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jpf566

07 YZ450 tiny hole on right side of engine, coolant leak

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Hey Guys, Whats this hole on the side of the engine, looks like a weep hole of some sort? http://imgur.com/3thLRRk As you can see its a new head and something had previously leaked out of it... I just bought the bike and am paranoid somethings wrong... Thanks

Edited by jpf566

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YZ and WR all have it, I spray a little WD40 in there once in a while ( stops the spark plug from rusting up ).

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That is a drain hole for any water that may find it's way in with the top of the spark plug. The stain you see is from rust on the spark plug.

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The color of that stain, I'd be concerned that it was coolant. As long as it's not, no worries.

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The color of that stain, I'd be concerned that it was coolant. As long as it's not, no worries.

I'm pretty sure it's coolant. Thats the exact color of my coolant.. What does it mean if coolant is coming out of there?

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It would almost have to mean a crack in the head running from the coolant jackets to the plug bore, or porosity in the casting in that area if it turns out to be just coolant. There isn't a path for coolant from anywhere else to the spark plug well. Which takes me to...

The other thing it could be is coolant mixed with your oil, leaking from the cam cover gasket. Check your oil for contamination. If coolant gets in it, it will turn a nasty looking milky foam, something like the milk shake from hell. The reason the idea of a crack took me here is that there is maybe 8-10 mm maximum between the middle of the plug bore and the upper surface of the head. A vertical crack in that area would certainly end up pushing coolant into the crankcase.

On the other hand, if it's oil contaminated with coolant, the source of the coolant leak into the oil could be something other than a damaged head, like a leaking O-ring, or a base or head gasket.

First thing would be to check the condition of your oil, then pressure test the cooling system.

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It would almost have to mean a crack in the head running from the coolant jackets to the plug bore, or porosity in the casting in that area if it turns out to be just coolant. There isn't a path for coolant from anywhere else to the spark plug well. Which takes me to...

The other thing it could be is coolant mixed with your oil, leaking from the cam cover gasket. Check your oil for contamination. If coolant gets in it, it will turn a nasty looking milky foam, something like the milk shake from hell. The reason the idea of a crack took me here is that there is maybe 8-10 mm maximum between the middle of the plug bore and the upper surface of the head. A vertical crack in that area would certainly end up pushing coolant into the crankcase.

On the other hand, if it's oil contaminated with coolant, the source of the coolant leak into the oil could be something other than a damaged head, like a leaking O-ring, or a base or head gasket.

First thing would be to check the condition of your oil, then pressure test the cooling system.

ARG!... Alright thank you so much for all the info! I'll have to check the oil. I actually have the bike scheduled at the local shop for a leak down test because I was worried there may be some issues with the top end. (just bought the bike from craigslist and I'm getting the feeling the seller wasn't honest about the condition of the bike) Would a leak down test help diagnose what you think may be wrong or should i also tell them to do a coolant system pressure test?

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Oh yeah and the other thing... I already have a bad water pump seal (getting coolant leaking from the bottom weep hole by the water pump) so even if I do find coolant in my oil that could possibly just be from the bad water pump seal right?

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Oh yeah and the other thing... I already have a bad water pump seal (getting coolant leaking from the bottom weep hole by the water pump) so even if I do find coolant in my oil that could possibly just be from the bad water pump seal right?

There are 2 seals for the water pump. The first one seals oil inside the crankcases. the second one keeps coolant from leaking. If the first seal oil is leaking then the coolant and oil can contaminate. If only the second seal is leaking- coolant seal, you will have coolant leaking out the weep hole. I would drain your oil and see what color it is

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Oil and water mixing can't be blamed on the water pump. There is a outside vented gap between the two seals that prevents it by allowing either fluid to escape before invading the other volume. See the picture here:

http://www.thumpertalk.com/forum/showthread.php?t=940018

A leak down test may show the crack into the coolant or not, depending on whether the crack, if there is one, runs into the combustion chamber. You might have to run both tests.

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Alright! I drained the oil and it looks fine, no lightness or frothiness which was quite a relief. The only thing is, I just bought the bike so I haven't done more then some very short test rides in my small yard. (probably less than 10 minutes of running) If the previous owner had put fresh oil in before I bought it do you think that would be enough drive time for the coolant to get into the oil if that was an issue?

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Probably not, but it still depends on a lot of variables. Keep your eye on the fluids as you run the bike a little longer.

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