Coolant bleeding, temp sensor

[97tiger885]

I have some cooling issues.  I dont know if it is the temp gauge, the temp sensor or air in the coolant system. There are three symptoms.

First symptom: The temp gauge is working, but occasionally it will suddenly drop 1/2 inch,  stay there for 30 seconds or so, and then return to its former position.

Second symptom:  The fan seems to turning on more often and  the  gauge is at a lower position than previously.

Third symptom: I rode the mc into NYC in early October.  After exiting the tunnel, the mc started behaving as if it was overheating.  The gauge wasnt pegged.  It was about 3/4.  I turned the fan on manually but it didnt seem to help much in stop and go traffic. 

It was not a successful mc trip.  I was leaking oil badly and no garage around W 42nd would take the mc even though the  web sites of several  stated they did.  Ended up riding 200 miles to the city, dropping off my gear, riding back home the same day and going back to the city by train the next day.  There is a Triumph dealer in NYC but it was Sunday and I didnt want to wait until Tuesday to deal with it. 

Any ideas?  Not a big issue now that it has cooled off, but it needs fixed before summer.

I did replace the coolant recently.  Maybe I have air in the system.  How do I tell if I do and is there a method for bleeding the coolant sytem.

[Sin_Tiger]

I would suspect the water pump, depending on your milage. You may also have a problem with your electrics. You mention that you switched the fan manually, makes me wonder if a previous owner has had similar issues and has tried to "fix" it thinking it's been the fan thermostat switch. It would be a good idea to have a close inspection of electical connections, at this age they are prone to breakage near the connectors through corrosion.

[Mustang]

there are two sensors .

1 . in the left hand side of cyl. head next to water pipe . it controls the gauge reading .
they do go bad . cheap enough to replace .

2.  is in the radiator , and this one controls turning the fan on  and off. this one usually quits turning the fan on when bad .

3/4 up the gauge in stop and go traffic is perfectly normal . even with the fan on .

any trapped air should have been purged by now after a few hundred miles .

[97tiger885]

I would suspect the water pump, depending on your milage. You may also have a problem with your electrics. You mention that you switched the fan manually, makes me wonder if a previous owner has had similar issues and has tried to "fix" it thinking it's been the fan thermostat switch. It would be a good idea to have a close inspection of electical connections, at this age they are prone to breakage near the connectors through corrosion.

I had the manual switch for the fan installed by a local shop because of my experience with my K bikes.  The fan doesnt come on that often on the K bikes causing the fans to seize from nonuse.  You dont know until the mc starts overheating and the fan doesnt come on.  A solution is to rig a manual switch.  This allows you to do two things:1. check to see if the fan is working and 2. turn the fan on occasionally to stop it from seizing. I have to do the Trident next.

[97tiger885]

there are two sensors .

1 . in the left hand side of cyl. head next to water pipe . it controls the gauge reading .
they do go bad . cheap enough to replace .

2.  is in the radiator , and this one controls turning the fan on  and off. this one usually quits turning the fan on when bad .

3/4 up the gauge in stop and go traffic is perfectly normal . even with the fan on .

any trapped air should have been purged by now after a few hundred miles .

Looks like I will have to replace the gauge sensor.

Still not sure if I have the oil leak fixed.  Nothing else gets done until I figure that out.

Thanks for the info.