ST1100 - She's Giving Up Smoking Like A Cigar But Now She's Hot!

[Uncle Phil]

UP, if you have not replaced the temp sending unit since installing the most recent non smoking engine see post #19. The last OEM sensor I installed only lasted 4,000 miles.

Yes, the temp sensor is practically new. The gauge works as it should because the fan kicks in at the same temp shown on the gauge as the other 3 ST1100s.

 

[St-Gerard]

Stupid question , have you pulled the Rad out to look at the inside?

 

[bdalameda]

Since the temperature seemed normal without the lower cowl and then runs hot with it there is something going on with airflow or coolant flow through the radiator. That being said if all the bodywork is stock this would indicate a restriction through the radiator either with coolant internally or air going through the finned tube section is restricted. When there is more flow through the radiator without the cowl and more surface area of the radiator is exposed to reject heat, it is making up for the reduced heat rejection capacity of the radiator either internally with coolant flow or with air flowing through the radiator. Have you cleaned the radiator of any dirt, bugs etc. that could be blocking airflow through it? If it is clear for proper airflow it must be plugged up internally and not all of the radiator is rejecting heat. It is acting like the radiator is too small.

 

[CruSTy]

Yes, the temp sensor is practically new. The gauge works as it should because the fan kicks in at the same temp shown on the gauge as the other 3 ST1100s.

Silly question but could the fans be connected with reverse polarity? That would cause incorrect airflow across the radiator. Installing the cowling would make it worse. It would cool ok at low speed but not as well when moving.

 

[bdalameda]

Silly question but could the fans be connected with reverse polarity? That would cause incorrect airflow across the radiator. Installing the cowling would make it worse. It would cool ok at low speed but not as well when moving.

Interesting thought - not sure if this could happen, depending on the motor design. I do remember that the first year of the Goldwing 1800 (2000?) Honda designed the cooling fans to blow outward (forward) instead of the standard inflow direction. I guess they thought the only time the fans would cycle would be in a stopped or very slow condition. Well owners started having overheating problems in certain conditions such as having a headwind coming at them in traffic or when going slowly and effectively canceling out the fans effectiveness. They recalled these bikes and changed the fans direction. Not sure if it was just wiring changes or the fan blade or motor that was changed.

 

[ST1100Y]

hmm... could it be as simple as omitted deflector panels?
(P/N 19070MT3000 & 19170MT3000 )

 

[sirbike]

Now that the problem is happening after the cowling install, does taking off the cowling improve the situation or did putting the cowling on just happen to correlate with the problem.

 

[Uncle Phil]

Now that the problem is happening after the cowling install, does taking off the cowling improve the situation or did putting the cowling on just happen to correlate with the problem.

That is a good question.

As far as the fan goes, the electrical connection only goes one way.
The issue is not the fan as it will not cool down properly when doing 70 mph on the interstate for a period of time (compared to the other 3 ST1100s I have).
The fan does keep it from overheating when stationary - which is what it is supposed to do.

 

[Mellow]

That is a good question.

As far as the fan goes, the electrical connection only goes one way.
The issue is not the fan as it will not cool down properly when doing 70 mph on the interstate for a period of time (compared to the other 3 ST1100s I have).
The fan does keep it from overheating when stationary - which is what it is supposed to do.

But... standing still, are you sure the fans are turning in the correct direction? If reversed - somehow - it would be pushing air forward vs back towards the bike... it would still cool... but if moving forward it could be negating the effect of a reversed fan...

Doesn't seem like the connection could be reversed as honda is good about connectors only going on a certain way but is it possible that wire is spliced somewhere else and the polarity was reversed? Will the fans actually even work w/reverse polarity and spin the opposite direction?

 

[Obo]

@Mellow St1100's don't have reverse....

 

[catcher]

Remove the rad, lay it submerged in a pan of liquid with an acidic component. Any good rad shop ought to be able to provide a recipe/formula. You probably have a tote box which you can use as a bath pan. Let it soak for a couple of days, then flush thoroughly. This method should get the rad clean both inside and out. Can't hurt to have a clean rad!

 

[Uncle Phil]

The issue is not the fan - the issue is it does not cool off when going down the highway at 70 mph - the fan should not be running at highway speeds because there should be sufficient air flow from the movement of the bike.

 

[St-Gerard]

Okay don't want to suggest this but by chance does the thermostat fit in upside down?

 

[Uncle Phil]

Okay don't want to suggest this but by chance does the thermostat fit in upside down?

Nope. The diagrams are very clear which way the thermostat fits.

 

[St-Gerard]

Nope. The diagrams are very clear which way the thermostat fits.

Can't count how many times I have looked at a part and some how put the dang thing in backwards(inner pump gear on a 350 chevy transmission). Usually when I was partying to much the night before.
Have ran into wires been wired wrong from the factory. Too of a long storey
Comes back to the Rad problem

 

[Uncle Phil]

If it were in backwards, it would not cool at all because it would not open (the opening part would be on the wrong side of the engine coolant).

 

[St-Gerard]

If it were in backwards, it would not cool at all because it would not open (the opening part would be on the wrong side of the engine coolant).

Which is why I didn't want to suggest it being in backwards , but weirder stuff has happened
What temp theromstat in it and Oem or Aftermarket?

 

[Uncle Phil]

Tried both OEM and Aftermarket - not much difference in either case.

 

[tnbill]

This is pointing more and more to either a radiator or water pump issue. If its the same radiator from the smoker that had no issues than the water pump just migjt have an issue with not moving water properly.

 

[dwalby]

This is pointing more and more to either a radiator or water pump issue. If its the same radiator from the smoker that had no issues than the water pump just migjt have an issue with not moving water properly.

since UP has 3 other ST1100s for comparison, for $99 you could compare the radiator thermal patterns of the good ones vs. the bad one and see if that provides any clues.

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I'm not sure how much you'd need to spend on a known good replacement radiator, so maybe $99 isn't worth it to do a little troubleshooting vs. just replace the rad and see what happens.

When I had my infamous water pump corrosion where all the impeller blades were gone and it was just a set of arms with no blades, my temp gauge would read normal at speed. So, your water pump would have to be in pretty bad shape to get the symptoms you're seeing, but every failure is unique so I'm not gonna rule out the water pump either.