07 YZ450 Water in oil

5 replies to this topic
  • ean3x

Posted December 13, 2009 - 06:33 PM


Problems with the Yamahammer

I went riding for a few hours today and during the last 20 minutes of the ride I thought I had boiled the coolant. I saw a small amount of steam coming from the front of the bike. I checked the coolant level and I had not lost much. I got on the road and hauled butt back to the truck which was about a mile away hitting WOT for about a 1/4 mile. Thats when I noticed that white oil was dripping out of the breather tube after letting it cool for a while. I checked the coolant again and couldn't see any. Panic set in and I'm still worried.

This is my first 4 $troke so I have a few questions. I have researched and found that the problems could be the following.

"The water passage between the right engine cover and the crankcase.

> The water passage between the crankcase and cylinder.

> The head gasket (most likely, unless you messed up on the crankcase cover when you did the water pump)

> A crack in either the cylinder or head.

> A leaking coolant jacket plug (center of the head in the cam box)"

Q1. What is the best order to begin looking for the problem?
Q2. What do I look for as I punch down the list
Q3. Does the engine need to come out of the bike?
Q4. Is the milky oil going to cause the bearings to rust?
Q5. How do I get the milky oil out?
Q6. How do I prevent this in the future?
Q7. What else could be damaged, what else do I need to look at?

I am confident in my mechanical abilities, I just need a little guidance in what to look for.

Thank you in advance

  • grayracer513

Posted December 13, 2009 - 07:24 PM


The first thing to do is to see what your oil really looks like. Pull the dip stick. If it looks normal, odds are there's no problem. If you need more reassurance, drain the oil, and pay particular attention to what first comes out. If there's coolant in the oil, it will be at the bottom.

It's not unusual in colder, damper weather to have condensation form in the breather and drip off later. The most likely cause of coolant loss in an '07 is the water pump seal.

  • ean3x

Posted December 13, 2009 - 07:34 PM


Thanks Gray,
There is definitely coolant in the oil. I pulled the drain plug out of the stator side and it is white. There is no separation of oil/water, its completely homogenized. I was hoping that it was condensation after seeing some of your other post and went out and checked. The coolant level in the radiator has drop past the top of the cooling fins also. I checked it right before I made the 1 mile trip back to the truck and it was at the normal level.

I thought it was impossible for cross contamination due to a bad H2O pump seal. So my guess is 1. head gasket, 2, passage between crankcase and cylinder, 3. Cracked head/cylinder, 4. etc. Where do I go from here?

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  • grayracer513

Posted December 13, 2009 - 08:18 PM


Head gasket. At least, I'd assume that. Be sure you change the base gasket, too. They are a coated steel multi-layer type, like the head gasket, and there isn't an O-ring around the water passage.

You are right about cross contamination at the w/pump.

  • ean3x

Posted December 14, 2009 - 11:39 AM


What's the best way to get the bad oil out of the engine and do I need to worry about bearings rusting? My thought is take out spark plug, drain as much bad stuff as possible, fill with fresh oil, turn engine over, drain, repeat.

I've never seen a blown gasket, is it going to be obvious that that is the problem? Where else do I need to check for damage and what do I look for?

Do I need to replace piston rings?

Does engine need to come out of frame?

  • grayracer513

Posted December 14, 2009 - 12:32 PM


The "blown" gasket will probably not be at all obvious, although it might be. With a stacked shim gasket like this, you might be able to detect a trail, or missing sealant, etc., but don't be alarmed if you can't.

It certainly won't hurt to refresh the rings. Everything else should be inspected, and replaced as required.

To flush out the water, drain whatever will drain, and remove the contaminated oil filter, cleaning out the filter well at the same time. Then fill the engine to the crankcase mouth with alcohol (absorbs water. Note that several kinds of alcohol are available form hardware and paint stores in gallons. All of it is toxic, and you should avoid contact with denatured, ethyl, and particularly methyl alcohols to the extent possible. You can also use isopropyl (rubbing) alcohol, but it may cost more due to the small size of the containers).

Also fill the oil tank through the dip stick hole. At this point, just let it sit for a half hour or so without circulating it. Slosh the crank a couple of turns in each direction, but don't spin it through very much. Then, drain it all back out.

Now, pour a couple of quarts of alcohol into the crankcase, and remove the oil filter cover. Leave the oil tank section empty. Hold the cam chain up to keep it from fouling, and turn the engine forward until fluid begins to pump steadily from the filter well and appears fairly clear. Then cover the filter well and proceed to spin it through until fluid pumps out at the cylinder base, and continue until it looks relatively clear. Drain everything, including the filter well, and let it sit empty for a while.

When you refill, use a high quality oil so that you can be sure it will contain a good amount of detergents and dispersants. Before you put the top end on, pour oil over the crank and turn the engine through until it pumps oil out at the cylinder base again. Run the engine long enough to warm it up well without putting much load on it, then drain and replace the oil with your normal engine oil.

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