Tilt/Trim leaking down, mystery fluid ?

[Moody Blue]

Had the boat out last weekend (1992 Mariner 40 4 cyl)and discovered that the tilt/trim slowly lowers by itself. Takes only a few minutes to go from half raised to completely lowered. No troubles before this outing. No external leaks and I checked fluid level per the manual. Fluid level was a little high if anything BUT, it was pink in color and the consistancy of dish soap but oily. What the heck is that? I thought it was supposed to be transmission fluid? Anyone?

 

[Chris1956]

Re: Tilt/Trim leaking down, mystery fluid ?

Moody, I think you should suck out the current fluid and replace it with the correct stuff. If the trim still lowers, you have an issue with the piston seal or perhaps the control valve.

 

[sleepinin]

Re: Tilt/Trim leaking down, mystery fluid ?

You might check and make sure the manuel release screw is tight.

 

[studlymandingo]

Re: Tilt/Trim leaking down, mystery fluid ?

Sounds like the fluid is ATF which is acceptable for the unit. There is probably an internal leak which is causing the bleed-down of the cylinder.

It is possible that you only have some air in the system. First thing I would try is raising and lowering the unit several times, keep depressing the button after it has reached full in or full out. Then with the motor in the full-tilt mode, open the fill screw, if you get a whoosh of air pressure, do the same thing again until you have bled out the excess air.

 

[Moody Blue]

Re: Tilt/Trim leaking down, mystery fluid ?

Well I've tried all of the above with no success. I've also sprayed the outside of the entire assy with leak detection fluid and found nothing. Must be something internal. Where do I look next, pump/reservoir or the cylinder itself. I understand there is a check valve that sometimes leaks. There is a possibility I might have overtightened to manual bleed screw at some time. It was REALLY tight when I tried to unscrew it.

This is a single hydraulic cyl with a motor/reservoir mounted beside it. Sierra #18-6777.

Any help would be greatly appreciated.

 

[Moody Blue]

Re: Tilt/Trim leaking down, mystery fluid ?

Any takers?

 

[Chris1956]

Re: Tilt/Trim leaking down, mystery fluid ?

Moody, It sounds like you have isolated it to either the piston seal or the check valve. You might like to price a repair kit for the piston seal (if one exists) and the check valve (if one exists), to explore your options. On my Mercury PT/T, it has always been the piston seal, and never the check valve. FWIW.

 

[Moody Blue]

Re: Tilt/Trim leaking down, mystery fluid ?

Thanks Chris, upon further investigation I've found that after operating the unit through several full cycles that the fluid is foamy or full of bubbles. Thats why it looked pink the first time I opened the fill port. Does that indicate one type of failure over the other? The unit thats on there is a Sierra marine part. Do you suppose they are repairable?

 

[rickdb1boat]

Re: Tilt/Trim leaking down, mystery fluid ?

Indicates air and or moisture in the system. Keep bleeding it and see what happens.. Might take 10-15 times up and down. I would drain it and refill if it doesn't get better.