Doesn't sound right

[stanell]

I was just given a 1970 280S by my dad who had it sitting in his garage for the past 4 years. I am not a mechanic although I grew up working on GM models with my dad. I just got the report back from the mechanic, who comes highly recomended, that the MB needs a ring and valve job. It appears that the # 3 valve was stuck and burned and the pressure in the cylinder is 85 compared with the other one which are around 120.He is not sure if the pistons need to be replaced and will have to wait and see. I supected something serious due to the large amount of white smoke coming out of the tailpipe when the engine gets warm. I quess my question is how much should I expect to pay for this work plus parts. I'd appreciate a ballpark figure so I will be able to judge if I am getting taken for a ride.

[Todd Miller]

Consider this: When a valve burns, it stops sealing off to compression pressures. Almost always, this results in compression readings at or near zero psi. The second test in a cylinder with low readings is to squirt in some engine oil into the combustion chamber and then do another compression test. If the compression figure rises, you know you have worn or broken piston rings and/or worn cylinder bores. This is because the oil you've squirted in temporarily seals the rings and cylinder walls, hence artificially improving the compression. On the other hand, if you still have the same low reading after squirting in the oil, you know you have a bad valve. This is because the engine oil can't seal the valve seat.

To me, a reading of 85psi indicates stuck piston rings. I would adjust the valves to make sure I didn't have a valve being partially held open by too tight of an adjustment, and do the test again. Not to mention doing the "oil in the cylinder" test. Based on those results, I'd decide what to do next.

If the tests indicated the leakage was due to rings, I'd change the engine oil and filter, and start driving the car as much as possible with a lot of varried loads and speeds. Then I'd recheck the compression in that cylinder in a week and see if it was improving. I've seen engines like this come back to life with a couple weeks of everyday normal use and a couple good hour long runs on the freeway.

Your white smoke is a seperate concern however, and you may have a blown headgasket. Not all blown headgaskets will leak water into the engine oil, so the "does the engine oil look like a milkshake" test isn't always accurate. You can have the steam in the radiator tank tested for containing exhaust gasses using either a chemical test where blue dyed fluid inside a turkey baster looking device will turn yellow in the presence of Carbon Monoxide, or you can have a shop with an exhaust gas analyzer "sniff" the steam and see if the analyzer picks up any CO and HC's (hydrocarbons).

Prices for repairs will vary depending on what's being done and who's doing it.

Cylinder head repairs can be in the $1,000+ range depending on what's found once the head is removed and taken apart. Complete engine rebuilding will run in the $6,000+ range, if not more, for a real quality rebuilt.

[mercmad6.3]

It sounds like it just needs a good run to seat a dirty valve seat and the white smoke can be brake fluid from a leaking master cylinder ( via the booster ) and the modulator on the trans leaking and sucking up trans fluid.
Get a better mechanic to run a "Leak down " test NOT a compression test. it will soon sort out the symptoms as to what exactly is wrong if anything .

[todds]

So the symptoms are white smoke and low compression. Couldn't BOTH of these things be caused by a blown head gasket? If your compression was leaking out through the blown gasket into the cooling system I believe that would account for it. Look for bubbles in your coolant. Maybe you can get off with just a new head gasket!

[Skippy]

I second the blown head gasket theory.

[cth350]

If you have access to a competent machinist to do the bench work on the head (and by competent, I mean he does lots and lots of mercedes heads), be prepared to give him about 500$ to get back a good head. Invest about 100$ in the special tools you're going to need and the service manual (on CD), and then have at it. Throw a head gasket kit in there as well of course.

When you get to the point were the head is on a bench, check the cylinders for wear. It will probably be OK, unless a piece of a valve broke off and got scoured into the wall.

-CTH

[ja17]

Hello,
American cars use softer rings. Mercedes engines hardly ever need rings. In fact this is so rare that the factory sells very few sets and sells them at a very high price. I do not have the facts but I would guess your local dealer will be asking for at least 1K for a set of rings! Don't despair, you can buy aftermarket rings at a reasonable price. However, these engines rarely need rings. They will usually outlast the rest of the engine. Most often the cylinders wear beyound permissable limints or the piston grooves wear out long before the hard rings give out. Less than five thousandths of wear is permissable in the cylinders. Thats less than three thousanths on each side! So if you have a cylinder ridge you are in for oversize pistons with rings. Re-ringing an engine with worn oval shaped cylinders is asking for problems. The old rings have grown into the wear pattern of the cylinders and should be left in place if they are not worn out.

I suggest you remove the head inspect the block and pistons from above and unless you see damage just recondition the head and re-install. This cures the issues 90% -95% of the time.

Just making a broad statement that the engine needs valve work and rings is a safe but expensive approach. If you need this kind of work check with Metric Motors for their short block prices. This seems to be the most logical and inexpensive way out for most owners.

Yes good idea to check for a blown head gasket. Also, a ruptured transmission modulator diaphram will cause a lot of white smoke and the fouling of #6 spark plug as the engine sucks in tranny fluid.

[t walgamuth]

Even high quality rings can stick with sitting, too, and the benz engines of that era were known for burning valves on a regular basis....every 30 or 40k miles.

Blown head gasket is possible too but most likely if its that you will get coolant in your oil or vice versa.

[ja17]

Good point t walgamuth, yes the rings can be stuck. Float a little trans fluid in each cylinder when the head is off. If any cylinder drains dry long before the others, you may have some stuck rings. However, if the cylinders are not corroded and you do not have water or crud in them, chances are the heat from the running engine may free any slightly stuck rings without additional tear down.

I may want to disagree with the idea that these engines burned valves at 30k to 40k miles. I know many well maintained MBs of the era with over 100,000 miles and have never had the heads off. Typically I have found that they could need head work at 60k to 100k especially if they have not been driven or maintained.

[stanell]

Thanks guys for some good input.

[wbain5280]

I've been overhauling The M180 from my 65 220S. I've taken classes at the local Community College to do this. It's very expensive. MB pistons were quoted to me at $1200. I got them from England for about $600, and some other engine parts.

If you want to overhaul the engine, find a school close to you and sign up. Machine shop costs will eat you alive. You will have the pride and knowledge of doing the overhaul yourself.

You can always find another engine.

220S M180 Engine Work

[ja17]

Hello William,

Next time price new oversize pistons with rings and wrist pins from aftermarket sources. You will be fine if you stick with original manufacturers OEM like Mahle, etc. You may be surprised that the cost of these is less than the cost of new rings only from Mercedes. Be sure to measure the ring groove width on your old pistons. Ring grooves wear and become too wide causing the skinny top ring to twist and break.

[stanell]

Everyone if right. I had a blown head gasket,burned valves and a foreign object that damaged # 3 piston and cylinder.It looks unrepairable and the only solutions offered is a sleeve or another shortblock.

[todds]

Sorry to hear that. You know, it'd probably be cheaper to just get a good used engine at that rate. If the car is rust-free it'd be worth it to save it. There are plenty of rusted out 108's with fine motors out there I'm sure.