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So, I finally got around to working on my EX this weekend. I had to adjust the mixture screws due to a replaced air filter, which worked great - runs better than ever.

While I had things apart, I was also going to check the O-rings on the coolant tubes that extend into the head (I've had some coolant leaking issues). BUT... after draining the existing coolant, I somehow got ahead of myself and refilled the coolant. :-[ It was too nice of a day to drain all over again, so I'm going to leave this to another weekend.

My concern now is that the old coolant was very dark - almost black, so I'm suspecting oil? Does anyone know if this is possible due to those O-rings, or do I have a bigger problem on my hands?
 

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My experience w/ this is years ago & with cars. For anyone new to the problem:

Generally a head gasket will get leak between an oil galley and a coolant passage. Generally the oild will be under higher pressure & get pushed into the coolant. Oil oughta be less dense, lighter, than the coolant & so float to the top when it doesn't have a chance.

The particulars of this occuring in an ex-500, and any ommissions or corrections to the above... will have to come from the re-build veterans here.
 

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Lucky#13 said:
When the two mix it's usually milkey in color , not black .
I knew that coolant in oil gave a milky appearance, but I'm thinking the mix ratio is flipped here, hence the black. I'm suspecting a head gasket problem myself, as MrSciTrek mentioned.
 

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I only know of 2 things that will make coolant black:
1) Really old coolant (your bikes too new)
2) Exhaust (burning coolant)
What you should do is find where you have a leak by using a coolant system pressure tester. Remove you spark plugs and test buy pressurizing the system and turning the motor over . If water leaks outside then the problem is external , if it comes out of plug hole then its internal . Could be loosing coolant thru exhaust . You'd have a mysterious coolant leak that couldn't be seen but could be smelled.
 

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Administrator said:
Lucky#13 said:
When the two mix it's usually milkey in color , not black .
I knew that coolant in oil gave a milky appearance, but I'm thinking the mix ratio is flipped here, hence the black. I'm suspecting a head gasket problem myself, as MrSciTrek mentioned.
It would still be milky either way .
 

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More than likley the Blackness is really rust from the exposed steel cylinder liners, and the Old coolant that lost it's rust inhibitors. There is no high pressure Oil passages through the head gasket. only drain back holes the high pressure oil to the cam bearings is delivered through the oil lines in the back of the head. The only likely place that oil can enter the coolant system is at the inboard water pump seal. and then even if the oil seal fail the drain hole would have to be plugged and the water seal fail as well. In a nut shell there ain't any oil in your coolant , unless you put it there.

FOG
 

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Discussion Starter #8
FOG said:
More than likley the Blackness is really rust from the exposed steel cylinder liners, and the Old coolant that lost it's rust inhibitors. There is no high pressure Oil passages through the head gasket. only drain back holes the high pressure oil to the cam bearings is delivered through the oil lines in the back of the head. The only likely place that oil can enter the coolant system is at the inboard water pump seal. and then even if the oil seal fail the drain hole would have to be plugged and the water seal fail as well. In a nut shell there ain't any oil in your coolant , unless you put it there.

FOG
Huh. Well, since I still need to drain the coolant soon in order to check the coolant tube O-rings, I suppose I'll get a chance to look at the fresh coolant then to see if there's still any blackness. 'Cause I sure didn't put it there.

Thanks all.
 
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