2007 Volvo penta 4.3 gxi-j blowing hose of thermostat housing.

[Topcat2vin]

I took my boat out the other day and after a few minutes it blow the hose from the thermostat housing to the engine pump off. I have now removed the housing to check the thermostat and it seem ok. Holes are also ok. I was going to check risers and drained the manifold and block. No water came from block. Could it be the engine pump is not pumping the water?

Thanks for any advise

 

[BRICH1260]

I`d say is pumping water but it`s blocked up somewhere and causing excess pressure on the supply line. I`d check the thermostat housing closely and make sure the Tstat is in properly. Do a test by removing the Tstat and running it briefly to see if it blows off again. If it does not, it`s the Tstat. Perhaps installed upside down?

 

[Lou C]

When the engine is cold, the water from the impeller pump has to bypass the engine to the exhaust system, where it then exits overboard. There is a bypass port in the thermostat housing that has to be open for this to happen, the other possible cause is that your exhaust elbow are clogged with rust, is the engine overheating?

 

[Topcat2vin]

The Engine did not overheat, I was only out a few minutes and the temperature was sitting at 150F then I noticed it fell to 100F when I looked in the engine bay the hose was off with some water gushing - i was close to a pier so moored up and done a quick repair before coming back to the ramp at idle.

I have a 4.3 gxi and I could not see how to remove the thermostat from the housing - it seems to be lodged into it from the bottom and held in with an O ring - it is original. I taped up the holes in the housing and poured hot and cold water into the housing. The thermostat seems to be opening OK.

I also taught it might be a block in the risers and went to drain down the manifolds and engine - it was then I noticed no water in the block. Manifolds were full.

Would a bad impeller be the problem. It was replaced at the end of last year. I would have expected if it was an impeller I would not have been able to build up pressure in the housing to blow the pipe off.

 

[Lou C]

The o ring holds the thermostat in the housing, you have to pry the o ring out then the stat will come out. OMC & Volvo used the same exact thermostat housing. If there was no water in the block, the temp sensor has no water to read so the engine could have been hot but with out water there's nothing for the temp sensor to read. Are you sure there are no raw water leaks on the engine, like from drain plugs and/or core plugs? If the manifolds were full of water, and the were drained for storage, I doubt that the impeller is bad but need more information to really judge.