Thermostat replacement - Kawasaki Vulcan 750 Forum : Kawasaki VN750 Forums
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post #1 of 12 (permalink) Old 09-12-2016, 06:20 PM Thread Starter
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Thermostat replacement

Hi all!

My bike runs really close to the red after I get into stop and go traffic. I recently fixed a coolant leak, and flushed and bleed the system. So, next I thought I would replace the thermostat to see if that works. I know that the fail safe 160f thermostat for a Honda Accord works but does anyone know if the 180f fits as well? The Autozones and Oreilly's near me are all out of the 160f. Thanks for your help!

Brett
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post #2 of 12 (permalink) Old 09-12-2016, 06:33 PM
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Not sure about the t-stat compatibility, but a faulty t-stat would lead to high temperatures even out of traffic since none of your coolant would make it to the radiator.
It sounds more likely that your fan isn't coming on. That could be either a bad fan motor, a bad temperature sensor, or a bad fan relay.

It might be worth checking those parts first. (it's free to check!)

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post #3 of 12 (permalink) Old 09-12-2016, 06:41 PM Thread Starter
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Thanks for the quick reply, Thorn! The bike does run hot even on the highway. By the end of a 30 minute drive the needle will be past the thermometer and just a few needle widths away from the red. Then once I get off the highway and sit at a few lights it really gets close to if not slightly touching the red. The fan comes on kind of sporadically but only when it's very hot and usually only once I stop and turn off the engine. The motor seems to work because the fan is definitely spinning fast at that point. Is there a sensor that controls at what temperature the fan turns on? Thanks!
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post #4 of 12 (permalink) Old 09-12-2016, 06:51 PM
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the temp rating isnt going to change the size, just the temp it opens fully at.

double check everything before jumping on the thermostat. while not hard to replace, the free stuff is the 1st place to start

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post #5 of 12 (permalink) Old 09-12-2016, 07:23 PM
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Yes there is a fan switch at the lower left front of the engine, the fan normally kicks on at or just above the midpoint of the gauge. If you ground the wire on that switch, the fan should run.

The blue fan wire at the JB was loose in the plug on my bike, kept the fan from running.

Not cooling at highway speed does seem to point to a coolant flow problem, like a clogged radiator, sticking thermostat, bad water pump. It should cool just fine without the fan at highway speed, say 40 mph and higher.

As posted, the different temp rating on the t-stat won't matter on fit, as long as it's the correct part number. Not a fan of using 160 t-stats.

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post #6 of 12 (permalink) Old 09-12-2016, 07:51 PM
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27010-1167, fan switch. Located at bottom left corner of the radiator.

Since the fan does come on at extremely hot temperatures, shorting across the switch isn't going to tell you anything.
I would imagine the thermostat would have to open to let hot coolant through the radiator before the fan switch would trigger the fan to blow air through the radiator. Since you're running hot even at high speeds when the fan wouldn't normally be on, the thermostat does sound like the likely culprit after all.

*EDIT*
Always refresh your screen to prevent posting an inferior version of what Spockster posted while you were away from your computer!

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Last edited by Thorn; 09-12-2016 at 08:26 PM.
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post #7 of 12 (permalink) Old 09-13-2016, 02:16 AM Thread Starter
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Thank you guys so much for your advice! I checked that the fan switch and temperature sensor were connected properly and they were. I'm not sure how to short the switch to see if it's working the way it should so I left it alone for another day. I had already purchased the 180f thermostat so figured I would go ahead and change it in just to see if that would help. After what seemed like an eternity of trying to get the damn thermostat housing out and open (the hoses and bolts were corroded and stuck tight!) I found that it was empty except for some orange goo. The previous owner must have been dealing with it overheating and tried to solve the issue by taking the thermostat out. I guess that didn't work for him. Wish he had told me about this issue when I bought the bike (actually I wish I had thought to ask!). Anyway, I put the thermostat that I bought in, although I don't expect it to make a difference in the bike overheating as coolant was already free to get to the radiator. My next idea is to take off the radiator and do a back flush. Does that seem appropriate? Can I just spray into the hoses with water from garden hose? I've been told to only use distilled water when I flushed the cooling system before. I am having a lot of fun learning about how the bike works and get into it a little bit, but it is nerve wracking to have my only vehicle be so mysteriously fussy! Thanks again for your wisdom!
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post #8 of 12 (permalink) Old 09-13-2016, 02:39 AM
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Obviously, the fan works at some point. I just added the info about test grounding the switch as an aside, not a suggestion. The test is, touch a wire to the terminal on the switch, touch the other end to any ground, like the frame, engine block, etc.

Sounds like someone has possibly mixed dexcool and green antifreeze, which results in mud.

If there's no calcium/lime buildup in the radiator, I'd suggest a flush with dishwasher powder, dissolved in water before adding to the system. With straight water and no antifreeze, run engine then rinse until clear, repeat as needed. This will clean out the mud. Calgon brand is good, it even produces heat when mixed with water.

The new thermostat may cure it. In a system this small, the coolant probably never stayed in the radiator long enough for cooling to occur. So it just kept cycling increasingly hotter coolant. Can happen with a 160 t-stat too.

Best to get that mud out of it first. Use green antifreeze, not red. I take dexcool out of anything I find with it. They call it deathcool for this reason.

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__________________________________________________ ____________
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Owner's Manual: http://www.mediafire.com/file/nscb5f...ers+Manual.pdf

Last edited by Spockster; 09-13-2016 at 02:41 AM.
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post #9 of 12 (permalink) Old 09-13-2016, 02:47 AM
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If you do the calgon flush... and the t-stat keeps it cool... ride it some with the calgon in it before flushing it out. I just did it the same way with a car, drove the thing half a day with the heat on. Before the flush, all the coolant looked like chocolate pudding and just as thick, it's squeaky clean now.

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__________________________________________________ ____________
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post #10 of 12 (permalink) Old 09-13-2016, 02:57 PM
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So I will say that since getting this harley, I will never have another liquid cooled bike. It is sooooo easy to work on....well I haven't had to work on it at all really. Your ass gets hot with that 200 degree oil tank under your butt on a 95 degree day but it's all good :-)

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