Topic: oil getting thinned out

[toy tractor]

ok after wheeling for an hour or so my oil gets water thin, this is after changing it on the trail. using 10/40 castrol gtx. does not look like a head gasket leak, the oil does not change color just gets thin and the motor starts to knock. in need of some help on this one, any ideas ?

[79coyotefrg]

sounds like the diaphram  in the fuel pump is gone letting fuel pump right into the timing cover mixing with your oil

[toy tractor [OP]]

so you think if i replace the fuel pump it should fix the problem ?

[BigMike]

Well,

All liquids become more thin (more viscus) the more heat you add to it. And since you are using a multiweight oil, one with polymers, its ability to change viscosity will also change with the amount of heat added.

When it is cold, the oil is thick and follows the 10-weight principle which means that it's thickness is able to change rapidly, and when it is up to operating temperature, it becomes much more thin and follows the 40-weight principle which means that it's thickness is not able to change rapidly (more constant, stable viscosity).

I am sure you already know this, but the point is that as oil is heated up it will become very thin. This however, is not a problem at all! The oil is designed to work and still lubricate your engine at this lower viscosity (thinner).

So having thin oil is not a bad thing, but what you want to be sure about is how sticky the oil is when its thin, or what is know as its film strength.

Next time you get your engine good and warm, pull out the dipstick and touch the oil at the end of the dipstick between your free hand's thumb and index fingers. Then let go of the dipstick, and touch your fingers together over and over. Pull your fingers apart really really slow and notice how far you can pull your fingers apart without the oil separating. This represents the oil's "film strength".

Good, Fresh oil will allow you to separate your fingers by almost a 1/4" before the oil separates. This is a very high film strength. But when oil gets worn out, its film strength decreases alot.

Do you follow me? Its kind of hard to explain I guess..

But this is how I check the life of my current oil in my engine. Most people go by the color, but even oil that "appears" clean may have already lost its film strength. And this film strength, or stickiness, is VERY IMPORTANT for the oil to stick to and cling to moving parts. If the film strength becomes too weak, then the oil may be thrown naturally from moving parts just from the centrifugal forces that are present on any rotating object.

You can try to use a single grade "straight-weight" oil, such as a 40W oil, which would resist its change of viscosity, but once it gets hot, it will be just as thin.

Regards,
BigMike

[BigMike]

Well you could smell the oil and see if it smells like gasoline, and you can also check the underside of your oil cap for any moisture build-up, which would indicate water in the crank case.

[toy tractor [OP]]

the oil almost looks it could have fuel in it, but doesnt smell like fuel. i will check the cap for moisture. thanks big mike

[BigMike]

Sometimes it may smell like gasoline if you have worn out cylinder walls or piston rigs, and the crank case oils are receiving "gasoline poisoning".

But if it is the mechanical fuel pump is really leaking into the cylinder head, then there would definitely be a noticeable amount of fuel mixed in there that you definitely would be able to detect.

Might I also note that this fuel pump issue only applies to Carbureted engines; Is your 1985 Carbureted of Injected?

[toy tractor [OP]]

85 22r carburated, only mods on motor is a header

[79coyotefrg]

geeze   talk about a short answer 

i was assuming it was carbed 

[Rocksurfer]

geeze   talk about a short answer 

i was assuming it was carbed 

Since when does he answer anything that doesn't read like a thesus?

[kyle_22r]

running too rich can waste an engine by washing down the cylinder walls.  the oil film in the crosshatch gets washed away by the gasoline, and creates friction that rapidly wears out the rings and pistons.