Universal M12 Overheating on E28+

J

jbg

Junior Member
My Universal M12 on my 1985 e28+ keeps overheating. I replaced the sea water impeller which was still working fine. Sea water flows freely out the transon exhaust. I replaced the thermostat. I removed the coolant pump which had been replaced by the previous owner. It spins freely and the seals are tight. The impeller on the water pump was slightly rusty but seemed OK. The heat exchanger is cold. Strangley, after the engine overheats, the hot water tank for the sink and shower water system is still cold. That indicates that something is not circulating. The hoses on each side of the water pump are both hot. Any ideas where else to look?:confused:
 
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mherrcat

mherrcat

Contributing Partner
Seems the problem is on the fresh water/coolant side of the system; maybe the heat exchanger? That would be my next thing to remove and check that it is not blocked. Maybe a dumb question, but have you checked that there is sufficient coolant?
 
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F

Frank Langer

1984 Ericson 30+, Nanaimo, BC
A bit of a long shot, but after you work on the cooling system are you bleeding out any air bubbles to ensure the coolant is flowing? On my engine there is a small valve near the thermostat that I can open to let out air bubbles until only coolant is coming out; if I don't do this, the engine is sure to overheat until they work their way through the system.

Otherwise, I would agree with Mark and check for any blockage in the line going into the heat exchanger, and then the heat exchanger itself. I had replaced our heat exchanger about 5 years ago, and when I had it cleaned/serviced recently they said it was getting clogged again with calcium and whatever. They said if I left it much longer the engine would have started overheating.

Good luck!

Frank
 
mherrcat

mherrcat

Contributing Partner
Not sure but I think the coolant goes to the hot water heater before it goes to the heat exchanger. Your hot water heater could also be the problem.
 
J

jbg

Junior Member
M12 Still Overheating

Thanks for your input. Everything seems to be clear. I disconnnected the water heater, heat exchanger, reservoir, and all items flowed properly. I removed the thermostat and poured water through the engine and it flowed freely out the coolant pump. It overheated again within 10mins of restarting. Still no circulation. Coolant pump was pulled and reinspected. It still looks good!


Jim G
 
C

cruis-n

Member II
Likely air in the system

As Frank points out, you likely have an (more like more than one) air bubble in the system. You will need to bleed the air out. While the engine in running, crack open the bleed valve (on top of the thermostat housing or near-by) to let the air out. Be careful, it's hot! It will take several minutes to get all the air out (open till coolant come out, close, wait for the next bubble to accumulate in the thermostat housing, open till coolant comes out, close...). I hold a paper towel over the bleed valve to catch the coolant and keep the hot steam/air from spraying. Be careful, it's hot! Did I mention to be careful, that it's hot?

If you have a temperature gauge, an assistant can watch the gauge and tell you when the air bubble has arrived and it's time to bleed it off by rapidly rising temperature noted on the guage.

Best of luck,
Paul
 
Tom Metzger

Tom Metzger

Sustaining Partner
FWIW - On some boats, like my E-34, the thermostat is not the high point in the system, or not the only high point. I have a petcock on the high point of the hose going to the water heater from the thermostat. I bleed the system from this petcock.
 
U

unequaltee

Member II
over heating engine

My guess is the thermostat is not opening. You could test it by bringing it to the boil in a saucepan of water on the stove. You did not say if you left it out after pouring water through the engine, as this might eliminate it as the cause as well.
Good luck
Ian
 
mherrcat

mherrcat

Contributing Partner
The thermostat could well be the problem. As I recall, there is a correct orientation for them when they are installed; it is possible to install them backwards (not upside down) and this might also be part of the problem.

My engine had the wrong thermostat installed. It was pretty obvious when I removed the housing as the T-stat was rattling around inside the housing! How some idiot figured that was supposed to work I don't know...

Torresen Marine has the thermostat, but it is $60. You may want to try to source one from a Kubota tractor dealer and see if you can get a better price. I got one from John Featherman, but he is no longer in business.
 
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J

jbg

Junior Member
Overheating Problem solved.

Thanks for all your words of wisdom. I bypassed the water heater and the motor cooled down. I was suprised due to all the efforts that we had previously put into bleeding the air out of the system after we changed the thermostat and bleeder valve. It must have been an air lock. Now running @165 degress.:)


Jim G
Muskegon
 
Stu Jackson

Stu Jackson

C34IA Secretary
You're right, sorry about that. Thanks for noticing.

Try this:

http://c34.org/bbs/index.php/topic,3133.0.html

Also, that overheating with the hot water heater requires BURPING the coolant water system. Try this, reply #6:

http://c34.org/bbs/index.php/topic,4518.0.html

I used to use the "open the petcock" method, but it was chilling (pun intended) to have to watch the temperature gauge go up past 220!!! It worked, but it's easier to remove the air first.
 
P

PDX

Member III
Stu Jackson said:
You're right, sorry about that. Thanks for noticing.

Try this:

http://c34.org/bbs/index.php/topic,3133.0.html

Also, that overheating with the hot water heater requires BURPING the coolant water system. Try this, reply #6:

http://c34.org/bbs/index.php/topic,4518.0.html

I used to use the "open the petcock" method, but it was chilling (pun intended) to have to watch the temperature gauge go up past 220!!! It worked, but it's easier to remove the air first.
Click to expand...

Thanks much.
 
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