How long can you run a diesel engine without a load

I think it's a load of smoke and mirrors. How much empirical evidence is there? Has anyone run two identical engines through predetermined regimes with measurements before and after to determine what if any differences there are in bore glazing and wear rates.

Or is it just guestimates?

I'd be interested to see experimental conclusions.
 
Bit like the additives thing.

A few people I respect have told me that it used to be the case, but that with modern engines it makes no difference.

What would have made a difference to me would have been starting my engine this afternoon without checking the coolant level...... near miss!
 
If I spend too much time in slow moving traffic I must take my BMW and thrash it to within a gnats-wotsit of the red-line, overtaking everything in sight and definitely NOT use the indicators.

It says so in the manual.

(OK, it says give it a good workout at higher revs to clear accumulated carbon deposits).

Engines are best warmed up quickly under modest load, as most damage occurs on cold starts.

Best to either lay up thoroughly and leave well alone, or, once-a-month start her up, run at moderate rpm in reverse against the warps.

This will ensure faster warm-up, and also help it reach a higher temperature, as marine diesels are way over-cooled.

This was proved to me when a load of living creatures occupied my water strainer. I had just done a head job and was seeing how much better she ran. After 30 mins or so at low power with no problems, after about a minute at full power the temp. alarm came on. Running at low revs again allowed it to cool and run without the alarm.

So you need some revs and load to get it warm. I would suggest a minimum 20 minutes, maybe 30 mins if raw water cooled. Raw water engines tend to run at around 50-60 deg max to prevent scaling deposits. This is about as hot as the hand can stand, so if the casting is that hot, you know you are there.

Run it too slow for too long and the head will start to get choked with soot.

I think using too good a grade of oil in an older engine is probably a better way to glaze the bores than excess idling.
 
Re: The Oil Additive page ...

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Bore glazing is not a myth, it does happen, generally on diesels that never have to work hard. So going easy on the throttle to 'save the engine' is again not a good thing.



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Bore glazing is certainly not a myth. The Gardner in my fishing vessel is over 60 years old. A few years ago we were traveling about 3 hours each way to the fishing grounds at normal cruising revs of about 1000. When there we had the main engine idle for a couple of hours while we drop lined. After a few weeks we started to leave quite a smoke trail from the exhaust on the way home, from reports it was about half a mile long. Oil consumption increased dramatically. I added a product to the fuel that is made in Queensland. With in two days the smoke stopped and the oil consumption dropped to a couple of litres a week.

I mentioned this to my mate who ran an industrial supplies shop. He tried it in his little cruiser with an Italian diesel. After that he started to stock the product himself.
Its not like a normal diesel additive, you only add it when needed.
 
[ QUOTE ]
I think using too good a grade of oil in an older engine is probably a better way to glaze the bores than excess idling.

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I agree. Getting harder to find a single grade oil thats suitable. I have to shop at oil depots that cater for industrial/truck companies.
 
10,000 hours at least at a rough guess. Personally I don't hold with the rumours that running a diesel off load will kill the engine.
Cliff, You have another convert.

Running the engine for a short period will not in anyway damage it! However running the engine cool definitely will. All diesels, modern or old need to be fully heated to achieve there maximum performance.

Although leaving the engine ticking over will eventually get the water upto temperature it will not full heat combustion chambers, valves and the oil. We have to remember that these engines are compression ignition so they need to be fully heated to burn the diesel fully, that’s why many smoke when cold. If they are constantly run cool they will form carbon on exhaust valves and chambers. Which is where the rumour of running it flat out does it good. Absolute Bowllocks!

Me, I have an old Ford and does that smoke! you bet it does, until fully heated and that is about 1hr under load!

In short, you won’t "glaze" the bores unless you run it at tick over from now until Easter!

Tom
All, of corse, in My humble opinion!
 
Cliff
just for once, dont let it go to yur head mind! I agree, had this post years ago, got quite heated, modern diesels and oils not a problem.
Stu
 
Re: The Oil Additive page ...

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I added a product to the fuel that is made in Queensland. With in two days the smoke stopped and the oil consumption dropped to a couple of litres a week.


[/ QUOTE ] So your rings were gummed up then. No addditive is going to deglaze bores. You need to hone the bores to do that.

Someone else mentioned running temperature. Perhaps the wrong, or worse still, no thermostat may be the culprit there.
 
[ QUOTE ]
Cliff
just for once, dont let it go to yur head mind! I agree, had this post years ago, got quite heated, modern diesels and oils not a problem.
Stu

[/ QUOTE ]Gee - Thanks....... /forums/images/graemlins/wink.gif
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hammer.thumb.gif
"Artificial intelligence is no match for natural stupidity"
sailroom <span style="color:red">The place to auction your previously loved boatie bits</span>
 
Re: The Oil Additive page ...

Right. That's my winter regime sorted. Every second or third Saturday up to the boat with the chaps, turn on the engine, run down to Hampton as fast as the river will allow. Moor up and visit the "all you can stuff in for a tenner" curry place. Return to berth, working the engine harder agaisnt the stream. There will be a sunstantial amount of curry being carried on the return journey which willensure that the engine does some work for its living.

Result:-)
 
Curry ....

Just had 2 days on a ship with Indian Cook ....... Master gave instructions to him - What he wants ...

Boy !! Biriani ... Dahl ...... Veg Curry sauce ...... Chicken Tikka ..... etc. !!!!! Yep - I indulged in pukka stuff !!!
 
Re: Curry ....

I had a thought about this the other night. Someone told me that bore glazing occurs when the engine is run with no load on it because under such conditions it runs very weak and the combustion chamber temperatures are very high - which burns the oil on the bores to a "glaze".

Now this sounded vaguely plausible until I realised that he might have been talking about petrol engines. My understanding is that a (simple) diesel engine - as found on many small boats, can't run "rich" or "weak" because it has no throttle plate. The amount of fuel it gets is governed only by the position of the throttle lever. The amount of air it gets is governed only by the speed. I agree that if the engine was over-propped and labouring such that the throttle was wide open but the revs couldn't reach maximum, it would run RICH because it would be getting more fuel than the corresponding amount of air but I can't see any situation that would make it run "weak".

Any thoughts anyone?
 
Boat vs truck / car ....

I still have trouble reconciling the fact that a boat does a lot less work than a car / truck engine ... and literally lasts only a fraction of the time.
I've asked engineers about it and never really get a satisfactory answer ... most shrug shoulders ...
When I've asked about on / off load running .... usual answer I get is as long as it doesn't get run for long periods frequently off load ... why worry...... with odd comments like - boat engines often don't work that hard anyway .... which brings us back to sq.1

My Perkins 4-107 in SA is well over 30yrs old ... it gace us a scare other day when we think she had a water hammer occur. Possibly condensation back through the system ? Anyway thats cleared and engine still runs sweet as a sewing machine .. it has stood for months through winters / summers with no lay-up care etc. It gets a good thrash when in clear water to clear gunge ... but majority of time is at fast idle speed when motoring etc.

Is it that the problem is more acute or apparent when engine is marginal or just over what is required for the boat ? I can see that if you have a marginal size engine .. you don't want to lose power at any time ... but many boats nowadays are powered much better than not so long ago ... and the engines lighter / more reliable.
 
Re: Boat vs truck / car ....

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I still have trouble reconciling the fact that a boat does a lot less work than a car / truck engine ... and literally lasts only a fraction of the time.


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Leisure boat engines dont wear out, they are usually killed by corrosion as they sit around waiting to be used.

Workboat engines, running up as many hours in a week or so as the average raggie engine in a year go on for a long and fruitful life and can run longer than their road counterparts as long as they receive regular servicing.
 
Thats how I imagined the problem ...

We all know of the workboats running around ... old Listers, Volvo's, various ancient antiques .... but still doing their jobs day in day out ...

Look at the Perkins in my boat .... taken out of a Rustler 30 some years ago ... cause it was lazy starter (suspect gummed rings) and had a touch of smoke. Owner swapped for new Beta ... Perkins went into shed for 2 - 3 yrs ...

My engine was seized after launching boat half full of water ... I was a few 000' kms away at time .... so we swapped em over ... That engine from the shed runs well ... touch smoky at start up ... yes still lazy to start ... but in all honesty - not worth the issue of stripping down etc. She plugs on and on and on .... couple of engineer's have looked at it after arrival here with view to overhaul. Both said why ? She's steady, sounds nice ... good engine ... don't fix what aint broke.
 
Phil
I agree.

I would never knowingly run a marine diesel "off load" for extended periods - just because - but what's an extended period?

We had a couple of club members actually take the key out of a club boat ignition without stopping the engine - don't even ask /forums/images/graemlins/tongue.gif

Result was engine (Volvo 4 cyl) ticked over from 16.00hrs Sunday until 08.00hrs Monday with the ignition off.

No glazed bores & the alternator still worked, bit of blue smoke coming from the exhaust but a quick thrash for 30 minutes sorted that out.

With the way most yotties use their diesels to charge batteries, motor off/on to moorings etc, if all this glazing and hobgoblin chemical stuff was true we'd be up to our oxters in dud & dying engines.

I'm not saying that starting an engine and running it for say 10 minutes then stopping it is good for it - if you keep doing it - but providing you give it the odd thrash every now and then it should be OK.

Don't forget that diesel burns at about 1250degs C- petrol is 650C. So all those parts that are in contact with the burnt fuel tend to heat up quite quickly, valves, pistons, rings and bores. Although the engine temp gauge might be reading 85C that doesn't mean the internal engine temp is running at that - in fact I can guarantee it's far hotter than 85C.

BTW many years ago I did some work for Ford Motors research at Laindon and at that time they were having a lot of problems with their V6 petrol engines failing - back pot would explode for no apparent reason. So they got an engine and rigged it up with loads temp sensors and then ran it - temp gauge said 88C steady, back pot sensor said 183C.
If an engine (standard 2 cyl, 20 Hp) is running at 85C constant with 2+ gallons of cold water being pumped round it can you imagine the actual temperture alongside the head & liners?

Peter.
 
'He told the farmer to work the tractor, but he left it idling for some time to 'run her in''

A lifetime ago I worked in Ford's tractor factory where the dyno testers did exactly this (among other modes of running) for hours before the engines were fitted to the tractors. Mr Ford apparently was not convinced by all the BS abt running under no load.
 
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