YM155D issues: maybe head gasket, maybe radiator, maybe?

clemsonfor · Mar 29, 2017

The marine version will run cooler esp if it's pulling in outside water in or even if it has a heat transfer on the keel still probably run cooler when all is well.

Anyway I too would vote for keeping it simple and don't add additional gauges that are not necessary. Keeping that radiator clean of seeds dirt and grass and an occasional flush is all that you need to do , followed with fresh 50/50 green antifreeze.

I can't remember from my manual but the light comes on just over 200 (or is it like 215?)I think. Winston and California probably remember without consulting the source?

winston1 · Mar 29, 2017

Left hand light should be oil light. Ditto making sure the lights work and trust them. You are more likely to see a light come on then to see a gauge go up or down. According to Hoye the light comes on at 220 degrees. How Hot Should My Tractor Run?

careyo63 · Mar 29, 2017

I agree with just using the lights. Last month I've owned my YM2000 I bought ASIS. not Refurbished 9yrs. ago and put over 600hrs on it. Keep everything clean with the fluids changed as needed and if the lights are in correct working order should be all you need. Your see them even if they randomly flash. I've seen my oil light easily flash at low RPM's close to stalling the motor. I also just stick my hand under the dash and feel the air temp. getting blown back and feel how hot I'm running.

California · Mar 29, 2017

I looked for the YM240 temp sender spec, can't find it here in my computer files. I think the info is in the I&T manual out at the ranch. I recall a diagram in that manual showing a sensor being tested on a kitchen stove, in a pot of high-proportion antifreeze coolant along with a candy thermometer.

Related: YM186D Parts Manual:
"Switch, thermo, 110 degree Celsius". That's 230 Degrees Fahrenheit.

That matches what I recall, that the thermosiphon engines don't run a high proportion of antifreeze so maximum temp (and the sensor) are somewhere around 220 degrees. But the models with a water pump, with their higher proportion of antifreeze (and a 13psi cap) won't boil until around 245, so they use a higher temp sensor.

Can anyone confirm that YM155 has either/both a water pump and thermostat?

At any rate Hoye's replacement 220 degree sensor should be fine for any model.

winston1 · Mar 30, 2017

"Can anyone confirm that YM155 has either/both a water pump and thermostat?"

Has neither according to the parts manual. Thermosyphon system.

The 220/226 repair manual states the light should come on at 230f. Parts manusl confirms that with 110c given with parts listing 121250-44901. This is a water pump and thermostat model.

135/155 repair manual page 77 states on at 248f + or - 5.4f, off at 233.6f + or - 5.4f, part numbers in parts manual 124450-44901 and 124450-44902

Far as I can tell Hoye only sells one sensor for the light and one sensor for the gauge. I have to believe Yanmar did use different sensors originally.

clemsonfor · Mar 30, 2017

California said:
I looked for the YM240 temp sender spec, can't find it here in my computer files. I think the info is in the I&T manual out at the ranch. I recall a diagram in that manual showing a sensor being tested on a kitchen stove, in a pot of high-proportion antifreeze coolant along with a candy thermometer.

Related: YM186D Parts Manual:
"Switch, thermo, 110 degree Celsius". That's 230 Degrees Fahrenheit.

That matches what I recall, that the thermosiphon engines don't run a high proportion of antifreeze so maximum temp (and the sensor) are somewhere around 220 degrees. But the models with a water pump, with their higher proportion of antifreeze (and a 13psi cap) won't boil until around 245, so they use a higher temp sensor.

Can anyone confirm that YM155 has either/both a water pump and thermostat?

At any rate Hoye's replacement 220 degree sensor should be fine for any model.

Sorry wasent calling you out on that. Was kind of a joke about how good yall guys are at this stuff. I think my Yanmar 240 shop manual is on my bedside table. If I remember I will pull it. And it is high I think, yall are right. And yea that's the way to test auto thermostats as well. I surely would not be boiling the stuff in my house though, maybe a camp stove or propane burner outside but not in the house.

California · Mar 30, 2017

clemsonfor said:
Sorry wasnt calling you out on that. Was kind of a joke about how good yall guys are at this stuff.

Never occurred to me to take it that way!

The way I see this forum, with these orphan models it's up to us owners to find and share the information that would be common knowledge in a shop that sees them all the time.

These never go to a repair shop, and the importers who brought their product up to spec before sale are no longer posting here, so we're the only 'culture' of interested persons to maintain and share the 'common knowledge' that helps keep them in use. Sorry if I come across as blunt or abrasive at times, that's not my intent. I hope I'm mostly right in the information (and opinions

) that I post! I'm not at all offended if someone responds with more accurate information or a different viewpoint that broadens my/our understanding of these.

careyo63 · Mar 30, 2017

Now that you believe you have the problem solved I would go one step further and check just how much pressure you have in the radiator. You can rent or borrow a tester at most any auto store. You just attach it to the radiator cap and watch to see how much pressure is being applied. To much means bad HG.. The water pump and or pistons are blowing pressure into the Radiator through the Head Gasket.

Here's one @ Radiator Pressure Tester Kit

clemsonfor · Mar 30, 2017

California said:
Never occurred to me to take it that way!

The way I see this forum, with these orphan models it's up to us owners to find and share the information that would be common knowledge in a shop that sees them all the time.

These never go to a repair shop, and the importers who brought their product up to spec before sale are no longer posting here, so we're the only 'culture' of interested persons to maintain and share the 'common knowledge' that helps keep them in use. Sorry if I come across as blunt or abrasive at times, that's not my intent. I hope I'm mostly right in the information (and opinions ) that I post! I'm not at all offended if someone responds with more accurate information or a different viewpoint that broadens my/our understanding of these.

I too am blunt. I didn't take what you said offensive, was just hoping you did the same from me :thumbsup:

Now that you say that I have not seen any importer or dealer or anyone other than Hoye post on these forums since the lawsuit. I guess that was all part of the deal? But their authorized dealers of fredericks stuff are still legal under the terms and we no longer see Spalding post, who never did much before anyway.

I wonder if any of the old importers etc have joined under a different name and are posting here but we just wont ever know due to them wanting to remain anonymous??