I have a 1987 hunter 35' with a yanmar 3GM30F the problem is the burp tank fills and does not recycle back to engine, I have put on new radiator cap new burp tank, head gasket is ok, I have a small pump and I manually move the antifreeze back to engine. I also moved the burp tank higher. Thanks for any suggestions, RONSAIL
Leaky burp tank
- Thread starter Ronsail
- Start date
Hi Ronsail and welcome to the site.
When you say "burp tank" I'm presuming you're referring to the overflow tank ? Have you checked the coolant heat exchanger for level, after the overflow tank fills. If it's filled with air, Les has the answer. My money is on the seal under the rad cap being deformed and pulling in air when the engine cools. Let us know what you find.
I wish you were right, I have sanded where the radiator cap goes and have bought 2 caps. That was my first thought ! How do you check the level in heat exchanger? I have cleaned the heat exchanger and put it back together with new seals. I also borrowed from a auto part store, a pump to check radiator cap and to pump air into system and it did not show sign of loosing pressure. There is also no sign of water in oil."Thank God" The mystery continues!! Thanks for the reply RONSAIL Wife says time for another THOUSAND hire the pro "I AM STUBBORN"
I have tried, I have replaced all hoses, and radiator cap!! Thanks for the input. RONAL
Remove the rad cap and look into the heat exchanger body. It most likely has the same volume of air in it as the overflow tank has AF.
A one way leak is common. The rad cap may hold back pressure but is able to suck air back into the heat exchanger body as the engine cools.
Deck fill caps for most Hunter sailboats
Stainless, nylon, in all the shapes and sizes, replacement caps are in stock.
See the product
You replace all the hose running to burp tank and the cap and little piece of hose running to bottom of tank. When engine cools and if there is even a pin hole leek in any of that it will suck air instead of water
You may have a head gasket leak that allows compression gasses into the cooling system when the engine runs. Do you have positive pressure in the heat exchanger when you remove the sealing cap? If you still have the pressure testing tool you can install it onto the heat exchanger while the engine is running. If the pressure builds quickly it would be a confirmation. Note, the pressure will build as the coolant warms up. This is what drives the coolant into the expansion tank. If there is excess pressure in the coolant system it would could possibly stop the draw of the coolant out of the expansion tank.
Thanks, for the reply I will check, I have been on holidays away from service and have not been to boat enough but that is about to change, Thanks