Article [13] ST1300 - Water Pump Weep Holes

[Igofar]

What people are calling the "square hole" is not a hole at all, but rather the edge of the front cover where it meets the front engine case.
I would NOT blow anything in this area, as you could damage the small rubber sealing O-ring, and make what ever leaks you have worse.
You may want to remove the water pump cover and replace the O-ring while your at this point to save you from doing everything twice.

 

[CYYJ]

...I am in the process of finding and fixing some coolant leak from the V and I am wondering if it could be helpful to use compressed air to clean the drainage path?

Hi Jacques:

I agree with Larry (@Igofar ) - I don't think it is a good idea to use compressed air to try and clean that drainage path. It is unlikely you would gain any benefit from doing that, and as Larry pointed out, you could do considerable damage.

The pathway that leads down to the 'square hole' outlet is intended to allow water that might accumulate in the 'V' of the engine to drain out. About the only time I think you would get any accumulation of water in there is when you are washing the motorcycle with a hose and you squirt the water into the sides of the engine. Any water that might somehow get in there when you are riding will be evaporated very quickly once it lands on the hot engine case... so no need to worry about water accumulation when riding.

What you could do, if you so desire, is to deliberately shoot some water from the hose into the 'V' of the engine, then observe to see if water then drains out of the square hole. If you do see water drainage, that's a good enough result, it proves to you that the pathway is open. That means that if in the future, a coolant hose up in the V of the engine starts to leak, you will see evidence of coolant having leaked out of the square hole (dried green stains below the square hole).

If you squirt water up into the 'V' and nothing comes out of the square hole, that means the passageway is blocked... but personally, I don't think that keeping that passageway open warrants the massive amount of disassembly you would have to do to clean it out. Better to wait until you have the throttle bodies off for some other reason - that will allow you to check the entranceway to the drain passage and see if the entranceway is plugged up with something. Or wait until you have to work on the water pump and you have the smaller, right-hand portion of the cover on the front of the engine case off.

Michael

 

[dimitris katsikostas]

Well, it looks like I have some work to do. I have not ridden the bike for a few months. I have started it up every week or so and let it warm up on the side stand. I started it and moved it the other day. As I parked it, I saw a small pool of coolant, maybe 3 ounces, under the front of the bike. I removed the right side covers and saw that it had been coming from the SQUARE hole. I thought the pump seal must be bad until I came here and read this thread. So, I gather the leak is probably a hose to or from the T-stat. Argh! Anyway, I really appreciate this thread. The workshop manual misleads you in a way. Since this hole is under the water pump, your natural inclination is to look at that section of the manual, and I saw no discussion there of the square hole. I assumed the water pump shaft seal must be bad even though there is no further flow at this point running the bike on the side stand. I guess there's no way around removing the tank, airbox and throttle body to get to the T-stat and the valley this hole drains. Thanks.

Hello. I am facing the exact same thing today. Only clean coolant comes out of the square hole. If I understood from what you said, this is not a pump leak? Is it something more serious? Please help . I need to know before going to a technician. In my country, the technicians do not know this model at all. Thanks

 

[woodybelle]

Most likely it is a loose hose clamp. If you remove the air cleaner and the radiator you can get to most of the hose clamps. A lot has been written on this forum about these leaky clamps, a bit of searching will most likely be of great benefit.

 

[cyclenut57]

There are two 'weep holes' on a ST 1300 motorcycle. They serve entirely different purposes and have nothing to do with each other. Because the two outlets (the "round hole" and the "square hole") are located very close together, this sometimes causes confusion.

I'm not sure which hole you are talking about... your question suggests that you are asking about the "round hole" (the water pump drain), but that hole is very unlikely to get plugged up. The hole that is at greatest risk of getting plugged up is the "square hole".

Below you will find a series of photos that illustrates the path liquid travels before it drips out of either one of these holes.

First, let's identify the two holes. The photo below is of a 2012 ST. Early production models did not have the metal elbow and rubber drain hose extension on this hole -they just had a round hole. I think the elbow and rubber hose were added at the beginning of model year 2007 or 2008 production.

Drain Holes
View attachment 294174

The round hole (upper hole) is the simplest and easiest to understand. It allows engine coolant to drain out of the water pump if there is a failure of the seals within the water pump. The two photos below show you everything you need to know about the approximately two-inch long path from the innards of the water pump to the round hole outlet on the side of the engine.

Front View of Round Hole
The snowflake-shaped thing is the water pump.
View attachment 294180

Rear view of water pump
You can see the little molded channel leading from the inside of the water pump to the round drain hole - look at the 4 o'clock position.
View attachment 294175

That's all there is to the round hole. Very simple, very straightforward, a very short drainage path that serves one purpose only. If you discover coolant (or, God forbid, oil) leaking out of the round hole, the water pump will need to be replaced.

- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -

The Square Hole

The purpose of the square hole is to drain liquid from the 'V' between the two banks of cylinders. The 'liquid' could be anything - perhaps clean water from sources external to the motorcycle that gets into the V between the cylinders when you are washing the motorcycle, perhaps oil that leaks from somewhere (who knows where) into the V, or (most probably) small amounts of engine coolant that leak from hose connections in the 'V' area.

The next series of pictures will follow the path of liquid that drains out of the square hole, but in reverse. In other words, the pictures will start at the outlet of the square hole and work their way back until reaching the bottom of the V at the front of the engine.

Front of Engine (Water Pump Cover Removed)
Here you can see the square hole outlet in the lower left, and the inlet to the channel leading to the square hole.
View attachment 294176

Same picture as above, but before cleaning things up
When the water pump cover is installed, it creates a square channel that allows liquid and debris (usually sand that gets thrown up into the V by the rear wheel) to flow out the hole at the top, down the channel, and out onto the ground.
View attachment 294177

The opposite side of the above photo
The hole at the tip of the arrow is the same hole as the upper hole in the picture above.
View attachment 294178

This photo is taken from the front of the moto, looking aft at the front of the engine, after the big cover in the three photos above has been removed.
Note that the liquid (and debris) enters from the hole at the top, drops down about half an inch, then exits via the hole shown in the photo above. This chicane creates a problem: if there is a large amount of debris, the drainage path will plug up at this point, and it is very difficult to clean it out without full disassembly.
View attachment 294181

Finally, where it all starts
This photo shows the drain hole in the V at the front, top of the engine. It is the opposite side of the photo directly above.
View attachment 294179

If the drainage path between the hole in the V shown directly above and the square hole on the side of the motorcycle (shown on the first picture at the very top) becomes plugged, water will not drain from the V between the cylinder banks. The bottom part of the alternator may become submerged in liquid, and debris that accumulates in the V may be carried into the alternator by the liquid.

I hope this answers your question.

Michael

Excellent pictures. Big help.
Looks like the Honda manual fails to mention the fact that the crankcase cover needs to be removed too.
This post verified it. I thought I was missing something reading the service manual. Looks like I lost my mechanical seal as I can watch it drip while idling out of the round hole through the drain elbow and hose.
I have some work to do.