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Old 20-10-2019, 08:02   #61
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Re: Does anyone replace thermostat...

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I won't disagree with any of this, but it is worth noting here that there is a risk pulling things apart and putting them back together again.


I'd like to suggest that it is more risky to fiddle with it than to leave it and use it.


The flip side of that is after ten or fifteen years of those bolts never having been removed, you may shear one off when you have to.

Scheduled maintenance is well, scheduled and is most likely performed where parts are available, unscheduled maintenance is performed out in the boonies, where parts are not available.
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Old 20-10-2019, 08:36   #62
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Re: Does anyone replace thermostat...

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No. Always carry a spare though..
Why would you do that? (with all the other more important spares you really need to carry on a cruising boat

Most every kid I knew with an overheading engine would pull the thermostat first and throw it in the trunk (or tool box) to see it that was the problem.

If so, replace on payday, when you can afford to, when you have time, or before Winter!
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Old 20-10-2019, 09:00   #63
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Re: Does anyone replace thermostat...

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Why would you do that? (with all the other more important spares you really need to carry on a cruising boat

Most every kid I knew with an overheading engine would pull the thermostat first and throw it in the trunk (or tool box) to see it that was the problem.

If so, replace on payday, when you can afford to, when you have time, or before Winter!

Operating for a day or two with no thermostat or a thermostat stuck open is not really a big deal. Doing so for several days or weeks or months is not a good idea, because the engine never reaches optimum operating temp. You could of course throttle down the cooling water, but the potential overheating might be an issue. The engine is designed to use a thermostat, so use a thermostat. Just to get the boat home or into harbor, sure, run without a thermostat. But a spare is cheap. Especially if there is an automotive or agricultural equivalent that will work, and you have freshwater cooling. I keep mine with my spare impeller. I have spare starter. Spare alternator. Spare belts and hoses. I normally have spare injectors but I have not got around to getting them yet for this boat. Spare injector lines ditto. Spare prop, washers, shaft key, nut and locknut, cotter pin. Filters. Especially fuel filters. A bad batch of fuel can have you going through a lot of filters. Circuit breakers. Fuses, including main fuses. Actually I don't have a spare prop yet for this boat but I always get one for all boats I own, eventually. Zincs, a bunch of them. A couple thousand bucks worth of spares is a good investment. Or whatever you can afford, starting with the cheap stuff like thermostat, zincs, belts, impeller.
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Old 20-10-2019, 09:50   #64
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Re: Does anyone replace thermostat...

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Operating for a day or two with no thermostat or a thermostat stuck open is not really a big deal. Doing so for several days or weeks or months is not a good idea, because the engine never reaches optimum operating temp. You could of course throttle down the cooling water, but the potential overheating might be an issue. The engine is designed to use a thermostat, so use a thermostat. Just to get the boat home or into harbor, sure, run without a thermostat. But a spare is cheap. Especially if there is an automotive or agricultural equivalent that will work, and you have freshwater cooling. I keep mine with my spare impeller. I have spare starter. Spare alternator. Spare belts and hoses. I normally have spare injectors but I have not got around to getting them yet for this boat. Spare injector lines ditto. Spare prop, washers, shaft key, nut and locknut, cotter pin. Filters. Especially fuel filters. A bad batch of fuel can have you going through a lot of filters. Circuit breakers. Fuses, including main fuses. Actually I don't have a spare prop yet for this boat but I always get one for all boats I own, eventually. Zincs, a bunch of them. A couple thousand bucks worth of spares is a good investment. Or whatever you can afford, starting with the cheap stuff like thermostat, zincs, belts, impeller.
Right, which is why you don't go for weeks or months if you plan to run your engine a lot, but we are talking sailboats here

Some sailors rarely even use their engines

You might have to sail a bit more until you can get a replacement

It's not like a thermostat has a high rate of failure or that it will leave you stranded. It's just like back in the day as a teen. You can get by without one for a while especially in Summer
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Old 20-10-2019, 10:43   #65
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Re: Does anyone replace thermostat...

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Right, which is why you don't go for weeks or months if you plan to run your engine a lot, but we are talking sailboats here

Some sailors rarely even use their engines

You might have to sail a bit more until you can get a replacement

It's not like a thermostat has a high rate of failure or that it will leave you stranded. It's just like back in the day as a teen. You can get by without one for a while especially in Summer

Did I mention that a thermostat is cheap? It's a good spare to have. If you don't, it isn't the end of the world, no, but I prefer to have one. Along with all the other inexpensive and small doodads that make the diesel and other systems run happy.
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Old 20-10-2019, 10:49   #66
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Re: Does anyone replace thermostat...

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Did I mention that a thermostat is cheap? It's a good spare to have. If you don't, it isn't the end of the world, no, but I prefer to have one. Along with all the other inexpensive and small doodads that make the diesel and other systems run happy.
Nice.

Everyone does it their own way.

I have a spare fuel filter, impeller, tools, and quite a bit of tape

I also try to carry 2-3 gallons of extra gas
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Old 20-10-2019, 13:36   #67
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Re: Does anyone replace thermostat...

Ref a spare thermostat. Why not?
Look at it this way, thermostat goes bad, you remove the old one, put in the new one and your done. Other wise your taking things apart twice, which is no big deal, but it is less work, less chance of diluting the coolant etc.
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Old 20-10-2019, 15:31   #68
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Re: Does anyone replace thermostat...

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Ref a spare thermostat. Why not?
Look at it this way, thermostat goes bad, you remove the old one, put in the new one and your done. Other wise your taking things apart twice, which is no big deal, but it is less work, less chance of diluting the coolant etc.
The old thermo goes bad, you cook the engine and you are stuck somewhere. It's not like you get a message in the mail that the part is about to fail.
What I don't understand is why all thermo's are not "fail safe". I can't seem to find one to fit my Perkins, but If I had a Chevy it would be no problem. Why do they have them fail closed? It makes no sense.
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Old 20-10-2019, 18:14   #69
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Re: Does anyone replace thermostat...

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The old thermo goes bad, you cook the engine and you are stuck somewhere. It's not like you get a message in the mail that the part is about to fail.
What I don't understand is why all thermo's are not "fail safe". I can't seem to find one to fit my Perkins, but If I had a Chevy it would be no problem. Why do they have them fail closed? It makes no sense.

Usually it is possible to simply remove it, and the coolant system is then wide open. This has the engine running cold, but it will run, and it will get you where you are going with no real damage. Continued operation without allowing the engine to reach correct operating temperature can cause problems, but in the short term no real harm is done.
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Old 21-10-2019, 18:57   #70
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Re: Does anyone replace thermostat...

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That is how I like to do things, complete systems, then you usually have years before you need to worry about it again.
Most people lose a hose, so they replace that hose, then later the thermostat goes, then a little later the heat exchanger clogs, etc. etc.

I just went though my cooling system, hoses, coolant flush, heat ex etc. however my water pump concerns me, itís not even seeping and they usually go slowly, but mine is decades old and I wonder if I shouldnít have changed it too, but Yanmar pumps are ridiculously priced.
Are the aftermarket ones OK? Should be, there isnít much to a pump.
Marine Maintenance in PCB got me a Yanmar coolant pump for less than $300 as I recall. I didn't take the time to research alternatives and given the expected lifespan price didn't seem out of line. Mine was barely and I mean barely weeping. I probably could have motored to the Keys with it but the time was right to make several things new.
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Old 22-10-2019, 10:01   #71
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Re: Does anyone replace thermostat...

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Marine Maintenance in PCB got me a Yanmar coolant pump for less than $300 as I recall. I didn't take the time to research alternatives and given the expected lifespan price didn't seem out of line. Mine was barely and I mean barely weeping. I probably could have motored to the Keys with it but the time was right to make several things new.
The Yanmar pump was $187.45 but with T-stat, a variety of gaskets, and shipping it came out to $292. I had ordered the hoses previously and had them in reserve. Now I have what I think are fully functional but used hoses in reserve.
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Old 22-10-2019, 16:54   #72
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Does anyone replace thermostat...

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What I don't understand is why all thermo's are not "fail safe". I can't seem to find one to fit my Perkins, but If I had a Chevy it would be no problem. Why do they have them fail closed? It makes no sense.

Fail safe thermostats are marketed, but they really arenít fail safe. Basically more marketing lies.
This is Stantís FAQ, and I trust Stant myself.
http://www.stant.com/index.php/engli...rmostats/faqs/
Read the FAQ about how a thermostat works by wax melting and expanding and pushing the valve open against a spring and water flow, and itís pretty easy to see how any leak in this wax capsule will result in a failed close thermostat.

I think itís because the design requires the thermostat to be in a closed position so the engine will heat up, then any failure of it to operate means the thermostat remains closed.

Aircraft oil coolers have thermostats, when cold the oil flows through both the cooler and the bypass, but when hot the bypass is closed off, so that when they fail, there is oil flow though the cooler and bypassed. Itís a fail safe design, not a fail safe thermostat though.
I feel sure that if a fail safe thermostat were possible, you would find them in aircraft where shutting an engine down isnít always an option.
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Old 22-10-2019, 17:07   #73
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Does anyone replace thermostat...

If replacing a thermostat and the replacement doesnít have a jiggle pin or a notch or whatever, I drill a small hole in the flange, to let air through.
Itís not strictly necessary in a design that doesnít require it, but Iíve found it makes life easier when changing coolant, less chance of a large air bubble in the engine. Of course the small hole does let some water flow when the thermostat is closed, but there should be flow anyway, usually through a bypass. There has to be some flow or hot water wouldnít get to the thermostat to open it.
In other words in my opinion the 1/16 hole or so hurts nothing and may make it easier to bleed a cooling system.
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Old 22-10-2019, 18:50   #74
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Re: Does anyone replace thermostat...

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Originally Posted by Ecos View Post
The old thermo goes bad, you cook the engine and you are stuck somewhere. It's not like you get a message in the mail that the part is about to fail.
What I don't understand is why all thermo's are not "fail safe". I can't seem to find one to fit my Perkins, but If I had a Chevy it would be no problem. Why do they have them fail closed? It makes no sense.
Not correct.

Thermostats do give signs they are about to fail (gauge heads all over the place - usually down), and also when they do fail they usually jam part way, or completely open. I've never seen a thermostat fail shut and overheat an engine - and I've run commercial diesels my whole working career.

If you dont have a working cylinder head over-temp alarm, you're a mug and you're going to get burned.
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Old 23-10-2019, 12:51   #75
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Re: Does anyone replace thermostat...

[QUOTE=a64pilot;3001571]Fail safe thermostats are marketed, but they really arenít fail safe. Basically more marketing lies.
This is Stantís FAQ, and I trust Stant myself.


Well Stant need to get with the 21st century. MotoRad thermostats have a dual action and lock open with an overheat.
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