[Strassenkreuzer]

My '89 300SE is now rounding 180,000 miles on the clock. She burns a quart of oil every 600-800 miles or so. My questions are these:

- At what point can I no longer wait to have the crankshaft, transmission, and U-gasket seals—and valve stem seals—replaced? In other words, what kind of indication, aside from oil consumption, makes this a now-must-do repair? I don't want to drive it so long under these conditions that I do some sort of super-expensive damage elsewhere to the engine.

- What should I expect to fork out as a reasonable price for the above repair at my private mechanic? I cannot do this work myself.

- I also assume that one should do a valve job and replace the fuel injectors if doing the above repair. Is this a true statement?

Thanks, gents!

 

[TexFinn]

Crankshaft? Now you are already talking about bottom end. And as far I've figured out, the bottom end on the M103 is pretty solid, so you shouldn't have to touch that unless something really catastrophic happens.

But since yours is already consuming (not leaking?) quite a bit of oil, it might not be a bad idea to take the head off and put new head gasket, valve seals/guides, valve cover gasket etc. in there.

If you think the car is otherwise worth it. If not, then might as well run it as long as you can and then move on to something else. Never done it on a M103, but I'd imagine paying somebody to do that is going to be a bit pricey. Parts are not expensive, but labor is...

 

[Strassenkreuzer]

Thanks. Sorry; I didn't mean to include the crankshaft as I've also been told the bottom of the engine is bullet-proof. I meant the valve cover, front and rear seals and the valve stem seals—and, while we're at it, maybe a valve job.

I guess I meant to ask whether there's a point at which the excess oil consumption becomes something more than just a nuisance, i.e., is there some indication that it's "absolutely time" that this job has to be done.

 

[ianrandom]

I think just the amount of oil loss would become unreasonable at some point. It's a very durable motor.
Valve seals probably need doing around now. Has it not had the head gasket thing happen yet? That seems to be their main Achilles Heel.

 

[John350]

Oil can get out two ways: burning and leaking. Neither in and of itself represents a danger to the longevity of the engine, as long as you don't let the level get too low.

Leaking oil can, however, cause problems elsewhere, like fumes or deteriorated rubber parts. Excessive oil burning can clog catalytic converters.

As far as burning goes, there are two prime suspects: rings and valve guides. Valve guides will show up as smoke under deceleration whereas rings show up more under acceleration. If you're unsure which it is, have someone follow you while you hold it in second gear and first accelerate at full throttle to near red line then decelerate (foot off the pedal, no brakes).

 

[wooky_chew_bacca]

The head gasket, mentioned before, is notorious for "blowing" and leaking oil. Also if you've ever pulled the valve cover there is a horseshoe shaped seal that fits at the upper timing cover that if not installed correctly will leak (ask me how I know :grin)

 

[dadrab]

So, you're sure it "burning" the oil? Any leaks? How about smoke?

 

[rumb]

at about 200K my head gasket was horribly leaking oil so I replaced that. I had a machine shop install new valve guide seals - cost like $40 labor. I now burn hardly any oil at all. valves and seats where still fine. new timing chain and upper guides got rid of @12 degrees of stretch and gave me back a LOT of horsepower. I did not replace the tensioner. It is oil pressure activated with an anti back out feature. Very hard to fail.

The cylinder walls still had a great cross hatch pattern on them. The bottom of this engine is very reliable.

at 240K today and car runs strong.

 

[Strassenkreuzer]

It looks like I never circled back to thank you guys for posting replies and to close the loop on this thread. So thank you; my apologies for the really tardy reply and appreciation for your input. I started a new job and have been neglectful of my MB forum buddies. :wink

Sometime in the near future I'm going to have the valve guide seals replaced, as I know this is the major source of oil consumption. However, with my last oil change I added a 10-oz can of LiquiMoly, and it seems that I get more miles between oil light appearances--somewhere on the order of 800-1,000 miles with 10-40. Not bad. That doesn't mean the seals don't need replacement, but it's a sign that the molybedum is plugging microscopic irregularities; plus, the engine seems to run smoother--except for the annoying occasional misfire at idle which is likely either a worn cam lobe (not good) or a cranky injector (far less expensive). Doesn't happen at all when RPM is much above idle.

I still need to do a compression test, but she still appears to run strong—though I have no other M103 in a similarly-equipped 126 with which to compare.

Meanwhile, she starts instantly, though I do get some occasional lifter clatter for a few seconds at startup. Oddly, it's irregular, and I don't know why. And she passed her STAR station-required (it's evidently more thorough) smog test last week with amazingly flying colors--FAR below the EPA max values for CO, NO and CO2. So I'm happy about that, particularly since she does burn a smidge of oil.

I can easily get the parts for the valve guide seals, but is this a repair that a novice can undertake--or should I rely on my mechanic to do it and just bite the bullet labor-wise? I replaced all my HVAC vacuum pods last summer—a painstaking undertaking—but digging into the engine scares me.

Have a good weekend, gents.

 

[Strassenkreuzer]

So, you're sure it "burning" the oil? Any leaks? How about smoke?

No smoke—at least that I can see. I've deliberately done some kick-down-to-first accelerations, and I haven't noticed any. So that's good news for the rings. And I haven't seen smoke on deceleration, either.

 

[Strassenkreuzer]

at about 200K my head gasket was horribly leaking oil so I replaced that. I had a machine shop install new valve guide seals - cost like $40 labor. I now burn hardly any oil at all. valves and seats where still fine. new timing chain and upper guides got rid of @12 degrees of stretch and gave me back a LOT of horsepower. I did not replace the tensioner. It is oil pressure activated with an anti back out feature. Very hard to fail.

The cylinder walls still had a great cross hatch pattern on them. The bottom of this engine is very reliable.

at 240K today and car runs strong.

This is encouraging. For my part, I don't think 200K miles on a well-maintained M103 is all that many. But that's easy for me to say because I love my car and drive it all the time. Even in SoCal you don't see very many 126s anymore, and most of those that are still on the road are closer to Hoop-Ds than they are classic 126s. That's too bad, but as we all know, it takes a certain kind of MB owner to properly TLC an old 126, and most people aren't willing to make those investments of time and money.

Frankly, my 300SE is not an overly-expensive car to maintain. At this point, my repairs average around $750-1,000/year, and while gas is relatively expensive given its thirst factor and that the straight six has to work reasonably hard to propel the 4,000-lb car, it's still a LOT cheaper than a new car with its payments, insurance, registration, depreciation, etc. I can burn a lot of gas and do a lot of repairs before I even get close to what I'd spend on a new car whose longevity and build quality is questionable. Besides, if I did buy a new car, it would be a used hybrid.

Now, if we add the paint job I'd like...for around $7K? Yeah, that's in most people's eyes not a worthy use of car money. But as we all know, we don't make return on investment the primary driver for owning a 126. They're not yet old enough, and sedans appreciate at a slower clip than coupes.

 

[wooky_chew_bacca]

It looks like I never circled back to thank you guys for posting replies and to close the loop on this thread. So thank you; my apologies for the really tardy reply and appreciation for your input. I started a new job and have been neglectful of my MB forum buddies. :wink

Meanwhile, she starts instantly, though I do get some occasional lifter clatter for a few seconds at startup. Oddly, it's irregular, and I don't know why. I replaced all my HVAC vacuum pods last summer—a painstaking undertaking—

We'll let it slide THIS time Mr Kreuzer :grin (probably next time too :wink)

The 300SE I had did the lifter clatter every now and then too, I figured that as long as it went away right quick there was really no point in trying to "fix" the problem. Doing the pods was almost as bad as being head-first upside-down in a boat bilge servicing a stern-drive :eek NOT something I'd want to do very often but when in there take care of everything you can so it'd be another little while before having to do it again

This is encouraging. For my part, I don't think 200K miles on a well-maintained M103 is all that many. But that's easy for me to say because I love my car and drive it all the time. Even in SoCal you don't see very many 126s anymore, and most of those that are still on the road are closer to Hoop-Ds than they are classic 126s. That's too bad, but as we all know, it takes a certain kind of MB owner to properly TLC an old 126, and most people aren't willing to make those investments of time and money.

Frankly, my 300SE is not an overly-expensive car to maintain. At this point, my repairs average around $750-1,000/year, and while gas is relatively expensive given its thirst factor and that the straight six has to work reasonably hard to propel the 4,000-lb car, it's still a LOT cheaper than a new car with its payments, insurance, registration, depreciation, etc.

Yeah, when I sold my SE she had 238K on the clock and would still push you back in the seat just a tad bit. I had just recently completed a "proper" tune up and another round of fluid/filter changes (you wouldn't believe the look of the plugs having over 100K on them :eek I was surprised that she was even running but run fairly good she did. I think the problem was a plugged cat because when I installed the "test pipe" I put together ALL the sluggish lack of power issues vanished (sold it with pipe still there as we don't have smog checks out here where I live)

Around here you don't see too many 126's (out here in the 'burbs) and most of what I've seen look like crap with bad paint and ragged interiors so one has to assume that the mechanical servicing has a lot to be desired and when you see their owner pumping the cheap gas . . . . . . . .

I'll agree also with the not too expensive to maintain (even my coupe once I did the stuff that needed to be re-done on the front-end) and many things I've done to both probably won't need to be done again for a long time due to me not getting the "cheapest" parts and ANY car that's "paid for" will be cheaper to operate because of no payments, the required full coverage, and the higher ad-valorum (I paid the "one time" amount of $275 when I bought the coupe and now it's a mere 20 bucks a years for my tag from now on) I happened to see what some guy was having to pay for his two year old car, 900 bucks :eek and that was before they came out with the "one time" option

 

[rumb]

The valve guide seals are not hard, but are very tricky to do with a air hose connected in the spark plug hole to hold the valves up, but it is still easy to push to hard and drop the valve into the cylinder. you also will need a valve spring compressor tool.

The bigger question is that eventually you will need to replace the head gasket and all the hoses that are on top of the engine. a lot of them will break from age when you take the head off. the chain and guides and the front crank seal are also eventually needed. at your mileage I would bite the bullet and have it all done at once and then never worry about it again. good time to replace water pump and fan belt tensioner while there.

with the head off a machine shop can easily tell if there is any valve guide or stem wear. My engine at 200K only needed the seals and just that dropped oil consumption to almost nothing from need a quart or two every 3000 miles.

 

[wilson1010]

Your car is not "leaking" oil, at least outside of the block. A quart of oil ever couple of weeks would look like a hazardous waste site in your driveway if it was. Forget that.

If all the M103 is doing is burning a quart of oil every few weeks miles, leave it alone. First, they are notorious for burning that much, mine did. Second, you can't count the things that can be done wrong on an upper engine rebuild. This is like getting a shoulder replacement so you can continue to shoot 130 on the public course. Leave the clubs at home and walk the course.

 

[rumb]

I guess it all depends on your expertise and desire. You either work on your own cars or you dont.

If you like playing golf then get the surgery.

 

[wilson1010]

I guess it all depends on your expertise and desire. You either work on your own cars or you dont.

If you like playing golf then get the surgery.

If you were of a certain age, you would know the shoulder surgery usually does not actually work, at least to return to golf.

 

[rumb]

I'm probably that "certain age", but I don't play golf. But I do engine work from time to time.

:grin

 

[wilson1010]

I'm probably that "certain age", but I don't play golf. But I do engine work from time to time.

:grin

If you're doing Strassenkreuzer's upper engine rebuild, I am sure you will do a fine job. I know a couple of guys who would be happy to work on that shoulder if you want to take up golf. :grin

 

[tusabes]

Agree with Wilson , if the only issue is oil consumption just add oil when needed . Too many brittle unknown bits will break if disturbed and additional problems could surface .