Running hot - Kawasaki Vulcan 750 Forum : Kawasaki VN750 Forums
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  • 1 Post By GDI
  • 2 Post By Spockster
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post #1 of 5 (permalink) Old 05-28-2018, 07:51 PM Thread Starter
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Running hot

I hope everyone will be patient with me as this is the first time I've had to deal with my bike alone and I need advice.

In February I bought a 2005 VN750 and it is running hot when it is idling, stuck in traffic. I shut it off once it hits the top of the white zone and with the fan running it seems to cool down pretty well. Last week it seemed to run a little warm (about 3/4 to the top of the gauge) even while riding on the highway. I drained the antifreeze and replaced it, I left the radiator cap off while running it to ensure that there was no air in the system and that there was enough coolant. I took the bike for a ride today and it is still running hot while idling at stop lights or in traffic. I've read previous posts about flushing (backflushing) the radiator, can someone explain to me how to do that? Also, I'm thinking it could be the thermostat. Is that hard to change? Where is it located on the bike? Do you order the part online or can it be bought at an auto parts store?

I tried Google and YouTube for answers and came up with nothing so I didn't know who else to ask.

Sorry for so many questions. i have already had to replace the battery, front tire, and got the oil and filter changed. I simply cannot afford to keep bringing it to the shop. Thanks in advance for any advice you have!
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post #2 of 5 (permalink) Old 05-29-2018, 12:15 AM
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It does sound like your bike is running a little hot. Mine will run at or below the thermometer symbol (midway in the white zone) on the temp gauge while riding on the highway. It will run at or above that when I'm stuck in traffic. I haven't had my 750 Vulcan all that long, but I did change out the thermostat last year. The stator on my 2003 went out last year, so thought it best to make sure that the cooling system was operating at its best.

I ordered my thermostat from Partzilla.

See part 49054.

The thermostat is located in a housing that is under the gas tank directly behind the coolant filler. There is an air bleed screw there that you can loosen while you're refilling the coolant. This feature allows you to re-fill without having to worry about trapped air, but you will have to remove the gas tank to gain access to it.

There is also a coolant drain plug under the engine close to the right front foot-peg. Is that how you flushed the system?

If you want to be really thorough about going through the whole cooling system, you could pull the radiator, and the coolant overflow bottle and flush each of them separately. I like to fill the coolant overflow bottle with crushed ice and shake it to clean out any sediment that has collected in the bottom.

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post #3 of 5 (permalink) Old 05-29-2018, 10:57 AM
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My guess would be a sticky thermostat or partially clogged radiator.

At one point, Dexcool (deathcool) was the recommended coolant for this bike. If your coolant is red, or you see red mud on the cap, overflow tank, etc., a full flush and clean should be done. Then add silicate-free green antifreeze mixed with distilled water. But even without the deathcool problem, any system can get plugged with scale and residue over many miles.

Repair manual can be downloaded free, it would help you a lot.

The thermostat is under the gas tank in an aluminum housing, just follow the hoses. For testing, you can put the t-stat in a pot of water and heat it up. Observe how well it opens/closes. If it hangs open when cool, or doesn't open fully when hot, replace it. Ebay is the first place I check for parts.

While you have the t-stat and hoses removed, you can flush with a garden hose. Flush in all directions of flow, this backflush can remove suspended gunk (remove the drain plugs on the radiator and engine). A long soak with a radiator flush chemical can help, but those have been made weaker in recent years. Distilled white vinegar does pretty well, you could fill the whole system with it and run until good and warm, even ride a while, then flush with clear water. I like those brass, twist open nozzles that will fit inside the hoses.

Any time your bike overheats, getting up to 25-30 mph should cool it off if there's no major mechanical or flow problem in the system.
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post #4 of 5 (permalink) Old 05-31-2018, 08:51 PM Thread Starter
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Thank you. I feel a little more confident about replacing the thermostat now that I know where to find it. I ordered a thermostat online, it should be here in a couple of days. I will also take your advice and flush the system with distilled vinegar.
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post #5 of 5 (permalink) Old 06-02-2018, 09:38 AM
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Ran across this Youtube video. Watching this would be helpful to see how everything goes together. He does a good job of explaining the various parts and pieces and what they do, etc.

I didn't remove the thermostat housing when I did mine. I chose to do mine in place, but mine wasn't as dirty as the one in the video.

Watching the video reminded me that I did remove both of the water tubes (front and rear cylinder), and replaced the o-rings. I used a special plumbing grease that I bought at the hardware store to help lubricate and seal up the new o-rings. Says it safe to some ridiculously high temperature, and it worked because I don't have any leaks. This is the second bike I've done this on. Also did my son's Kawasaki 454 last year. I had to replace one of the water tubes on that bike as well as it had deteriorated to such a degree that it wasn't viable any longer. Partzilla had replacements, so no big deal.


Last edited by GDI; 06-02-2018 at 10:05 AM. Reason: spelling. . . . D'oh!
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