Overheating still

[wonko]

I got some good advice last time, tried it all and still having the overheating problem.<br /><br />Scenario: Volvo TAMD41A diesel engine, <1000hrs on it and it starting overheating. Found some pieces to an impeller that disintegrated in the oil cooler and thought we solved the problem, but that wasn't it. It idles fine all day, but when brought up to anything close to 3000 RPM, the temp goes up to 200 and we shut it down. (The exact engine sitting beside it doesn't hardly even get to 160).<br /><br />Things we've tried:<br />Removed and cleaned oil cooler<br />Removed and cleaned closed water heat exchanger<br />Removed and cleaned aftercooler<br />Removed and inspected the water pump<br />In the process of the above we ran a "snake" through every hose to make sure that it was clean<br />Got underneath the boat to check the thru-hull, it was clean<br />Strainer was clean<br />Replaced the thermostats (wrong ones maybe?)<br />Tried two different gauges<br />Opened the valve to the thru-hull all the way (bad valve?)<br /><br />I know on gas engines a busted head gasket can make it overheat, what about a diesel? Any other ideas would be greatly appreciated.<br /><br />

 

[petryshyn]

Re: Overheating still

Is the cooling system pressuring up? Is the overflow bottle getting over-filled?<br />Start the engine cold and look for bubbles in the fill neck of the cooling system. If bubbles = head gasket leak.....

 

[wonko]

Re: Overheating still

Never noticed any bubbles, but then again, never looked, I will do that.<br /><br />On a side note, it has two thermostats side by side in the same housing, the original ones have two different ratings, any idea why?

 

[petryshyn]

Re: Overheating still

I'm just guessing, but I'll bet 2 of the same temp would cause hunting between the two and result in up and down temperatures.<br />(just a guess)

 

[trevorcday]

Re: Overheating still

I'm no big expert on Volvo's so take this for what it is worth. We had one in with the same symptoms and what the problem turned out to be was a leak in the suction side of the system between the sea water pump and the pickup. The pivots for the drive were all worn and this caused a swivel joint to open up and allow air into the system. When the boat was not on plane it didn't matter since the leak was under water. Once the boat planed it would suck air and overheat. Again I'm not sure what model this was relative to yours but maybe this will be worth looking at.