Technical valve broken

[zag07]

Hi All,

On my Hymer MotorHome engine (Sofim 8140 43 S/ Fiat 2.8JTD 2001/ 105 000kms) I get one valve broken , cam belt is ok , engine is dead & I'll do complete standard exchange engine turbo included .

I don't explain what happen ??? Valve seat seems melted .

Any htoughts ??

Thanks for your comments.

 

[varesecrazy]

Sorry to see this damage..

Looking how 'shiny' looking this #1 cylinder is

My guess is weak mixture..( not enough diesel injected..) hot spots

Make sure you dont just refit your current injectors

 

[portland_bill]

Firstly, somoething has been rattling around in there, but of course that is the head of the valve after failure, so not representative of the cause.

The valve seats look dirty. My guess is that the valve clearances are adjustable, and have not been adjusted, or checked at the required service. An valve not sealing properly will create a hot spot where the combustion leaks past, which gives you the melted appearance. The heat also causes, eventually, the head of the valve to fall off, more likely if the valve is sodium cooled, which is quite likely. Inside the head of the valve is sodium, which helps the heat transfer to the head, keeping the valve cooler, but does create a weak spot if problems occur.

How many miles?
Are the valve clearances adjustable?

IMPORTANT
When the replacement engine is fitted, it is very important to clean the inlet manifold thoroughly. With some oil residue in the manifold, it becomes sticky. With a failure like this, some debris will have been ejected into the manifold, and got caught. If not cleaned, soon after first start, it will be drawn back into the engine, to rattle around and cause damage. Best case is a nasty rattle for a few seconds, worst is another wrecked engine. Make sure it is clean.

 

[oigle]

Sorry to see this damage..

Looking how 'shiny' looking this #1 cylinder is

My guess is weak mixture..( not enough diesel injected..) hot spots

Make sure you dont just refit your current injectors

If that is a diesel, which I assume by specs., then that is not correct mate. One cannot run a diesel "lean". They are always oversupplied with air/oxygen, not like a petrol engine. The less fuel injected in a diesel, the COOLER it runs.

Ian.

 

[zag07]

How many miles?
Are the valve clearances adjustable?

Engine is 20 years old & have 65 K miles . Yes clearances are adjustable by shims.

I think that these valve have recessed on his seat then get no gap then get combustion leak . It explain perhaps why valve seat is partly melted .

2 or 3 days before it happen I have had small metalic noise when I start the engine which goes out when rpm increase ??

(It happen in August when I was in Norway at polar circle .......)

I use a lot engine brake on low gear when down hill on mountains roads & have a tune chip fitted.

Now my MH is at the garage waiting for a reconditonned engine (echange standard in french) , all will be new except the engine & cylinder head block(frame) wich come from an old engine.

And it cost a lot .... First with repatriation from Norway , second with engine change but stay under the price of the MH . Repairs in France are half price than in Norway

 

[Ocwobio]

If that is a diesel, which I assume by specs., then that is not correct mate. One cannot run a diesel "lean". They are always oversupplied with air/oxygen, not like a petrol engine. The less fuel injected in a diesel, the COOLER it runs.

Ian.

If I've got this right, no fuel injected will increase the cylinder temp. Reason I say this, is because at work, we have large, 4k HP diesels which have a programmed routine to help burn off carbon deposits, whereby one cylinders fuel supply shuts off while the others increase no load rpm, allowing non firing cylinder to increase temps within. This removes some of the deposits from the combustion areas. That's what I was told, anyway. The engine are GM 4 strokes, the proprietary name for the procedure is called 'Skipfire'. If the tuning box is fairly recent addition, I'd remove it. They aren't ideal as they overfuel in all conditions, unlike a correctly applied remap, which yours is not able to have, possibly? The later 2.8 JTD's can, but I don't know about the '01 models.

 

[oigle]

If I've got this right, no fuel injected will increase the cylinder temp. Reason I say this, is because at work, we have large, 4k HP diesels which have a programmed routine to help burn off carbon deposits, whereby one cylinders fuel supply shuts off while the others increase no load rpm, allowing non firing cylinder to increase temps within. This removes some of the deposits from the combustion areas. That's what I was told, anyway. The engine are GM 4 strokes, the proprietary name for the procedure is called 'Skipfire'. If the tuning box is fairly recent addition, I'd remove it. They aren't ideal as they overfuel in all conditions, unlike a correctly applied remap, which yours is not able to have, possibly? The later 2.8 JTD's can, but I don't know about the '01 models.

As I said before, with diesels, no fuel = no heat. Less fuel = less heat. Many engines have failed from excessive fuel combined with excessive boost. Piston failure from excess heat.
Ian.