670 milky oil - Snowmobile Forum: Your #1 Snowmobile Forum

sled head dave · 12-17-2004, 01:11 AM

Another question .. Brothers 97 670 mxz keeps making the injection oil milky after a few tanks of fuel. Can't see where its coming from. Doesn't seem to lose much coolant. crankcase is empty, lines are good. Anybody had anything similar? wondering if oil tank is cracked? even though it doesn't leak..
Thanks

**smallengineguy** · 12-17-2004, 07:03 AM

It's milky in the injection tank? Don't those share the oil/anti-freeze tanks in one unit? Might want to check there first.

YamahaVector · 12-17-2004, 08:14 PM

Does he fill it to the top? Is there condensation in there?

sled head dave · 12-19-2004, 10:37 PM

Small engine guy, your right in that the coolant and oil tanks are attatched. although barely, just a thin strip between the 2. I can't seem to find a leak between them. I pressure tested the coolant tank at 11 psi and nothing, but i'm thinking maybe the heat of the antifreeze, and a pinhole maybe blow through? Never seen anything like it though. Can't imagine there would be that much pressure to force it through? What else can it be, other than a leak between tanks?
As to the last reply, usually it is filled to the top before 1/2 tank is reached. But since it's been doing this. tried emptying tank completely, and filling with new oil, comes back after a few tanks of gas.
Guess easiest thing would be to change the tank, but was hoping somebody had a cheaper idea.
thanks again
Dave

**smallengineguy** · 12-20-2004, 06:29 AM

If it's not condensation, it's gotta be the tank. Are you also adding coolant now and then?

sled head dave · 12-20-2004, 11:30 PM

Can't say for sure how much coolant is being added since its my brothers sled. But as far as I've seen, little or none has been added. If it is coolant, and not coming from the tank, is there anywhere else for it to come from? I tried letting some oil from the tank settle in a jar,,wouldn't seperate. As opposed to mixing some together, they always seperate. We mixed water and oil, coolant and oil, in jars, always seperated. this stuff doesn't do that. Had the sled since new, till I sold it to him, was good all these years. Can't figure out why tank would leak now..Think I'm gonna try a new tank ..

**smallengineguy** · 12-21-2004, 06:14 AM

Try a different brand oil. It may be foaming (getting a bunch of tiny bubbles in it) from all the vibration, etc. while riding. Then get a tank if that's not it.

700 Doo · 12-21-2004, 07:08 PM

Hey SEG correct me if i'm wrong but doesnt the rotary valve engines have an oil inlet between the cylinders and an oil outlet in bottom of crankcase to oil the rotaryvalve gear and waterpump gear?Mabey waterpump is leaking into crankcase mixing with oil and is curculated back into the tank through the return line that goes to the oil tank?

**smallengineguy** · 12-21-2004, 07:55 PM

I know a lot of them had a separate tank for rotary valve oiling, but if what you said were the case, wouldn't you also get oil in the coolant?

700 Doo · 12-21-2004, 09:00 PM

Didnt think there would be enough presure there as it more or less just runs through as where there is presure on the cooling system. just an idea.

**smallengineguy** · 12-21-2004, 09:46 PM

Just looked at the online microfiche for it. It only has one hose coming out of the bottom of it...No return. Great suggestion, though!!! Now I'm stumped.....

Jeremy · 12-23-2004, 03:42 PM

Could you be getting some water in the oil? I do some work with lubrication on some large manufacturing equipment. When our oil is milky, it usually means there is air entrainment or water in the oil. Try taking a sample out and let it sit in a clear container. Does water settle out? You could also pour some on a hotplate. If it sizzles, that's the water.

TopOfTheRockies · 04-14-2006, 01:37 PM

The seals on your rotary valve shaft are bad.

1. Drain oil and coolant from engine and lines.
2. Remove water pump cover, washers, and support plate on exhaust side, followed by the rotary valve cover and rotary valve on the carb side.
3. Mark the rotary valve and shaft on the case when the mag side piston is at TDC so you can put it back together without having to worry about re-timing.
4. Remove rotary valve shaft from engine (either use the proper pusher or "fight" it out with a rubber hammer from the coolant side . Be sure to put a nut on the shaft threads so that you do not damage them.
5. Inspect shaft bearings, springs, and seals. Local dealers usually have these in stock. Chances are if you're leaking oil but not coolant than you only need the oil seal but I suggest you do the pair of them together. This will keep them from mixing together later on.
6. Put the rotary valve shaft back in the engine, making sure to line up your timing marks on the valve from earlier.
7. Slide the oil and coolant seal onto the valve shaft from the exhaust side, making sure to put them on the correct way and leaving a slight gap in between them for the weep hole (this is why you noticed a leak in the first place - it's good not to accidentally cover it up!)
8. Put washers, impellers, and covers back on both sides of engine, and re-attach all hoses. This is a good time to inspect your oil hoses from the reservoir as they age/rott over t ime.