In reference to my article of today on my engine overheating. I think I have found the problem.Following the advice in Calder's book "Marine Diesel Engines", I found that air bubbles appeared in the heat exchanger will the engine was running. According to Calder this indicates a blown head gasket. Question: Must I take the heat exchanger off to get the head off? Advice on the steps needed for getting the head off would be appreciated. Thanks
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mechanic
Bill, I would buy Yanmar's service manual if you're determined to replace the head gasket yourself. My advice to you is to not take how-to advice from the well-intentioned folks here regarding the procedure on head gasket replacement. The wrong advice could cost you the motor. I don't know how much of a 'motor-head' you are, but you will need a high-quality torque wrench, and one that will fit in the confined space of the motor compartment. (The motor head is supposed to be re-torqued every two years anyway - according to my Yanmar mechanic - so it will come in handy in the future) I have done several engine tear-downs of the ordinary street variety, and if it were me, I would most likely farm the head gasket job out to an experienced Yanmar mechanic. Those little Yanmar motors are so expensive to replace....I would be inclined not to take the risk of wrecking it. If you do decide to take that job on yourself, think about whether or not you will need to have the head machined - it may be warped. A warped head might be the cause of your blown gasket. And putting a warped head back on with a brand new gasket will be ineffective to say the least. And I confess I speak from painful experience..... Good luck if you decide to forge ahead. Mike
Bill, I would buy Yanmar's service manual if you're determined to replace the head gasket yourself. My advice to you is to not take how-to advice from the well-intentioned folks here regarding the procedure on head gasket replacement. The wrong advice could cost you the motor. I don't know how much of a 'motor-head' you are, but you will need a high-quality torque wrench, and one that will fit in the confined space of the motor compartment. (The motor head is supposed to be re-torqued every two years anyway - according to my Yanmar mechanic - so it will come in handy in the future) I have done several engine tear-downs of the ordinary street variety, and if it were me, I would most likely farm the head gasket job out to an experienced Yanmar mechanic. Those little Yanmar motors are so expensive to replace....I would be inclined not to take the risk of wrecking it. If you do decide to take that job on yourself, think about whether or not you will need to have the head machined - it may be warped. A warped head might be the cause of your blown gasket. And putting a warped head back on with a brand new gasket will be ineffective to say the least. And I confess I speak from painful experience..... Good luck if you decide to forge ahead. Mike
Another Thing to Check
Reduced raw cooling water flow will cause the seawater to heat up beyond the design temperature. I believe the design temperature os is 140 degrees. What you could be seeing is the water boiling. Chech the sea water pump (and impeller) outlet for good flow. You should also check the mixing elbow since they tend to need replacement every few years.
Reduced raw cooling water flow will cause the seawater to heat up beyond the design temperature. I believe the design temperature os is 140 degrees. What you could be seeing is the water boiling. Chech the sea water pump (and impeller) outlet for good flow. You should also check the mixing elbow since they tend to need replacement every few years.
Check the Hose
Bill, Something to check before you get into tearing the engine down is the hose that goes into the FW overflow. As the engine gets hot it pushes the hot excess fluid into the overflow bottle. As the engine cools down it is supposed to draw the fluid back into the engine. If the hose is cracked, or the bottle cap is cracked, it may allow the fluid to move into the bottle but allows the closed system to "suck air" instead of fluid during the cool down period. You will essentially have a partially filled radiator. The hose might cost < $1.00 instead of the larger amount you will have to put out for a head job. Les Andersen s/v Mutual Fun
Bill, Something to check before you get into tearing the engine down is the hose that goes into the FW overflow. As the engine gets hot it pushes the hot excess fluid into the overflow bottle. As the engine cools down it is supposed to draw the fluid back into the engine. If the hose is cracked, or the bottle cap is cracked, it may allow the fluid to move into the bottle but allows the closed system to "suck air" instead of fluid during the cool down period. You will essentially have a partially filled radiator. The hose might cost < $1.00 instead of the larger amount you will have to put out for a head job. Les Andersen s/v Mutual Fun
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