My '88 300 SEL seems to have all the classic symptoms of needing work on the valve guides or seals (high oil consumption, a rare puff of blue smoke, occassional rough idle, pushing 100k miles, etc.) as I've read through many postings on the subject. Otherwise, she runs great. Evenso, I'm taking her to my mechanic to get a more precise diagnosis next week. I'm curious as to the repurcussions of just living with the symptoms (as none are particularly severe) depending upon the $$ we might be talking about here. I've heard elsewhere that the catalytic converter could suffer some if I don't take action, but that the problem is otherwise relatively innocent - I just have to keep topping off the oil with about 0.5 quarts every 100 miles or so - around once a week in my case. Also, what kind of labor hours should I expect for repair of valve guides or seals, and is their anything else I should look at while I'd already be into the labor costs of opening up?

you will clog your catlytic converter and pay sooner or later $400+ dollars. I thinks replacing the seals is a 3-4 hours job for your car. I have added 1Q of oil to my car every 400 miles until I got sick of popping the hood and buying oil. I rebuilt the head and no more oil consumption at all between oil changes so far. It's your choice. Pay $$$ now or pay $$$$ later.

__________________
Meza
1993 190E 2.6
Advanced Diesel Systems Test and Research Engineer

A quart every 200mi. is already pretty much.
Repercussions:
Fouled Spark plugs. Major oil deposit will gradually accumulate on spark plug tips resulting in appreciable loss of power and hard starting,
Oil/carbon deposit on pistons and inside the combustion chamber:
Increased compression ratio, subject to pre-ignition, poor performance, sicking rings (worsening of oil consumption and weak compression.) and blow-by
Cat Converter: Already covered.
additional gasoline consumption as spaks/ignition deteriorates
As long as you keep the oil level up, there should not be any catastrophic beakdown of the engine, but gradually, you will loose power.
good luck
JackD

.5 qts. every 100 miles - seems to me you'd be blowing a fair amt. of smoke - more than just the occasional puff of blue.

Are you sure that the bulk of your loss is not external leakage?

The possibility of damaging the converter is real. Beyond that the only issue is the oil consumption. Very severely worn guides can eventually result in a broken valve, but that is rare.

If you want to keep the car for at least two more years a complete rebuild of the head would be a good thing to do, and you will recover some of the cost when you sell it as a fully serviceable car rather than an oil burner.

The alternative is to just sell or trade it now.

Duke

I don't know about MB engines specifically, but industry standards recommend taking action if oil is burned at a rate greater than a quart every 500 miles, probably for the abovementioned reasons.

__________________
95 E320 Cabriolet, 159K

I helped a friend out who had problems after ignoring slight smoke in her Mitsubishi. The engine absolutely refused to rev out and felt like it was retarded 20 degrees.

I removed the cat and looked inside. It was clogged up so much it was hard to believe that the car ran at all.

Suggest you do the job.

__________________
Steve

1982 380SL

Previous cars of interest
1981 500SE
1976 Jaguar XJS
1974 Rover 3500
1953 Riley (before they became scarce)

Thanks to everyone for sharing your knowledge with me. I'm taking the car in next week to see exactly how extensive the situation may be. Hopefully a valve seal job will do the trick... guess I might as well have the catalytic conv. inspected while I'm at it. Once I get the wheels refinished, then maybe I can get a picture posted to the 126 roll call thread (and feel better about what's under the hood too. :-)

Contracting for a valve seal job is a good idea, but be prepared for a head rebuild. Once the valve springs are off a good mechanic can detect excess wear by wiggling the valve stems. If the clearance is excessive you should probably have the head rebuilt unless you don't plan to keep the car for an indefinite period.

New seals will probably reduce current oil consumption, but the guides will continue to wear and will eventually need replacement.

The 103 engines have fairly short guides, and they are known to be a wear item.

Duke

Well, technician is 75% confident that I need the valve job - we'd both like to be closer to 90%. We're going to try some rounds with an oil additive to help clean out engine, then maybe do a cylinder leakage test if the consumption doesn't go down. Am told that there is a chance that after doing valve job, if oil consumption and smoking persist, that then I would need to look into replacing the whole engine since problem may be with oil control ring, etc. Does all this sound legit? Am also told that labor to do valve job is 14 hours, which ends up puting job at about $1500 (for guides, seals, plugs, etc.). What do you guys think?

I can understand the need for a valve job at your mileage, but although not impossible, I would be extremely surprised if you would need a complete engine rebuilt.
The bottom end of those engines are extremely robust and very rarely need work. There is a taxi operator in our town with a 1989 300E (same engine) with over 650K on the original engine. Except for valve work, the bottom end of the engine has never been touched.
On my car, the valve guides/seals were done at about 125K and the valve seals were done again at 240K. The top of the pistons and cylinder walls look as if they were still brand new at 125K.
$1,300 to $1,500. for a complete valve job seems OK.
jackd

It would be unusual if there is a bottom end issue. Get the cylinder head rebuilt and then see what you got. That will, in all likelyhood, cure your oil consumption issues.

__________________
Jim

UPDATE: Per my mechanic's recommendation, instead of jumping into the valve job, we changed the oil and added in some "Marvel Mystery" to see if how the oil consumption rate might respond. Before doing this, my consumption rate was 0.5 quarts every 90 miles, like clockwork. Since doing this last change (in conjunction with 20W/50, instead of 10W/30), I've now gone over 350 miles without needing to add any oil under similar usage and outside temperatures. If nothing else, it appears that I've bought some time to raise funds for a valve job if that's still imminent. As we were only 75% confident that the valve job was needed in the first place (based on symptoms), could it be that the true issue was actually something else (with similar symptoms), which the Marvel Mystery and 20W/50 has somehow rectified? I read in another post (man I love this forum!) that the cleaning agents within Marvel Mystery can remove varnish build up, which could improve hydraulic lifter action... I have no clue what that really means or if it even applies to my car, but something has improved the performance - even if only short term. I'll be taking her back in after another 200 miles to change the oil/filter again. She still runs a little rough, but we're pretty sure this relates to the spark plug fouling that occurred prior to adding the Marvel Mystery - am thinking now to change the plugs when we change the oil, run Castrol 20W/50 without the Marvel Mystery, and see how it goes. What do you guys think?

Now you have to wonder how much the improvement was due to the cleaning action of Marvel Mystery Oil and how much was due to the higher viscosity oil. I don't see how cleaning the internals of the engine would decrease oil consumption. I think most of the benefit was from switching to 20W50 oil.

__________________
95 E320 Cabriolet, 159K

as the price of fuel has been getting steep of late, ive been using 87 octane gas. now oil consumption is noticeable; more recently, the fuel cost has declined a bit, and i went to 91 octane, and the oil consumption problem has stopped (for now)

just reporting an observation, im making no claims or saying this is a scientific observation.

also, had my car "e-tested" to meet enviro laws, and it passed with flying colours, well under the maximum allowed, so my cat is working well