Hydraulic Cover Leak

I have a hydraulic cover leak at the front, right corner of my grandfathers MF 35. It has a diverter valve installed just above the leak. Should I just tighten and torque the nearby bolts, or loosen them all and torque them all? I ask such a simple question out of an abundance of caution. May 2, 2015.

It’s possible the leak is coming from where the front cover is bolted to the rear axle housing, and tightening the bolts may solve the problem. Like any casting, torque the bolts to prevent warping or cracking.

However, it is also possible the leak is from where the diverter valve attaches to the top cover. If that is the case, clean the area around the leak, remove the diverter valve, clean the surfaces, replace the O-ring, replace the valve and tighten the bolts.

The O-ring should be one with a high Duro rating, that’s the hardness of the rubber. If the O-ring is softer, has a low Duro rating, it will leak. You should have the MF part number for the O-ring in your parts book and with that information should be able to cross-reference it to determine the dimensions and correct Duro rating. If that does not stop the leak, you will have to pull the top cover and replace the gasket.

FYI there are several gasket part numbers that can be used. The gaskets vary from a thin, brown kraft paper gasket to one that is thick and has a metal core. For the most part, the gaskets are interchangeable. As the operating pressures were raised for the hydraulic system and the top cover thickness was increased, the gasket thickness and durability was increased. The correct gasket part number can be determined from the serial number.