Does anyone replace thermostat...

[charliehows]

yeah, 2qm20, gave the manifold a pretty thorough massage with a dirty big screwdriver to encourage the white gunk to go on its way. Mine doesnt have a drain tap on the manifold so no probs there. Didnt block the bypass, just removed the thermostat and re-gasketed the housing, my intention being to encourage constant raw water flow through both engine and manifold at all times - same dirty big screwdriver is employed when lower anode nut is removed from front eng. water input area as this has concreted up in the past with anode residue. There doesnt appear to be much difference in the heat up rate with or without the thermostat in place, I like the original design idea of a quick heatup bypass but I think I've heard a tiny bit of disrespect from other quarters for the...sincerity and dilligence of the manufacturer which leaves me unrepentant in varying their design to suit my own prejudices

[charliehows]

dammit - now you've got me thinking about it, I might block the bypass to force all the flow from eng. thru. manifold to exit...I've been puzzling over whether there is much water passing through the bloody pipe from the eng across to the manifold...I thought it best to leave well enough alone in just taking out the thermostat...maybe I'll give a try to blocking the bypass...let you know the results in a few weeks. Cheers.

[Compass790]

Originally Posted by charliehows

dammit - now you've got me thinking about it, I might block the bypass to force all the flow from eng. thru. manifold to exit...I've been puzzling over whether there is much water passing through the bloody pipe from the eng across to the manifold...I thought it best to leave well enough alone in just taking out the thermostat...maybe I'll give a try to blocking the bypass...let you know the results in a few weeks. Cheers.

I'm interested as to what pans out in this experiment. If you have an infrared thermometer could you check the head temp & the manifold temp before you make the changes? Several measurements as it warming if possible. No worries if it's too much of a PITA.
Sorry for the thread drift but curiosity killed the cat.

[jamhass]

No real opinion on the lifetime of a T-stat, but ...

It is a lot easier (and safer) to change out a T-stat on a cool engine (with a cold beer nearby) than on a hot engine (under duress.)

[Wotname]

Originally Posted by jamhass

No real opinion on the lifetime of a T-stat, but ...

It is a lot easier (and safer) to change out a T-stat on a cool engine (with a cold beer nearby) than on a hot engine (under duress.)

This is so so true

It highlights the fact that you can choose when/where to do scheduled maintenance but the engine decides when/where to do unscheduled maintenance - I know which I prefer!

[Compass790]

Originally Posted by charliehows

yeah, 2qm20, gave the manifold a pretty thorough massage with a dirty big screwdriver to encourage the white gunk to go on its way. Mine doesnt have a drain tap on the manifold so no probs there. Didnt block the bypass, just removed the thermostat and re-gasketed the housing, my intention being to encourage constant raw water flow through both engine and manifold at all times - same dirty big screwdriver is employed when lower anode nut is removed from front eng. water input area as this has concreted up in the past with anode residue. There doesnt appear to be much difference in the heat up rate with or without the thermostat in place, I like the original design idea of a quick heatup bypass but I think I've heard a tiny bit of disrespect from other quarters for the...sincerity and dilligence of the manufacturer which leaves me unrepentant in varying their design to suit my own prejudices

Thinking about your experiences it seems it wouldn't be that critical having a thermostat in your case any way as with Sydney water say 20oC & thermostat fully open at 52oC with the temp difference being only 32o it's not comparable with a heat exchanger equipped engine where the temp difference would be around 60oC.
More thinking ( dangerous perhaps lol) leads me to believe the thermostat is on the exhaust manifold as that probably heats up faster than the head & block on the large 2QM20.
I'd imagine your 2QM20 would take an age to heat up unless it was put under load anyway.
Whilst it would seem to be always preferable to have a thermostat rather than not I can see, in your case, the problems it causes make it not worth it.
Have you had to replace the exhaust manifold in your ownership?

[charliehows]

Has original manifold. t.stat on manifold. My attitude to the heating up of the engine - irrelevant, but gentle use of engine on the assumption that its mostly running a bit cold. Give it a bit of a blowout when I know its been running long enough to be up to temp. Current plan - incorporate a tap into by-pass hose. My only concern in diverting all flow through eng. + manifold is pressure.
as they say on TV; 'dont try this at home, kids' but if you have a 40 yr old 2qm20 this may be of interest to you...

[Wotname]

Originally Posted by charliehows

Has original manifold. t.stat on manifold. My attitude to the heating up of the engine - irrelevant, but gentle use of engine on the assumption that its mostly running a bit cold. Give it a bit of a blowout when I know its been running long enough to be up to temp. Current plan - incorporate a tap into by-pass hose. My only concern in diverting all flow through eng. + manifold is pressure.
as they say on TV; 'dont try this at home, kids' but if you have a 40 yr old 2qm20 this may be of interest to you...

Hmm... I don't see anything to worry about - assuming the waterways in the manifold are mainly clear of crud. There is no substantial pressure in the raw water cooling circuit, it is essentially open to the atmosphere or at least open to the back pressure in the exhaust system.

When the thermostat is fitted and the thermostat is in the cold position, all cooling water passes directly from the pump to the exhaust injection point via the bypass hose and none though the block/head/manifold.

When the thermostat is fully hot, all cooling water passes though the block/head/manifold and none though the bypass hose.

Your tap (when closed) in the bypass hoses is just replicating a fully hot thermostat. IMO, the tap (or any permanent blockage) is essential if you remove the thermostat.

[CassidyNZ]

Originally Posted by charliehows

yep, in theory. try telling that to a 40 year old engine still running like a sewing machine.

The function of the thermostat is to keep engine temperature up. The reason is two-fold - firstly hotter engines experience less wear and secondly hotter engines use (infinitesimally) less fuel. As an non-marine example, I have a V12 BMW that runs a higher pressure cooling system and the normal operating temperature is 108 degrees C. Because the car is inherently thirsty, the high temp is ostensibly to reduce fuel consumption. But honestly, I put a custom thermostat (85 degrees) in and have noticed no difference.

But engine wear? Well, I don’t expect the engine to last more than 600,000kms anyhow A Yanmar would probably also not notice any difference.

To come back on topic, I can’t recall ever replacing a thermostat that wasn’t faulty. Thermostats always fail to open when faulty - my fallback then is to remove it and get a new one when I next can. It’s really no biggie.

[a64pilot]

If it wasn’t necessary then it’s not likely that Yanmar would have wasted the money to install one.

[Pizzazz]

I occasionally test mine by forgetting to open the raw water seasick. The warning starts with a hissing sound from the alarm before the high pitched alarm kicks in. I would not recommend this method though .

[Compass790]

Originally Posted by Pizzazz

I occasionally test mine by forgetting to open the raw water seasick. The warning starts with a hissing sound from the alarm before the high pitched alarm kicks in. I would not recommend this method though .

You are not the only one to use this method lol

[CassidyNZ]

Originally Posted by a64pilot

If it wasn’t necessary then it’s not likely that Yanmar would have wasted the money to install one.

Along with every other engine manufacturer on the planet Astonishing how often methods proven over a century of development are wiped off the table by folks who think there’s a better way.

[Compass790]

Originally Posted by CassidyNZ

Along with every other engine manufacturer on the planet Astonishing how often methods proven over a century of development are wiped off the table by folks who think there’s a better way.

Actually progress/improvements are only made by people who think there is a better way not those that blindly follow what has gone before.
Yes plenty of mistakes are made thinking you have a better way but also sometimes there is a better way.
Not that I'm arguing it's better not to have a thermostat!
However, in charliehows case it causes problems.
It's hard to have blind faith in engine manufacturers when you come across obvious flaws in their design.
What I find astonishing is that people think that engine manufacturers are infallible. YMMV

[redneckrob]

What exactly is the failure mode on a bimetal strip connected to a spring and plunger? I'm sure one has failed somewhere sometime but it has to be vanishingly unlikely. Far more likely that it's jammed with crud, which wouldn't require replacement, and far far more likely as several have pointed out that the hoses need to be preventively replaced. Proactively replacing a thermostat annually as it sounds like one engine manufacturer recommends is just lunacy!