Ralph Halstead of Marmet, West Virginia, asks:
"My Perkins 4-236 is a great engine and has an external cooling system. Recently I’ve noticed some drops of water on the dipstick after use. What do you think might be causing this condition?"
Nigel Calder replies:
It could be a number of things. I would first check whether water is siphoning in through the exhaust system from the raw-water cooling system. There should be a siphon break somewhere between the raw-water pump and the point at which the raw water discharges into the exhaust. If your system has that break, check the valve and make sure it is clean. If you don’t have a siphon break, you should install one.
Next check the raw-water pump impeller for damage. If you’re lucky, this could be your problem; if it isn’t, the fix gets a lot more complicated and expensive. If the engine has an oil cooler, this is another place to look. If the oil cooler uses fresh water, look in the header tank for oil. If the system is raw-water cooled, look for oil coming out of the overboard discharge. You could also remove the oil cooler and have it pressure-tested by a radiator shop.
There’s also a chance that you could have a leaking cylinder head gasket, leaking seals around the cylinder liners, or a cracked or corroded cylinder liner.
If any one of these conditions is the cause, you’re looking at an extensive rebuild that might not be warranted on an old engine.