Replace #1 piston on 617 with engine in car? - Page 2 - PeachParts Mercedes-Benz Forum

barry123400 · #16 06-28-2010, 04:45 PM

Running too long with the same fuel filters or anything else that may contribute to low fuel supply pressure in the injection pump base. May contribute to excess wear in the number one cylinder. When the pressure is low the number one cylinder works harder than the others I believe.

This takes a long time to occur but it is almost certain it will with time. Of course I am not positive. Yet over time a lot of evidence is building..Too much to ignore totally now in fact.

On the 616 four cylinder it is even more important to have decent pressure. I almost will state that driving a 240d long term and not knowing the fuel supply pressure is really taking a risk. Lesser with the five cylinder but still there. Both engines will inform you of the abuse with their number one rod bearing failure and cylinder wear.

Your compression readings to me indicate that as the most probable cause. A ten dollar fluid dampened 30 pound pressure gauge from a place like harbour freight tells the story. The number one cylinder could also run a little hotter with cooling design issues. I do not disagree with this but suspect there is more to the story.

With your posted compression readings I might tend to leave the engine together and get the fuel supply pressure where it should be to reduce the load that cylinder is suffering.. It probably has seen low fuel supply pressure for a long time. The engine will not only thank you for it. It will run better as well.

leathermang · #17 06-28-2010, 05:56 PM

Why would the number one cylinder work harder due to ( anything ) ?

barry123400 · #18 06-28-2010, 10:29 PM

This goes a long time back to a member once asking me why it was always or almost always seemed the number one rod bearing failed on 616s. At the time I was aware of the slightly greater cylinder clearance and had also heard it might be the oil passage length through the crank shaft was the accepted probable cause.

I just decided to keep an open mind and keep my eyes open. As I really did not have a clue at that time other than the accepted logic was perhaps flawed.

The common beliefs at least where easy to discredit as the oiling passage was shorter than the 617 so the 617 should have destroyed the number one bearings at a faster pace. Actually the second rod bearing should have failed with the same frequency and the number one even more so on the 617.

The difference in normal power loading with the 617 usually having a turbo was only equilised at best with the oil jets. The rod bearing was treated the same except for higher loading. Yet it was not dropping out as often.

What also saves the 617 in my opinion to some degree is the more frequent powerstrokes. They do not fail with the same frequency although there are far more of them on the road than 616s. The 617 still can fail though as everyone is aware.

Yet again the same applied logic was used with the 617. If it was thermal since both blocks were very simular there should be equal failure rates.

When the time came that we got involved with the relief valve spring pressure and milli volt thing certain things seemed to indicate that at low base injection fuel supply pressure. The number one cylinder might be somewhat more advanced or getting greater fuel than the other cylinders or a combination of both. .I decided it was probably a combination of both. So it would obviouisly be working much harder in proportion than the other cylinders.

Once the fuel pressure came into line the engine sounded smoother was another clue. Plus exhibited greater power. There had to be an imbalance at lower pressures to enable that senario.

Plus some reported milli volt readings led me to a simular conclusion that it was a good but hard to conclusivly prove possibility. As time has moved forward nothing has arrisen to change my mind yet. Instead evidence has just increased the unproven possibility over the last year or so. There were many reports that also indicated it was the possible answer.

The frequent reports of changing out semi obstructed fuel filters for example increasing overall fuel milage. A balanced engine uses less fuel. There just where too many incidental things that indicated this was at least a good valid possibility.

That is why I try to stress like a broken record to make sure you have decent operational fuel pressure in the base of the injection pump.

After this ideal was developed I started to track a lot of reports of more wear in the number one cylinder bore like this poster has. This would be typical of an engine that has spent many years. Still at present or in the past being operated with low fuel supply pressure.

I can not really prove it totally to my satisfaction. On the otherhand if it is correct and I suspect it is. Why risk it as the other proven facts of having good base injection pump pressure are proven and obvious by now.

As for the coolant being a little warmer in the area of the number one cylinder that should reduce wear if the coolant does not boil.

I have to wonder if mercedes has figured the cause out even yet as I still see the attempts to improve the head gaskets mentioned. Maybe if they read our site.

I estimate it would take less than a day to absolutly prove the concept in a well equiped engine lab. Identification of the cause with an engine with good base injection pump feed pressure is almost an impossibility. I suspect that is what they have done over the years.

If anyone can come up with a better ideal please do so. I spent a considerable amount of time time thinking about this issue before going out on a limb originally.

layback40 · #19 06-29-2010, 12:28 AM

leathermang,
I dont doubt that it is possible to remove the liner with the motor in the car. If you check the standard bore of the liners that are supplied, you will find that they are substantially smaller in the bore than the piston diameter, they need to be bored to suit once the liner is in place in the block. Probably a portable boring tool exists that could do the job. Why muck around doing a Micky Mouse job when you can simply remove the block and do it properly?

t walgamuth · #20 06-29-2010, 06:38 AM

Quote:

Originally Posted by layback40

leathermang,
I dont doubt that it is possible to remove the liner with the motor in the car. If you check the standard bore of the liners that are supplied, you will find that they are substantially smaller in the bore than the piston diameter, they need to be bored to suit once the liner is in place in the block. Probably a portable boring tool exists that could do the job. Why muck around doing a Micky Mouse job when you can simply remove the block and do it properly?

I agree. If the bore could not be reused with the existing liner it would be time to pull the motor in my book.

If I were stranded in the middle of a desert and needed to fix it to live and somehow had along all the parts and tools needed to do the repair and food to survive for a month while I filed the top of the liner flush and bored the sleeve by hand then maybe I would attempt to do all that myself.....

leathermang · #21 06-29-2010, 08:00 AM

I suspect several of you do not have MB FSM's or have not read them.
The instructions are very specific. AND low tech. There are hydraulic pullers for this sort of thing BUT the FSM shows manual slide hammer removal. Place a cardboard plug at the bottom of the bore, drop a sack of dry ice into the old bore for a short period, remove , begin extraction.

The usual distinction between boring ..which requires much more substantial tool strength and control.... and HONING... which is just increasing the diameter of an already concentric and properly oriented bore.... looks like it is being mashed together in your analysis of the needs and potential cures for this engine.
.
If you place a new sleeve into the bore then it only has to be honed to take it out to the size to fit that particular piston. This can be done with simple and relatively cheap tools which fit into a 1/2 inch electric drill. Patience is required. Multiple checks of the progress is required. But even a lot of patience/light labor may come out WAY ahead of pulling the entire engine to work on it. And what will need to be done will not be different out of the car than now....

People reading this who might need something like this in the future should also consider exactly what kind of pulling tools / engine mounts / heavy moving equipment they have available.. these are heavy engines even when the accessories are removed.

barry123400 · #22 06-29-2010, 08:08 AM

The oil spitting seems to indicate something is happening though. If the oil spitting was absent at 300 pounds compression I would otherwise live with it.

I would also look for a loose valve guide on the number one cylinder. Not too likely but it could introduce excess oil into that cylinder. It never hurts to check out all possibilities even if the odds are against them.

I do not know if there still are portable cylinder boring/honing units around now. They only refference the top of the deck but where used for years. I would not use this type of boring machine today for a general rebuild .

The boring machine would have to refference the crankshaft centreline bore to satisfy me. That type of boring machine is far from portable. This way you could use an oversized piston if the bore turned out to be worn out of spec or had a scoring that was not too deep.

I have always wondered why mercedes does not mention that running an arc weld bead up the inside of the old liner will shrink it to remove much easier. Of course sealing up the bottom of the bore to eliminate any weld splatter.

Anyone have any ideal of the pressure required to install a new liner? Could you measure the actual length of the pulled liner and pre machine the new liner in length before Installing? Or is this impossible because of different bottoming possibilities? More likely damage to the gasket sealing surface during installation might require the overlength replacement though.

leathermang · #23 06-29-2010, 08:14 AM

Barry, you keep using the term " BORING" when I am describing HONING the new sleeve. Very different processes. Honing is low tech and low pressure... Boring is NOT.

vstech · #24 06-29-2010, 08:30 AM

leathermang, what type of honing would properly handle the increase from a new liner to the size of the new piston? you mean the FSM explains how to hone a new liner with a three jaw hone stone that fits in a drill? really? that's amazing.
I would NOT attempt this on a worn out of round cylinder to an oversized piston. perhaps if there is a line hone available for a drill that might work.

barry123400 · #25 06-29-2010, 08:34 AM

No I agree with you that honing some material off is much different than boring off a lot of material and honing as a final stage. I corrected my last post.

Basically honing only indicates then there is little distortion to the new liner if any when installing one?

barry123400 · #26 06-29-2010, 08:42 AM

Quote:

Originally Posted by vstech

leathermang, what type of honing would properly handle the increase from a new liner to the size of the new piston? you mean the FSM explains how to hone a new liner with a three jaw hone stone that fits in a drill? really? that's amazing.
I would NOT attempt this on a worn out of round cylinder to an oversized piston. perhaps if there is a line hone available for a drill that might work.

Unless there is an adjustable fixed hone the old liner would have to be bored first probably. The fixed hone should probably be refferrenced as well if worked on an unbored used liner.

A flexable type is only usefull to apply a finish to a good concetric bore to help seat the rings or dress the surface a very little I would think. I am thinking three to perhaps five thousand on the outside. Could be wrong.

t walgamuth · #27 06-29-2010, 09:58 AM

I have pressed out my liners at my favorite machinists shop numerous times. We use a hydraulic press strong enough to shatter the block 30T IIRC. The force required is always enough for me to think about the possibility of shattering the block if I happen to place the spacer wrongly.

It groans and creaks like a bridge collapsing!

vstech · #28 06-29-2010, 10:01 AM

the press in my garage is 30T... I'd not place my block in it and pump the handle myself... I like the idea of dry ice and a slide hammer...

leathermang · #29 06-29-2010, 10:26 AM

Quote:

Originally Posted by vstech

leathermang, what type of honing would properly handle the increase from a new liner to the size of the new piston? you mean the FSM explains how to hone a new liner with a three jaw hone stone that fits in a drill? really? that's amazing.
I would NOT attempt this on a worn out of round cylinder to an oversized piston. perhaps if there is a line hone available for a drill that might work.

Yes, that is what I am saying .... except it may be a four jaw hone ...yes, that fits in a regular drill...
It is not so much the machine but the technique which is important .. regular measurement and then addressing the section which is not the same as the other.. of patience and time and technique...

Honing, as mentioned already, is not for correcting either taper,out of round, alignment of the center line, nothing except the diameter of the bore... and then planning ahead a few thou and changing to a proper stone grit to leave the correct hatch marks in the sleeve to facilitate the break in of the new piston rings. The angle of the crosshatch left from the last stones is important and is the result of the speed the drill is running in relationship to the speed the drill body is being moved up and down.. I think 60 degrees is considered optimum.