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Volvo D12 675 overheating alarm at low speed

Cuky1

New member
Hi, have a overheating problem on the princess 50 2006 on Volvo D12 675 port side engine only (stb side is Ok). When I'm in navigation and the engines running abut 1100rpm or more(also on maximum), both engines are on 86-87 degress, then If I slow down under 1000rpm, left engine is going very fast to overheating alarm??? Impeler is new, termostat also, heatexchanger is cleaned with "barnacle buster", new temp senzore..., the engine has only 400 working hours...does anyone had a similar problem??

Thanks, and sory for my bad language
 
Sounds very strange that it overheats only at low rpms. Have you checked that it is really overheating using an infrared heat gun etc? If it is really overheating I would first check for air leaks between the raw water pump and the water pickup (through hull). At 400 hrs you shouldn't have issues with the water pump itself but maybe an air leak in the strainer or piping? An small air leak may cause low water flow when the impeller is spinning slowly but let enough water through when it is spinning faster. There are probably seals inside the pump that might cause this type of effect also but I would expect to see small drips of water from the relief hole in the pump if these were leaking. Have you checked to see that the strainer is staying full when you are at the overheat rpms?
 
Hi,
I have the exact problem, i have D12 with only 300 HRS, port side is over heated on low RPM.
change impeller, system clean with barnacle buster, no leaks, new thermostat.
anyone ? any idea?
 
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