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Discussion Starter · #1 ·
Hello, I am new here so please let me know if I am doing anything incorrectly.

Recently while riding, I noticed my bike was overheating. I've never had this issue previously. I was only a few miles from home so I delt with it. When I arrived home, I noticed a coolant tube was off (image attached). I put it back on and tightened the ring. I then flushed the coolant, filled the radiator, and filled the reservoir to a bit over the low mark. When I rode next, I noticed coolant splashing out of the reservoir at higher RPMs (~12k+).

This issue only happens when in gear at higher RPMs. I have driven it a few miles at low RPM and there was no change in reservoir level. All it takes is one rip of the throttle and the reservoir will go from "low" mark to well over "high". During this throttle rip, the bike will also almost instantly overheat (~249F or 120C) before slowly cooling back down. Before the incident, its never experienced overheating issues.

Things I have tried or noticed so far:
  • Can't recreate issue when in neutral
  • When in neutral and revving, I can see small bubbles in reservoir
  • No coolant in oil or vice versa
  • No performance issues
  • Water pump works fine
  • Temperature sensor works fine
  • Fans work fine
  • Replaced radiator cap
  • After recreating issue, when bike is off, reservoir coolant slowly lowers back down
At first, I suspected it was a head gasket issue, however since there is no performance issues or mixing of oil/coolant, I think it is a low chance of it being the problem. I would love to do a leakdown test, however I lack the tools and the experience to do so (local shop does it for $360 but I'd like to avoid it if possible).

Thanks for reading this far. Please let me know if you have any ideas!

Bike: 2017 R6 Raven (I've heard the color matters)
 

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I’m assuming once you did the coolant flush you left the radiator cap off with the bike on a rear stand. Once the temperature gets warmer put the cap back on right away before it comes out. Try squeezing the coolant hoses when you first start it. Thinking you may just have a lot of air.
 

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filled the radiator, and filled the reservoir to a bit over the low mark
Doesn't hurt to put too much in the reservoir after a refill. The typical vehicle and over the next several hot/cold cycles, will push air out of the cooling system. That drops the level in the reservoir. So I always fill my reservoir in anticipation of that.

Best case scenario, something entered that disconnected hose and is plugging your cooling system.

Been on the forum for some years and have never read of a confirmed head gasket issue. However I think this thread may be (my) first exception. Treat insufficient coolant, as you would insufficient oil. STOP the engine until you get sufficient water levels in there. Then flush it once you get back home. A "Block Test Kit" allows you to test the coolant for the presence of combustion related particles.
 

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Discussion Starter · #5 ·
I’m assuming once you did the coolant flush you left the radiator cap off with the bike on a rear stand. Once the temperature gets warmer put the cap back on right away before it comes out. Try squeezing the coolant hoses when you first start it. Thinking you may just have a lot of air.
I have tried bleeding the coolant however I have not tried massaging the hoses. I will try it out!
 

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Let us know what happens. Also we kind of assumed that coolant mix is proper, but that may not be the case. It could simply be boiling out of the reservoir.
 

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Discussion Starter · #8 ·
[Update]

Hey everyone. I massaged the radiator tubes when bleeding the bike and also used the Block Tester kit I received today. I tested it twice and both had no hints of yellow (combustion gasses). I have not tested the bike after bleeding it more thoroughly. I will do that tomorrow and post another update. I really do appreciate both of your help so far!
 

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Discussion Starter · #10 ·
Hey everyone, I tested out the bike and it is still having the same issue. Many have told me it may be an air bubble, but I find that hard to believe. If anyone has any ideas, I would greatly appreciate it.
 

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Glad it wasn't a head gasket. 👍 I guess they virtually never have confirmed head gasket issues.

Personally never heard of a bubble resulting with an outright block in a cooling system.

The manual has diagram of the cooling system. It will show its design and routing.

One of the things that prevents it from boiling over at a low (212F) temperature is an increase in pressure. The RADIATOR CAP is responsible for that increase in cooling system pressure. Does this only occur once it's around 212F or does it start pushing out immediately? Either way, check the cap and sealing surfaces. It seals your system.

Cooling systems are simple. Either it's the cap, there's a block, severe restriction or the hoses are misrouted.
 

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Discussion Starter · #13 ·
Glad it wasn't a head gasket. 👍 I guess they virtually never have confirmed head gasket issues.

Personally never heard of a bubble resulting with an outright block in a cooling system.

The manual has diagram of the cooling system. It will show its design and routing.

One of the things that prevents it from boiling over at a low (212F) temperature is an increase in pressure. The RADIATOR CAP is responsible for that increase in cooling system pressure. Does this only occur once it's around 212F or does it start pushing out immediately? Either way, check the cap and sealing surfaces. It seals your system.

Cooling systems are simple. Either it's the cap, there's a block, severe restriction or the hoses are misrouted.
Great, I will take a look at the manual! The issue occurs at any temperature. I reproduced it today while it was ~150F. Seems to push out immediately once I hit 14k+ RPM (I nearly redlined it the other day to test and the reservoir cap almost exploded and got coolant on my dash 😒).

Also, I replaced the radiator cap however the issue persists.
 

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If anything I believe it would be stuck closed. I did test it today and the coolant within the radiator does not flow until ~155F. I believe my thermostat is working properly.

Do you believe this issue may be caused by a radiator blockage?
Right stuck closed is what I was trying to say. Blockage would make sense or perhaps the water pump not working, due to the shaft being broke or something similar. Does the weep hole under the water pump have any black residue or coolant leaks? The propeller in there may not be flowing coolant causing it to build pressure and relieve where ever it can
 

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Great, I will take a look at the manual! The issue occurs at any temperature. I reproduced it today while it was ~150F. Seems to push out immediately once I hit 14k+ RPM (I nearly redlined it the other day to test and the reservoir cap almost exploded and got coolant on my dash 😒).

Also, I replaced the radiator cap however the issue persists.
Either the cap is defective or/and the hoses are misrouted or/and there is a serious restriction(s) in that cooling system. Sometimes the oil cooler on the front of the engine gets damaged in a serious crash but I don't recall whether any coolant passes through there. (and don't want to bother looking it up)
 

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Discussion Starter · #17 ·
Right stuck closed is what I was trying to say. Blockage would make sense or perhaps the water pump not working, due to the shaft being broke or something similar. Does the weep hole under the water pump have any black residue or coolant leaks? The propeller in there may not be flowing coolant causing it to build pressure and relieve where ever it can
There is no residue or coolant leaks in that area that I have noticed. The water pump seems to be working at well
 

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Discussion Starter · #18 ·
Either the cap is defective or/and the hoses are misrouted or/and there is a serious restriction(s) in that cooling system. Sometimes the oil cooler on the front of the engine gets damaged in a serious crash but I don't recall whether any coolant passes through there. (and don't want to bother looking it up)
I will try sealing the cap further with tape. By misrouted hoses are you referring to the hoses being connected incorrectly? They have not been changed so I don't think that is the issue. This issue started when the bottom coolant hose was disconnected. I cant think of why that would cause this issue though. Maybe gunk got in through the hose?
 

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Cap itself should never come off or leak. Is it being screwed on past the safety catch? Is the radiator broken, unable to retain the cap? What pressure is listed on the cap?
 

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Discussion Starter · #20 ·
Cap itself should never come off or leak. Is it being screwed on past the safety catch? Is the radiator broken, unable to retain the cap? What pressure is listed on the cap?
It is being screwed on correctly. I do not have a pressure gage on my cap. Do you recommend getting one? Also, I plan on draining my coolant and inspecting the water pump again as well as the hoses when I have time.
 
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