Bad noises following rebuild

[pandos]

I have just partially rebuilt my MD21B. It was reluctant to start and I suspected timing was out

I took it apart and redid the timing and it was possibly a tooth out. All marks now line up perfectly, including the timing mark in the pump (including the internal one )

It started pretty easily then but was very noisey...as it was late I left it...

It was turned over by hand and it seemed fine with very high compression...

Plenty of oil and it was well oiled when being assembled.

Any suggestions on what I might try to establish if the thing is crocked ...

In the absence of a better suggestion I propose to run it for half an hour to see if it explodes or improves...

I think I can retard or advance the pump timing by adjusting the fixings on the pump so I might try this...

I could take out the heater plugs and do a compression test...and take out the injectors and listen for piston slap...

Anybody got a cheap md21b for sale ??

 

[Boater Sam]

Did you have oil pressure? Did you fill the oil filter before fitting it?
Which part did you rebuild?
Where is the noise coming from?
If it starts easily and is not chucking out white or black smoke the timing must be close to being correct.

 

[Slowboat35]

With timing a tooth out it'll likely not start at all, if it does it'll do so reluctantly and with a lot of commotion and smoke and run like a dog on three legs. It'll sound awful. You'd need a heart of stone to let it endure that!

 

[pandos]

With timing a tooth out it'll likely not start at all, if it does it'll do so reluctantly and with a lot of commotion and smoke and run like a dog on three legs. It'll sound awful. You'd need a heart of stone to let it endure that!

Precise description of how it ran on first attempt following the work....

I have since striped it and re-did the timing and it still sounds awful but starts easily and runs...

The work done consisted new rings, bearings, oil seals head gasket incl skim, reseated valves cleaned manifolds, elbow heat exchangers etc. etc...

There is oil pressure afaik...certainly it seems to be circulating and the filter is filled and the light goes out.

I have just been looking at a video of its first run and there is a puff of smoke out of the forward end of the exhaust manifold so perhaps that needs to be snugged up tighter so maybe a simple issue...

 

[pandos]

Finally got around to looking at the engine again today.

thete is exhaust getting into the intake ..wet sooty stuff...

i am guessing stuck valve...

only question is whether it is stuck because of a slap from a piston or just stuck due to some crap in the tappet or push rod department..

I'll have a look again tomorrow and would welcome any suggestions, but it Looks like head off again?.

 

[Slowboat35]

I can't offer help on injection timing - above my paygrade.

How did it get reluctant to start? Progressively? Suddenly?

My first reaction on encountering a reluctant diesel is to get the injectors overhauled/serviced. These are probably the most critical part of a diesel engine and also the most overlooked. Few people ever bother to touch them and they do reteriorate over time. Are your injectors 100A1? If not certain best take them to the injection shop for a look-over. It's the first easy fix.

You have compression. It isn't that. Poor compression on only one cylinder will show a marked and uneven reluctance to start.

Noisy in what way, mechanical (rattle/banging) or just loud? (Air filters and exhaust as you're used to? Is this on the bench or on board?)

Nonetheless your fix to get the "timing marks line up perfectly" and subsequent ready start and run suggests you're well on the way.

How is it not "running right"? What is the matter? Vibration? Odd noise? Uneven running?
If you've disturbed the injection pump timing you probably need a workshop manual or an expert to ensure it is correct.

Assuming you are comfortable the above is all in order it is probably right to suspect (a) sticky valve/s as the problem - sooty reflux in the inlet manifold - valves possibly suspect.
As it now starts and runs readily there isn't anything fundamentally wrong with the engine's configuration (ie cam timing is correctly set) Rough running now is probably summat else.
A sticky valve is usually caused by a bent or rusted-up valve stem. (which you surely won't have failed to notice in the rebuild...) or a rocker corroded onto its shaft but again post rebuild - you could hardly have missed that either. (valve bent by piston strike will leave unmistakable witness marks on the piston crown and is only possible with a cam belt failure. You have pushrods so not an OHC engine so most unlikely it's that).
(nonetheless all this makes me think sticky valve isn't likely to be the problem, if you're capable of rebuilding an engine to this extent surely you'd have noticed?)
No such thing as crap in pushrod affecting valve action.
Fortunately a sticky valve should be easy enough to diagnose.

Anyhoo;

1) To eliminate rocker binding rotate crank until exhaust valve is closed and loosen tappet adjuster. Exercise the rocker by hand. Any binding will be immediately felt. Repeat with other exhaust valves. They should move totally without effort or resistance. If any are stiff to move this is likely your problem; find out why.

2) That done, next step is to eliminate sticky valve.
Remove rocker shafts from head. Turn crank so no piston is near TDC. Take a light hammer and brass/ hardwood drift and just strike the valve-stem head hard enough to bounce the valve off its seat. Rhythmically repeated gentle, light taps getting increasingly firmer is the way to go - until you find the force required to move - bounce the valve 5mm or so (about it's normal travel) You'll immediately notice the difference in sound and action of a sticky valve.

3) If a sticky valve is found it's (sorry) head off, valve out and troubleshoot from there, bearing in mind that the valve guide may have been damaged too - but if you've caught this quickly you may get away with that.

But having written all this it occurs to me that another likely cause is a mistakenly set tappet clearance. If you've got one out of sequence because you've set it on the wrong part of the cycle you'd get similar symptoms.
We're all human!



Best of luck!

 

[pandos]

Thanks for that long response.

It occurred to me on the drive home that it could be swarf from the skimming of the head holding the valve open. (I saw this happen before)

I checked the tappets when the timing was out.

(As the valves are timed and adjusted separate to the crank shaft I do not see how the tappets could be at fault now... If I am incorrect in this maybe someone could explain...)

all of the valves at that time were pretty much bang on and I suspect therefore that all were opening and closing properly...

I am going to have a go at seeing if I can get the valve to close by applying wd40 into the intake (Incase a bit of crud is holding the valve open... and tapping with the hammer etc.

I do not see it as impossible that something could be in a tappet and therefore holding a push rod up and a valve open.

I don't think it is injectors and the pump timing is set perfectly according to the manual, and the ease with which it starts seems to confirm this.

Head off, which I can do in place is not such a big deal...compared with full rebuild...

 

[black mercury]

Take the rocker cover off and double check your valve clearances, also check for a broken valve spring. While cover is off, rotate the engine by hand and watch the valves opening and closing to confirm all is in order. An exhaust valve not opening will cause the exhaust gasses to expell out the inlet when the inlet valve opens. The engine would continue to run but make a racket. Check all your pushrods are in place.

 

[ghostlymoron]

Not likely to be injector problem as they tend to deteriorate gradually.

 

[pandos]

Mystery is solved...a piece of something suspiciously like a piece of steel swarf or a broken drill bit was in the cylinder. Clearly it was in the head after it had come back from being skimmed...(it was not in the newly honed, just fitted with new rings cylinder when the head went on...)

So now I need new piston,,, head,,,...take engine out etc etc...

Anyone know a good source...

 

[Mr Cassandra]

Mystery is solved...a piece of something suspiciously like a piece of steel swarf or a broken drill bit was in the cylinder. Clearly it was in the head after it had come back from being skimmed...(it was not in the newly honed, just fitted with new rings cylinder when the head went on...)

So now I need new piston,,, head,,,...take engine out etc etc...

Anyone know a good source...

What a pain is it possible to identify the piece of stell and go back to the outfit that machined the head.

 

[Boater Sam]

How bad are the dents? Is the rod still straight? I have cleaned up pistons and heads when this has happened and the still work fine providing the rings are not trapped in the grooves.

 

[pandos]

I think these are beyond repair,

I expect a poor attitude from the guys that did the work.

These are Peugeot engines...

I have found an original new old stock head on a french suppliers site but they are difficult to deal with in terms of information and their description and photo are contradictory...

Not sure if the combustion chambers and valve guides are included.

 

[pandos]

How bad are the dents? Is the rod still straight? I have cleaned up pistons and heads when this has happened and the still work fine providing the rings are not trapped in the grooves.

you might be right....

I had a calmer look at the head again today and the valve seats are probably ok, once the soot was removed the surface is rough but could probably be smoothed out with some wet and dry, there is a margin of about 10mm at the edge where there is no damage.

The valve is not bent but there is something amiss with the sleeve it passes through, in that it is almost impossible to push the valve stem into place. Ill bring my lapping tools and spring compressor with me on Monday and maybe if I can get the valves to seal I will take a chance on it... I suspect limited and easy motoring for no more than 30 hrs will not do too much harm and will give me a few weeks sailing between now and October.

Any suggestions for an easy way to smooth out the face of the piston and head ?

.

 

[Boater Sam]

If the valve stem is tight in the valve guide, the valve is bent. Careful tapping it side ways may straighten it. Take it out and roll the stem on the edge of a table and see if the head oscillates.

I would planish the dents with a light hammer rather than remove metal. They are insignificant in a diesel engine unlike a petrol engine where preignition can occur.

Can we have photos?

 

[pandos]

If the valve stem is tight in the valve guide, the valve is bent. Careful tapping it side ways may straighten it. Take it out and roll the stem on the edge of a table and see if the head oscillates.

I would planish the dents with a light hammer rather than remove metal. They are insignificant in a diesel engine unlike a petrol engine where preignition can occur.

Can we have photos?

the valve fits fine in other positions and other valves also stick in the damaged sleeve so I think it is the sleeve rather than the valve.

I had to look up planish.... yes I have a small nifty hammer so that would be a good bet...

I was not sure what the problem with roughness was, whilst I could recall that there was a problem with hot spots...thanks for the reminder about preignition,

I have tried to post photos and failed I will try again when my phone is charged...

 

[pandos]

 

[vas]

all this battering on the cylhead surface done from this small piece of metal?
was the head planed as part of the rebuilt process or just cleaned?
not an expert but that looks like a minefield not a combustion chamber...
would be good to have a pic on the other cylhead to compare

 

[Boater Sam]

To me that is minor dimpling, I have seen much worse. Planish out the worst, removing metal will drop the compression ratio. Just put it together and run it, it will be fine.

I had an engine that ate a self tapping screw, it was much worse than yours. The screw was embedded finally in the piston crown, about 3mm deep. After a bit of fettling it is still running fine, preignition doesn't happen with diesels.

 

[anoccasionalyachtsman]

What a pain is it possible to identify the piece of stell and go back to the outfit that machined the head.

As @pandos has learned, it's incumbent on the rebuilder to give the head a good clean when it comes back from work - not least to wash out any abrasives that fell off when the seats are ground.