Coolant dump?

ST Gui

240Robert
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if the radiator cap was failing wouldn't the coolant escape from there rather than being forced into overflow reservoir?
Because it's boiling it will expand along the path of least resistance. Unless the seal itself between the cap and the radiator failed that path of least resistance is the overflow reservoir.
 
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JimGregory....dude, you do me proud!
HA..thanks. Just noticed OP is across the pond. White phone may not be so easy.
Green bits may be clogging up the radiator. This system needs a flush at least. Sounds like maybe it's never been done or you don't know when it was last done AND you don't know if distilled water was used or the wrong type of coolant or what.
 
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if the radiator cap was failing wouldn't the coolant escape from there rather than being forced into overflow reservoir?
one more detail that hasn't been mentioned, there are two sealing surfaces on the cap. One seals the top edge of the filler neck so coolant can't escape out of the filler neck. The other seals on a lower edge and when pressure exceeds that seal, it allows coolant into the area where the overflow hose is attached and it flows to the tank. However, the top seal prevents the coolant from leaking at the neck. I think this may have been what you were asking.
 
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one more detail that hasn't been mentioned, there are two sealing surfaces on the cap. One seals the top edge of the filler neck so coolant can't escape out of the filler neck. The other seals on a lower edge and when pressure exceeds that seal, it allows coolant into the area where the overflow hose is attached and it flows to the tank. However, the top seal prevents the coolant from leaking at the neck. I think this may have been what you were asking.
Yes indeed, that is a good clarification for what I was saying in my last post.
 
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Howard
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It always amazes me how little I know☺. I'm still doing the flush etc but think I have identified the relay as the culprit. I'll get another one and I'll see. I'll let you know.
 

Blrfl

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(Didn't finish writing this until after Howard's last post, but I'll leave this here for posterity.)

I'm going to take the opposite side of the radiator cap diagnosis.

First, while a radiator cap failure is possible, these bikes don't have a history of it. It's been the same part since 2002, and if Howard's 2008 had a failure, we'd probably have seen it multiple times on older models.

Second, I don't think the system would boil if only the radiator cap had failed. Some back-of-the-napkin math says that if the boiling point of 50-50 mix is 265?F at 15 psi (which is what the ST's cap is supposed to maintain) and the boiling point rises 3?F for each additional pound above atmospheric, the boiling point of the coolant with a completely-failed or outright missing radiator cap is 220?F. It would be reasonable to think that the ECM is programmed to start the fans at or just below that point (which, as others have observed, it does) to prevent boil-overs and engine damage in cases like that.

Third, the heat from the combusion process has to go somewhere. If the air around the radiator is stagnant (i.e., the fans don't run when they should), I could easily see the coolant accumulating the extra 45? required to get from the fans-on point to boiling, even under full pressure.

What would be really helpful is for Howard to start his bike and stay with it to observe what the temperature gauge does. If it reaches four bars and the fans don't run, there's the problem. I've done this experiment on my bike: it will idle with fans cycling and three bars pretty much indefinitely. Disconnect them and the temperature reaches four.

--Mark
 
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Howard
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I think you have it spot on Mark. I let the bike run last night again to see what happened and about 20 mins in the gauge went up to 4. I turned off at this point and noted the fans had not come on. Did the fan check with a battery and could not get it to click. New one ordered. Fingers crossed.

I meant relay check.
 
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OP
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Howard
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New relay fitted and fans come on as should. I replaced the thermostat with new and flushed coolant system. Still has slight surge from 2000 rpm to 2500 rpm before dropping to 1200 when warming up. Hope this doesn't indicate another issue. Thanks for all the brilliant advice and guidance. It helped so much and have me the confidence to address the issue myself. Also fitted the elvitek led headlights whilst the plastic was off. Very straightforward and vast improvement.
 

Blrfl

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New relay fitted and fans come on as should.
Glad it was something simple. Most times it is. :)

Still has slight surge from 2000 rpm to 2500 rpm before dropping to 1200 when warming up. Hope this doesn't indicate another issue.
1,200 is a little high for warm idle, but that takes a minute to set from the outside using the throttle stop adjuster near the front of the right cylinder head. Adjust that first (1,000 ? 100 rpm) and see how the cold idle settles out. If you find the fast idle uneven, I've had good luck cleaning the linkages between the throttle bores and the wax engine. No rush to fix that.

--Mark
 
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Clean the 5 way Tee, replace the rubber lines, lube the throttle cables, then do a TB sync. This will probably cure your surge and improve the overall running of the bike.
.o2
 
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