Spark Plug Horror! Look! - PeachParts Mercedes-Benz Forum

Merkey · #1 10-21-2006, 12:39 PM

Looking for our hot misfire on my sons 88 300TE.
Car has done 67,900 miles.
I put these plugs in new about 2500 miles ago.
Oil was changed just before that, and has been changed again last week.
The car is loosing oil, but we thought it is mainly leaking from the pan gasket.
Coolant was changed when we did the leaking radiator... 100 miles ago. We used the correct Zerex clear stuff, and the level has not moved since.
we use 91 ron gas, and we did pull the ignition timing resistor yesterday, to see if it made any difference. It didnt.
I planned to do a compression test this morning...
I pulled these plug about 5 mins ago...
We started the car from cold... drove it into the garage and pulled the plugs.

I was stunned by the condition of the #1 plug... enlarged pic below. Plugs are in order... left #6 to #1 on right.
Duty cycle was set to about 45% last time I did it about 2000 miles ago... it was about 70% before.

I will do a compression test now and post when we are done.
I will clean the plugs up and check the duty cycle again.

What the hell are those deposits????
I have never ever seen anything like that before!

Ideas?

Gilly · #2 10-21-2006, 12:45 PM

Yeah, you need valve stem seals, and badly. Possibly guides to, but you're at pretty low miles to need them. Fairly low for the seals too, but it's old enough that the seals have probably hardened over time.
Gilly

jhodg5ck · #3 10-21-2006, 12:49 PM

the resistor style plug isn't helping your cause any either.. Get some proper non-resisotr plugs (NGK, Beru, even champion if you must..).

But yes, VGS look to be in order given the overall low mileage.

What weight oil are you running? If you're not running 20/50 (Dino) I would switch.

Jonathan

manny · #4 10-21-2006, 12:53 PM

I can see the misfire on # 1 for sure ( bridged gap ).
That greyish fluffy-looking stuff, is ashes that are left over after the burn.
Conventional oil used?
Of course " Gilly " is right about the valve guide seals.
AGE is the killer of them, so is not running the engine, as for example on vehicles that are store for extended periods of time.

Gilly · #5 10-21-2006, 12:56 PM

Manny, can you do me a favor and drop the quotation marks around my user name? It's just my nickname. Tanks
Gilly

Merkey · #6 10-21-2006, 01:04 PM

Thanks Guys!
I guessed it was oil being burned!
The plugs were bought from Phil!
Did we get the wrong ones?

Oil was 5/30, but we put in 20/50 this time.

Ok we just did a compression test with my Craftsman good quality gauge.
1/ 180
2/ 180
3/ 185
4/ 185
5/ 195
6/ 190

Would the oil leakage past the seals account for the hot misfire?

david s poole · #7 10-21-2006, 01:29 PM

yes no doubt about it classic case of screwed up valve stem seals.replace them and the plugs and the car will run like new.

124Bill · #8 10-21-2006, 02:05 PM

i wonder if it is DIY job to replace stem valve on engine 103 and how much it would cost at good shop. i have the same problem on my 1986 300E.

Merkey · #9 10-21-2006, 02:07 PM

Well, now we know!

We did put 20/50 in this time, so that should help until we can get to it.
Is there any risk in leaving it for a month or so?

I saw that the stem seals can be done without pulling the head.
We seem to have a coolant weep from the back of the head, so I guess it would be best to replace the headgasket and all at once.
Anything else that you guys think we should cover if the head comes off?
Where can I find out if the valve guides will need doing ... is it obvious?

david s poole · #10 10-21-2006, 02:14 PM

you will not need to pull the head at your mileage.you need very special tools to do this job so not diy.should cost about 500 including parts.

RAYMOND485 · #11 10-21-2006, 02:54 PM

1984 300d Turbo 140,000
I Did A Valve Stem Seals With A Kit $75.00 On A 5 Cyl Deisel 8 Hrs
Guide Book, Push On Tool, 5 Extra Lock Nuts, 10 Seals, Plastic Covers For Valve Stems, Oil Seals Overnight No More Smoke, Move Ea Cyl To Top Positon Then Replace The Camshaft,$175.00 Rockers $280.00 , Camshaft ,4Bearing Towers $150.00 Adjust Valves,diy

Gilly · #12 10-21-2006, 03:22 PM

Best/easiest way to do the 103 valve stems seals is to use compressed air to hold the valves up, but there is a fairly specialized tool normally used to compress the springs. I imagine a little ingenuity would go a long ways to getting this done, any thing you could come up with to compress the springs with the head on. Might need a failry large tank compressor, although once the cylinder is pressurized it shouldn't take too much to keep it under pressure. There are ways to get around this that I'd heard of too, such as feeding rope into the cylinder with the piston down, the bringing the piston up until it won't turn any more, then removing the springs. Amything to keep from letting the valve drop into the chamber.
You are OK to drive it this way.
If your coolant leak is on the left (drivers) side rear, it may be an o-ring, the part that the heater hose attaches to has an o-ring around it and these often get brittle and crack and cause a coolant leak. Sometimes the leak follows the angle to the right and will drip off the right side of the rear of the block. Be sure of where the leak is from. Should take less time than Raymonds diesel.
Gilly

Merkey · #13 10-21-2006, 03:33 PM

Thanks Gilly,
Do those Engine compression reading look about right to you and balanced enough??
The coolant leak looks to be off the back of the head on the passenger side under #6 exhaust bolts. I have looked on the other side and it looks ok, but I have been wrong before!

.

I have a 5hp 50g tank compressor that will do 90psi easy.

I could knock the porcelin out of one of those Resister plugs, and get our fabricator at work to TIG a length of pipe and air hose fitting to it. Would that work?

Gilly · #14 10-21-2006, 03:40 PM

Compression reading look great.
To pressurize, if you want to go the route you mentioned that would work, then just come up with a coupler to attach your compressor too. If you have a compression tester (with a quick release coupling) or cylinder leakdown tester you should be able to make either one of those work, we always just used a leakdown tester, works fine with no modifications.
If you have a pressure tester, test the coolant leak with a stone-cold engine, and watch the drivers side of the block near the oil filter for drips coming from under that heater hose down onto the block, then the drip runs down the back of the head and down the other side of the block, really sounds like the classic "heater hose nipple o-ring" leak, very confusing as it drips on the other side of the engine.
Gilly

Moneypit SEL · #15 10-21-2006, 04:28 PM

Do the seals. All my plugs looked like your worst one, and I've got more than twice your mileage. I went from a quart of oil every 300 +/- miles to nearly 3000 miles. The valve seals are very DIY. A universal valve spring tool is all you need. Don't have compressed air to pressureize the cylinders? Put a length of thin rope in through the spark plug hole and turn the engine by hand to hold the valves in place. I suggest using a replacement lawnmower start cord. It's the right size, costs only a few bucks, and has a handle on one end so you can't accidentially lose the other end of the rope in the cylinder.

If you decide to pull the head, then you might as well do the valve guides at the same time, though I doubt they're already shot.

EDIT: Letting the job go for a while is probably not a good idea. Oil through the engine and out the exhaust will eventually kill the catalytic converter. Leaving it for a few miles should be OK. IIRC, I did about 1000 miles between the time I replaced the converter and when I did the seals. Still passes emissions.

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