Loss of all transmission fluid

[sailingwife]

An interesting thing happened while out this past weekend. Our Perkins 4-154 with a Borg-Warner 71CR after heating up lost all transmission fluid into the bildge leaving us without any forward gear. After being towed back to the dock and filing the fluid again, all is well.

There was no wind and we had been running it at a higher RPM than normal to check for engine heating issues. We have only had this boat for less than 6 months so we are still finding these "issues".

Any thoughts or has this happened to anyone else?

[pigslo]

Transmission cooler not working and you boiled it out?

[Faster]

On some transmissions oil can blow out the dip-stick tube vent under certain conditions.

The fix is to drill an extra hole just below the threads near the top of the tube, but so that it's just inside the transmission housing. That way the tranny case can vent without pushing oil up and out the vent.

[sailingwife]

Good information. One theory a dock mate had was that there was some type of pressure vent or overflow with a tube that created a siphon and once started went until all the fluid was drained.

[jones2r]

My instincts tell me that Pigs is on the right track. Any design or installation issues should have been sorted out much earlier.

One analysis is that either the cooling system, assuming there is one, has a problem, or something internal, such as a bearing, is failing, causing excessive heat generation.

It's possible that the fluid cooler is cracked and is leaking. I would look at it first. Flush it out and pressure test. There might be a hose or line leaking if the cooler is external to the transmission. This analysis is saying that the fluid escaped and then the trans overheated, not vice versa.

It's possible that if you were trying to push the boat past its hull speed, the trans was simply overloaded, with slippage causing the heating.

You will want to flush out all of the fluid to eliminate the residual burned fluid remaining from the overheating. Removing and flushing the cooler will help achieve that end. If, in the flushing process, any solid material is dislodged, the cooler should be replaced (discard the old one; it's NOT suitable for a spare) and consideration be given to inspecting the transmission.

Just my thoughts.