Two-cylinder diesel: one hot, one cold!

[Wotname]

Excellent and well thought out post Jimbunyard!

[charliehows]

Lets see – you had a problem – difficult engine starting, which you misdiagnosed as being somehow caused by the engine running too cold (but which in fact is probably more likely caused by air leaking into the fuel supply system indicated by the leak you mentioned in your photo post).
You've modified your cooling water flow which has caused a different problem which most of this post has been about chasing.
Incidentally, my yanmar 2qm20 is nearly 40 years old, raw water cooled, runs cold enough to hold your hand on the rockerbox, and has a manufacturer installed thermostat so your engine is not too old to have a thermostat.
Before you start bashing your Injectors with a hammer, as one helpful poster suggested, may I propose the following simple basics; 1; fastest thing to kill an engine – no oil. 2; (pay attention now) second fastest thing to kill an engine – too much heat. 3; most likely thing to go wrong with poorly maintained diesel engine – air leaks in fuel supply system (if diesel can leak out, air can leak in).
At least you havent damaged your oiling system.
I apply a simple rule of thumb when problem solving on engines; Do one thing at a time. Then you only have to backtrack one step at a time if it has no effect or a detrimental effect.
I'd recommend you return the cooling system to the state it was in when it was working properly and then go look at your fuel supply system.
Good luck.

[Cadence]

Originally Posted by charliehows

Lets see – you had a problem – difficult engine starting, which you misdiagnosed as being somehow caused by the engine running too cold (but which in fact is probably more likely caused by air leaking into the fuel supply system indicated by the leak you mentioned in your photo post).
You've modified your cooling water flow which has caused a different problem which most of this post has been about chasing.
Incidentally, my yanmar 2qm20 is nearly 40 years old, raw water cooled, runs cold enough to hold your hand on the rockerbox, and has a manufacturer installed thermostat so your engine is not too old to have a thermostat.
Before you start bashing your Injectors with a hammer, as one helpful poster suggested, may I propose the following simple basics; 1; fastest thing to kill an engine – no oil. 2; (pay attention now) second fastest thing to kill an engine – too much heat. 3; most likely thing to go wrong with poorly maintained diesel engine – air leaks in fuel supply system (if diesel can leak out, air can leak in).
At least you havent damaged your oiling system.
I apply a simple rule of thumb when problem solving on engines; Do one thing at a time. Then you only have to backtrack one step at a time if it has no effect or a detrimental effect.
I'd recommend you return the cooling system to the state it was in when it was working properly and then go look at your fuel supply system.
Good luck.

Modifying a design to cure a previous none existent problem is not the way to go. I wish him luck.

[NevisDog]

Originally Posted by charliehows

Lets see – you had a problem – difficult engine starting, which you misdiagnosed as being somehow caused by the engine running too cold ...

Absolutely incorrect.

Let's see - had a problem with engine almost dying each time I engaged gear, or went from fwd to reverse gear - a particularly unsafe situation. Couldn't alter propeller pitch (not that I'd want to) or reduce prop size (not that I'd want to) or boost revs at idle (already a fast idle) so I tried increasing engine temperature above stone cold. Brilliant! At 80C, no hesitation at engaging gear, no problems hitting reverse and waiting with baited breath for revs to recover (from around 1RPS!) - first problem solved, three months ago.

However 80C at the temp gauge (on exhaust jacket/manifold) is too high for salt water. No problem, I'll simply open vv a little further and adjust temp down to around 50-60C. I've decided to stick with set-up as no way do I want to return to previous, dangerously low power when engaging propeller.

Now we have a different problem that has developed slowly over past 3 weeks of starting engine once a week for an hour, just to keep it in good shape and check its performing as before. First week the temp gauge at idle stayed low, around 50C, so I checked engine and found it slightly warmer at fwd end of exhaust jacket - not much problem, but something to watch. Temp sender is in middle of manifold. Second week, same low temp but fwd part temp seemed even hotter and aft end perhaps cooler. This week the difference was extreme, so time to sort this new problem.

Now this new problem is certainly easier to spot because I'm running engine hotter, and certainly any blockage would become more significant, and at a quicker rate, because I've reduced flow of raw water to engine. But if it is a blockage (and that now seems most likely explanation) then it would have gradually gotten worse anyway - passages certainly needed cleaning - so I don't see this as being caused by the bypass mod.

Fuel leak is something I need to attend to (along with a million other little jobs - engines are never top priority on a sailboat - sails are) and something which most likely explains six or eight throws of starter motor each time to get it going, but that problem is no better and no worse than it's ever been. Some day I'll find the time to fix it.

I've searched the manual and there is no thermostat located on this engine, I'm almost certain. Just as there was no thermostat on my old Watermota, and none on the old hand-crank lifeboat engine in my last diesel-powered setup. You can't find what ain't there.

Note also, fwd part of manifold is the hottest, and that's where the water would be returning under pressure from the bypass Tee, if there was any reason for it to push back against the flow from the engine. This tells me the water is not being returned to the engine from the bypass.

I'll take this steady, clean out the mess inside the water chambers as best I can, then let you know if problem is solved.

[NevisDog]

Originally Posted by jimbunyard

... in the video below you can see the proper setup.

Yes, that's much neater setup in video. PO was a bit slapdash for sure.
Note that, soon as engine starts, water is pouring from exhaust; this tells me there is no thermostat.

[NevisDog]

Apologies for wrong diagnoses will be accepted. Positive encouragement only required for this mechanically-challenged sail-handler , my thanks go to those who have bin so supportive and encouraging.

[charliehows]

Thanks for the comprehensive information at post no. 34 when no-one is looking anymore – have a look at your original post – the only problem you mentioned is difficult starting.

[NevisDog]

Originally Posted by charliehows

... have a look at your original post – the only problem you mentioned is difficult starting.

Solving a problem three months ago didn't seem at all relevant, it still doesn't - only when folks began complaining about my modification did I recall the real reason for doing it.

[NevisDog]

Also, all those early replies, based on the [B]relevant[B] information I provided, seemed very helpful and on-the-money - things began to go way off the central problem as we progressed.

[Wotname]

Originally Posted by NevisDog

Yes, that's much neater setup in video. PO was a bit slapdash for sure.
Note that, soon as engine starts, water is pouring from exhaust; this tells me there is no thermostat.

As explained earlier, a RWC thermostat acts differently to a closed loop thermostat.

A RWC thermostat (when cold) simply diverts water away from the head and directly into exhaust injection point. When hot, it directs the water though the head etc before going into the exhaust.

Counter intuitively, this is why a RWC engine will overheat if the thermostat fails in the "cold" position; the water is simply going directly into the exhaust and not though the engine.

I dunno if you have a thermostat or not but your reasoning above is not evidence. As posted earlier and by several members, it is unusual for any post WWII engine not to have a thermostat - but never say never .

[NevisDog]

Originally Posted by Wotname

...A RWC thermostat (when cold) simply diverts water away from the head and directly into exhaust injection point. ...

Darn, I knew that, cos you told me so, about three minutes back.
(I have the memory retention of a gnat.)

So this engine running cold meant it either (a) had no t'stat, or else (b) a failed t'stat in the 'hot' position (or possibly even (c) a failed t'stat in the 'cold' position that PO has removed and tossed)? Since I'm never going to find it, and since the stuck-down page from the manual doesn't show it - either way I have no t'stat.

But a failed or removed t'stat would certainly explain why engine never warmed up. My thoughts were the PO had replaced raw water pump and it may be bigger than original, but who knows?

Now, let's see if I still remember this tomorrow....

[jimbunyard]

Originally Posted by NevisDog

Yes, that's much neater setup in video. PO was a bit slapdash for sure.
Note that, soon as engine starts, water is pouring from exhaust; this tells me there is no thermostat.

Um...no. What this tells you is that, as plumbed, no water is going through the engine passages, because, as advised previously, the water will seek the path of least resistance, and pass directly from the r/water pump, through the 'T' you've added, into the hose connecting the outlet in the exhaust manifold cooling jacket and the exhaust mixing elbow and out the mixing elbow.

Once again, and for the final time (for me at least), run the plumbing as I described and as shown in the video, fix the fuel leak and try again. As Charlie advises above, there really isn't a 'too cool' mode (within reason).

I really thought I was way over-emphasizing the point, but the flow of water through the engine is critical for proper operation; the flow is designed to remove heat from the engine at a controlled, graduated rate. Changes in this configuration should only be taken with/from/in an informed perspective; for instance, applying pressure to an orifice designed as an outlet is very counterproductive...

As an example, raw water cooled Mercruisers in proper operating condition will often not move the gauge while idling (in or out of gear) at all; they must be under power (on plane) to get the engine up to 'correct' operating temp...

[NevisDog]

Originally Posted by jimbunyard

...Once again, and for the final time (for me at least), run the plumbing as I described and as shown in the video,...

Umm, NO.

I do much appreciate advice, yours in particular, but decision is mine alone.

[NevisDog]

No one warned me that vinegar not only softens the lime/calcium/crud but also seems to dissolve it in some aggressive chemical reaction, producing masses of bubbles (of what gas I know not) that eventually push all of the vinegar back out the tubes connecting to pump and bucket. So my overnight soak was kinda wasted, as when I pumped vinegar back in, all those bubbles start over. I doubt that the little electric pump I have is designed for continuous running so will just have to keep pumping liquid back in there until it stops fizzing.

[NevisDog]

And I've looked closely at those photos of RWC thermostat housings on Yanmars: the one and only possible location for such a gadget on this engine that I can see would be the front end of the (marinised) exhaust water jacket box, around where that pipe elbow exits, taking the hot water to the exhaust elbow mixer at the back end. The front end has a removable cover but the pictures in the manual (I can't read the text) show this cover is just a cover for the alternative attachment point for the exhaust exit bend - just a blank over an empty hole. So, now I'm quite certain - there is no RWC t'stat housing on this Lombardini tractor engine, marinised by Arona.