Replacing The Fresh Water Circulating Pump On Our Ford Lehman 120

If you had read our previous post, we discovered the fresh water circulating pump on the front of the engine had developed a leak and needed replacement. The great folks at American Diesel were quick to get the replacement shipped to us and in my discussion with Bob Smith, he suggested that we replace the engine belt at the same time and be sure and replace it with the proper belt to assure there would be less likelihood of another issue with the pump soon. We agreed and had a belt shipped with the pump. The replacement was actually quite easy.

The first step is to completely drain the fresh water system. This can be accomplished by removing the drain plug for the "fresh water side" of the heat exchanger. Expect at least a couple of gallons to drain out, so have enough containers to catch most of it. Once all of the coolant is drained, we removed the hoses from the circulating pump to the manifold. Expect to also loose some coolant here, so we placed a small bucket under the hoses as we removed them.

Next step is to remove the alternator adjustment bracket and then remove the engine belt. The alternator need not be completely removed. We found it easier to next remove the belt pulley from the pump to make access to the pump mounting bolts easier, but this is not necessary at this time. Once the old pump is unbolted and removed, the pulley needs to be swapped from the old pump to the new one. Again we waited until the pump was mounted to re-install the pulley. We took this opportunity to put a fresh coat of engine paint on everything. In addition we replaced the connecting water hoses from the pump to the manifold.

Once the paint was dry the new pump could be installed. The surface where the pump is to be mounted needs to be clean and smooth and care taken to remove all of the old gasket material. With that done, the new gasket needs to have a sealer applied to both sides of it and placed properly where the pump will mount. The sealer should hold the gasket in place. Position the pump carefully so as not to move the gasket and insert each bolt and just turn down hand tight. We like to apply anti-seize to all bolts. With all bolts insert and started, including the bolt for the alternator adjustment bracket, snug them all up. Once they are snug, tighten them down more, in a staggered sequence, until they are all tightened adequately. With the pump body mounted we attached the belt pulley and tightened down the pulley bolts. Once completed, we turned the pump shaft by hand to be sure it moved easily. The bolt for the alternator adjustment bracket is then removed and the bracket re-attached and the alternator loosely bolted to the adjustment arm.

One of the oddities of the Ford Lehman is the fact that if the engine belt was to break or be in need of immediate replacement, this can only be accomplished by draining the fresh water system and removing the hoses attached to the circulating pump. This does not lend itself well to fast repair and getting back under way quickly, especially if you are dealing with hot coolant. A little trick passed on the me by another trawler owners is to place a replacement belt strategically over the hoses in anticipation of an emergency. This would eliminate the need to drain the system and remove the hoses. So before the final attachment of the water hoses we place the belt over the hoses and wire tied it back on the engine so it would not get fouled in the new belt or any of the pulleys. With that done, the remaining hoses were attached using new hose clamps. With the pump, pulley and hoses all reattached, the alternator could be adjusted for the correct tension on the engine belt. It needs to be tight enough not to slip, but not too tight to again put strain on the pump and cause future problems.

With everything tightened and adjusted properly, the only thing left is to refill the fresh water coolant. We prefer to use a premixed solution of 50/50 coolant but if we use straight anti-freeze we always mix it to a 50/50 solution using distilled water. Once the coolant is added the engine is run long enough to open the thermostat, then shut down and more coolant added as needed. With that done, we ran the engine for approximately 30 minutes more to check for any possible leaks. Everything went as planned and no leaks were detected. At this point we have replaced the oil and transmission coolers, replaced the circulating pump, cleaned the heat exchanger, added the recovery neck to the fresh water coolant tank replaced all of the engine water hoses and clamps and replaced the fresh water coolant. All in all, Beach house should run at her proper operating temperatures for quite a while. But we still do have a few more projects to complete.

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