I've got a Universal M50 5444 44 HP diesel. Once the engine gets to around 160, the thermostat opens and temp drops to around 110 and when running at 1800-2000 rpms it won't get about 130 degrees. Put a new thermostat in and it is doing the same thing. Why won't it close after it has opened?
Thermostat
- Thread starter T33
- Start date
It's sea water cooled with a heat exchanger and antifreeze. It started overheating and I went through everything, sea water pump, water pump, heat exchanger, thermostat, hoses, finally flushed out the engine and years of junk came out and that solved it. But the thermostat issue has been going on before the overheating and after. Thermostat just doesn't seem to be closing after it initally opens.
Thermostats aren’t the most precise parts of an engine. It’s pretty easy to put it in a pot of hot water with a thermometer and watch what happens as it heats/cools.
Assuming the ambient cooling water temperature from the ocean where you are is low, the engine might not develop sufficient heat to exceed 130 degrees.
Assuming the ambient cooling water temperature from the ocean where you are is low, the engine might not develop sufficient heat to exceed 130 degrees.
Themostat is new. I'll try heating it up in water to see what happens. It is suppose to open at 160. It is working. After running 15 mins. or so, the engine will heat up to around that temp and it does open. After it opens, the engine runs very cool - 100 - 120 and stays there. Water temp in Puget Sound is usually in the high 40s. Today it is 49 degrees.
If you've got an IR gun, try shooting around the stat housing when up to temperature to see if you have higher temps. anywhere else.
My understanding is that the stat sets the ideal water temperature for optimum fuel combustion and also allows the recommended crankcase oil to do its job. Just what I read.
Good suggestions. I've heard is not good for a diesel engine to run cool. They like to run hotter. I think the previous owner had put a can of bar's stop leak every year for a long time for because he heard it was good for the water pump. There are no leaks. All that Bar's clogged the engine over time. I flushed it all out. Took 10 minutes of chocholate foam coming out before it ran clear. Also have a new 3 in. heat exchanger. Add the cold Puget water and maybe running 110 - 120 is ok. I'll use an IR gun and test the thermostat in hot water.
Bit of advise to all - engine was overheating and we looked at everything, themo, sea pump, water pump, heat exchanger, hoses, nothing we did worked. Then noticed gunk build up on inside of thermo housing, sea water pump and water pump. After flushing, overheating problem was solved. Be careful about additives.
Bit of advise to all - engine was overheating and we looked at everything, themo, sea pump, water pump, heat exchanger, hoses, nothing we did worked. Then noticed gunk build up on inside of thermo housing, sea water pump and water pump. After flushing, overheating problem was solved. Be careful about additives.
When you check the thermostat in water, check the opening temp and the closing temp. I would cycle it a couple times and write down the results. Also, are you certain that the thermostat is the correct one? If the PO put in a wrong one, and you just pulled it and replaced with an identical, maybe it isn't correct.
jssailem
SBO Weather and Forecasting Forum Jim & John
- Oct 22, 2014
- 21,344
At 1800-2000RPM, you are running your engine at 60%. Your engine specs say it is rated at 44HP at 3000 RPM, which would be about 85-90%. The engine and thermostat may be just fine. Try running it at 3000 RPM to see if the temperature at WOT rises to what you expect. Be sure you are running the engine under load. Tied to the dock but with the prop spinning if you must.
Have you confirmed that the TACH is calibrated?
Here is the data from Westerbeke
universal_m50.pdf
Have you confirmed that the TACH is calibrated?
Here is the data from Westerbeke
universal_m50.pdf
The thermostat should be able to keep the engine at temperature at any RPM and load. It should close off nearly all water to the heat exchanger when it is below its opening temperature.
thanks Ralph, I guess that makes sense.
My little 2GM20F runs “warm”, but overly hot.
I shoot the engine in different spots with an IR thermometer occasionally to see how well itmis cooling.
I was really surprised when I put my foot in the exhaust water while motoring…. Barely Luke warm at that point in the flow.
Greg
Standing on my swim platform, auto-pilot driving the boat….that was death defying.That sounds positively death defying.
I flashed my foot through the exhaust water, braced for scalding hot water….and it was
