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06-07-2019, 13:21
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#1
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Registered User
Join Date: Mar 2013
Posts: 5
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Yanmar 1GM Overtemp Alarm / Thermostat
Yanmar 1GM. Overtemp alarm. Replaced impeller. Still alarm. I have manual.
Thermostat: my experience with cars is thermostats "fail open" - so if a thermostat fails, the car is slow to reach temperature (because thermostat is wide open) - but a bad thermostat generally won't cause overheating.
What about these Yanmars ? I understand the thermostat directs water either into engine or bypassing it. If thermstat fails, does it send all the water into engine ? Or all bypassing ?
Obviously I need to look at obstructions, sending unit, and other parts of system.
Thanks !
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06-07-2019, 18:51
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#2
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Moderator Emeritus
Join Date: Oct 2013
Location: Jacksonville/ out cruising
Boat: Island Packet 38
Posts: 31,351
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Yanmar 1GM Overtemp Alarm / Thermostat
Your car experience will carry over here as well.
First thing I’d do is buy an inexpensive IR thermometer and measure the thermostat Neck when the alarm goes off or keep checking before to see if you really have an overheat or just a bad switch.
If it’s a real overheat, first and easiest is to check the thermostat, it should begin to open at set temp, full open 15 or so degrees higher, if thermostat is good I’d move onto heat exchanger and from there the exhaust manifold.
Sometimes however you can have a worm pump cover and it not pump much water.
Thermostat usually blocks water flow, but there is a type that is longer than normal and has a large washer on the bottom that may bypass.
This may help
http://www.stant.com/index.php/engli...s-thermostats/
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06-07-2019, 18:58
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#3
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Moderator Emeritus
Join Date: Oct 2013
Location: Jacksonville/ out cruising
Boat: Island Packet 38
Posts: 31,351
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Yanmar 1GM Overtemp Alarm / Thermostat
Last thing, I believe on my Yanmar anyway the overheat and low oil pressure are the same alarm sound, you have to look at the light to determine which it is.
I don’t know about yours
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06-07-2019, 19:10
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#4
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Moderator and Certifiable Refitter
Join Date: Jan 2008
Location: South of 43 S, Australia
Boat: C.L.O.D.
Posts: 20,305
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Re: Yanmar 1GM Overtemp Alarm / Thermostat
Quote:
Originally Posted by Delawaredave
Yanmar 1GM. Overtemp alarm. Replaced impeller. Still alarm. I have manual.
Thermostat: my experience with cars is thermostats "fail open" - so if a thermostat fails, the car is slow to reach temperature (because thermostat is wide open) - but a bad thermostat generally won't cause overheating.
What about these Yanmars ? I understand the thermostat directs water either into engine or bypassing it. If thermstat fails, does it send all the water into engine ? Or all bypassing ?
Obviously I need to look at obstructions, sending unit, and other parts of system.
Thanks !
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Welcome aboard D-dave.
In the closed (cold) position, the IGM directs all the flow to the exhaust mixing point bypass the engine. In the open (hot) position, it directs all the flow though the engine before exiting it to the exhaust mixing point.
Usually fails in the closed (cold) position thus causing overheating but I have had one fail in the fully open position. In this case no alarm, just a engine rising way to cold.
__________________
All men dream: but not equally. Those who dream by night in the dusty recesses of their minds wake in the day to find it was vanity: but the dreamers of the day are dangereous men, for they may act their dreams with open eyes, to make it possible. T.E. Lawrence
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06-07-2019, 19:11
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#5
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Moderator and Certifiable Refitter
Join Date: Jan 2008
Location: South of 43 S, Australia
Boat: C.L.O.D.
Posts: 20,305
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Re: Yanmar 1GM Overtemp Alarm / Thermostat
Quote:
Originally Posted by a64pilot
Last thing, I believe on my Yanmar anyway the overheat and low oil pressure are the same alarm sound, you have to look at the light to determine which it is.
I don’t know about yours
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Correct for the xGM series
__________________
All men dream: but not equally. Those who dream by night in the dusty recesses of their minds wake in the day to find it was vanity: but the dreamers of the day are dangereous men, for they may act their dreams with open eyes, to make it possible. T.E. Lawrence
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06-07-2019, 19:49
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#6
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Registered User
Join Date: May 2016
Location: Hanging out along the Gulf Coast
Boat: 81 Hunter Cherubini 27
Posts: 372
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Re: Yanmar 1GM Overtemp Alarm / Thermostat
Remove the thermostat and then run the engine. No alarm? You've got a bad thermostat (replace as necessary). If not, check your salt water intake thru-hull strainer on the outside of the boat. Barnacle and sea growth will prevent proper salt water suction (and add wear and tear on the new impeller you just installed). The water temp sensor may have failed as well (should not come on when you turn the key on and start the engine....if it does? Bad sensor).
In normal operation the 1GM never really gets too hot to touch. If it does, then the three things which I have listed above are the most likely culprits. Good Luck!
__________________
Cruising highly skilled Marine Electrician. Will work for beer, smokes and slip fees...and other important boat stuff
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06-07-2019, 20:05
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#7
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Registered User
Join Date: Feb 2010
Location: Melbourne
Boat: Compass 28
Posts: 431
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Re: Yanmar 1GM Overtemp Alarm / Thermostat
I guess you've already looked to confirm acceptable water flow out the exhaust?
You can check the thermostat by heating it in a saucepan of water with a thermometer to see when it opens. If you're still unsure, reassemble the cooling system but leave the thermostat out, run up close to operating temperature, then close the bypass line (use a small vicegrips to squeeze the hose). This way you are guaranteed full flow through the engine, and now you can run it hard to see if the alarm still goes off. If you just remove the 'stat without constricting the bypass almost all the water will go through the bypass and the engine will quickly overheat.
I had a problem years ago that drove me nuts - I checked and replaced impeller, 'stat and hoses, and soaked the passages in vinegar, but still got an alarm after about 20 min at 3/4 revs. I finally rodded the CW seacock and thru hull with a very long screwdriver, and found in there a long hard piece of marine growth the like of which I'd never seen before. I put the old impeller and 'stat back in just to check: good as gold, except for about a hundred bucks and 20 hours of my time down the drain.
Cheers, Graeme
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06-07-2019, 23:09
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#8
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Moderator and Certifiable Refitter
Join Date: Jan 2008
Location: South of 43 S, Australia
Boat: C.L.O.D.
Posts: 20,305
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Re: Yanmar 1GM Overtemp Alarm / Thermostat
Check the overheat sensor. Remove and heat in water, check with ohmmeter, the contacts (between the terminal and the body) should close around 60C.
__________________
All men dream: but not equally. Those who dream by night in the dusty recesses of their minds wake in the day to find it was vanity: but the dreamers of the day are dangereous men, for they may act their dreams with open eyes, to make it possible. T.E. Lawrence
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06-07-2019, 23:14
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#9
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Moderator and Certifiable Refitter
Join Date: Jan 2008
Location: South of 43 S, Australia
Boat: C.L.O.D.
Posts: 20,305
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Re: Yanmar 1GM Overtemp Alarm / Thermostat
Quote:
Originally Posted by lockie
....
If you're still unsure, reassemble the cooling system but leave the thermostat out, run up close to operating temperature, then close the bypass line (use a small vicegrips to squeeze the hose). This way you are guaranteed full flow through the engine, and now you can run it hard to see if the alarm still goes off. If you just remove the 'stat without constricting the bypass almost all the water will go through the bypass and the engine will quickly overheat.
...........
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This ^^ cannot be emphasised enough - read and memorise
__________________
All men dream: but not equally. Those who dream by night in the dusty recesses of their minds wake in the day to find it was vanity: but the dreamers of the day are dangereous men, for they may act their dreams with open eyes, to make it possible. T.E. Lawrence
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07-07-2019, 02:14
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#10
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Senior Cruiser
Join Date: Mar 2003
Location: Thunder Bay, Ontario - 48-29N x 89-20W
Boat: (Cruiser Living On Dirt)
Posts: 49,139
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Re: Yanmar 1GM Overtemp Alarm / Thermostat
Greetings and welcome aboard the CF, Dave.
Basic Engine Gauge Theory and Testing ➥ http://www.cruisersforum.com/forums/...sting-645.html
__________________
Gord May
"If you didn't have the time or money to do it right in the first place, when will you get the time/$ to fix it?"
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07-07-2019, 02:58
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#11
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Registered User
Join Date: Mar 2013
Posts: 5
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Re: Yanmar 1GM Overtemp Alarm / Thermostat
Thanks everyone for your valuable input !!!
After I replaced the impeller, I ran engine in mooring for 15 minutes (timed) at idle. No alarm. Assumed "problem solved".
Then went out on river, alarm went off within few minutes at cruising revs (around 2000)
I don't know if above "means anything". Hot summer I would have thought the idling would have brought on alarm if a problem.
Hopefully down to boat today to try everyone's suggestions.
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07-07-2019, 04:57
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#12
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Moderator and Certifiable Refitter
Join Date: Jan 2008
Location: South of 43 S, Australia
Boat: C.L.O.D.
Posts: 20,305
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Re: Yanmar 1GM Overtemp Alarm / Thermostat
Quote:
Originally Posted by Delawaredave
Thanks everyone for your valuable input !!!
After I replaced the impeller, I ran engine in mooring for 15 minutes (timed) at idle. No alarm. Assumed "problem solved".
Then went out on river, alarm went off within few minutes at cruising revs (around 2000)
I don't know if above "means anything". Hot summer I would have thought the idling would have brought on alarm if a problem.
Hopefully down to boat today to try everyone's suggestions.
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Very little fuel is burnt at idle so very little heat is produced; much more fuel burnt at 2000 rpm under load so much more heat is produced.
For the other posters, please remember this engine is raw water cooled.
__________________
All men dream: but not equally. Those who dream by night in the dusty recesses of their minds wake in the day to find it was vanity: but the dreamers of the day are dangereous men, for they may act their dreams with open eyes, to make it possible. T.E. Lawrence
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07-07-2019, 11:17
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#13
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Registered User
Join Date: Aug 2018
Location: Bristol uk
Boat: Vertue 11
Posts: 3
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Re: Yanmar 1GM Overtemp Alarm / Thermostat
Hi All.
First post. I have had both a !gm and a 2gm. They both had the same overheating problem when I first obtained them in that the pipe above the pump had become clogged with a scale like substance. Easy fix. Strip and clear.
I expect you have checked these but sometimes it is worth stating the obvious.
Cheers. john
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08-07-2019, 01:57
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#14
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Senior Cruiser
Join Date: Mar 2003
Location: Thunder Bay, Ontario - 48-29N x 89-20W
Boat: (Cruiser Living On Dirt)
Posts: 49,139
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Re: Yanmar 1GM Overtemp Alarm / Thermostat
Greetings and welcome aboard the CF, John.
__________________
Gord May
"If you didn't have the time or money to do it right in the first place, when will you get the time/$ to fix it?"
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08-07-2019, 07:09
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#15
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Registered User
Join Date: Nov 2015
Posts: 372
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Re: Yanmar 1GM Overtemp Alarm / Thermostat
Water strainer plugged a bit? Inlet thru hull?
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