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Discussion Starter · #1 ·
Hello everyone, I had a missfire issue with my cylinder 4. I took the van to the dealer and dealer estimated to replace the engine for $19K. They said no pressure on cylinder 4 and the engine has to be replaced. Is there anyone had similar issues?
 

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Welcome to MetrisForum and super sorry to hear about your serious trouble.

Cyl #1 and #4 have come up before, there's a couple threads on it ...

I guess your van is out of warranty due to years of use or mileage?



One of the threads mentions a leaking fuel injector ...
 

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Hello everyone, I had a missfire issue with my cylinder 4. I took the van to the dealer and dealer estimated to replace the engine for $19K. They said no pressure on cylinder 4 and the engine has to be replaced. Is there anyone had similar issues?
No direct experience, thank goodness, but I have come upon several engines with a similar problem. In one case (Subie) an exhaust valve was burned. In another case (Porsche) a valve spring (intake IIRC) broke.

In both cases the problem was remedied by pulling the head and fixing the burnt valve or the broken valve spring.

Assuming the no pressure in #4 cylinder is correct and other cylinder pressures are within acceptable levels a leak down test is often used to try to identify why the cylinder pressure is low.

The cylinder is pressurized with air through the spark plug hole and signs (sounds) of air leaking out at the intake port (via a leaking intake valve) or at the exhaust port (via a leaking exhaust valve) or from the oil filler cap (via bad rings) are checked.

A further test would be to inject a bit of oil into the cylinder and rotate the engine a few RPMs then retest. If the rings are the source of the no pressure the oil can possibly for a bit of time allow the rings to seal the cylinder.

You didn't mention any issues from the cooling system so I'm assuming there is no head gasket leak into the cooling system. And adjacent cylinders, make that the adjacent cylinder, #3, is not misfiring so #4 cylinder is not leaking into the #3 cylinder through a bad gasket and #3 cylinder is not leaking into the #4 cylinder.

Given the engine is fuel injected and directly fuel injected a (severely) leaking injector would have to be checked for.

The valve cover would probably at some point be removed to allow for inspection of the valve train. A flat lobe on the camshaft or something wrong with the valve hardware which results in insufficient (or no) valve lift would be checked for.

The point of the above is it is possible the problem can be addressed by a repair of the existing engine rather than a replacement of the engine.

The repair cost will be less than the cost of an engine replacement but there are risks. The shop doing the work must be capable of doing the job properly. This involves identifying the source of the no pressure, and determining if the engine is a good candidate for repair or would it be better to replace the engine.

If the engine has not suffered from overheating, low oil supply/pressure, if the clean side of the oil system is free of metal debris (such as might arise if a valve lobe went flat), then the engine is probably ok to repair.

Of course a shop capable of the above is not on every corner. To make matters worse a shop can have a good rep but since it obtained this rep has changed hands and the rep may no longer apply. Changed hands or what is often the case the best tech or techs move on to another indy shop (or as I have observed) move on and end up working at a dealer service department.

I would have to offer that engine replacement is probably the best route. The replacement engine comes from the factory and should -- double check! -- come with a warranty on both labor and on the engine.

Absent a repair or replacement engine the van's value is low. Essentially it is classified as a "roller" and can have a value of (my 2nd hand experience) of several thousand dollars. 'course, times change. The van's value may be inflated due to the current situation with the used car market. A rising tide raises all boats...
 

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Discussion Starter · #5 ·
Thanks for your great reply. I had no issues with the overheating but there was a metal parts in the oil filter so, since mercedes dealer wants $19K I decided to take down the engine myself. I opened the cylinders and I found the issue #4 piston head was broken. Luckily it didn't damage the block.

The think is that I am trying to understand. There was a little oil inside the coolant. How did they mixed? When the piston leaks, how did they mixed with the coolant?

Please advice me what else should I replace while engine is down? I dont want to have similar issues in the future.

Thank you so much your valuable time and information.
No direct experience, thank goodness, but I have come upon several engines with a similar problem. In one case (Subie) an exhaust valve was burned. In another case (Porsche) a valve spring (intake IIRC) broke.

In both cases the problem was remedied by pulling the head and fixing the burnt valve or the broken valve spring.

Assuming the no pressure in #4 cylinder is correct and other cylinder pressures are within acceptable levels a leak down test is often used to try to identify why the cylinder pressure is low.

The cylinder is pressurized with air through the spark plug hole and signs (sounds) of air leaking out at the intake port (via a leaking intake valve) or at the exhaust port (via a leaking exhaust valve) or from the oil filler cap (via bad rings) are checked.

A further test would be to inject a bit of oil into the cylinder and rotate the engine a few RPMs then retest. If the rings are the source of the no pressure the oil can possibly for a bit of time allow the rings to seal the cylinder.

You didn't mention any issues from the cooling system so I'm assuming there is no head gasket leak into the cooling system. And adjacent cylinders, make that the adjacent cylinder, #3, is not misfiring so #4 cylinder is not leaking into the #3 cylinder through a bad gasket and #3 cylinder is not leaking into the #4 cylinder.

Given the engine is fuel injected and directly fuel injected a (severely) leaking injector would have to be checked for.

The valve cover would probably at some point be removed to allow for inspection of the valve train. A flat lobe on the camshaft or something wrong with the valve hardware which results in insufficient (or no) valve lift would be checked for.

The point of the above is it is possible the problem can be addressed by a repair of the existing engine rather than a replacement of the engine.

The repair cost will be less than the cost of an engine replacement but there are risks. The shop doing the work must be capable of doing the job properly. This involves identifying the source of the no pressure, and determining if the engine is a good candidate for repair or would it be better to replace the engine.

If the engine has not suffered from overheating, low oil supply/pressure, if the clean side of the oil system is free of metal debris (such as might arise if a valve lobe went flat), then the engine is probably ok to repair.

Of course a shop capable of the above is not on every corner. To make matters worse a shop can have a good rep but since it obtained this rep has changed hands and the rep may no longer apply. Changed hands or what is often the case the best tech or techs move on to another indy shop (or as I have observed) move on and end up working at a dealer service department.

I would have to offer that engine replacement is probably the best route. The replacement engine comes from the factory and should -- double check! -- come with a warranty on both labor and on the engine.

Absent a repair or replacement engine the van's value is low. Essentially it is classified as a "roller" and can have a value of (my 2nd hand experience) of several thousand dollars. 'course, times change. The van's value may be inflated due to the current situation with the used car market. A rising tide raises all boats...
 

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Thanks for your great reply. I had no issues with the overheating but there was a metal parts in the oil filter so, since mercedes dealer wants $19K I decided to take down the engine myself. I opened the cylinders and I found the issue #4 piston head was broken. Luckily it didn't damage the block.

The think is that I am trying to understand. There was a little oil inside the coolant. How did they mixed? When the piston leaks, how did they mixed with the coolant?

Please advice me what else should I replace while engine is down? I dont want to have similar issues in the future.

Thank you so much your valuable time and information.
That looks to be quite a catastrophic failure -- hard to believe any of the piston rings are intact. First thing I'd like to know is why it failed. Oil deprivation? Overheating? Massive pre-ignition? Bad #4 rod bearing or piston wrist pin?

If there was metal in the oil filter, that must mean there is or was metal in the oil galleys or at least the oil pan. I'd remove all the rod bearing caps and inspect for bearing damage, not necessarily removing the 3 good pistons. With over 100k miles on an engine rated for 155k, I'd replace all bearings and maybe rings too if the cylinder condition would allow it with just honing, no shop machine work.

I'd also remove the crankshaft main bearings to inspect for damage. And while you're there, I'd throw in a new water pump, hoses and belts, maybe even a timing chain.

Best of luck!
 

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Thanks for your great reply. I had no issues with the overheating but there was a metal parts in the oil filter so, since mercedes dealer wants $19K I decided to take down the engine myself. I opened the cylinders and I found the issue #4 piston head was broken. Luckily it didn't damage the block.

The think is that I am trying to understand. There was a little oil inside the coolant. How did they mixed? When the piston leaks, how did they mixed with the coolant?

Please advice me what else should I replace while engine is down? I dont want to have similar issues in the future.

Thank you so much your valuable time and information.
That is certainly a broken piston.

Oil in the coolant? Did you drain the coolant and find oil in it after the drain? Oil drops will be on top of the coolant.

If so then one way oil can get in the coolant is by a head gasket leak. A careful check of the head gasket should spot the leak.

Also, it is possible the oil could have some coolant in it. May be too late now but a drain of the engine oil and collecting a proper sample to have analyzed is a way to know if any coolant is in the oil. The analysis turns up the present of anti-freeze compounds in the oil.

Another way for oil into the coolant is through a crack (or porosity) in the head (or block). But these are rare failures.

For checking for cracks in aluminum heads (and blocks) a penetrating dye process is used. The block and head is thoroughly cleaned in a "hot tank" that is suitable for cleaning aluminum parts. Using the same "hot tank" that is used for cast iron block and cast iron heads (and crank and rods) I believe will ruin the aluminum parts.

All oil and coolant passage plugs are removed prior to the cleaning. After all oil and coolant passages need to be cleaned. I used a rifle cleaning kit to clean the oil passages/holes after getting the block, heads, crank, and rods back.

At any rate once the block and head are clean they can be checked using the dye. I didn't check the (iron) block or aluminum head but relied upon the automotive machine shop I selected to properly clean these and perform any machine work on the block to do this.

What else needs to be replaced?

Well, it depends.

But first the block deck needs to be checked for flatness, or any "damage" from a leak which can erode the block deck. If necessary a minimal clean up cut can be done. Likewise the head is checked for flatness and again if necessary just a minimal clean up cut can be done. I believe I had access to the factory manuals which detailed how much material could safely be removed form the block or head and how large the cylinders could be bored.

Once you are sure the block and head are ok then if the crank and rod journals are ok -- no worn undersize or scored -- new main and rod bearings. New rear and front main seals. New gaskets. For the engines I rebuilt I replaced the oil pump with a new one. I coated the gears with Vasoline to help ensure the oil pump would "prime". I was able to spin the oil pump using an electric drill motor to verify the oil pump primed and keep spinning the oil pump until oil came out of all cam lobe oil holes, etc.

If the cylinders are within spec stock size new pistons/rings can be used. In the case of one engine I borrowed a portable Sunnen hone from work (machine shop) and hand honed the cylinders to "rough up" the cylinder walls to help the rings seat. Of course I used new piston pin clips/retainers. And don't use pliers on these. These must be installed with the right tool to avoid even the slightest surface damage. Any damage can result in a stress fracture with the retaining clip failing and the pieces of the retaining clip an d piston pin will tear up the cylinder wall.

I used a new camshaft. New cam chain sprockets, new cam chain, new guides/tensioners.

In one engine, an OHC design, the cam bearings were just (precisely machined) holes through aluminum towers. I checked these and they were not worn and didn't show any signs of scoring. With another engine I installed new cam bearings in the block and fitted a new cam.

And I believe I used new valve hardware: lifters or cam lobe followers. New valves. New valve stem seals. Oh, in one engine I had the valve guides replaced. New valve springs. New spring washers. New valve locks/retainers.

To condense the above, pretty much except for the block, head(s), crank, rods, piston pins, all new parts were used.
 

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Discussion Starter · #10 ·
Thanks again for your great information. I will answer all of your questions but first I would like to show a picture of the broken piston side #4 cylinder tube. I can't say it's a deep scratch. It does not come to the nail but, I can feel it. Please advise.

That is certainly a broken piston.

Oil in the coolant? Did you drain the coolant and find oil in it after the drain? Oil drops will be on top of the coolant.

If so then one way oil can get in the coolant is by a head gasket leak. A careful check of the head gasket should spot the leak.

Also, it is possible the oil could have some coolant in it. May be too late now but a drain of the engine oil and collecting a proper sample to have analyzed is a way to know if any coolant is in the oil. The analysis turns up the present of anti-freeze compounds in the oil.

Another way for oil into the coolant is through a crack (or porosity) in the head (or block). But these are rare failures.

For checking for cracks in aluminum heads (and blocks) a penetrating dye process is used. The block and head is thoroughly cleaned in a "hot tank" that is suitable for cleaning aluminum parts. Using the same "hot tank" that is used for cast iron block and cast iron heads (and crank and rods) I believe will ruin the aluminum parts.

All oil and coolant passage plugs are removed prior to the cleaning. After all oil and coolant passages need to be cleaned. I used a rifle cleaning kit to clean the oil passages/holes after getting the block, heads, crank, and rods back.

At any rate once the block and head are clean they can be checked using the dye. I didn't check the (iron) block or aluminum head but relied upon the automotive machine shop I selected to properly clean these and perform any machine work on the block to do this.

What else needs to be replaced?

Well, it depends.

But first the block deck needs to be checked for flatness, or any "damage" from a leak which can erode the block deck. If necessary a minimal clean up cut can be done. Likewise the head is checked for flatness and again if necessary just a minimal clean up cut can be done. I believe I had access to the factory manuals which detailed how much material could safely be removed form the block or head and how large the cylinders could be bored.

Once you are sure the block and head are ok then if the crank and rod journals are ok -- no worn undersize or scored -- new main and rod bearings. New rear and front main seals. New gaskets. For the engines I rebuilt I replaced the oil pump with a new one. I coated the gears with Vasoline to help ensure the oil pump would "prime". I was able to spin the oil pump using an electric drill motor to verify the oil pump primed and keep spinning the oil pump until oil came out of all cam lobe oil holes, etc.

If the cylinders are within spec stock size new pistons/rings can be used. In the case of one engine I borrowed a portable Sunnen hone from work (machine shop) and hand honed the cylinders to "rough up" the cylinder walls to help the rings seat. Of course I used new piston pin clips/retainers. And don't use pliers on these. These must be installed with the right tool to avoid even the slightest surface damage. Any damage can result in a stress fracture with the retaining clip failing and the pieces of the retaining clip an d piston pin will tear up the cylinder wall.

I used a new camshaft. New cam chain sprockets, new cam chain, new guides/tensioners.

In one engine, an OHC design, the cam bearings were just (precisely machined) holes through aluminum towers. I checked these and they were not worn and didn't show any signs of scoring. With another engine I installed new cam bearings in the block and fitted a new cam.

And I believe I used new valve hardware: lifters or cam lobe followers. New valves. New valve stem seals. Oh, in one engine I had the valve guides replaced. New valve springs. New spring washers. New valve locks/retainers.

To condense the above, pretty much except for the block, head(s), crank, rods, piston pins, all new parts were used.
 

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Thanks again for your great information. I will answer all of your questions but first I would like to show a picture of the broken piston side #4 cylinder tube. I can't say it's a deep scratch. It does not come to the nail but, I can feel it. Please advise.
The cylinder bores must be measured -- I used a dial bore indicator -- to determine the amount of wear and type of wear present.

One can "zero" the dial bore gauge in a section of unworn cylinder. Then move the bore gauge up/down the cylinder to determine the amount wear. Also the cylinder wants to be measured say at 3 different positions to determine by how much -- if any -- the cylinder is out of round.

If the wear is within what the factory allows one can just -- as I touched upon in a previous post -- prepare the cylinders for new rings and pistons.

But too much wear requires the cylinders be bored oversize -- assuming there are suitable oversize pistons/rings available.

Besides wear cylinder damage also requires the cylinders be bored out enough to remove the damage but not so much as to make the cylinder walls too thin. And of course there must be suitable pistons/rings to fit these oversize cylinders.

It is up to a qualified automotive machinist to make the determination if the damaged cylinders can be cleaned up without removing too much metal and of course brought to a final diameter for which suitable oversize pistons/rings available to assemble the engine.

Don't know if I mentioned this before, but I was advised to avoid rebuilding an engine that had suffered overheating or oiling related problems. Or any that had suffered from internal mechanical failure. In this case the block or crank or even head can be compromised. It is very hard to know this before hand but if it is it can make this known when back in the car and operating on its own power.

Rather than attempt to rebuild this engine and if you don't want to go the expense of a new replacement engine, sourcing a suitable engine from a err make that M-B (not MINI: where did this come from?) salvage yard might be a possibility. But this is not without some risk. Ideally one would like to be able to at least run a compression check -- or a leak down test -- on the engine. Before doing this a check should find the engine has a proper amount of reasonably good looking oil in the engine. The engine should not show signs of being disassembled then reassembled and should be pretty much intact. Also, it should not show signs of having been out in the weather.
 

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Not being a mechanic myself - I admire people 100% who have it as a profession or can DIY any multitude of things on their vehicle - buying a scrapped van, or used engine, maybe an already rebuilt engine on its own if there's such a thing with a bit of warranty ? ... is the route I'd look at versus trying to get somebody to rebuild, parts, trial, error ...

I'm thinking I could hire an indie mechanic to do an engine swap at their shop, a day or two of labor ? ... versus potentially going down the rabbit hole rebuilding, parts issues, ...
 
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