Hello All..

I have a Mercruiser 502 mpi with open water cooling and my p/s system went empty and I can't seem to find where it's going. I used trans fluid so it seems like it would be easy to find a leak, the steering ram is dry along with the pump and lines. I thought it may be leaking inside the cooler but I don't see anything inside there either. I'm at a loss at this point, anybody got any ideas... Thank in advance.

Pressure test your pwr steering cooler - a not completely drain upon winterize can ruin them also saltwater apps and just plain old father time.

You are not going to see an internal leaking pwr steering cooler as it pass out with water most likely with the exhaust water side or another form of bypass depending how your app is set up.

tested one last week as how I do it. Use a gear case pressure checker and pump air into the cooler.

From what I've read, the fluid passes through the cooler on the return side so it's under very little pressure... I "assumed" the cooler would have to have a very visible leak if it was leaking inside the cooler..
Also the cooler had been sitting empty on another boat for a 15 years...

How many psi did use in the pressure test?