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Ask Dominick Your Own Question
Dominick, Marine Mechanic
Category: Boat
Satisfied Customers: 1009
Experience:  25 Years Experience as Mechanic, 20 Yrs Boat Yard Owner/Mechanic, Factory Certified
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My header tank on my 40hp Diesel lister petter is building

Customer Question

Hi my header tank on my 40hp Diesel lister petter is building up a lot of pressure and spraying out the tank after motoring in yesterday when the main belt came off the engine causing the engine to over heat and the header tank empty not realising what was happening till the engine cut out hope you can help
Submitted: 2 years ago.
Category: Boat
Expert:  Tan replied 2 years ago.
Hello. My name is***** you refilled the cooling system replaced the belt and run the engine? When an engine over heats it will blow all the coolant of of the cooling system. Now the possible issue you could have are a blown head gasket or cracked cylinder head if it go hot enough.
Customer: replied 2 years ago.
Hi yes I field the tank and It took quit a bit of warter started it up with the new belt on and within a few minutes started to pressurise
Expert:  Tan replied 2 years ago.
Ok did you leave the cap off to bleed off all the air in the system? We have to get all the air out of the system to be sure it has coolant in the engine only. Does the engine run Ok? Do you see signs of water in the engine oil? The oil will be milky colored.
Customer: replied 2 years ago.
Yes the engine is starting ok but not ticking over and is cutting out and I haven't tried to bleed the System as I'm not sure how to do it but I could get someone to do it. The oil doesn't look milky but could do with a chane but the warter that came out the tank looked a bit black.
Expert:  Tan replied 2 years ago.
To bleed the system just leave the cap off for a few minutes. Then shut engine off. Let cool some then refill. Repaet the procedure a couple of times. If it doesn't take anymore water then you have all the air out of the system replace the cap and run engine does it over heat? Now the system will build some pressure up to 15 psi which is normal. Water boils at a higher temp under pressure. Now the black water could just be dirty water. If the black is floating on the water this could be exhaust gases from a blown head gasket. Can you do this procedure and post back with findings?
Customer: replied 2 years ago.
I didn't have the engine running long enough to see if it would over heat as it was spraying out the tank with the cap on. The warter disn't seem to have oil floating around in it just looked dirty black. The bleeding seem pretty simple I'll have to try it tomorrow.
Expert:  Tan replied 2 years ago.
Yeah the engine will start building pressure real fast if you still have air in the system. We must be sure all the air is out to get the correct diagnosis of what could be the problem. If it is just trapped air you are in good shape. But if it doesn't change after we have bled the system then we have a more serious issue. If it still builds to much pressure we will have to do a combustion leak test. Post back with questions.
Customer: replied 2 years ago.
Ok I'll let you no how it goes thanks for you help so far.
Expert:  Tan replied 2 years ago.
Ok thanks.