M103, removed head to replace gasket. Have a look. - PeachParts Mercedes-Benz Forum

danwatt · #1 09-29-2015, 02:57 AM

Bought a 300CE a couple of days ago for dirt cheap, excellent body, excellent interior, blown head gasket. No big deal, while I've been away from MB for awhile I've replaced a few m103 head gaskets years ago and never had a problem.

However, it looks like the seller really drove this into the ground. While there miraculously was no milkshake in oil or coolant, there was what appeared to be a ton of stop leak in all the coolant passages. No big deal, just a lot of cleaning work and maybe a new rad/heater core.

But the combustion chambers themselves looked pretty nasty.

The two center cylinders were wet, lots of scale on them. That cleaned up easily. But there is a good amount of pitting evident on both the piston top and the cylinder head on these two cylinders. I'm guessing that the head warped enough to let coolant into cyl's 3+4 through the coolant jackets. This cativated leading to these lovely pits.

I'll grab my feeler gauges and straight edge out of storage tomorrow but I'm questioning whether I should bother saving this engine or just grab a long block from the junkyard. I saw a 300TE with 70k there yesterday.
I've never come across such heavy pitting before and while I can't find any cracks in the head nor any pitting in the cylinder walls I'm thinking that if I can't get the pits out its just going to cause hot spots which will lead to predetonation which will kill the bottom end (if its not dead already from that, just realized that!)

So I'm posting this to get opinions. Get the head milled down and salvage this engine or just start (junkyard) fresh?

Piston:

gatorblue92 · #2 09-29-2015, 05:22 AM

That looks pretty nasty. Where are you located? I have a good M103 with around 250-260k miles I'll sell cheap.

Stretch · #3 09-29-2015, 06:33 AM

You might want to measure the piston heights and see if you've got some bent connecting rods - alternatively take the bottom part of the engine to bits too.

It is possible to replace the pistons and the head but what else is wrong?

You'll have to cost it up.

Hirnbeiss · #4 09-29-2015, 07:26 AM

I think you can sand the head down to a satisfactory finish, but you probably want a new piston (could also sand down, assuming you can still keep good compression). The question is more like you asked, what needs to be done on the bottom end? My guess is you'll probably want to do enough work on this engine that the engine swap will look more attractive.

duxthe1 · #5 09-29-2015, 09:19 AM

That damage is from the engine swallowing something. Luckily whatever it was wasn't large enough to cause serious damage. I'd break any sharp edges and call it ok to run.

Hogweed · #6 09-29-2015, 11:58 AM

i have a short block and a complete motor in Pa

Quote:

Originally Posted by danwatt

Bought a 300CE a couple of days ago for dirt cheap, excellent body, excellent interior, blown head gasket. No big deal, while I've been away from MB for awhile I've replaced a few m103 head gaskets years ago and never had a problem.

However, it looks like the seller really drove this into the ground. While there miraculously was no milkshake in oil or coolant, there was what appeared to be a ton of stop leak in all the coolant passages. No big deal, just a lot of cleaning work and maybe a new rad/heater core.

But the combustion chambers themselves looked pretty nasty.

The two center cylinders were wet, lots of scale on them. That cleaned up easily. But there is a good amount of pitting evident on both the piston top and the cylinder head on these two cylinders. I'm guessing that the head warped enough to let coolant into cyl's 3+4 through the coolant jackets. This cativated leading to these lovely pits.

I'll grab my feeler gauges and straight edge out of storage tomorrow but I'm questioning whether I should bother saving this engine or just grab a long block from the junkyard. I saw a 300TE with 70k there yesterday.
I've never come across such heavy pitting before and while I can't find any cracks in the head nor any pitting in the cylinder walls I'm thinking that if I can't get the pits out its just going to cause hot spots which will lead to predetonation which will kill the bottom end (if its not dead already from that, just realized that!)

So I'm posting this to get opinions. Get the head milled down and salvage this engine or just start (junkyard) fresh?

Piston:

danwatt · #7 09-29-2015, 12:25 PM

I'm in southern California, Orange County to be exact. So a bit far but thank you.

I'm sending the head to the machine shop right now to have them check it out. Going to check rod length after work today and see where I stand there.

I never started the car but I did turn it over a few times to make sure fuel and electrical worked. For what its worth everything sounded perfectly normal. I know that all this really tells me is that I don't have a busted rod but it does give me a bit of hope. I will keep this thread updated as I go.

97 SL320 · #8 09-29-2015, 06:08 PM

Do you have any pics prior to cleaning?

Do you have a pic of the head gasket for these cyl ?

Did you do a leak down prior to removing the head?

While being mindful of the timing chain, turn the engine clockwise so a piston rises in the bore then starts down about 1 1/2" inches, stop turning. Press down on the piston top, if it goes "clunk" the rod bearings / crankshaft journal are worn out. No need to press so hard that you make the crank rotate.

I don't think something was bouncing around because the piston bowl is undamaged but the quench areas are. The leads me to thing the rod bearings in these cyl are worn and the piston is hitting the head. ( carbon gets enbedded in the surfaces from contact. )

When coolant enters the combustion chamber, it steam cleans carbon off if run long enough. Were these 2 suspect cyl much cleaner than the others? Coolant in the combustion chamber also raises the compression ratio ( sometimes a lot ) and this can cause pre ignition.

engatwork · #9 09-29-2015, 06:12 PM

Quote:

That damage is from the engine swallowing something.

That is what it looks like to me too.

danwatt · #10 09-29-2015, 07:23 PM

More pics prior to cleaning:

No leak down test.

So you can tell by the pictures that the center two cylinders were much cleaner, carbon wise. The rust build up was because it had been sitting for a month or two within being fired up. The piston wasn't rusty, it was just residue from the cooling system that wiped right up.

danwatt · #11 09-29-2015, 11:28 PM

Rotated crankshaft to check each piston, each one goes over deck surface by about 1mm (eyeballed). Don't feel any looseness in any of the Pistons. Oil looks good, no metal at all.

Stretch · #12 09-30-2015, 06:22 AM

You don't seem to be any further forward.

I wouldn't run the engine like that - it seems like others would.

What are you going to do?

Is slamming things back together and then trying it out worth your time? Or would you rather take the gamble with another engine? Or do you think a strip down and rebuild is the way to go?

danwatt · #13 09-30-2015, 05:55 PM

I've gotten myself a really bad cold/strep throat so all work on the car has ceased at the moment. The head is at the machine shop getting milled down and having new valve guides installed so can't do too much until its back.

Of course a strip down and rebuild is the way to go which I am going to do. But not on this engine! I found a low mile M104 3.0 CIS at the junkyard in a 1990 300CE. Junkyard is having a half price day soon so I'm going to go back and pull it for $100 or so and rebuild it in my spare time. This is a hobby fun time car so I'm looking forward to it, not like I need it to get to work or anything.

Now as far as this 103 engine goes I'm going to sand down the piston smooth and install the head once I get it back from the machine shop. I still need to finish getting all the stop leak gunk out of the coolant passages but thats almost done, nasty nasty work.

But again, won't be doing anything for a few days until this cold clears up. Maybe once my head isn't killing me I'll make the smarter decision and just rebuild the bottom end!

97 SL320 · #14 09-30-2015, 06:17 PM

That brown sludge looks more like never having the coolant changed than any type of sealer. If this motor goes back together, on the block side clean out the coolant holes / slot between the cylinders.

This was not run with a coolant to cylinder leak very long, the combustion chambers in cyl 3 and 4 are still way to dirty. Given the pictures I'd say a sudden coolant to cylinder leak cause compression to go high and preignition to nibble away at the piston tops only in the quench areas. ( Quench is an area where the piston comes up to the cylinder head and nearly touches, this action stirs the mixture in the combustion chamber. ) This is only if the rod bearings are good on cyl 3 and 4.

Looking at the head, cyl 2 and to a lesser extent 5, they are running rich / drippy injector.

For my push on the piston test to be valid you must turn the motor so the piston is headed down the bore ~ 1 1/4" the push down on the piston. Checking at TDC will only pickup the bearing being completely hammered out.

Since this is your car and not a customers, putting it back together if rod bearings are good is an acceptable risk. The only other risk would be loss of piston ring tension from overheating leading to oil consumption. All it costs is a couple of gaskets and time to give it a try.

danwatt · #15 09-30-2015, 06:44 PM

Quote:

Originally Posted by 97 SL320

That brown sludge looks more like never having the coolant changed than any type of sealer. If this motor goes back together, on the block side clean out the coolant holes / slot between the cylinders.

This was not run with a coolant to cylinder leak very long, the combustion chambers in cyl 3 and 4 are still way to dirty. Given the pictures I'd say a sudden coolant to cylinder leak cause compression to go high and preignition to nibble away at the piston tops only in the quench areas. ( Quench is an area where the piston comes up to the cylinder head and nearly touches, this action stirs the mixture in the combustion chamber. ) This is only if the rod bearings are good on cyl 3 and 4.

Looking at the head, cyl 2 and to a lesser extent 5, they are running rich / drippy injector.

For my push on the piston test to be valid you must turn the motor so the piston is headed down the bore ~ 1 1/4" the push down on the piston. Checking at TDC will only pickup the bearing being completely hammered out.

Since this is your car and not a customers, putting it back together if rod bearings are good is an acceptable risk. The only other risk would be loss of piston ring tension from overheating leading to oil consumption. All it costs is a couple of gaskets and time to give it a try.

I confirmed with the seller that he did use some Block-Seal in it. The car had good maintenance history prior with the first owner, second owner not so much. Coolant was changed five years ago according to the paperwork, of course there is always the possibility it wasn't actually changed.

I'm familiar with what the push-on-the-piston test should feel like if the rod bearings were gone and it didn't feel like that at all, very firm at all piston heights on all pistons.

I did find a bag full of injectors in my storage unit from years ago, I'll test them all and install the best ones. Found a bag of new insulators and seals too!

In the mean time I've completely taken everything on the intake apart for cleaning, testing and lubing. Also cleaning every inch of the engine bay while I have the head out of the way. I hate dirty engine bays.