Hydraulic fluid dipstick question

[WV NATIVE]

I’ve got an odd question about the hydraulic fluid dipstick on my B7500.

When I pull the dipstick on my hydraulic fluid it is barely touching the stick but when I insert it again and pull it back out it shows full.

Anyone else have that issue?

It’s the only piece of equipment I own that’s acts like that. I thought the vent may be clogged up but it breathes free.

Not sure which reading I should believe.

Pictures aren’t the best representation but you get the idea. First pull of the stick looks dry - second doesn’t.

 

[leonard65]

Ok same exact thing on my B2320 I never posted it because I didnt want anyone to think I was crazy.Also so hard to read, clear fluid on the orange stick.

 

[WV NATIVE]

Ok same exact thing on my B2320 I never posted it because I didnt want anyone to think I was crazy.Also so hard to read, clear fluid on the orange stick.

If you’re crazy then I guess I am too.

 

[North Idaho Wolfman]

Put a piece of black shrink wrap on the dipstick or dye in the fluid, to read it better.

 

[Runs With Scissors]

I vote for “dye”.

Cheap, easy and effective.

 

[WV NATIVE]

I can see the fluid - the stick is dry the first time I pull it.

I can’t understand why it’s on the full mark after it’s reinserted.

 

[BAP]

As far as the oil being on the dipstick, believe the second reading. I think that because the dipstick has a tight fit at the top, it traps air and doesn’t allow the oil to come up the tube to proper height when the dipstick is in place. When you pull it out, the oil then can fill the tube up properly. Metal dipsticks like in the engine, don’t have that really tight fight at the top so the air can move out of the tube and allow the oil to maintain the proper height.

 

[imarobot]

As far as the oil being on the dipstick, believe the second reading. I think that because the dipstick has a tight fit at the top, it traps air and doesn’t allow the oil to come up the tube to proper height when the dipstick is in place. When you pull it out, the oil then can fill the tube up properly. Metal dipsticks like in the engine, don’t have that really tight fight at the top so the air can move out of the tube and allow the oil to maintain the proper height.

Be interesting to pull the dipstick out just enough to let air in and wait a bit before pulling it out all the way to see if the oil level on the dipstick went up.
I would try this myself, but I don't have one of those machines.

 

[D2Cat]

If at any time the dip stick shows a higher reading then other times go by the highest reading. No matter the physics involved, the fluid is in a container (transmission) and the actual volume doesn't change in any circumstance you describe.

 

[imarobot]

If at any time the dip stick shows a higher reading then other times go by the highest reading. No matter the physics involved, the fluid is in a container (transmission) and the actual volume doesn't change in any circumstance you describe.

Very true, but I'd still like to see the physics of why this happens

 

[nbryan]

The o-ring seals near the top of the dipstick prevent the transmission fluid from filling the dipstick tube from below.

The o-rings seals stop the trapped air under them to escape and allow the oil below to rise up and level with the rest of the tranny oil in the case.

Just pull the dipstick and re-check after a few seconds. It's always been like this for my B2650.

 

[Bee-Positive]

Put your finger on one end of a straw.
Put the open end of the straw in a glass of water.
Note how far the water goes up into the straw.
Take your finger off the end of the straw.
Note how far the water goes up into the straw.