Thermostat problem?

[Clydo]

Anyone have this problem? After replacing small formed hose on front of engine
in fresh water cooling system ran engine for ten (?) minutes when overheat alarm
sounded and temp gauge up to top of range. Shut down eng and let cool. Asked my
son in law to remove "radiator" cap to check if water circulating. Said thought I
would crank eng to see if flow. He didn't want to because would loose antifreeze.
Water hot but antifreeze coming out of plastic overflow cold. Replaced cap and
fired up eng. Ran fine and temp in normal range. Took boat out and ran about
hour from max rpm to cruise rpm and stayed at normal temp. Possible thermostat
problem or air lock? Appreciate any answers.

Clyde Thorington
C310 # 245
ILEAN TOO
San Jose, CA

 

[Clydo]

Should have included in post boat is 2003 ( 14 years old) model with about 420 hours
on engine.

Clyde Thorington
C310 # 245
ILEAN TOO
San Jose, CA

 

[markwbird]

Generally, if you are getting the overheat alarm and the engine is obviously not that hot, i.e. the antifreeze is cool, the cap is cool and you can remove it, etc. then it is either the thermostat or the sensor. Remove the radiator cap and run the engine to see if the water is circulating. What about the raw water pump? Is that working?

 

[Clydo]

Generally, if you are getting the overheat alarm and the engine is obviously not that hot, i.e. the antifreeze is cool, the cap is cool and you can remove it, etc. then it is either the thermostat or the sensor. Remove the radiator cap and run the engine to see if the water is circulating. What about the raw water pump? Is that working?

Raw water pump work really well. Normal output out stern.

Clyde Thorington
C310 # 245
ILEAN TOO
San Jose, CA

 

[Bill Roosa]

Common issue when refilling coolant. An air bubble forms under the thermostat, air is a great insulator so the thermostat does not open till heat is conducted through the thermo housing. The engine temp sensor is (I bet) lower on the engine so it saw the hotter engine parts and or coolant. Once the thermo opened after shutdown the air bubble escapes and you just need to check the coolant level. The over flow tank should have taken care of it for you and all you need to do is fill the overflow tank.

 

[Tom J]

What bill said plus one. Very common issue when replacing hoses, etc. Your test run indicates the cooling system is working normally.

 

[Stu Jackson]

Engine Overheating 101 - How to Burp Your Engine (Reply #6) http://c34.org/bbs/index.php/topic,4518.msg26462.html#msg26462

 

[Clydo]

Common issue when refilling coolant. An air bubble forms under the thermostat, air is a great insulator so the thermostat does not open till heat is conducted through the thermo housing. The engine temp sensor is (I bet) lower on the engine so it saw the hotter engine parts and or coolant. Once the thermo opened after shutdown the air bubble escapes and you just need to check the coolant level. The over flow tank should have taken care of it for you and all you need to do is fill the overflow tank.

Thanks a bunch guys really helpful.

Clyde Thorington
C310 # 245
ILEAN TOO
San Jose, CA

 

[JK_Boston_Catalina310]

Read Stu's link. The answer is in there.

By the way, look at post #14 and see who Mainesail addresses this issue. I did this on my C310 and have never had an air bound issue.

 

[MitchM]

great advice on the burp procedure.! another thing to check if you still have an overheat is that many engine models have a feed into and out of an oil cooler assembly. this feed hose on the yan mars is a formed hose that 'necks down' as it enters the oil cooler assembly. that is a likely spot for a hose failure is this neck - down area. we had one overheat due to a piece of raw water impeller breaking off and traveling into the heat exchanger. after fishing that piece out, cleaning the ht x for good measure, redoing its special gaskets etc--- and replacing lost antifreeze, --- the engine was still running 'hot. ' sure enough , from this one engine overheat, the feed hose into the oil cooler had developed a leak at the neckdown.. .. wrapping it with miracle silicon tape held it till we got the expen$$$ive replacement hose from yan mar. now we always carry 1) a tube of form a gasket , since if you have to t take apart the ht x to get the impeller piece out, the original gaskets on both cap els may be shot... 2) an extra formed oil cooler ho$$$e.