Question about transmission coolant on the V-P MD17C in an A-25

[NickScheuer]

I drained all of the coolant from our engine and transmission last Fall and have forgotten which way to turn the transmission drain cock. The four drain cocks on the engine block all turn clockwise ("righty tighty") to close. Is the drain cock on the transmission the same?

[WillieC]

Mine has plain old plugs. Do the valves look like the ones on the engine?

(Side question, does your transmission use raw water for cooling or is it run through the same heat exchanger used for the engine? I am assuming you have a heat exchanger. I don't think they were OEM but rather aftermarket installed.)

[NickScheuer]

No heat exchanger, engine and trans cooled by sea water drawn in through a through-hull with shut-off valve, through the trans first, then past the water pump, then into the engine, then out with the exhaust. The valve is not like the four valves on the motor, which is the reason I don't know which way to turn it "closed". I reworked all of the motor valves to get gunk and debris out of them so I know how they are designed.

Hoping to launch Fri. I'll know if the trans valve is "open" by mistake if I see water coming out of the trans after I start the motor. However, the valve is hard to reach with the engine box still in place.

[NickScheuer]

The plugs on the engine valves have handles made of 1/8" brass rod. The trans valve plug has a handle formed from brass sheet stock; not nearly so robust.

[WillieC]

It sounds like a radiator drain of old. Same principle. Righty, tighty etc....

Do you not run your engine for test purposes before splashing? Pretty easy to set up.

[NickScheuer]

Did not test on trailer. Launch in our local river is convenient. Right though, test without changing coolant to antifreeze is easy, except where the DuNORD is stored in a pole barn now doers not have water.

[NickScheuer]

I was also thinking of those old auto radiator drains, WillieC. That was the last time I saw one of these pressed metal drain valves.

[WillieC]

Barn without water is a problem.

It took me a while to figure out how to run the VP on the hard. I replumbed the intake after the seacock with a tee and a plug for attaching a hose to a bucket I place outside the hull. But you do need water running into the bucket. I let the raw water pump pull from the bucket but since the hose is empty at the start I help it by using the garden hose to force prime the system. You don’t want the impeller running dry too long.

I just modified my pickup hose to also quickly attach to the outlet side of the transmission so I can backflush it through the strainer out through the seacock under city pressure. I also tried filling the empty transmission water jacket with vinegar overnight. It knocked a little crud loose. I may try something stronger in the future. These trannies are scarce so I want to keep it as long as I can.

[NickScheuer]

Thanks! Didn't know crud in the tranny could be a problem. Engine failed to cool during Fri test. Will be isolating components to determine what isn't working. Larsen Marina in Waukegan gave me some ideas. I've found it fairly easy to just unclamp inlet hose from thru-hull and position it in a bucket of water.

[NickScheuer]

The GOOD NEWS is that my water pump works fine! I disconnected the inlet hose from the thru-hull valve and put the end in a bucket of water. Then I disconnected the outlet hose from the pump (to motor) and used a short length of miscl hose to direct discharge into the same bucket. When I started the engine and ran it for a couple of minutes the water flow was fine. Since the inlet water ran through the tranny on its way to the pump, I know that is OK, too; no "gunk" there. Now I've got to find why the motor temp gauge is indicating hot (needle in red). The Service Manager at Larsen (arguably one of the best diesel mechanics in the Midwest) suggested removing the hose connection to the thermostat housing to see if any broken pump impeller blades are plugging the inlet. I don't think I'll find any because I've changed impellers several times over the years and never found one that had shed any blades. However, since I know the new thermostat is a positive obstruction to water flow until it opens, I believe I'll remove the thermostat and see how the engine runs without it.

[NickScheuer]

Maybe I just need to refill the motor with cooling water (it was drained for winter) in order for the thermostat to work properly. and removing the thermostat for a trial run will do that, eh?

[dkirsop]

While you are at it test your thermostat too. Use your wife's best pan and favourite candy thermometer to see if it opens at the correct temperature when slowly heated on the stove. See which one reaches the danger zone first.

[NickScheuer]

Good idea, while I have it out. It's a new one bought from Larsen over the winter. The original (old at least) tested ok in a pan on the stove, but I just thought a change was overdue.

[WillieC]

Don’t forget the exhaust elbow. Once that plugs up your water flow will be greatly impeded. I think that may be difficult to check while in the water. Removing the thermostat should surely allow as free a flow as you could get. Without a heat exchanger, that you could remove the cap and verify coolant flow, I am not sure how you can be certain water is circulating.

Oh, put your hand on the exhaust elbow. If it is plugged or restricted, even though the pump may be good, it will become quite hot fairly quickly.

[NickScheuer]

After finding that the water pump works fine I studies the exhaust system and noticed a copper tube extending from thermostat housing to exhaust elbow. It would seem that this tube transmits cooling water to the elbow OUTSIDE the exhaust manifold by bypassing the thermostat. If no water is exiting the transom, it would seem to indicate the elbow is completely clogged. Any thoughts?