trail has tapered off. I will keep monitering it and the overflow tank. When the time comes again to remove the plastic I will tackle the mystery location, mystery plug, replace T-stat, and tighten the clamps. Too bad this didn't show up when Mellow helped me with the valve clearance and brake bleed a couple of months ago.
Well there you have it....Mellow caused it :d1: I was only Joking :rimshot1:
 

Blrfl

Natural Rider Enhancement
Joined
Aug 24, 2005
Messages
5,602
Age
55
Location
Northern Virginia
Bike
Fast Blue One
STOC #
4837
As the weather is getting warmer the coolant trail has tapered off.
Leaky hose clamp. And I'd bet money that as the leak has tapered off, you've also passed the point where your low temperatures are below 50.

--Mark
 

Afan

... and this is my real name.
Joined
Jun 2, 2014
Messages
521
Location
Urbandale, IA
Bike
1998 ST1100
STOC #
8832
Leaky hose clamp. And I'd bet money that as the leak has tapered off, you've also passed the point where your low temperatures are below 50.

--Mark
Mark (or anybody else), why coolant leaks in lower temperatures?
 

Afan

... and this is my real name.
Joined
Jun 2, 2014
Messages
521
Location
Urbandale, IA
Bike
1998 ST1100
STOC #
8832

Blrfl

Natural Rider Enhancement
Joined
Aug 24, 2005
Messages
5,602
Age
55
Location
Northern Virginia
Bike
Fast Blue One
STOC #
4837
And, in this case we're talking about couple drops, not a 1/4 or 1/2 cup of coolant, right?
It really depends on which clamps are leaking, how many heat cycles the clamps have seen and how cold the fittings are when you start up. There are a lot of places for it to pool, like in the vee and the nose of the fairing, so you could end up seeing just a few drops on the ground after you warm it up and have the rest dribble out of the bike after you get underway. I had everything from light dribbles to the occasional decent puddle before putting in spring-loaded clamps.

Just noticed that you have a 1100, which may leak differently.

--Mark
 

Afan

... and this is my real name.
Joined
Jun 2, 2014
Messages
521
Location
Urbandale, IA
Bike
1998 ST1100
STOC #
8832
It really depends on which clamps are leaking, how many heat cycles the clamps have seen and how cold the fittings are when you start up. There are a lot of places for it to pool, like in the vee and the nose of the fairing, so you could end up seeing just a few drops on the ground after you warm it up and have the rest dribble out of the bike after you get underway. I had everything from light dribbles to the occasional decent puddle before putting in spring-loaded clamps.

Just noticed that you have a 1100, which may leak differently.

--Mark
Thanks Mark
 
Joined
Mar 13, 2016
Messages
24
Location
Ardmore Ok
Bike
2007 Honda ST1300
I was having the exact issues as described. In My case the water pump o-ring gasket was leaking. It took me two tear downs to find it. On the first teardown I tightened all the clamps I could see after removing the radiator and covers. Drove it for about two weeks and was still loosing water. On the second teardown I removed the fuel tank and air filter housing to inspect the hoses on the top of the engine. I ran the engine for a few minutes before removing the throttle body just to see if I could see the leak but all was dry on the top side with no visible signs of leaking anywhere. Not really feeling the need to pull the throttle body and suspecting a leaky water pump cover gasket, I decided to pull the water pump cover and quickly found my issue. The o-ring seal was leaking right where the alignment dowel is. I could probably reassemble with the same seal and some silicone sealer but I think I will order a new gasket anyways. Parts on order:D
 
Joined
Dec 27, 2004
Messages
829
Location
Medina, Tennessee
Bike
2021 Tracer 9GT
STOC #
375
Mark (or anybody else), why coolant leaks in lower temperatures?
My experience is 1100s are much worse about leaking under the carbs than 1300s are about leaking under the TBs in cold weather.

You have to pull the carbs to get to the hoses. Not fun if you have never done it, and do it in a warm environment. Heat, lube, a long JIS screwdriver and leverage are your friends. Replace the hoses while you are in there.
 
Joined
Dec 27, 2004
Messages
829
Location
Medina, Tennessee
Bike
2021 Tracer 9GT
STOC #
375
I didn't do it but was helping to my friend when he was doing it on my bike. Not fun at all. :cry:


How long? Recommendation (Amazon preferred)?
18" should do. It is hard to find a JIS that long. You could just use bits and an extension. Back in the day I cheated and used a Phillips. The problem is getting to the band screws that hold the carbs to the boots. Then getting the carb assembly back on.
Silicone, heat and leverage. I made a wooden "jig" to apply pressure to the carb base using a rope tied to the frame and a long pipe.
 
Joined
Mar 13, 2016
Messages
24
Location
Ardmore Ok
Bike
2007 Honda ST1300
I was having the exact issues as described. In My case the water pump o-ring gasket was leaking. It took me two tear downs to find it. On the first teardown I tightened all the clamps I could see after removing the radiator and covers. Drove it for about two weeks and was still loosing water. On the second teardown I removed the fuel tank and air filter housing to inspect the hoses on the top of the engine. I ran the engine for a few minutes before removing the throttle body just to see if I could see the leak but all was dry on the top side with no visible signs of leaking anywhere. Not really feeling the need to pull the throttle body and suspecting a leaky water pump cover gasket, I decided to pull the water pump cover and quickly found my issue. The o-ring seal was leaking right where the alignment dowel is. I could probably reassemble with the same seal and some silicone sealer but I think I will order a new gasket anyways. Parts on order:D
This is just an update to my previous post.

I replaced the water pump housing gasket and used a small amount water pump grade silicone sealer during re-assembly. Didnt know how that would work out being the factory didn't use any sealer at all. All went well for about a month until I started the bike on a 50 degree morning and it dumped about a tablespoon of antifreeze on the ground. Hasn't dumped any since but have not had any mornings that cold since. Now the slight aroma of antifreeze is back like it was before. I guess it will just have to leak until riding season is over. Ill tear it down again and see.

Sent from my SAMSUNG-SM-G900A using Tapatalk
 
Top Bottom