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Thermo Switch and possible cooling problem.

Started by MikeScoot, April 19, 2020, 01:16:48 AM

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MikeScoot

While bench running my motor yesterday the temp went very close to the red and coolant steamed out. Not sure where it was coming from (I was on the left side of the bike doing something else) but may have been from a coolant pipe. This problem solved, but still curious about thermo switch mentioned below. The problem was that one of the coolant pipe O-rings had sheared during installation.

Today I tested the thermostat and it opened well in boiling water. So I set about re-testing fan, relay and thermo switch. All good until I did the Haynes test on the switch. It seemed an odd test and I suspect it only applies if a motor is prone to overheating. The reason I suspect this is that the test is done WITH THE SWITCH OMITTED FROM THE TEST ALTOGETHER (unless I read it incorrectly). I'm assuming the switC is normally open-circuit and closes when hot. I fail to see how a test which completely bypasses the switch can determine whether the switch functions.

So then I tested both switches I have in boiling water and they both remained open-circuit (no continuity). Not good, so I am in the market for a new one.

Also, when I removed the coolant drain plug/bolt on the water pump housing, very little coolant came out. Is that normal? Plenty came out from the radiator hose and from cylinder coolant plugs. CAUSE OF ISSUE IDENTIFIED (I thinkl) When I filled the system with coolant I did so through the cap opening in the radiator. Thus, the coolant had not filled high enough to flow down through the top hose which joins the radiator near its very top. I should have filled it through the 'burp' hole in the ''T' piece which houses the thermostatic switch.

Thoughts on all this would be appreciated,

  Thanks,
   Mike
Both Luthers had their dreams,
But I've just got one Vision.
Theirs got them into strifes,
Mine just takes me fishin'.

The Prophet of Doom

#1
The Haynes test doesn't test the switch, it just tests that everything else is working, and if you are getting overheating (from the fan not turning on), then by inference the switch is faulty.

You are correct, the switch is normally open.  It closes at 102-108C and opens again at 96-101C.  You can't test the thermo switch in boiling water because water never gets that hot (102-108C) unless under pressure.

You can do the same test as the sending unit, but use engine oil rather than water.  Boiling oil splashes will do you no end of harm - eyeballs especially, so take a LOT of care and wear appropriate PPE if you want to do this test. They are pretty rugged switches, I've not seen a failed one, but apparently dropping them can break them internally.

BTW, you don't have to fill through the burp hole, fill through the cap but then burp it.  Repeat this after a few km of riding and repeat till it burps no more.  Sometimes two or three times as water bubbles make their way to the top.

MikeScoot

Thanks for your informative reply, Prophet Of Doom. I'll keep the thermo switches and not 'trash' them since they may well be OK.

Not sure about filling through the radiator cap hole. Too easy to not fill enough (and slowly enough) for the coolant to travel down into the motor (on the closed side of the thermostat), though I'm sure it works for people with the right experience at doing such things.

lolol Know what you mean about dangerous hot oil. I got stung with hot oil myself today and will probably have to bandage my right index finger with a large bandage tomorrow or the next day. I went to quench a large and heavy frypan my daughter had on the stove - without knowing she had already added oil. What followed was both EXTREMELY spectacular and painful! Kitchens are blo0dy dangerous places!

Cheers,
Mike




Both Luthers had their dreams,
But I've just got one Vision.
Theirs got them into strifes,
Mine just takes me fishin'.

jefferson

I have always filled through the radiator until no more will go in and then I fill through the burp hole until it's full and have never had a problem. The bypass hose helps in the filling process so you don't need to worry about the closed thermostat.

Rikugun

Quote from: Prophet Of Doom on April 19, 2020, 05:26:37 AM
.....but use engine oil rather than water. 
No, no, no. Use olive oil. Simmer for 20 minutes then reduce the flame to  med low. Then add the garlic.
It is far better to grasp the universe as it really is then to persist in delusion, however satisfying or reassuring.  Carl Sagan

Walt_M.

Should it be extra virgin olive oil? If you're sauteing the garlic, add it before the oil gets up to temperature.
Whale oil beef hooked!

MikeScoot

This is very difficult to write. My entire body is bandaged at the moment.
I followed all the steps you mentioned but something pretty bad happened (which I can't remember at all) when I went to fuel the bike for a test run. Also, the house is gone - just a pile of charcoal now. Maybe I had the heat a bit too high?

Both Luthers had their dreams,
But I've just got one Vision.
Theirs got them into strifes,
Mine just takes me fishin'.

Rikugun

It is far better to grasp the universe as it really is then to persist in delusion, however satisfying or reassuring.  Carl Sagan