Westerbeke Diesel overheating

jviss · Jun 28, 2018

You might have an air lock in the fresh water coolant side, stopping circulation. Have you tried bleeding it?

31seahorse · Jun 28, 2018

Hello Steph, If the recent overheating has occurred following any work in the engine compartment consider what has changed. The change of position of any tubing could have created an air blockage. Do what is necessary to insure that the tubing is full of antifreeze, not just looking at the coolant level at the fill cap. Cleaning the heat exchanger might have created the condition. We experienced that situation years ago in a Universal engine. We had slightly changed the position of one of the coolant tubes when we changed them.

BarryL · Jun 28, 2018

Hey,
I am not familiar with that motor but from your description of coolant and exchanger I believe it is fresh water cooled with a seawater heat exchanger. You have verified good raw water flow out of the exhaust. Have you tested the engine water pump, the one that circulates coolant? Those do wear out. You can test this by feeling the hose going to / from the heat exchanger. If those hoses are not hot then coolant is not circulating. This could be caused by a bad thermostat or by a bad water pump. An easy test is to remove the thermostat and see if the problem goes away. If so, the thermostat is bad, if not the water pump is probably bad.

Good luck,
Barry

jviss · Jun 28, 2018

Barry, from my knowledge and first-hand experience with coolant circulating pumps of this type, a failure mode of loss of circulation is extremely unlikely. Water pump failures are usually related to the bearing or seal or both. If it's not leaking or making noise and the pulley isn't wobbling around, it is most probably circulating coolant. The exception to this is if a part of a vane on the pump breaks off, it can clog up the coolant passage. You might just take the pump off and have a look, to see if all of the pump vanes are there. (Make sure you have a fresh gasket on hand).

Thermostats are easy to check, in a pot of water on the stove and a thermometer. It will obvious open at the set temp if it's good.

As perhaps was mentioned, an IR thermometer, which can be had for under $20, is very handy for debugging cooling and heating issues.

On the other hand, air in the cooling system is often the culprit for the symptoms described. I've had this on a Universal M25 (Kubota D-850). The W-13 manual says to fill to the top of the filler neck, and the overflow tank to the bottom line, which I assume you did. On my M25, because of the circuitous water hose routing, I found I could purge the air by opening the net on the top of the thermostat housing and pumping coolant into the block drain petcock.

Do you have a water heater installed?

31seahorse · Jun 28, 2018

+1 to what jviss said about a water heater in the fresh water (coolant) part of the system. Perhaps a closed valve or a blockage. Could you force liquid through that part of the water heater while having one hose disconnected to watch fluid circulate? Into a catch basin or jug of course.

Meriachee · Jun 28, 2018

The water heater on the 270 is in the lazarette and it’s actually higher than the rad cap, which is usually the gauge for the level in the overflow tank. Ours had air up there, and did exactly the same thing your is doing. I’d put money on an airlock.

MitchM · Jul 1, 2018

i'd pull your raw water impeller and be sure it did not lose part of a vane downstream to be trapped inside one of the little holes in the heat exchanger. a piece the size of a small pencil eraser can drive your temp up significantly... (while you are at it change the impeller. )

SG · Jul 5, 2018

Assuming you don't have a blockage of the coolant flow within the engine...Did you take that heat exchanger to a radiator shop to have it ultrasonically cleaned? Simply trying to clean it with brushes or acid doesn't always work. The coating on it interferes with the heat transfer.

jviss · Jul 5, 2018

Steph said:
Got rid of the airlock (yea!) and temp was fine when running in gear, tied up at the dock. BUT then when motoring out of the marina, after 10', she overheated unless at idle...... I'm ashamed to say I didn't pull the boat last year so there is probably a lot of growth on the hull.... could this be "overloading" the engine causing the overheating? Thx for your input. Steph

I would think that if you overloaded it de to a dirty bottom it would smoke, not overheat. But just my intuition. It seems to me you haven't solved the cooling problem. It could be there are multiple system faults. Was the raw water flow good when you overheated? Maybe something blocked the through hull on the outside when you moved.

Charles Erwin · Jul 5, 2018

Take the radiator cap off the filler neck and run the motor until warm - that way the thermostat will be open. You will see the coolant flowing. If there is an air lock or a coolant pump failure you will not see the coolant flowing. There is a possibility the thermostat itself is bogus. One caution - if you have a water heater located above the coolant fill neck then it will drain back and overflow out the neck. So to do this test you would need to bypass the water heater so the circulation hoses are below the fill neck. In other words make the fill neck the highest point in the coolant flow circuit if possible. (Sometimes you can't because the thermostat housing is too high and they did not extend the height of the fill neck. If that is the case you need to purge air from the coolant system at the top of the thermostat housing - the highest point - when the test is over. )

The amount of sea water necessary to cool the exchanger at idle is quite low. So you need to make sure there is no restriction from the sea water inlet all the way to and past the mixing elbow. Common problems are impeller debris lodged in the line (or the heat exchanger core) or a hose collapsing internally on the suction side of the pump - perhaps an air leak in your strainer- maybe a kink in a hose between the intake and the sea water pump . A sea water hose collapsing under suction is something you can't see. It will work at idle but not when suction increases as the motor revs up. The last possibilities are the mixing elbow (including the fitting at the elbow that carries sea water into the exhaust and overboard) and the intake itself. Intakes get growth, plastic bags, sea weed, what-have-you that blocks inflow. Mixing elbows and their fittings accumulate debris internally that blocks outflow. So check these sea water components. Replace hoses with new if you are in doubt.

Charles