Bore Glazing -Diesels

[carey]

Can anyone tell me how long I can run a 120 hp engine with no load without possible glazing of the bore?
Also what causes the bore to glaze?and what effect does this have on the running of the engine?
Thanks John

 

[Chris_Robb]

With a large engine like that, you must treat bore glazing seriously. Do not use the engine to charge the batteries even at a fast idle.

You must run under good load. So don't run at one third throttle for long periods.

As to how long it takes - don't try to find out!

Most boat engines fail through lack of use, and gentle handling.

 

[DepSol]

Soltron are running test on this and have found that with use bore glazing is reduced. nothing to back it up yet but initial results look good.

If I get any more info I will update you.

Dom

I am boating again ;-)

 

[Guest]

In practice though

Considering the environment and lack of care for most boat engines .... they last reasonably well compared to many other applications ... in an ideal world we would all try to stop glazing, no-load running etc., but life is generally not that accommodating !!!

 

[Chris_Robb]

Re: In practice though

I agree with your comment, although in the back of my mind, I know I cannot afford to replace my good old Perkins 4236 - so I look after it - I suppose I almost paranoid with preventative maintenance! I hate running it for 5 mintes from cold just to get out of the marina.

I do like to keep the beers cold though...........

 

[johnt]

Re: Vereee Interesting ........

HMMM ..I notice Vyv hasnt said anything ..yet ! dont blame her

 

[johnt]

Ohh small point .......how do you get an engine to run No-Load?....the gearbox, altenator, water pump, fuel pumps etc probably take about 10/15% of the power produced........

 

[pvb]

Errr.. Vyv is a \"him\"! (nm)

 

[summerwind]

I think I am right in saying that the glazing is caused by the incomplete burning of fuel. This is added to by the engine not getting sufficiently hot and therefore allowing a residue to build up in the piston grooves. This causes the piston rings to stick in the piston, thereby reducing the gas seal of the cylinder.

Whatever the cause, there is no doubt that it occurs with running the engine for periods when it is not under load. There is also no doubt that you should give your engine a very good, HARD work out on a fairly regular basis. This gets the designed operating heat right through the whole angine, loosens up and blows out carbon deposits and flushes plenty of hot oil, and importantly the detergents it contains, through the oilways.

The alternator etc will definitely not put enough load onto the engine to work it hard, especially one rated at 120hp! Unless you are powering the whole marina of course

 

[SteveA]

Re: Errr.. Vyv is a \"him\"! (nm)

10/15% load is no where near enough power to stop glazing - as an ex marine engineer I would endeavour to run any 4 stroke Diesel engine at no less than 65% load - large slow speed 2 strokes engines do not suffer from this problem and can be run for extended periods at low power.

 

[johnt]

Re: Errr.. Vyv is a \"him\"! (nm)

ooops..........sorree .........

 

[Guest]

My understanding is that bore glazing is caused by using excessively slippery modern oils being used in engines not used to them or designed for them. Modern synthetic oils are full of polymers and other components designed to enhance lubrication in modern high stressed max. power to weight ratio turbo diesels. Many boat engines were not designed for these oils and need something rougher, to keep the rings bedded. I may be a little bit out of date on this but oils are rated as API ??, the question marks being in place of the actual rating letters. The rating is often in very small letters on the can but basically API CC is good old agricultural stuff (e.g. Castrol Rotella, ideal for Perkins 6.354, most Listers, most naturally aspirated DAF's, Gardners etc). API CD or CE is a little more slippery (and API CE glazed my DAF in no time), and API CF or beyond is for boy racer engines. Check with your engine manufacturer (and don't take my word as gospel), but don't think that spending a fortune on Castrol Magnatec or the likes is necessarily going to be good for your BMC Captain or whatever.

Low load running is never good for a diesel, and generator sets can be the worst due to the inherently varying load. A good thrash occasionally can work wonders. There are additives that you can use to minimise or allegedly eliminate bore glazing but I have never felt that they work well enough. Best course is a glaze busting wheel (basically an abrasive flap wheel on an electric drill) down the bores and give them a bit of a hone. Best to draw the pistons first, but a layer of grease at bottom dead centre on each pot in turn usually catches the abrasive particles and I have engines that have run for years after a lazy glaze bust such as that with no problems at all.

 

[Guest]

would be interested in your comments on the probs that I currently have.
engine is a 20hp rawwater cooled yanmar driving a 4.5 tonne cat (arguably under engined) it is 300 hrs / 2 years old and has suddenly developed an alarming oil consumption at 1 litre per 20 hrs run. oil is partly being burnt but mainly coming out in cooling water.
engine never used for charging alone - quite honestly has been fairly hard worked on long journeys.
removal of head shows no problems with head or valve gear, but some bore glazing. efforts with a hone (pistons in situ) have not cured the problem so it looks like a piston out job over the winter.
oil used is castrol 15/40 diesel engine oil from supermarket, just as with its predecessor which lasted 15 years.

 

[chippie]

It sounds like stuck or worn oil rings. Unfortunately you are right in that the pistons will have to come out to check.

 

[Guest]

But it keeps going !!! reagrdless what I don\'t do

I run an old 4-99 Perkins, glow-plugs just bunged up and I'm back to Easy-start ... makes her smoke a bit on start-up, takes a few minutes to clear, engineer told me she's low on compression - normal at this age, mostly run at 1/3 throttle as she is too big for the boat - so literally never loaded enough !, needs a top-up of oil every now and again, has drip on one injector every 10 secs or so, heat exchanger has been patched up and should be replaced, .........

But the thing keeps going, plods away day after day, has never failed me - except when I forget to put the stop button back in !!!!!, pushes my boat along at a fair old lick - in fact will outpace virtually all other sailboats I sail with ....

Actually I think this year I will change the oil and filter !! Give her a birthday !!!!!

 

[Chris_Robb]

Re: good old perkins!

Hopefully mine will last as long! Yes uses load of oil, drips from main crank bearing, - benefit is that she will have a running oil change all season!. spill used to go into the ocean, but now I collect it and dispose of.

Only time I could not start it was the same reason- doh!

 

[Guest]

Re: good old perkins!

Have to laugh ..... one time in marina - NOT mine I must add !!! I was visiting !

A Charter boat 3 pegs up from me ... young lasses / crew etc. sitting in cockpit having breakfast - I'm waiting to start up and leave to go home ! So they finish breakfast, pass plates etc. back down the hatch .... I take my cue and press the start button.

I called across to the young lass who has by now been subjected to a lifetimes equavalent of Woodbines !! "I waited for you to finish breakfast .......!!!"

 

[Chris_Robb]

old smokey

We had a charter boat some years back in Greece, - when starting we would have to warn all the nearby boats as the first 30 seconds of running gave out a dense smelly blanket of oil smoke! - Allways started at first press of the button though!

 

[Guest]

Re: old smokey

If I could stop it I would ..... but no-one's given me any advice how to !!

Still all I have to do at moment is stay 'down-below' when I start-up and not 'poke me 'ed' out of hatch for others to see !!!

 

[Chris_Robb]

Re: old smokey

Stick a potatoe up the exhaust - when the boat opposite is hit by a low flying potato...............................