View Full Version : Overheatingloosing coolant

03-22-2010, 07:37 PM
"I have 350 6ly yanmar diesel. It has been loosing coolant for some time and overheating at wot. Recently it started overheating at lower rpm's. I have checked thermostat, impeller in pump and mixing elbow. All seem to be fine. I have heard about "buildup" and "flushing" of coolant system, particularly the exhaust manifold. What should I do and how?"

03-29-2010, 04:58 PM
You should have the heat exchanger bundle cleaned and pressure checked. You can take the raw water hoses off of the heat exchanger and pressurize the fresh water side. If you have any antifreeze comming from the heat exchanger raw water ports, you have a defective heat exchanger or seals. The bundle of the heat exchanger may be cleaned with a 50/50 mixture of muratic acid if very well rinsed. A better solution is Trac Ecological Marine’s Barnacle Buster. Just follow instructions.

03-29-2010, 04:59 PM
Also test coolant cap!

07-27-2015, 07:17 AM
Loosing coolant and overheating does point towards potential leakage. I work for a company called Vestas aircoil who design and manufacture charge air coolers and it has been known for engineers to block leaking tubes just to allow things to limp along a little longer. Although this is by no means a long term fix.