New Issues:
Bukh DV 20 engine:
Had a mechanic work on the raw water cooling system.I'm familiar with it and can take apart and replace impeller and check the thermostat and reinstate etc. However, lst time I started up the engine, first time since mechanic finished working, there was no water pumping out of the exhaust. Usually a healthy flow. Around the big ' heat exchanger unit' which is at the starboard stern with large inlet and outlet hoses it sounded very ' baffly' and louder than usual ; not the normal low noise output with decent water flow out from the port exhaust.
I turned off sharpish and investigated. As best I could see all of the stop cocks had been turned back on but it was dark and I had no light source under the galley sink. SO this may be my problem. I am going to check today. I also checked the impeller and that seemed fine. Was new and has not been used. The previous one was also new, but there was no water pumping out. After many hours took it apart and found the inner ring had parted from the fins and was just spinning around without moving them. I will check this one again today/tomorrow and see if this has happened again. All hoses and copper pipes are Bukh spares and brand new with correct gaskets etc.
However, if it is not then, having read up on this kind of issue, it takes me out of my current knowledge zone. I watched the mechanic, when he was on the boat, remove the raw water filter. He then cleaned the glass tube, made new gaskets and reinstalled it. I made sure the water in stop valve was in the correct ( horizontal mode and open). From reading it seems a common cause of no water being pumped out/through the cooling system is an airlock? This led me to read about self-priming pumps and filter (s) and the process of ' priming them' if the air lock exists/persists?
I could not see any water inside the glass tube of the raw water filter. I will take the right light today and double check. If thee is no water in it does it need 'priming' and how would I do this. My limited understanding is that if it is low enough/below the water line it will be able to self-prime through gravity? It is directly in line with the level of the deep galley sink. The top of the filter is in line with the top of the sink in the under sink recess and the bottom is about half way down the level of the sink. I will get a photo.
I think my water /impeller pump is self priming too?
I don't know how to prime that if that is the problem?
My problem diagnostic sequence will be:
I intend to start with all of the through hulls, taps and hoses and check for blockages and correct 'on' positioning inline.
Then check the impeller and reinstate it if OK; or replace it if defective.
Then test if the water flows. If not I would like to know how to prime, (if they need it) , the RW filter and the water pump please.
I can't think of anything else but will report back tomorrow when I have had a chance to see and/or act on any advice received before then about priming.
I have had replies mentioning an 'occluded exhaust' (thank you) and was also wondering if this is my problem? Barring anything ( except water) being sucked into the exhaust it would seem logical to me that any water in the lower sections would block the outflow of cooling water and also backwash to create the 'baffly ' sound in the cooling chamber?
If this is the case how do I unblock an excluded exhaust please? Presumably it needs some large pressure to force any water out ?
I don't know how to diagnose it other than above, or to check or clear it?
For all I know it may be another form of 'air lock'.
Thank you.
ONC
Bukh DV 20 engine:
Had a mechanic work on the raw water cooling system.I'm familiar with it and can take apart and replace impeller and check the thermostat and reinstate etc. However, lst time I started up the engine, first time since mechanic finished working, there was no water pumping out of the exhaust. Usually a healthy flow. Around the big ' heat exchanger unit' which is at the starboard stern with large inlet and outlet hoses it sounded very ' baffly' and louder than usual ; not the normal low noise output with decent water flow out from the port exhaust.
I turned off sharpish and investigated. As best I could see all of the stop cocks had been turned back on but it was dark and I had no light source under the galley sink. SO this may be my problem. I am going to check today. I also checked the impeller and that seemed fine. Was new and has not been used. The previous one was also new, but there was no water pumping out. After many hours took it apart and found the inner ring had parted from the fins and was just spinning around without moving them. I will check this one again today/tomorrow and see if this has happened again. All hoses and copper pipes are Bukh spares and brand new with correct gaskets etc.
However, if it is not then, having read up on this kind of issue, it takes me out of my current knowledge zone. I watched the mechanic, when he was on the boat, remove the raw water filter. He then cleaned the glass tube, made new gaskets and reinstalled it. I made sure the water in stop valve was in the correct ( horizontal mode and open). From reading it seems a common cause of no water being pumped out/through the cooling system is an airlock? This led me to read about self-priming pumps and filter (s) and the process of ' priming them' if the air lock exists/persists?
I could not see any water inside the glass tube of the raw water filter. I will take the right light today and double check. If thee is no water in it does it need 'priming' and how would I do this. My limited understanding is that if it is low enough/below the water line it will be able to self-prime through gravity? It is directly in line with the level of the deep galley sink. The top of the filter is in line with the top of the sink in the under sink recess and the bottom is about half way down the level of the sink. I will get a photo.
I think my water /impeller pump is self priming too?
I don't know how to prime that if that is the problem?
My problem diagnostic sequence will be:
I intend to start with all of the through hulls, taps and hoses and check for blockages and correct 'on' positioning inline.
Then check the impeller and reinstate it if OK; or replace it if defective.
Then test if the water flows. If not I would like to know how to prime, (if they need it) , the RW filter and the water pump please.
I can't think of anything else but will report back tomorrow when I have had a chance to see and/or act on any advice received before then about priming.
I have had replies mentioning an 'occluded exhaust' (thank you) and was also wondering if this is my problem? Barring anything ( except water) being sucked into the exhaust it would seem logical to me that any water in the lower sections would block the outflow of cooling water and also backwash to create the 'baffly ' sound in the cooling chamber?
If this is the case how do I unblock an excluded exhaust please? Presumably it needs some large pressure to force any water out ?
I don't know how to diagnose it other than above, or to check or clear it?
For all I know it may be another form of 'air lock'.
Thank you.
ONC
