Transmission cooler

[Coffeeguy]

I have a 2010 25-R tug that I purchased 3 years ago. During winterization I was informed that the transmission fluid was milky and that water from the cooler was leaking into the transmission fluid. Is this possible, or is the transmission fluid side pressure higher than the water side pressure which would just leak transmission fluid into the cooling water. I was also told the only way to replace the transmission cooler is to remove the engine and that this process would take about 40 man hours of labor ?

 

[BB marine]

Yes it is possible and happens often to older equipment that is used in saltwater applications. The tubes deteriorate and leak. The transmissions pump pressure while running should over come the leak and some trans fluid will leak out. Normally the leaks are not that big but eventually become large enough to cause issues. The water stays in the tubes when the engine is shut down. The oil in the cooler drained back to the transmission when the engine is shut down. This is why you should check your fluid level right after shutting the engine down for proper fluid level. When the fluid drains down any water that is leaking from a tube is now leaking into the shell side of the cooler where oil normally is when the engine is running. This water mixes with the oil and you have water in your transmission.

You did not state what power plant you have Yanmar? Cummins? The cooler is normally mounted over the transmission. But without knowing gear and engine I can't comment on replacement. I can comment on the transmission should be flushed and drained until all contaminants are removed ASAP. If not you will be replacing it too.

 

[Coffeeguy]

Hi Brian the Ranger has a Yanmar 150 with a ZF 45A transmission.

 

[dclagett]

On both ZF45A transmission I have had, one on a Volvo Penta and one on a Yanmar, the transmission oil cooler was mounted on the top of the transmission. It is a cylinder with 4 hose connections. There are two raw water connections, one on each end of the cylinder, one for input and one for output of raw water. Also there are two oil connections, one for oil coming from the trans and one going back to the trans. These oil connections are on the side of the cylinder. On both my trans oil cooler configurations it was very easy to swap out the trans oil cooler. Less than an hours effort. No engine removal required.

I would take a look at your configuration and ask some questions of your mechanic to understand what is different for your boat.