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Old 03-29-2013, 07:54 PM   #341
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Frankly, I'm surprised the thermostats in your engines didn't catch that and keep the temps the same after the synthetic was used.
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Marin is correct. A properly functioning thermostat should not allow an engine under load to "run cooler" than its open/close temp range This point is the Catch 22 of the whole discussion.
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Old 03-29-2013, 07:55 PM   #342
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I don't think it will Walt.

I think there was another reason the temp changed.
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Old 03-29-2013, 10:44 PM   #343
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It damn well better!!! ()
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Old 03-29-2013, 11:40 PM   #344
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Walt, you could change the thermostat and see if it helps your 192 degree temp, which doesn't sound bad at all for a Cummins like yours. I know that's not quite as sexy and exciting on the Tinker-meter as changing to synthetic oil, but it might rule out the thermostat as being the cause of your perceived high temp.
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Old 03-29-2013, 11:44 PM   #345
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Al I suggested some time ago that Capp change back to dino and re-take his temp.
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Old 03-30-2013, 12:03 AM   #346
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I don't think it will Walt.
It very well may not lower the temp but the engine will have better lubrication. If in fact the engine wants to run, say at 185, and the thermostat is full open, providing all the cooling it's capable of, but not enough to bring the temp to the desired 185, doesn't it stand to reason that better lubricating of the internal workings of the engine (Not the cylinder temps) reduces friction to the point that the full open thermostat can now reduce the overall temp?

If the thermostat is suppose to hold the coolant temp at a prescribed setting, why then, does the engine cool down at a reduced throttle setting. There's Less water being pumped through the heat exchangers, etc...Shouldn't the thermostat close to maintain the preset temperature point? I agree with Capthead that reducing friction in the engine will reduce the coolant temp by a few degrees. Just enough for the thermostat, when fully opened, to accomplish its task.

I'm rather tired of all this arm chair quarterbacking so I'm going to switch my oil to a synthetic and see what happens. The possibility of incurring damage to my engine is extremely remote.

How is what I am about to do any different than you, Eric, pretty much ignoring all the anchor data that's out there and testing the damn things yourself?

If the experiment is successful, there will be a lot of faces and only 3 ones. Conversely, if it doesn't lower the coolant temp the reverse will be the case. Either way, I think it's a small price to pay to expand our collective knowledge.
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Old 03-30-2013, 12:15 AM   #347
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Good points Walt.

Re the thermostat. Thermostats cease to have any effect after they are full open and before they start to open. And I'll bet their operating range of starting to open to full open (in degrees) vary from thermostat to thermostat.

But the oil MAY be the cause .. but I doubt it.

I'm more interested in the ability of the syn oil to place the soot only in the filter.
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Old 03-30-2013, 12:16 AM   #348
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Well, you've got a point there, Walt. Of course, the turbo not contributing at low rpm also will cause a drop in engine temp.

Thanks for being so willing to take this experiment on.
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Old 03-30-2013, 12:44 AM   #349
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It very well may not lower the temp but the engine will have better lubrication. If in fact the engine wants to run, say at 185, and the thermostat is full open, providing all the cooling it's capable of, but not enough to bring the temp to the desired 185, doesn't it stand to reason that better lubricating of the internal workings of the engine (Not the cylinder temps) reduces friction to the point that the full open thermostat can now reduce the overall temp?

If the thermostat is suppose to hold the coolant temp at a prescribed setting, why then, does the engine cool down at a reduced throttle setting. There's Less water being pumped through the heat exchangers, etc...Shouldn't the thermostat close to maintain the preset temperature point? I agree with Capthead that reducing friction in the engine will reduce the coolant temp by a few degrees. Just enough for the thermostat, when fully opened, to accomplish its task.

I'm rather tired of all this arm chair quarterbacking so I'm going to switch my oil to a synthetic and see what happens. The possibility of incurring damage to my engine is extremely remote.

How is what I am about to do any different than you, Eric, pretty much ignoring all the anchor data that's out there and testing the damn things yourself?

If the experiment is successful, there will be a lot of faces and only 3 ones. Conversely, if it doesn't lower the coolant temp the reverse will be the case. Either way, I think it's a small price to pay to expand our collective knowledge.
Walt

I agree with and appreciate your decision to pull off a true, full-replacement oil usage test and I pretty much agree with your last paragraph.

What I don't clearly see (agree with) is the why/how you figure on your statements about “full open” thermostat. Only reason the thermostat should ever reach fully open is because the engine coolant has reached or is surpassing the top limit of thermostat’s actuation #, i.e. its cooling capacity, in other words, the engine is for some reason already overheating as compared to the heat it is designed to put out. Thermostats are engineered to meet the cooling needs of specific engines, in accordance with the co-engineered cooling system’s capacity... thermostats are not supposed to ever need to fully open. They are designed to function in the engineered safe range of between closed and approx open to suffice for any of an engine’s heat produced due to loads applied, rpm reached... etc, etc. Now, I’m not saying that the syn oil might not bring your engine temp down slightly, maybe even more than that. But – it seems to me that if your engine is itself producing too high heat temp now while using good quality, clean dino oil, and, the thermostat is correct size, temp actuation #, and in very good condition... there is another problem than type of oil that needs to located and resolved.

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Old 03-30-2013, 12:48 AM   #350
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It will be very interesting to see if switching to synthetic makes any difference at all to the operating temperature of your engine. Synthetic offers some advantages in friction reducing perhaps, but I can't see it offering so much as to made that much of a difference.

A bit apples and oranges, I admit, but the manual for our new Ford pickup specifies three kinds of oil, all of the same multi-vis rating. Full synthetic, synthetic blend, or conventional oil. If the synthetic made that significant of a difference to the engine and its lubrication and operating temperatures, I very much doubt Ford would be so broad in their oil specifications.

But I agree, I doubt you'll hurt anything by switching to synthetic. I also doubt you'll accomplish anything, either, but that's an outcome that remains to be seen.

If I was really convinced my engine is running too hot, my first call would be to my friendly Cummins representative or mechanic. Perhaps your thermostat is not opening far enough. These things do crap out over time. Or perhaps you could be running a more effective coolant. Or perhaps you've got a hose starting to delaminate and collapse inside. Lots of reasons why the temp could be sneaking up on you.

While I don't have anywhere near the engine knowledge and experience of Tom or Eric or others on this thread, I just cannot believe that the lubrication differences between conventional oils and synthetics is so different as to actually cause an engine to run hotter or cooler. To my mind, it defies logic. Last longer, sure. Stay cleaner, sure. Stick to metal better, maybe. But be so different in lubrication ability that it shows up on the engine temp gauge? I just don't see it.
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Old 03-30-2013, 01:07 AM   #351
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Almost all of the heat produced by a Diesel engine comes from combustion, The frictional heat is minor.
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Old 03-30-2013, 01:32 AM   #352
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If I was really convinced my engine is running too hot, my first call would be to my friendly Cummins representative or mechanic. .
I've had Cummins come out and thoroughly go through those items and many more, several times! As I stated earlier, the thermostat has been changed, a new sender installed, coolant has been changed, new Impeller, exchangers pulled and cleaned and 2 gages hooked up so as to compare both readings. (one on the panel and one with alligator clips to the sender.) The boat was tested after each of these changes, all to no avail. I talked with Tony Athens at Boat diesel, their Cummins guru, and he suggested all the things we've tried so far. Even though the temp is within the Cummins specs, (203 max) Tony and my local Cummins rep both agree that my engine runs hotter than normal. dwhatty of this forum also has a 32 IG powered by the same make and model as my engine and his runs cooler as does another forum member in Florida who has a Nordic Tug with a Cummins 330B.

The only thing left to try is synthetic. (Capthead's experience) I have nothing to lose except a few bucks which will not kill me.

There's a lot of advice given on TF, possibly misguided and uninformed, which RickB used to point out. I think my experiment, no matter the result, will shed more light on the use of synthetics. Note: I don't expect to prove anything to those that run 40 year old Lehmans. They will have to do that themselves.

To quote Steve McQueen in the movie, Tom Horn, "you have my last word on the matter."
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Old 03-30-2013, 01:43 AM   #353
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Of course, another possibility is that's just the way your engine is. It's inside Cummins safe temperature range so maybe the temp you're seeing is simply the temp that engine's gonna run at come hell or high water. Every engine is a wee bit different from every other engine.

What are you going to do if the synthetic changes nothing?
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Old 03-30-2013, 07:12 AM   #354
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"but the engine will have better lubrication."

But will it matter a bit?

The only part of the engine that might be "better" lubed is the flat tappets running on the cam,the only place where the sheer ability of the oil is really used. Modern engines use roller tappets, no gain.

Synthetic is considered "better" because it allows less pressure to the system after a really cold start , and because it is easier to scrape down by the oil control rings .

The better fuel burn ( 1/2 to 1 1/2% ) using synthetic comes from this ability to be scraped.

Weather a 1% fuel decrease will pay for the 2x to 3x co$t of the oil will be determined by your daily or monthly operating hours.

IF the engine is not used for long periods , the loss of compression from the cylinders rusting , from the better drained oil , will lower the engine compression , probably more than negating a 1% fuel gain.
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Old 03-30-2013, 08:59 AM   #355
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Out of spec Diesel fuel will cause high coolant temps,When the cetane level drops below a certain value the fuel will not burn @ the proper time, Transferring the heat energy from driving the piston into the cooling system.
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Old 03-30-2013, 11:17 AM   #356
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I've had Cummins come out and thoroughly go through those items and many more, several times! As I stated earlier, the thermostat has been changed, a new sender installed, coolant has been changed, new Impeller, exchangers pulled and cleaned and 2 gages hooked up so as to compare both readings. (one on the panel and one with alligator clips to the sender.) The boat was tested after each of these changes, all to no avail. I talked with Tony Athens at Boat diesel, their Cummins guru, and he suggested all the things we've tried so far. Even though the temp is within the Cummins specs, (203 max) Tony and my local Cummins rep both agree that my engine runs hotter than normal. dwhatty of this forum also has a 32 IG powered by the same make and model as my engine and his runs cooler as does another forum member in Florida who has a Nordic Tug with a Cummins 330B.

The only thing left to try is synthetic. (Capthead's experience) I have nothing to lose except a few bucks which will not kill me.

There's a lot of advice given on TF, possibly misguided and uninformed, which RickB used to point out. I think my experiment, no matter the result, will shed more light on the use of synthetics. Note: I don't expect to prove anything to those that run 40 year old Lehmans. They will have to do that themselves.

To quote Steve McQueen in the movie, Tom Horn, "you have my last word on the matter."
Walt – my good ol’ TF buddy!

TY very much for the comprehensive explanation on what you have so far done to your engine in attempt to alleviate its out of the ordinary temperature rise you are experiencing. I have a clearer mental picture of your situation at hand. Now I better understand your dilemma which gives me a 1st hand platform to offer as a potential cause and effect.

I’d like to learn at what rpm the heat begins to increase over the norm, what temp it reaches at high and low cruise rpm, and at WOT; if it will even allow you to maintain WOT without chance of full-blown overheating. Also, does it ever overheat so much (i.e. too much) at even just a high cruise rpm... that it forces you to for a period of time decrease rpm in order for engine heat to dissipate?

Here’s what I experienced:

This happen in mid 1960’s to a brand new 185 hp Perkins diesel engine we (dad and I working alongside diesel engine installation professionals) put into our 37’ sport fisher, semi displacement, raised deck, FB, single screw, wood boat (what a beauty she was!). We were replacing its original and tired 155 hp Nordberg Knight, i.e. flat head, 6 cyl, 339.2 cu, 155 hp @ 3200 rpm, 4" bore 4.5" stroke, up-draught carburetor engine:

1. New Perkins perfectly installed
2. Sea tests during initial break-in period
3. Engine temp held within specs up to 1000 rpm
4. Temp unexpectedly raised on gauge at rpm above 1000 rpm
5. Cruise rpm temp was considerably higher than expected and higher than spec sheet... but, engine maintained its too high temp level at a low cruise without full-blown overheating
6. At high cruise rpm engine temp would slowly but surely creep upward and eventually get hot enough (after an hour or so) that we would need to reduce rpm and let engine heat dissipate
7. WOT – temp would very soon rise higher than acceptable and WOT could not safely be maintained for any reasonable period of time as temp continued its nonstop increase

Dad contacted Perkins and was told that was OK for a new engine and that it simply needed more run-time to be fully broken in. We ran that engine for several hundred hours in summer 1965. Engine too high temp condition prevailed. Relatively low cruising rpm could be held with higher than spec temps occurring but high cruise would raise temp too far and WOT was never plausible to run at due to chance of full blown overheat. That fall/winter dad went ballistic! He had area diesel expert mechanics sea-test and verify the temp circumstances and he then got into communications with Perkins HQ Executives demanding that they send qualified Perkins engineers to either repair or replace his engine. Dad was not a man anyone wanted to be reckoning with when he felt correct and lost his temper – man do I ever understand that! LOL

Long and short of this experience:

Spring 1966 Perkins HQ had two Perkins mechanical engineers arrive to our boat; Ed Waunakee’s boat yard, Hudson Canal, Freeport LI, NY. First they idled and tested engine in berth with all sorts of dials and gauges. They kept equipment on engine as we crept out the canal and got into some open water for sea-test. Dad did as they asked for putting the Perkins diesel through its paces. The engineers were in the engine compartment the whole time carefully checking everything. Engine temps did exactly for them what the temps had done to us. After about an hour of tests they removed their equipment and closed hatches while we idled down canal to our berth at Waunakee’s. Engineers admitted there was a temp problem but were not ready at that moment to provide a solution. Within short period of time Perkins contacted dad and told him there would be a new head arriving and they had a specialist in the area they would pay to install it. New head was installed. We never had a temperature problem with that Perkins diesel again... she could do any rpm and temp always stayed well within specs... Dad was happy – boy, me too!!

Turned out there was a hairline crack, or at least a malformation of some sort, in the head (I never did get a clear picture in my mind as to what the orig head’s problem actually was) that caused the too high temp problems. New head from Perkins’ OEM factory =Temperature Problem Solved!

I can only imagine the frustration you are experiencing and wish you best luck. Maybe my experience can be of assistance for solving your temp problem... I hope so. I’d say one thing for sure, there must be a reason for the high temp readings and it can be found... but at what $$$ / energy / frustration cost to you is the unknown.

Please, keep us all informed as to the progress you make! – Cheers!! - Art
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Old 03-30-2013, 11:27 AM   #357
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Walt since you've entered into this as a serious experiment I think the most objective results will be obtained by removing the thermostat. Check w Cummins to make sure running w/o the thermostat is totally safe. I don't see how the results could be considered stable enough to produce objective results w the thermostat in place.

Then adhere to the scientific method of 3. One experiment gets our attention. Two indicates that there's a strong possibility and they say you can take 3 to the bank. Of course 4 or 5 would make some folks feel better 3 is considered to be sufficient.

And then try to think of the many other variables that could take the experiment astray. If the sun has evaporated the dew on the foredeck but left it in the aft cockpit the boat will run at a higher angle of attack causing more load on the engine at the same rpm and thus cause the coolant to run hotter. I'm joking of course but there are likely unknown variables that will affect the outcome of the experiment. On your boat at the 8.5 knots you usually run full or light fuel and water could change the load enough to change the engine temp. That's the other extreme to the first example but you get the picture I'm sure.


Art re the hot Perkins ............ why didn't it loose coolant? Over all those running hours surely you would have had to add unusual amounts of coolant and included that in your account.
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Old 03-30-2013, 11:48 AM   #358
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Of course 4 or 5 would make some folks feel better 3 is considered to be sufficient.
LOL Do you really think I give a rat's ass as to what other people think?
This experiment is for my own edification and the rest of the world be damned!
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Old 03-30-2013, 11:50 AM   #359
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Maybe my experience can be of assistance for solving your temp problem... I hope so.
Interesting!

Thanks, Art.
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Old 03-30-2013, 12:00 PM   #360
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Of course, another possibility is that's just the way your engine is......That's very possible and I considered that a few years ago.

What are you going to do if the synthetic changes nothing?
Punt! What other alternatives are their? The engine is within spec, Cummins will have no obligation!
Why are so many people interested in what I'm doing? It's not as if I'm putting saw dust in the differential of an old Ford to sell it! The only thing at risk here is a few hundred dollars of which I can replace by panhandling on the corner for a few days.
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