Is this bad news??

[SpoogyWoogy]

Hi all,

I was doing an oil change on my 1991 st1100 and noticed this trail of old coolant.

I am still waiting on all the parts to arrive for my timing belt change but I’m not sure if this is a sign that the water pump is failing or if it’s just a leaky something or other from above.

Any advice or input is greatly appreciated.
I love the bike so far and would hate to destroy the engine…

Thank you.

 

[ST1100Y]

hmm, forward section (dripping down on left side of the clutch cover) would indicate something on the w/pump shaft seal...

leaks showing aft of the engine (dripping down by alternator/main stand) are mostly some leaking hoses* and/or fittings* between the cylinders/underneath carbs

*which I would inspect in the imminent future...

 

[SpoogyWoogy]

hmm, forward section (dripping down on left side of the clutch cover) would indicate something on the w/pump shaft seal...

leaks showing aft of the engine (dripping down by alternator/main stand) are mostly some leaking hoses* and/or fittings* between the cylinders/underneath carbs

*which I would inspect in the imminent future...

Thanks!

This is on the right side of the engine (from rider pov). Where the oil fill cap is.

I took off a bit of the timing belt cover and stuck a borescope in there to see how the belts are doing and they looked in good nick.
(But who know for how long if the coolant is getting in the timing belt area…)
I’ve attached a photo of what I saw through the borescope, teeth look good and I didn’t see any fraying or anything when looking around either.

Just worried about replacing the water pump as they are insanely expensive for the 1991 model and I don’t know if they can be rebuilt.

 

[kiltman]

The most common and easiest leak is from the overflow tube. Check the tube coming out of the radiator cap pointing forward of the bike. It tends to crack under the clamp. You may notice a lot of dried coolant.
Remove the tube, cut it back about 10mm and reinstall.

 

[SpoogyWoogy]

The most common and easiest leak is from the overflow tube. Check the tube coming out of the radiator cap pointing forward of the bike. It tends to crack under the clamp. You may notice a lot of dried coolant.
Remove the tube, cut it back about 10mm and reinstall.

Thank you!!
Will have a look tomorrow as it started bucketing down here today.
Really hoping it’s just dripping from somewhere but not 100% sure where the culprit may be.
Checked the v4 valley and it was bone dry (phew) but as I don’t have the space to completely strip down the bike it’s hard to just follow the streak of coolant to the source.

 

[Al st1100]

Just by age of the bike you need to pull the carbs off and inspect all the coolant hoses. It probably needs them.

 

[SpoogyWoogy]

Just by age of the bike you need to pull the carbs off and inspect all the coolant hoses. It probably needs them.

will be taking a closer look when I go to sync them. Depending on how well a sync works to improve how it runs I may dig in a rebuild/ clean them as well.
Not anytime super soon as I’ll be quite busy from next week onwards but perhaps in the coming months.

 

[bdalameda]

will be taking a closer look when I go to sync them. Depending on how well a sync works to improve how it runs I may dig in a rebuild/ clean them as well.
Not anytime super soon as I’ll be quite busy from next week onwards but perhaps in the coming months.

When you inspect the coolant hoses under the carbs - replace the o-rings on the tube fittings - consider replacing the fittings as well. The o-rings turn to mush on older bikes.

 

[SpoogyWoogy]

When you inspect the coolant hoses under the carbs - replace the o-rings on the tube fittings - consider replacing the fittings as well. The o-rings turn to mush on older bikes.

Good to know.
Will have to order some, unless they’re just standard orings but seems like nothing is quite that simple on this bike so far haha

Will take a look around for those fittings too. I have a feeling I saw them on webike the other day.

 

[kiltman]

On a side note, does this bike still have the original oil cooled alternator, or has it been upgraded to the 40 amp automotive style unit.
The original will still have the separate Voltage/regulator/rectifier on the left side below the fuse box.

 

[SpoogyWoogy]

On a side note, does this bike still have the original oil cooled alternator, or has it been upgraded to the 40 amp automotive style unit.
The original will still have the separate Voltage/regulator/rectifier on the left side below the fuse box.

I believe it’s original. The bike overall seems quite stock so just an assumption.
Will take a look when I can!