Here are a couple pictures of my pistons after taking the head off - Page 2 - PeachParts Mercedes-Benz Forum

#16 06-12-2003, 10:19 PM

Meza,

I had a similiar problem with a ford. I placed alternately each piston in the middle of its stroke and pored a fixed amount of atf in each cylinder. The liquid and the volume is unimportant. Measure the amount of time it takes for each cylinder to empty. A piston ring failure will be immediately noticeable.

Good Luck,

RandyR

Meza · #17 06-12-2003, 10:21 PM

The cylinderhead has all new valve guides, new seals, and new springs. A three angle valve job was done too. I hope that would take care of the problem and everything will be ok. Also, other parts that I will replace:
New timing and oil chain
New oil pump (while I am there)
all new chain guide rails (timing and pump)
New hoses
New idler pulley
new transmission cooling lines
new pan gasket
Transmission filter kit

Meza · #18 06-12-2003, 10:27 PM

Great Idea RandyR. I may just do that tomorrow after I get back from work.
Meza

Meza · #19 06-12-2003, 11:53 PM

I took a closer look at the cylinderhead after my wife picked it up and found that the black seals were put on the exhaust side and the yellow ones on the intake. I told the machine shop not to mix them and gave him the MB manual in case he need to look up anything and still did it wrong!!!!!!! It's going back first thing in the morning and must have it back the same day. He had it for two weeks. I guess I'll have to be late for work!

#20 06-13-2003, 07:26 AM

Okay Meza, you have come this far, don't put the head back on until you have fixed the bottom end problem.

I have never done it, but my Haynes manual says that you can block up the engine by loosening the motor mounts and raising the block. By doing this, you are supposed to be able to get the pan off without pulling the engine.

Remove the pan, disconnect the rods and keep the caps in proper orientation with each rod. If the bearings look good, just reuse them but in their EXACT original position and well oiled upon reassembly. Push out the pistons and clean off the scotchbrite residue from EVERYTHING. Replace the rings after thoroughly cleaning the pistons(not with scotchbrite please,) use a ring compressor and put the piston back into place.

Since you are seeing crosshatch everywhere, you should not have to mic the cylinders.

Putting the head back on to do a compression test is the WRONG approach. If you find a bad ring on 3, you will just have to pull it back off.

Again, you've come this far, now finish it up and you will be happy with the car, rather than starting over with another.

Good luck,

#21 06-13-2003, 10:58 AM

even if you have cleaned the visible part of the cylinder wall, there is still a faily long portion of the cylinder wall you can't reach., below the piston tops. Part of your scotchbright is now sitting on the piston rings.
Since you intent to replace the pan gasket, I would strongly suggest you take thoe pistons out and clean, clean, clean.
If you intent keeping the car, this extra effort will prevent you from doing this job again in a few months.
But it's your car.......
JackD

drbrandini · #22 06-13-2003, 11:43 AM

just for future reference....What is the correct way to clean the pistons?

#23 06-13-2003, 12:28 PM

The correct way to clean the piston tops is by scraping off the carbon. Don't do this with anything like a chisel or screwdriver that has sharp corners. In fact a piece of hardwood would be better to ensure that you do not scratch any grooves into the piston tops. Any scratch or gouge will provide a place for a crack to begin.

Once the pistons are out, since the tops are already cleaned, just clean them well in solvent, and then break an old ring and use it as a scraper to carefully scrape the carbon out of the ring grooves before installing your new rings.

Goetz makes good replacement piston rings.

Good luck,

RickM · #24 06-13-2003, 03:20 PM

When you're done replacing the piston rings and all is buttoned-up you may want to know how to properly break the engine in.

Below is a link which, for the most part, describes a method commonly accepted amongst the rebuild crowd. Credit due to members at the PP BBS for the link....

http://www.mototuneusa.com/break_in_secrets.htm

Best of luck!

RickM · #25 06-13-2003, 03:36 PM

Here's a pic with explanation......

"These Honda F3 pistons show the difference.

Both came out of race bikes, and their owners used the same type of fuel and oil. The only difference was the break in method they used...

The one on the right was broken in as per MotoMan's instructions.

The one on the left was broken in exactly according to the owner's manual. The resulting leaky rings have allowed pressure to "blow by" down into the crankcase on acceleration, and oil to "suck-up" into the combustion chamber on deceleration.
Needless to say, this bike was slow !!

It's up to you:
The loss in power from an easy break in and the resulting poor ring seal can be anywhere from 2% - 10% !!"

drbrandini · #26 06-13-2003, 05:02 PM

hmm... Im kinda skeptical to that theory. Isn't that comparing apples to oranges???

erubin · #27 06-13-2003, 05:54 PM

Always perform a compression test on each cylinder before digging into an engine with only a high oil consumption problem. Many shops just recommend doing a head job because thats how they'll make money when in fact 190Es are known to get a big improvement from just replacing the valve stem seals (check out MBs TSBs on 190Es high oil consumption). I worked on a friends 2.6l 190E car with same oil burning, spark plug fowling problem as yours. I replaced all his valve stem seals with the head in the car. It was a 1/2 day job and now, more than 8,000 miles later the oil burn and plug fowling has gone a way. The carbon in the combustion port will eventually burn away. The valve stem seals are very2 cheap.

Don't be surprised if the old valve stem seals look perfect. All of the ones i replaced were intact and only a bit stiffer from heat/age. But in the end it made all the difference with new ones. If your shop screwed up the installation then they probably didn't bother using the insertion tool (actually just a dinky plastic sleeve) that come with the new valve stem seal kit. The insertion tool prevent the valve stem from damaging the seals as they slide on. For the piddly cost you should have them put in a new set of seals and make sure they lubricate the insertion tool with motor oil.

Meza · #28 06-13-2003, 07:05 PM

Sorry guys but I will not remove the pistons. I just don't think the way I cleaned the pistons will cause all what was described. Even the wheel I used was not new from the box. it was more than half way worn out. If you all see the pictures, one of them (Piston #1) was clean and the other 5 still need cleaning. Well, it was cleaned by hand using a worn out non abraisive scotch brite on a sponge from my kitchen sink. I did that with all of them and then used the air drill to polish the top and I was careful. For the past 80K miles (since I bought it ) and the oil consumption problem was there. I have kept the oil level right because I checked it almost everyday. If I do have a problem with my bottom end, then I will overhaul the whole bottom end and not just put rings or sell the car. I just don't have time to do all that work decribed. It sounds easy, but it's time consuming and I don't have all that time not to mention my 1 car garage that I can't even move in it.

psfred · #29 06-13-2003, 07:55 PM

I'd not recommend much cleaning of piston tops for the very reason indicated -- abrasive residue in the rings. Just scraping the bulk of it off with a scrap of wood is fine -- the rest will burn off fast enough when you get the head on.

You will find out if there is any in there soon enough, I suppose.

If you've not overheated it and it has visible crosshatching, the rings are fine. If it has been overheated, the spring in the oil control rings can anneal, preventing the scrapers from removing the oil from the cylinder wall, so it will "pump" up into the combustion chamber.

There won't be any excess blowby in this case, as the compression rings are fine.

However, I suspect all the cylinders would be affected, not just one, and the amount of oil that can dribble down past worn-out guides is astonishing -- the head on my brother's 300D was actually dripping oil when we took it off. Quite enough to produce the fouling you saw.

The diagnosis here is that new seals only fix the oil consumption problem for a few months.

Best of luck -- it's a nice car when it runs, and I'm sure you will appreciate not having to fill the crankcase every other day!

Peter

Meza · #30 06-13-2003, 08:10 PM

Psfred,
I like your comments and I hope everything will be fine. I am almost sure my seals were the problem and the condition you saw is no surprise when it has been leaking for 100K miles getting worse day after day. Time will prove who's right or wrong!

I forgot to mention that although I did not do a compression test, I did attach a vacuum gage a few months ago and the needle read in the green zone (As far as I remember, it was 15-16 psi).