420SEL @ 245K, What to do?
 

Morning Guys,

So I'm facing some decisions when it comes to my 420SEL and I'm looking for some input/thoughts/comments/what would you do/etc.

It's got about 245,000 miles on the odometer. Hits about 17.3 MPG average with my driving.

The Bad:

1) Needs a valve job.

-Burns about a quart every 180 miles or so.
-Fouls out #8 plug (mitigated with spark plug non-fouler)
-Other plugs seem OK
-Perhaps this hints more towards a valve seal issue?
-Quoted 3500-4500 for job

2) A/C Leak

-Leak appears to be somewhere in the TXV or EVAP.
-New condenser (Parallel Flow)
-New dryer
-Compressor is young
-New seals everywhere up until TXV/EVAP

The Good:

-Complete suspension rebuild
-Steering gearbox rebuild
-Repainted, not car show grade but looks nice.
-Brakes are new
-Front/Rear windows replaced and resealed.
-Catalytic converter replaced (single cat unit now)
-New rims and tires.
-Timing chain, upper guides, tensioner, was replaced 36K ago.
-Interior is in pretty decent shape. No glaring issues or notable cuts/deformations/etc.
-New motor mounts.

The Unknown:

-Underbody rust. Last I checked it was fairly clean under there. There may have been surface rust on a few areas. By far the cleaner of all my 126's. I caught the rear window leak before rust could set in.

I've attached my maintenance/repair summary data if anyone was curious.

Just looking for some thoughts.

This is your turning point. How do you feel about the car? If its been good and you enjoy driving it ....drop a reman motor into it and drive it for another decade. It only takes a quick visit to the dealership to view a new S class and you will understand its financially a good decision. Also there are quite a bit of update items for 123, 126, and 140 to let you obtain some creature comforts.

Why a reman motor? Best I can tell prices range from $7-9K for a long block. That's double the valve job. I was under the impression that the M116 bottom end was fairly robust and should last quite some time. Top end on the other hand does need work periodically.

That's doable as well. I tend to go all in and get it done - but that's just me. The 116.965 can probably be had for $5K (ish). The 126 style is timeless and worthy of refurb. Once you get through the mechanicals everything else is fairly inexpensive.

Now $5K ish isnt bad. I was going by prices found online from Metric Motors. Do you know of another reputable vendor?

IMHO rust is the deciding factor. Get under the car with a screwdriver and start poking. Pull off the body cladding. Pull up the carpet. Fell up on the truck roof, where the rear window gasket is. If it's really rust free keep it going. If it's rotten find a better car :)

I'd think oil fouling the plug is more of a valve guide or piston ring issue. A compression test would be a good place to start.

Can the valve guides be replaced with the head installed? I'd think the valve stem seals could be at least.

-J

I would not do a valve job on a 250,000 mile engine. Its going to need bearings and rings soon enough. I would look for a complete engine on car-part and see if you can find a "euro specialist" in your area to swap it in for a reasonable price. A quick search shows there are plenty of 4.2 m116 engines out there for $1500 and less. That would also be a good time to do seals on the transmission if its been in there for a while.

I say this because this is not an AMG or otherwise special engine. I don't even bother with head gaskets on anything over 200,000 miles unless its a rare engine that needs to be rebuilt.

Another option is to see if you can just find a lower mile clean car with a price delta less than what you're looking at for repairs. Then let someone who is a more DIY get your car and keep it going.

How soon is soon you think?

Does your 200,000 limit apply to diesels too? I've got 321K on my 602, I think it may need a head gasket here soon. Just a hunch really.

If I owned the diesel I'd do a head gasket because they do go for quite a bit and run for a long time. However I don't know how much a shop would charge and I would have to do the math on that one.

I disagree on those mileage numbers. These Mercedes gas engines wear almost as well as the diesels. I've seen several gas Mercedes in the yards with more than 300K, I've even seen one with 450K, most of them were in accidents or rusted to hell. I bought a beat to crap 190E 2.6 once as a parts car, it had 209K miles, and left it at my mechanic's shop for a few days trying to get stuff moved around at my house. He was bored on a slow day and decided to get it running and did a compression test. It tested at factory specs on all 6 cylinders. I'd do a leak down test instead of a compression test, or you could do both. There will certainly be wear on the engine at 245K but I don't think it's probably anything you have to worry too much about. If you can find a good low miles engine for cheaper, that may be more cost effective but your engine might be salvageable.

Obviously you know nothing about the bottom ends of the M116/7s of this generation. You are the one that should be doing a search for information.



I vote for the top end. This style V8 beats the hell out of the top end every 100k, bottom ends do not go bad on them. Ask any tech. Only issue is the initial up front labor due to the block usually needing Helicoils. Once the block has the steel threads, top ends are easy.

Remember, I did a top end on my 300SEL around 270k, car has 320k on it now. Cylinder walls were beautiful and I have 160-170psi on all six...and the M103 did not have the Alusil linings these V8s have installed.

One of the shop owners on here had a customer's 420 that had around 700k before a rod bearing failed from what I recall. Steve Brotherton I believe.

Just one example - http://www.peachparts.com/shopforum/1789665-post8.html

TXV seals are not super hard. 134A is just going to leak due to molecular size. Run R12 since the rest of the system is new or R152A for R12 head pressures and $4/can.



Think of it this way Kris, if you spend say $4k for the top end... what can you buy that is worth a damn for $4k that does not need $5k put into it?

How do they get 4-5K for a valve job, esp. In NE Ohio where machine shops are as common as convenience stores?

If I din't want to pull the heads, I'd probably do the valve seals. They have to be fried to a crackly crunch at this age.

I own 2 M117 cars currently, both need engines, and have worked on a wide variety of cars. I can tell you that if OP has a car that is burning oil valves and valve seals are not the only thing that are on their way out. Are there nice high mileage engines out there? Definitely. The thing is those engines typically don't consume oil. I would not risk the cost of having a shop do a top end on a high mileage engine that may have possible bottom end issues. Not when you can buy a complete engine for about a grand.

For every engine that makes it to 500,000 miles be it an older Mercedes, a Cummins, or Honda there are 20 that gave up the ghost at 200,000 miles.

I think the number I have written down is $3500-4500. I would have to double check and see just what all that included exactly.

This is another idea too, buy a low mileage good running M116 and drop it in...

Or I suppose a M117 could too but I think there would have to be electronics change overs. EZL/ECU for sure.

I think my shop charged me somewhere around 600-800 to swap in a different M103 in my 190E. I figured $2,500 all said and done to buy a motor, address whatever seals/external things that you should do while its out and drop it in.

Or buy a rebuilt motor.

Adsit lists on at $5600 but they provide no details (suppose I could call) but I have not heard many good things about them. Idk.

Metric Motors is $8900.

The electronics of the M116(420) will run the M117(560) just fine; the differences in the calibration are minuscule, and with O2 feedback the mixture is kept at stochiometric anyway.
The M117, however, has different exhaust manifolds, crossover pipe, and down pipe. Those would have to be sourced with the engine.

I will be the contrarian. I would only fix it if it is less then $300 total otherwise dump the car. Old MBZ is bottomless money pit. Salvage some useful parts then part it out. There is a lot of car in the $2500 range. You drop an engine in then somewhere else will break, then back to square one.

I would disagree, at least at a $2500. You can find a lot of cars in that range but every single car I have looked at or bought in that price range has needed lots of suspension bits replaced plus a litany of other work. I'd say if his in good shape otherwise, both in a mechanical and cosmetic sense, he should fix it or he'll waste a lot more time and money on the new car than this one. It sounds like this one is otherwise well-sorted, it's had it's suspension redone, repainted, window seals, etc. If this one has rust then yeah, it's junk, but otherwise it's better to stick with a car you know than one you don't know. He'd do better looking at cars closer to $5k, they'd probably need a lot less work than something at $2500.

I am sure a lot of money had been spent on the car. That is why the OP is facing a dilemma. Personally I like to sort out the drive train before investing on paint, suspension or other cosmetics stuffs. You get a feel on the engine and tranny, say after 10k miles, then you invest on other stuffs. The car does not burn 1 qt oil per 180 miles overnight. If it were me, I would not spend the money on paint work and the rest with a questionable engine. Enough said, I am only offering an opinion, it is not my money.

James, from my experience replacing the evaporator will be very expensive because the car seems to be built around the evaporator ... requires removal of the dash and is a very involved process. I would confirm the refrigerant leak source before making a decision on engine work, unless you can live without A/C and the inherent benefits.

If it isn't rotted all to hell, why not just replace the motor and drive it into the ground?

Jake that's sort of what I'm leaning towards. IDK if that is full replace or just rebuild, etc. I have to look at options and see what can be had.

I spent some time on it today. I fixed my radio issue, got a new RCA cable ran and changed the amp. Fixed up a few interior issues too. I didn't see any rust in the areas I worked, just dust and dirt. Trunk was dry too, no issues there, well except for the leather cleaner bottle I left in there that leaked a bit.

I would like to do a more extensive rust investigation.

I rev'd the motor a few times checking for alternator whine..oh boy did that get messy at the tail pile. If I didnt tell you it was a gas powered car you'd think it was a diesel!

These cars solid bottom ends. My '87 300E had 250K on it with a valve job on the top end and was strong as all hell! Excellent compression, stopped burning oil after the valve job. MB gassers are almost diesel quality IMO.

I say do a top end job, call it a day. Keep driving it until the wheels fall off, literally. You already have so much into it now according to the PDF. Why stop now? It's served you well, and you've taken care of it. So breath some life into it and drive her like the MB manufacturers intended it. That's what I'm doing with my 98 E300 and 92 300D. My 98 is immaculate after repairing all the rust and paint, and my 92 held up so well after all these years I'll keep spending the money to fix them both.

As long as the under body rust isn't bad or is at least repairable/treatable I think that is what I'll do have the top end done.

I am also in the middle of rebuilding my 91 300D. Its was in a deer hit incident last year. It has 321K on it now. Body shop said its rust free! So it got a complete repaint (took it down to bare metal). New MB fenders, used hood, new mirror rubber. Got all the rear suspension parts in a box here, new front brakes,etc.

I got the radio alternator whine fixed (I think/hope) today. I had the car backed up against the garage and rev'd the engine a few times...

https://scontent-ord1-1.xx.fbcdn.net...98&oe=58458E2D

I'm interested in seeing your 321K 300D to see how its held up.

http://i.imgur.com/ea9NYxS.jpg?1

Here's mine at 310,052

Just to give you some extra options:

http://www.benzworld.org/forums/attachments/w126-s-se-sec-sel-sd/494239d1360219022-w126-replacing-m117-m119-does-work-satish_sec.pdf

Oil consumption indicates valve seals, but at that mileage the guides may be worn too, which would require rebuilding both heads, and it would be a good idea to replace all the exhaust valves since they are subject to thermal fatigue.

Valve seals can be changed without removing the heads, but then when you get the springs off and the valve stems wiggle in the guides it's off with the heads. Your estimate sounds pretty high for rebuilding the heads assuming you do the R & I.

The short block is probably okay. The embedded silicon bore surfaces (first used on the Vega) have one-fifth the wear rate of cast iron and will last virtually forever as long as they don't score. That was the problem on Vega blocks. The etching process was uneven resulting in some overetched areas and some with little or no etch. The latter allowed bits of aluminum to be torn off, which scored the bores. By the time GM gave up and licensed the process to Porsche and MB, the uneven etch problem was solved.

Pretty much the same with bearings. They don't actually wear as long as original clearances were not too tight, proper engine oil is used, and they don't get oil-starved due to insufficient oil in the sump, but will eventually spall due to fatigue, however, I expect they should be good for at least another 100K miles.

Duke

BTDT. You've got an active multi-thousand dollars a year money pit. I would cut bait on it and sell it on CL - while it's still running.

I agree with skid. At one point I had 3 benzes and my wife's car. These cars siphon you a few hundred dollars at a time, winds up being thousands per year. Multiply that times 3 cars, (that I had at one point) and you can quickly see this is not a cheap hobby.

Add insurance, plates, etc. and the mental clutter that owning so many cars will add to your mind.

I ended up getting rid of all of them, bought the wagon that I wanted, spared no expense making it right, and with all the extra money I saved I bought a 2010 E63 AMG.

Best of all, I no longer spend my weekends fixing a fleet of crappy cars. I can do some work to my wagon, if I want, or I can just enjoy driving a car that gives me 512 very reliable ponies.

What I am not clear on, was how many of his other 8 Mercedes Benz listed in his long list of used MB fleet, are also DDs. If he's got 8 cars to drive, then he could postpone repairs on the 420SEL, indefinitely.

I answered from personal experience of dumping $3K+ annually in my ONLY DD (Daily Driver).

To be honest, if the DD were a non-rusting W126 - 82 - 84 300SD, then, I could see trying to do your due diligence in keeping it on the road.

I would get under the car, and take a long, hard look at everything relative to rust formation before spending a penny on the engine. The suspension is rebuilt, so I assume that all the soft parts (e.g., bushings) were replaced. You didn't make any observations about the transmission or rear end, so I assume that they are original to the car. Was the transmission ever rebuilt?

Busy weekend!

300D:

Here are some pics from the 300D:

W124 300D - After Body/Paint - Album on Imgur

Here are some pics from the deer hit that caused all this repair/repaint work. The paint job itself was pretty horrible. It made those super cheap Maaco type paint jobs look good. Bubbling here and there, flaking off everywhere. It was bad.

2015-11-18 1991 300D Deer Hit - Album on Imgur

Back to the 420SEL though and its issues:

I did fix the radio issue! It worked. Its only taken me the better part of a year to actually climb into the trunk and deal with it! I'd been avoiding it but finally got tired of the noises.


Some clarification on the cars in the signature..I suppose it has been a WHILE since I've updated/added info. They are not all my cars, just cars that I have worked on and continue to help out with periodically:

82 300SD 145k --- Long term storage, eventual restoration project. It was my grandfather's car.
82 300SD 265k --- My dad's daily driver. An absolute rust bucket with very strong 617 and great shifting transmission. Not much more life to get out of this one.
87 420SEL 230k --- My buddy Mike's mom's car.
89 420SEL 210k --- The 420SEL in question here.
89 560SEL 118k --- My buddy Mike's old 560, since crushed.
90 300SE 262k RIP 5/25/2010
90 560SEL 154k --- My buddy Mike's current 560.
91 300D 2.5 Turbo. 241k --- My daily driver up until its deer hit incident.
93 190E 3.0 235k --- My 190E
93 300E 195k --- My buddy Mike's sister's car.

So in reality:

89 420SEL 210k --- The 420SEL in question here.
91 300D 2.5 Turbo. 241k --- My daily driver up until its deer hit incident.
93 190E 3.0 235k --- My 190E

Keep the 300d, and one other as a spare. I recommend keeping the more boring 190 as they are generally cheaper and easier to fix. Sell the other car and start applying those funds to the long term resto

Once the restoration is done on your grandfathers car, ditch the 190

This is great advice, take heed those who do not like their wallets vacuumed...

The 300D is very clean and nice.. What I aspire my 300D to look like. As mentioned, these cars aren't for the struggling. They're old cars, require work. Once everything is taken care of that's common issues, or age related they're very reliable good cars.

Rust is the killer on these cars though. Fix the 420, daily drive the 300D and keep the 190E as a backup car. Have more than one of these hobby cars is expensive.

The DD that was eating my lunch that I ditched was a 1980 Lincoln Town Car I bought new in December 1979. It had 270K on the odometer, and I had just paid for new suspension $2K new remanufactured long block and heater core replacement that was $3.5K. That was 25 yrs ago.

So then I came across a 1 owner 83 300SD with 93K. I paid $11,950.00 for the SD, and sold the Lincoln for $2,750.00. The SD was a dream come true in a low cost DD I drove to 305K. You'll never regret keeping a non-rusting, MB diesel - W123/126, IMO.

Installing Helicoils requires a drilling jig which could be hard to find.

The Mercedes Helicoils and new head bolts expense is significant.

I was looking back though the 420SEL's documentation. It has some engine work done in the past.

-Both cam shafts and rockers were replaced at about 140K.
-One of the heads had its head gasket replaced at about the same time.


The $3500-4500 quote was for the full job to be done by the shop. I would not be doing anything other than dropping it off.

I had to take some half-day vacation Thursday and Friday so I dropped by the shop to check out my 300D and have them look over the 420SEL to see how the underbody looks.

They were quite impressed with how solid it was and how old it was. They didn't see any major show stoppers. There were two spots that they would like to address that I had ****tily attempted to patch up 6 years ago. They said that they would not hesitate to put money into the car. It's going to be around for quite sometime. Case in point my green 300SD lasted 10 years with significant rust on it even when we first bought it was a rolling/running parts car.

Beyond that I talked to them about doing the valve stem seals as a short term solution until I save up for the valve job. They were actually doing a similar job on a VW in the next bay over.

We did see a significant oil leak coming from both valve cover gaskets. It coated a lot of engine's underside. No leaks in any of the areas that I had previously sealed up (oil pan/sensors).

I also mentioned the A/C leak issue and how I'd replaced all these seals and the condenser, dryer, injected dye but couldn't find anything. Compressor is only 5 years old if that.

He took out his UV flash light and a pair of sun glasses and probed all over the car above and below. He was telling me that if it was the evaporator usually you would see some of the UV dye in the drain tubes as the condensation would tend to wash it down there. He saw nothing in them.

We walked back over to the a/c compressor and found a good amount of dye around all three sections of the unit. He said there may be more up against the engine block. He said that was a pretty common leak point for that style of compressor.

So I think most of my major issues on the 420 are addressable. I am going to have him do valve stem seals ASAP. I am going to park my freshly painted 300D (when he is done with it) for the winter as I have a few other engine things to take care of before I put it back on the road..which means I'll be daily driving the 420SEL..and burning oodles of oil.

I took a bunch of photos too.

2016-12-09 W126 420SEL Underbody Inspection - Album on Imgur

James, it looks like you are missing a cover piece for the fuel pumps and fuel filter because normally they are fully enclosed. Is the sound encapsulation panel under the engine missing, or simply removed for the inspection? I agree that the underside of your 1989 420SEL is in good shape considering its age and mileage. Your tech's comment about UV dye being visible in the evaporator drains if it has failed is correct. That would be a "show stopper" for me ... BTDT and it is very costly to replace the evaporator.

I had 293,000 on my '85 380SE with the odometer still clicking when I sold it... she started to have a faint knock, but I was still driving her everyday. lol.

I bought my '88 300SEL in 2007 with 153,000 on the odometer which broke shortly after. I estimate we are up to about 200,000 on it now. It has been my moms car since 2011 and she does not drive to much. We should have got that odometer fixed, but we didnt.

Good luck to the OP... I guess it depends on how much you like the car, but again only if it is solid. If is rusty, I would find a nicer one and perhaps use all you can off of your current car or just sell it.