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Old 05-07-2017, 17:23   #1
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3YM30 coolant buzzer going off, but engine not overheating

I had lent the boat to some friends and they came back to the dock telling me they were hearing a chirping sound near the wheel, but couldn't figure this out. Was going on for quite some time, like an hour. Boat is 1.5 season old with 200 hours on the 3YM30AE. Oil changed over the winter for both saildrive and engine.

With a sinking heart I looked at the display and saw that the coolant/overtemp alarm was periodically chirping. Engine working just fine, full power, good discharge of water going over the side. Expansion tank was full of coolant.

Started engine next day at the dock, ran it up to 2500 in neutral , waited a bit, and started chirping again. Temp on the panel reading 120 C! (260 F). Got a yard tech who had one of those flir devices for his phone that reads temp and pointing at the intake manifold and block etc, was reading about 140F.

He didn't have more time to spend on this at the time, but said his initial thought is that the temp sensor is bad, wiring is bad, etc, and it is the electronics, not the engine. He said if I had run the engine for an hour at 260F it would have seized a long time ago.

Any experts here want to weigh in, and if so, what do do to fix this.
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Old 05-07-2017, 19:06   #2
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Re: 3YM30 coolant buzzer going off, but engine not overheating

Quote:
Originally Posted by jbinbi View Post
... Got a yard tech who had one of those flir devices for his phone that reads temp and pointing at the intake manifold and block etc, was reading about 140F.

He didn't have more time to spend on this at the time, but said his initial thought is that the temp sensor is bad, wiring is bad, etc, and it is the electronics, not the engine. He said if I had run the engine for an hour at 260F it would have seized a long time ago.

Any experts here want to weigh in, and if so, what do do to fix this.
Sounds like you already got the expert advice and which direction to go to fix the trouble.
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Old 05-07-2017, 22:07   #3
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Re: 3YM30 coolant buzzer going off, but engine not overheating

Yep, I would change out the temp sender (easy job) they just screw in place, put a little thread tape on the threads or sealant,some engines have two senders one for the alarm and one sender for a gauge (if fitted).

Checking temps would be best done on the heat exchanger side of the engine taking them at the start of the heat exchanger and again at the end (out let) as this tells you if the heat exchanger is functioning correctly and not clogged up with calcium deposits or failing water pump impeller (should be checked changed every season),
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Old 06-07-2017, 03:47   #4
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Re: 3YM30 coolant buzzer going off, but engine not overheating

Basic Troubleshooting of Gauges:

All Gauges:

1. Remove Sender Wire from “S” Terminal on Gauge, and Turn ON Instruments Circuit.

2. Test Voltage between “I” Terminal (External Power Supply) and Ground Terminal “G”.
Tested voltage must match nominal voltage of the Gauge (ie: 12V Gauge must test between 10 - 16VDC), and the Battery Voltage.
If no voltage - check Ignition or Instrument Switch(s) and/or Fuses.
If tests less than battery voltage, repair or replace (Violet) wire from Ignition or Instrument Switch.

If a Sender fails “Open” (Infinite Resistance), one or both (if Dual Station) Gauges will read Zero Scale.
If a Sender Fails “Closed” (shorted - Zero Resistance), one or both Gauges will read Full Scale.

Other confusing Ohmmeter results, such as readings lower than expected, could indicate a poor Ground Connection at the Sender Body (Sender to Engine Block). Check for pipe dope or tape on Sender Threads.

Temperature Gauges:

1. Disconnect Tan Sender Wire from Gauge (Terminal “S”) and turn Instrument Power ON.
The Temperature Gauge should indicate ZERO Scale (< Low Temperature).

2. Short the Gauge Sender Terminal “S” to Ground Terminal “G”.
The Gauge should deflect to FULL Scale (> High Temperature).

3. Measure Resistance from Tan Sender Wire (disconnected from Gauge) to Ground.
American Temp. Senders will read: 450 Ohms (Engine Cold @ 1000F)
or 29.6 Ohms (Engine Hot @ 2500F )
European Temp. Senders will read: 281 Ohms (Cold @ 400C) and 22 Ohms (Hot @ 1200C)

4. Disconnect Tan Wire from Sender on Engine Block.

5. Test continuity of Tan Wire.
Zero Ohms from Block End to Gauge End - If not, repair or replace Wire.


6. Measure Resistance from Sender Terminal (on Block) to Ground on Block.
Should read as per (3) above - If not, replace Sender.
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Old 06-07-2017, 04:17   #5
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Re: 3YM30 coolant buzzer going off, but engine not overheating

Quote:
Originally Posted by GordMay View Post
Basic Troubleshooting of Gauges:

All Gauges:

1. Remove Sender Wire from “S” Terminal on Gauge, and Turn ON Instruments Circuit.

2. Test Voltage between “I” Terminal (External Power Supply) and Ground Terminal “G”.
Tested voltage must match nominal voltage of the Gauge (ie: 12V Gauge must test between 10 - 16VDC), and the Battery Voltage.
If no voltage - check Ignition or Instrument Switch(s) and/or Fuses.
If tests less than battery voltage, repair or replace (Violet) wire from Ignition or Instrument Switch.

If a Sender fails “Open” (Infinite Resistance), one or both (if Dual Station) Gauges will read Zero Scale.
If a Sender Fails “Closed” (shorted - Zero Resistance), one or both Gauges will read Full Scale.

Other confusing Ohmmeter results, such as readings lower than expected, could indicate a poor Ground Connection at the Sender Body (Sender to Engine Block). Check for pipe dope or tape on Sender Threads.

Temperature Gauges:

1. Disconnect Tan Sender Wire from Gauge (Terminal “S”) and turn Instrument Power ON.
The Temperature Gauge should indicate ZERO Scale (< Low Temperature).

2. Short the Gauge Sender Terminal “S” to Ground Terminal “G”.
The Gauge should deflect to FULL Scale (> High Temperature).

3. Measure Resistance from Tan Sender Wire (disconnected from Gauge) to Ground.
American Temp. Senders will read: 450 Ohms (Engine Cold @ 1000F)
or 29.6 Ohms (Engine Hot @ 2500F )
European Temp. Senders will read: 281 Ohms (Cold @ 400C) and 22 Ohms (Hot @ 1200C)

4. Disconnect Tan Wire from Sender on Engine Block.

5. Test continuity of Tan Wire.
Zero Ohms from Block End to Gauge End - If not, repair or replace Wire.


6. Measure Resistance from Sender Terminal (on Block) to Ground on Block.
Should read as per (3) above - If not, replace Sender.
Crikey Gord, those engines run hot
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Old 06-07-2017, 04:35   #6
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Re: 3YM30 coolant buzzer going off, but engine not overheating

For the OP.

I don't know exactly how your temperature gauge and over temperature alarm is wired but most 3YM30 engines (that have a temperature gauge fitted) have two separate senders. One for the gauge and one for the alarm. It is possible that it has only one sensor with both functions inside it. This will then have at least two terminals and possibly three.

However it is done, the alarm and gauge functions are separate. You report that the alarm sounds and the gauge reads hot. It is unlikely that both senders are failing together (but possible ). If it a electrical problem rather than a genuine over heating issue, then I would look carefully at the wiring loom. Is it quite possible than something has chaffed somewhere and a short to ground on both wires would give both an alarm condition and a hot gauge reading.

When you find the issue, please let us know what it is!
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Old 06-07-2017, 06:44   #7
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Re: 3YM30 coolant buzzer going off, but engine not overheating

Thanks to all for their input. Not sure how the alarm is supposed to sound. It is not a continuous alarm, but rather an intermittent chirp. Every few seconds , but sometimes goes away for a few seconds (I think). I bring this up because I don't know if this is indicative of something wrong in the sensor (if it supposed to be continuous if the engine has overheated), or the way it supposed to work.

Also, the 2 sensor issue now has me more worried about the engine. Would it be true that running the engine for an hour at 120 C would seize the engine?
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Old 06-07-2017, 06:58   #8
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Re: 3YM30 coolant buzzer going off, but engine not overheating

Get yourself an infrared thermometer that you can aim at different points of the engine and make yourself a temperature map. That will tell you if the problem is your sensor or the engine is actually hot. You don't need an expensive one for this.

I would think it is the sensor or wire between sensor and alarm but a temp. map of the engine will tell you. A temp. map will come in handy in the future. Most trawler type cruisers check their engine this way on a regular basis.
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Old 06-07-2017, 07:03   #9
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Re: 3YM30 coolant buzzer going off, but engine not overheating

I do have one of these at home that I will bring to the boat. I also have 2 engines, so I can compare them. Worried that the thermostat or fresh water pump etc not working, etc. I guess this will be shown with a temp gun...However, I was trying to placate my fear that catastrophic damage has or hasn't been done while I am away until the weekend....
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Old 06-07-2017, 08:51   #10
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Re: 3YM30 coolant buzzer going off, but engine not overheating

i carry a temp lazer heat gun. Point and shoot . some times gages and sencors lie !
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Old 06-07-2017, 09:02   #11
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Re: 3YM30 coolant buzzer going off, but engine not overheating

A small suggestion. Check coolant level in engine (when cool, of course) rather than just at the overflow/expansion tank.

On mine, I have to be careful with this as overflow tank seems to get sort of "vapor locked", especially after changing coolant - i.e. level is fine in tank, but missing quite a bit of coolant in engine. Repeated inspections and filling through cap fixes it.
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Old 06-07-2017, 09:18   #12
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Re: 3YM30 coolant buzzer going off, but engine not overheating

I would suggest looking at the impeller for condition, if OK them replace the temp sensor and recheck
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Old 06-07-2017, 11:44   #13
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Re: 3YM30 coolant buzzer going off, but engine not overheating

I had a similar problem on a 1GM10 a few years back The warning buzzer and water temp light came on, checked the water and it was coming out normally and cool to the touch. The engine seized shortly after because the previous owner had connected the oil warning lamp in the place of the overheat light and vice versa. The lower oil transfer line had blown and dumped all the oil in the bilge. Check to see if you have correct oil level which if severely low could also cause the engine to run hot.
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Old 06-07-2017, 12:57   #14
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Re: 3YM30 coolant buzzer going off, but engine not overheating

thanks everyone. My oil level is OK. My overflow tank is OK, but I didn't check level by opening the cap, so thanks MGH for the suggestion. Assuming impeller is OK as it is spitting out water and increasing water amount with increase in RPM.

Still want to know if I ran engine at 120C for an hour if it would seize/permanently damage engine.
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Old 06-07-2017, 14:01   #15
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Re: 3YM30 coolant buzzer going off, but engine not overheating

Quote:
Originally Posted by jbinbi View Post
thanks everyone. My oil level is OK. My overflow tank is OK, but I didn't check level by opening the cap, so thanks MGH for the suggestion. Assuming impeller is OK as it is spitting out water and increasing water amount with increase in RPM.

Still want to know if I ran engine at 120C for an hour if it would seize/permanently damage engine.
I reckon you would know if it had seized
As for damage, I can't say for sure as I have never tried it. 120C is awful hot for these engines but what does it normally run at. If it ran at say 100 to 105, then 120 isn't that much higher but if it normally runs at say 80 to 90, then 120 is high. Again I don't know what the pressure cap is rated at (in PSI etc) but that would also be a clue as to how much heat the engine can take. Higher PSI, higher temperature.

EDIT: If the coolant level in in header tank is OK (i.e. looking under the cap), then no boiling has occurred. This would then suggest no real damage has occurred as most damage occurs after coolant boils.
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