Author Topic: Original 230SL, probable burnt valve after 50 years of perfect service  (Read 8122 times)

Mike Hughes

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I have been the custodian for well over decade of a fairly pristine original unrestored 230SL that has served me and its previous owners faithfully for 50 years.  A recent 150 mile outing during our unusually warm early winter ended with a rough idle as we were pulling into the garage.  I was concerned enough to immediately pull the plugs to do a quick check and found #1 was completely fouled while the rest were nice and beige.  While it was still warm I did a compression test and discovered:

#1 25, #2 140, #3 135, #4 130, #5 135, #6 140

I think that I have a burnt valve.

The engine has smoked a little in recent years so the idea of an eventual rebuild has been on my mind.  We don't have deep pockets but "she who must be obeyed" agrees our SL deserves to be returned to the road soon if it is within reason.

This is a numbers matching car and I would prefer to keep it that way.  I am open to suggestions about how and with whom to proceed with returning the engine to operational condition.
- Mike Hughes  -ô¿ô-
  1966 230SL Auto P/S
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Benz Dr.

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Before you go any further add a bit of oil to that low cylinder and spin the engine over a little bit to spread the oil around. Do another compression test and see if it goes up at all. If it doesn't move up very much it's a bad valve and if it goes up a lot it's probably a broken ring.  :(

 The rest of your cylinders are low but even and are down about 20 PSI on average. If you're lucky, you will only need a valve job but you could be in for the full brigade. If you only do the cylinder head I would be inclined to keep your RPM's under 4,000 which should help extend your engine for a few more years. Once you get down below 125 PSI it's full rebuild time anyway. You can continue to drive past that point but something will break  eventually. This may cost more then than rebuilding now.

Just trying to get you ready, so to speak.  :)
1966 230SL 5 speed, LSD, header pipes, 300SE distributor, ported, polished and balanced, AKA  ''The Red Rocket ''
Dan Caron's SL Barn

1970  3.5 Coupe
1961  190SL
1985   300CD  Turbo Coupe
1981  300SD
2013  GMC  Sierra
1965  230SL
1967 250SL
1970 280SL
1988 560SEC

Mike Hughes

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Hi Dan -

Messing around with antique cars for over 40 years I discovered long ago that half measures generally end up costing more in the long run than just doing it right once.  I did the oil test, too, and the compression readings were relatively unchanged.  The engine has 85K on it over 50 years with a period of near inactivity imposed by the 2nd owner so the writing has been on the wall for a while due to the smoking at idle and acceleration.  Gernold advised that I might need to deal with worn valve guides if the oil consumption got out of hand.  The thing is that it is only original once and has run so sweetly over the dozen or so years in my custody that I was more than willing to add the oil and carry on, confident in legendary Mercedes durability!

If I am going to do it once right, what do you recommend?
« Last Edit: January 23, 2016, 02:34:58 by Mike Hughes »
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  1966 230SL Auto P/S
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Garry

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Mike,

I think you are going to need deep pockets but I am sure Dan will tell you why.  I had very low milage, quite a bit lower than yours but also ended up having to do a complete rebuild due to the car sitting in a shed for long time and only being turned over a couple of times a year but not driven.
Garry Marks
Melbourne/ Kyneton, Brisbane. Australia
1969 MB 280SL 5 speed RHD SOLD.
1965 MB 230SL Auto RHD Lt Blue 334G, Top 350H, Tourist Delivery.
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Tyler S

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Might be worth pulling the valve cover just to verify the lash clearance. It's easy enough and worth a look. Maybe get lucky. Thats a big MAYBE.
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Benz Dr.

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I kind of like the original idea. Original wear, original rust, original problems. Service work should not effect the value of a car but lack of of it will.

 What would you rather have? An original car with a worn out engine or one with a fresh rebuild? :)

                                                            Just sayin'.

 
1966 230SL 5 speed, LSD, header pipes, 300SE distributor, ported, polished and balanced, AKA  ''The Red Rocket ''
Dan Caron's SL Barn

1970  3.5 Coupe
1961  190SL
1985   300CD  Turbo Coupe
1981  300SD
2013  GMC  Sierra
1965  230SL
1967 250SL
1970 280SL
1988 560SEC

ctaylor738

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"Most" or "a lot" of our cars get a head rebuild at some point and get on with their life.  Given the results of your wet test, I think this would be the case with your car.  There are a couple of local machine shops that can do the rebuild, or the gold standard is to send your head to Metric Motors for a rebuild.
Chuck Taylor
1963 230SL #00133
1970 280SL #13027 (restored and sold)
1966 230SL #15274 (sold)
1970 280SL #14076 (sold)
Falls Church VA

perry113

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Sorry to hear you are experiencing issues with your 1966 230SL.
I would go for the gusto and pull the engine and open it up and do a complete due diligence and do it right one time with no regrets. Part of this whole process involves making the decision to either do it yourself or choose the proper shop to do so.
Frankly just focusing on doing just the cylinder head makes no sense unless your looking for a short term Band-Aid.
Some one like Gernold or Metric Motors knows how to do the job one time correctly. I am not certain about other shops in your area. Maybe the forum might know someone in your area who is qualified.
Cheers
Peter
Peter Perry
1970 911T Bahia Red
1972 911T Albert Blau
1963 220seb coupe barn
1965 230SL Light Ivory automatic
1966 230SL Havana Brown 4 speed Barn Find
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Mike Hughes

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Clearly the having an original car with a worn out engine phase of this Pagoda's life is now over.  That is why I am reaching out to the 113 community for advice as to how to go about getting our SL back on the road.  I think it is fair to say that we all value your opinion so any suggestions as to options of how and with whom will be most welcome.  The joy of a Pagoda is not just the smile on one's face when looking at it, but the smile on one's face when going down the road in it.  Ultimately if it is not possible to drive it 'til the road wears out, what is the point of having it?
- Mike Hughes  -ô¿ô-
  1966 230SL Auto P/S
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ja17

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Hello Mike,

How many miles on your 230SL?  How is your oil pressure?  With 125 lbs this cylinder should still fire. Chances are you just have a leaky valve guide. It this was a well maintained engine, the bottom end could go to 200,000 miles. I would try a head reconditioning first. While the head is off you can inspect the bottom end. If you choose to venture, you can remove the sub-oil pan, remove the oil pump, and remove one or two piston assemblies for inspection. One or two main bearing caps can also be removed so you can inspect for bearing wear. Sounds like a lot of work, but only takes about 90 minutes additional for one experienced.

Also check the resistance of your plug wires and ends, in case your recent miss is caused by spark failure.

Joe Alexander
Blacklick, Ohio
1969 Dark Olive 280SL
2002 ML55 AMG (tow vehicle)
2002 SLK32 AMG (350 hp)
1982 300TD Wagon turbo 4spd.
1963 404 Mercedes Unimog (Swedish Army)
1989 flu419 Mercedes Unimog (US Army)
1998 E430
1974 450SLC Rally
1965 220SE Finback

Mike Hughes

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Hi Joe -

A bad plug lead was the first thing I checked:  Just pulled the wire and inserted a fresh plug, then grounded the plug and observed steady spark pulses across the electrodes.  That's when I pulled out the compression gauge.

#1 only shows 25 lbs. and there is a hissing noise on each compression stroke.  The other cylinders show anywhere from 130 to 140 lbs. and there is no hissing noise on the compression stroke.  I pulled the valve cover, screwed a compressed air adaptor into #1 spark plug hole, and with both valves closed applied 120 lbs. of air, which exits the exhaust pipe.  Oil pressure is good, just about pegging the gauge cold when spinning the starter with all plugs removed.
- Mike Hughes  -ô¿ô-
  1966 230SL Auto P/S
  Havana Brown (408)
  Light Beige (181)
  Cream M-B Tex (121)

Benz Dr.

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Hummm......... interesting info here. We still need an idea of mileage on the engine.

  Oil pressure while cold is not a indication of oil pressure when hot so I'm going to discount that. I've seen engines that had full oil pressure while running cold and nothing showing on the gauge when hot. I imagine yours is somewhere in between those two areas.

Can't agree that one of our engines will go 200K before needing a rebuild and 150K is really pushing it. Average cylinder wear, with really good service work, is about .001'' per 10,000 miles. The question arises, how well was your car maintained over its entire working life? Modern oils have improved greatly since 1966 but how do we know what was done 40 years ago? Most cars I see that need a rebuild are generally over or around 100,000 miles up to 130,000 miles. Cylinder wear will be in the .005 - .007 range which may not sound like a lot but at that amount your piston rings will start to vibrate ( my belief ) while trying to expand and contract against the upper cylinder walls at higher engine speeds; which is why I recommend keeping it under 4,000 RPM. A compression ring will eventually snap off about 40 mm from the ring gap. Keep in mind that the piston grooves will become worn as well and this will add to the overall movement of your top compression ring. The broken part of the ring will flop around horizontally until the piston groove wears enough that the broken ring will start to move into more of an up and down position. Eventually the broken ring will gouge out a spot on your cylinder wall and then it will pop out the top side of your piston. If the engine is at idle you will hear a very loud noise that will sound like a valve hitting a piston. If you are driving at road speed you will hear what sounds like pinging. It will last less than a mile of driving and then it will go away. This is what I call the '' death rattle '' and your engine is in  fact, dead. The noise you will hear when this happens is caused when that piece of piston ring starts bouncing around in the chamber between the moving piston and the cylinder head.

So, look at the cylinder walls carefully and inspect for scoring and wear. Without removing all of the pistons there's no way to know what condition your pistons and bearings are in. If you have a weak rod bearing, failure will happen after a valve job if the bottom end isn't looked at. If your pistons are in good condition you could use them again, get new rings and bearings, and put it back to work. I would highly recommend a new oil pump, crank gear and rails if you go that far.

You should also be aware that late 230SL's now use stepped pistons. It's not what the engine came with but that's all that's available now. I think I have a set of first oversize.










 
 
1966 230SL 5 speed, LSD, header pipes, 300SE distributor, ported, polished and balanced, AKA  ''The Red Rocket ''
Dan Caron's SL Barn

1970  3.5 Coupe
1961  190SL
1985   300CD  Turbo Coupe
1981  300SD
2013  GMC  Sierra
1965  230SL
1967 250SL
1970 280SL
1988 560SEC

Mike Hughes

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Hi Dan -

I mentioned 85K yesterday.  That was a little off as I actually had the 87K service done at the original selling M-B service department just a couple of months before the terminal drive.  The service booklet shows every 3K scheduled service has been performed at that same dealer since the car was delivered there new by the first owner, the second owner and by me.  The service manager once told me their service department has used Mobil 1 exclusively since the 1990s and he remembered taking care of the original owner in the late 1980's. The second owner rarely drove the car and only one 3K service was performed under his 14 year stewardship.  He put less than 400 miles per year on it and I don't believe he changed the oil annually in between dealer services as l have done.  That's one oil change in 14 years!  The 75K service was due when I bought it and that's the first thing I did after I registered it.  Oil pressure was never a problem.  As long as I've owned the car oil pressure hot has always been a little less than half up the scale at idle, going to peg immediately on acceleration.

The consensus of opinion on and off forum confirms my gut feeling that, while just redoing the head is the cheap way out, a full rebuild is more satisfactory and cost effective in the long run. This car certainly is in such fine condition otherwise that half measures would be silly. 

A couple of folks have mentioned Metric.  What is your opinion?

You mention "stepped pistons." Please explain.
- Mike Hughes  -ô¿ô-
  1966 230SL Auto P/S
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vande17941

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A full rebuild for a valve problem? Come on... Do a valve job on the thing.
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ja17

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With 87,000 miles I would definitely consider a valve job .  After head removal you can make the final decision. The difference in price is about 10K.  Its not a mater of taking the cheap way out, its a mater of over-reaction. Of coarse if you just want to do a total rebuild because parts and labor will not be any cheaper later, then that's another  story.

Joe Alexander
Blacklick, Ohio
1969 Dark Olive 280SL
2002 ML55 AMG (tow vehicle)
2002 SLK32 AMG (350 hp)
1982 300TD Wagon turbo 4spd.
1963 404 Mercedes Unimog (Swedish Army)
1989 flu419 Mercedes Unimog (US Army)
1998 E430
1974 450SLC Rally
1965 220SE Finback

Benz Dr.

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The block and the head are roughly the same to do in terms of cost if you are replacing pistons.  A lot depends on cylinder condition. Aside from that one cylinder, the others are fairly even but are showing signs of wear just by the numbers.
If the cross hatch is gone from the cylinders, which I except it will be, then you would need to remove the pistons and crank to put a cross hatch back on them. All of this is speculation at this point.
1966 230SL 5 speed, LSD, header pipes, 300SE distributor, ported, polished and balanced, AKA  ''The Red Rocket ''
Dan Caron's SL Barn

1970  3.5 Coupe
1961  190SL
1985   300CD  Turbo Coupe
1981  300SD
2013  GMC  Sierra
1965  230SL
1967 250SL
1970 280SL
1988 560SEC

Pinder

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Try putting compressed air down the spark plug hole when #1 piston is at TDC. listen for air from tail pipe. If you hear it then its your valve. That test has worked for me in the past to identify a bent valve. If its a worn valve as a last attempt to re-seat it maybe a light tap on the valve may dislodge carbon to make it seal better. otherwise pull the head. If you do the work yourself its possible to remove the head relatively easily. Hardest part is getting the exhaust manifold disconnected from the down pipes. I ended up taking the one down pipe that I could not get off along with the head.
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perry113

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I know Metric Motors seems to be the most regarded authority for rebuilding your M127 engine.

I am all about saving money and if it the issue was just in the cylinder head then surely why not do the head. The issues arise in terms of who is going to do the work? I don't think any qualified shop can stand behind the work without doing a complete assessment of the engine and to do that would require a complete disassembly. You could pull the head and look at the cylinder walls but just like Dr. Benz says you don't know what the condition of the pistons rings wrist pins or lower bearing are.

Are the any local shop you would consider doing the work? Would it be your local Mercedes dealer?

There must be some forum members who might know of some alternatives within your surrounding area. Maybe the way to go is to get a qualified shop to do the R&I work and to send the engine to Metric.

see:http://www.mercedesengines.net/

It would be good to call them to at least get the run down of what they would do and how they would stand behind their work.
Peter Perry
1970 911T Bahia Red
1972 911T Albert Blau
1963 220seb coupe barn
1965 230SL Light Ivory automatic
1966 230SL Havana Brown 4 speed Barn Find
1970 280SE living 3.5 donor car

ja17

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Its not really that much labor to do a valve job on a 230SL especially if it has no AC. Your only out the price of the labor and a head gasket if it does not work out. Sounds like a good risk 1.5k or 10k++
Joe Alexander
Blacklick, Ohio
1969 Dark Olive 280SL
2002 ML55 AMG (tow vehicle)
2002 SLK32 AMG (350 hp)
1982 300TD Wagon turbo 4spd.
1963 404 Mercedes Unimog (Swedish Army)
1989 flu419 Mercedes Unimog (US Army)
1998 E430
1974 450SLC Rally
1965 220SE Finback

Mike Hughes

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Re: Original 230SL, probable burnt valve after 50 years of perfect service
« Reply #19 on: February 01, 2016, 00:30:23 »
The best of all possible solutions has presented itself:  Local Pagoda Group members have offered to help assess and get my 230SL back on the road.  As I have seen the quality of their work on their own well regarded cars and they know and admire mine, I am in good hands.  Thanks so much to all who have offered advice and opinions - I'll update the Group on what ultimately needed to be done and the results when all is completed!

Cheers!
« Last Edit: February 01, 2016, 00:46:54 by Mike Hughes »
- Mike Hughes  -ô¿ô-
  1966 230SL Auto P/S
  Havana Brown (408)
  Light Beige (181)
  Cream M-B Tex (121)

Mike Hughes

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My local Pagoda Group friends, Chuck Taylor and Ray Schlicht, gave me a $3800 estimate to do the job, based on what I had described here and to them on the phone.  Once I had transported my car to their garage (and transported Ray's Pagoda home to store it for the duration) it turned out that there was much less damage than feared.  The #1 exhaust valve was well and truly burned but the seat was undamaged.  Less than $600 in machine work and about $600 in parts took care of new valves, guides and sundry gaskets, etc, and replacing a worn camshaft sprocket.  With their labour it came out to right around $2400 on the road.  Money well spent to cure my smoking problem and bring the engine back up to snuff for the next 50 years.  Now that it is spring I'm looking forward to getting a chance to drive it 'til the road wears out!
« Last Edit: May 08, 2016, 23:56:02 by Mike Hughes »
- Mike Hughes  -ô¿ô-
  1966 230SL Auto P/S
  Havana Brown (408)
  Light Beige (181)
  Cream M-B Tex (121)