Does anyone replace thermostat...

[Wotname]

Originally Posted by charliehows

actually when the t.stat opens on my manifold fitting it doesnt block the by-pass flow, it merely impedes it by intruding the sprung mechanism into the space normally open to the by-pass. Which is why I dont take the whole system very seriously. Also why the manifold is prone to blockage.

Interesting!

My 2QM20 thermostat definitely closes off the by-pass water once it is fully operated (hot/open).

The by pass water enters the thermostat housing via a 14mm ID hose. The housing itself has a restriction to 3.25mm in the by pass inlet. When hot, the top section thermostat closes against a face inside the housing preventing the by pass water to flow while at the same time, allowing the flow from the block/head/manifold.

Yours must be different. Or broken...

[charliehows]

Have to admit that fitting looks pretty similar to mine (much newer and shinier tho') – maybe I should put my bloody glasses on next time I examine it.
Fitted the little tap fitting I cooked up into the by-pass line and initial trial indicates – the thermostat/by-pass system has absolutely no significant effect on the heat up rate or the running temp. of my engine. But I like having a tap to play with. And I am fairly convinced there is a benefit to having more constant thru-flow to flush out anode residue.

[Compass790]

Thanks for reporting back charliehows. Suspected it mite not have much effect considering your engine is raw water-cooled & has a lot of mass for the hp. Be interesting to see how the anode reside problem plays out or have you already established that to your satisfaction?

[Wotname]

Originally Posted by charliehows

Have to admit that fitting looks pretty similar to mine (much newer and shinier tho') – maybe I should put my bloody glasses on next time I examine it.
Fitted the little tap fitting I cooked up into the by-pass line and initial trial indicates – the thermostat/by-pass system has absolutely no significant effect on the heat up rate or the running temp. of my engine. But I like having a tap to play with. And I am fairly convinced there is a benefit to having more constant thru-flow to flush out anode residue.

It wasn't that shiny until I ran it past the wire brush and phosphoric acid

I couldn't post a dirty housing on CF!

I was surprised to find the 3.25mm restriction in the by pass water inlet; initially thought it was more crud / corrosion but no, it looks like it is meant to be there.

Yep, it will be interesting to see how well the manifold flushes with more flow - shocking design though; what was Mr Yanmar thinking

[charliehows]

Originally Posted by Compass790

Thanks for reporting back charliehows. Suspected it mite not have much effect considering your engine is raw water-cooled & has a lot of mass for the hp. Be interesting to see how the anode reside problem plays out or have you already established that to your satisfaction?

given the restriction on the manifold I wouldnt be surprised if the residue continues to accumulate - the other problem area is just inside the eng. inlet - residue accumulates there as a result of gravity and i regularly give it a dose of screwdriver when i check the lower anode - probably still be dosing the thing every couple of years with double strength vinegar - but at least I dont have a thermostat to worry about...

[Wotname]

^^ which begs the question, does your drain outlet that is near the eng. inlet still work or is it also clogged with crud???

[charliehows]

Originally Posted by Wotname

^^ which begs the question, does your drain outlet that is near the eng. inlet still work or is it also clogged with crud???

I've had the boat 10 years, never tried to open it - theres really only one outcome of f..ing about with something that old and neglected. As long as its not leaking I politely ignore it.

[EmeraldCoastSailor]

At 10 years and 950 hours my 3YM30's coolant pump was suspect so I replaced it along with thermostat and hoses. I always wondered if I should replace thermostat sooner but never had any issues (I check engine with laser thermometer regularly).

[a64pilot]

Originally Posted by EmeraldCoastSailor

At 10 years and 950 hours my 3YM30's coolant pump was suspect so I replaced it along with thermostat and hoses. I always wondered if I should replace thermostat sooner but never had any issues (I check engine with laser thermometer regularly).

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, it’s not even seeping and they usually go slowly, but mine is decades old and I wonder if I shouldn’t have changed it too, but Yanmar pumps are ridiculously priced.
Are the aftermarket ones OK? Should be, there isn’t much to a pump.

[sailorboy1]

Originally Posted by a64pilot

Are the aftermarket ones OK? Should be, there isn’t much to a pump.

Of course and they are only about $130

[Redline452]

This summer I replaced the thermostat on my 1998 4JH2TE just shy of 1600 hours; no alarms but I had noted the galley hot water (heater on the coolant circuit) was extremely hot / steaming after extended motoring, while the water exiting the heat exchanger was just tepid. IR thermometer showed no part of the engine above about 86C, and for some reason I'm unable to keep the overflow tank above the 'low' line when cold.


End result seemed to be less steam in the galley, about the same heat exchanger output and engine temps. I have the old one in the garage and keep threatening to boil it in the kitchen to see where it does open, and will keep as a spare. Including a new gasket, the OEM part wasn't expensive - and is much cheaper than a new engine!

[sdj]

No. Always carry a spare though..

[GrowleyMonster]

Originally Posted by OrangeCrush

...as part of periodic maintenance? It's not listed in the manual as something that needs to be done at any maintenance interval, but then again I've learned that the manual is far from comprehensive. I'm planning to change the coolant in my 4JH5E this year and wondering if it makes sense to swap out the thermostat for good measure. Thoughts? Thanks

If the manual is silent on this topic, you can change it annually, or just pull it and check it annually, or you can just keep a spare and if it fails, you will know it. Assuming you watch things like water temp. If it fails and you do not have a spare, it is quite alright to remove it long enough to get somewhere where you can get a new one.

[sdj]

Originally Posted by GrowleyMonster

If the manual is silent on this topic, you can change it annually, or just pull it and check it annually, or you can just keep a spare and if it fails, you will know it. Assuming you watch things like water temp. If it fails and you do not have a spare, it is quite alright to remove it long enough to get somewhere where you can get a new one.

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've driven and maintained my own commercial diesels all my working life, and I have never seen a thermostat fail in a bad way. Usually they go soft and don't hold engine temperature, or they jam mid-stroke making sustained full power settings lead to an overheat.

The value of an over-temp alarm has already been observed here, and with this fitted and tested-good I'd like to suggest that it is more risky to fiddle with it than to leave it and use it.

[oldtom]

Originally Posted by charliehows

I occasionally test mine by throwing it in a pot of hot water on the stove – actually, I've recently removed it altogether because it promotes blockage of the exhaust manifold on my engine with anode oxidation residue – I do mainly short runs and the thermostat doesnt get warm enough to open and flush the manifold. There was no thermostat in place when I bought the boat, I didnt give it much thought, just bought one and stuck it in, but after quite a few years I realised it had been removed by the previous owner because of the above mentioned problem. Taking it out of the system is harmless in engineering terms and beneficial in that it forestalls a potentially damaging blockage.

the Thermostat in there so the engine block can get to operation temperature and coolant can remove excessive heat that water pump flow is a lot higher than required so by removing the only control for temp and flow coolant can,to pick up remove the heat from cylinders -head so the engine will run hot it will in the past old mechanic would just cut out the centre of a none working thermostat