What is hands down the most reliable, gets the most mileage and life out of the car, w126 model? Thinking about buying one and want it to be reliable and get the most mileage as I want to keep it for awhile. Thanks!

 

Your question is difficult to answer. While my experience with the 300sd has been excellent(1982-210,000miles-1984-400,000+miles), I have also seen many gas models with 200 to 300 thousand miles. You just have to know if you want a diesel model or a gas model. The 126 is in my opinion one of the best cars ever made. Take your time and spend the money up front for a nice one, repairs can be costly. (Stay away from 350sd/sdl, I don't know what mercedes was thinking)

 

All are good (if not abused and properly cared for), but if I were guessing, I would say that the later 300SD (1984-85) or a 86-87 300SDL, with the lowest miles you could find, or a 89-91 420SEL.

If I had to do it over again... I would strive to get a 83-85 300SD / 86-87 300SDL.

 

What is the difference in diesel engines 83-85 300sd versus 86-87300sds? Anything?

Also,why do people not like the 350sd diesel motor.

One more item. Is the 5 cyl diesel better than the 6 cyl diesel?

I was looking on auto trader.com and noticed very low prices for these old SD models

Nickel Mania

Nickel Mania

 

I am not sure... there may be no difference in the engines. Also- the 78-82 300SD should have the same engine as the 83-85 300SD. I simply said 83-85, because many people like to get the last couple of years of a particular body style that had the less "bugs", but I think that even the first 300SD's were virtually the same. There seemed to be no recall issues. At this point in the game- since they are now getting fairly old cars, I think it best to find the lowest miles, best well-kept model out there.

I think the 350SD is a less desired engine, because I think I have heard that it was more prone to head gasket failures or something? Someone correct me if I am wrong.

Good luck!

 

Here we go. The '81 - '85 300SD cars had a 5-cyl cast-iron eng, turbo diesel. The '86-'87 300SDL had a 6-cyl aluminum head turbo diesel eng. The 300/350SDL cars have a computer.

The 350 SD/SDL engines were made by MB increasing the stroke of the 300SDL engine, therefore increasing the torque. The rods seem to bend from the increase in the stroke/torque of the engine. Most were replaced under warranty by MB.

For reliability and ease of repair/parts, I'd go with an '83-'85 300SD. For comfort, bells/whistles, I'd go with the 300/350SDL. The extra long wheelbase of the SDL is a major PLUS if you have kids or haul people around frequently.

Jay

 

Jay, great post! After reading all the post, I believe the 81-85 300SD 5cyl is probably the best. Here is the big question. Can you get that reliable 81-85
5 cyl diesel in a long wheel base?

Nickel Mania

 

I don't think so. The designation of SEL that I've seen before the '86 model year in the w126 chasis, was the 500SEL. This model wasn't really a long wheelbase car. It was only a luxury option, from what I'm aware of.
The REAL long wheel base models are the '86+ SDL/SEL models. Besides, the 5-cyl turbo diesel doesn't have the torque that the 300/350 SDL has to push the big w126 chasis.

 

Thank you your help Jay. Would you say your 1987 SDL engine is as reliable as an 1985 SD? I actually like the look of your 1987 SDL better than the 1985. Just want to know is your engine is as good as the 5cyl. You get a lot of MB folks saying the 5 cyl is the absolute best. I dont Know though.

As far as back seat leg room goes, I want more room for the kids. I also own a 2007 MB E Class Saks 5th Avenue Edition. It does not have any back seat room.I love my new E but my adult passengers hate it when they ride in the back.

Nickel Mania

 

The 1981-85 SEL models are indeed long-wheelbase, no different than 1986+.

 

I was speaking of the diesel. No long wheel base diesel 81-85? Right?

Nickel

 

jay 123 wrote:

"Here we go. The '81 - '85 300SD cars had a 5-cyl cast-iron eng, turbo diesel. The '86-'87 300SDL had a 6-cyl aluminum head turbo diesel eng. The 300/350SDL cars have a computer."

Jay, I don't believe this is correct. I have a diesel resource at home (on the road right now) and I will double check, but the engine in the 300 SD was a 5 cylinder turbo diesel throughout the 126 model run (until the 350 appeared), with various enhancements to engine management as the years wore on, but very modest changes overall. That's why it's such a tank motor -- they were making it so long they worked out all the bugs. The same engine, which appeared in the 116 S class, had some initial teething problems, nothing that serious. Since the 126 is a better overall car, it pays to get the 5 cylinder turbo diesel in the 126 body. Good luck!

The 350 (available in SD and SDL trim) was a 3.5 liter 6 cylinder diesel that suffered from premature bore wear. Avoid this model.

Early 3.8 v-8s (81-83) have a single row timing chain which should be upgraded by 100k or it stretches and can cause interference. Most cars in the hands of enthusiasts have had this done already. The 3.8 is otherwise a very good motor, albeit one of more modest output. It is alloy, and has the advantage of not having the driveability issues of earlier v-8s, which suffered such issues due to newly imposed emissions controls. Early in the life of the 126, I think until US MY 1983, the 380 was the top of the line, available only in SEL trim. In 1984, the 500 sel joined the lineup and the 380 became the second most expensive S, and was available as the 380 SE only (I believe -- it's been a while). The 5.0 liter engine was made for one year in the US, 1985, and had 184 hp (500 sel trim only). The 560 joined the lineup in 1986.

The 4.2 v-8 is a bigger version of the 3.8. The 420 was only available in SEL trim. More power (201 v. 155) is the most noticeable difference, with not much of a fuel economy penalty. The 560's (again, started in '86) power advantage over the other motors is substantial (238) and the torque curve makes it feel more powerful than the numbers would suggest. The 560 has powerful acceleration, even by today's standards. It's also a pig on gas, but if you are driving a car in this bracket when new, I guess you shouldn't care. (But times have change, I believe.) None of the 126s, except for the diesels, really can manage above 20 mpg highway, for that matter.

Finally, you have the 3.0 straight six (177 hp) that appeared in 1988 - 1991 in 300 SE and SEL trim. This is an excellent motor as well -- extremely durable. It needs to rev to make power, however, and this car needs some encouragement, or a heavy foot, to get it quickly up to highway speed from a standstill. It's not slow, it's just that this was before various valve timing and other engine enhancements flattened the torque curve. Most Americans aren't used to revving the motor in their car to 3500 - 5000 rpm to get it moving. It can handle it. It's a lot like the BMW straight sixes of the same generation -- good power but they like to rev.

All of the MB v-8s of the 116 and 117 series are good motors, but they are suceptible to camshaft wear, especially if the oil is not kept clean. Other than this, and the standard issues that can effect any engine as it ages, these are robust motors, and can go 200k miles or more with proper care. I think the sixes last longer even. The diesels -- the sky's the limit if you maintain them. The thing that usually kills 126s is not the motor, but the fact that the rest of the car has been so ragged out by a certain period of time that they are simply not nice enough to repair, because they are still expensive cars to fix.

The advice I always give people, when asking this question, is to find the lowest mileage example you can (not a garage queen) with a documented service history from a MB dealer or MB specialist shop. Have it checked by that same type of shop (but I am starting to prefer the specialist shops for the 126 since a lot of the dealers in my area have techs who look like they were 3 years old when these cars were new. I want an older guy who has worked on the 126) and if it gets an "OK" you should be good to go. Maintenance is expensive, but if you find a rust free example with service records, these cars are the ones that helped build MBs reputation. In my opinion, they are some of the best cars ever built. You just want to start with a good one, because they are also some of the most expensive cars to rebuild. But that won't be necessary if the prior owner was conscientious about maintenance.

 

Check again guy. The 3.0 6-cyl turbo diesel (603) was only made from '86 -'87. The 3.5 turbo diesel came out around '90. The turbo diesel 5-cyl (617) was made from '81 - '85. Everyone can attest to this.

The '85 500SEL is not the same as the '86+ SEL/SDL body. It does not look like the same car, eventhough it is a W126 chasis.

Just find the best model that you can afford.

I've had no mechanical issues with my car, except the turbo. Everything else is pretty much past its life cycle. But its paid for and its mine. If anything were to happen to my 300SDL, I would most definitely try to find another since I would know exactly what to look for.

 

Jay, what diesel was used in the SD 88-89? I noticed you left those two years out of your comments in your first paragraph.

Jim

 

The W126 chasis didn't have a diesel during those years. The W124 chasis (E-Class) came with a 5-cyl turbo diesel eng (OM602) during those years. But thAT ENGINE IS nothing LIKE THE OM617 from '81 - '85. It is the same as the OM603 6-cyl turbo diesel aluminum head engine, except one less cylinder.
The OM602 also came in some 190Ds in turbo and non-turbo versions.
Instead of the diesel engine in the W126 cars, MB came out wih the 300SEL beginning MY 1988.

Hope this info helps all.
Jay

 

For me the 1986-1991 Gasoline 420 or 560 has proven itself to be most reliable. Some say the diesels last longer but honestly I could not deal with driving a Mercedes without the performance of the V8. The older 85 and under 500 series is also a nice vehicle that I have seen get real high miles without too much problem however they are not as nice as the 89-91 420's and 560's in my eyes. Gas milage for a V8 is about 14-17 MPG so says the window sticker.

 

The most reliable - simple, it's the one that has had the best maintenance.

Any W126 will last essentially forever with great maintenance. 400-500K miles can be had by any of the models, IF taken care of properly. Buy the model that blows up your skirt only after a thorough pre-purchase inspection, then take care of it.

Mike R.
'87 570SEC 200K miles
'87 560SEL 240K miles

 

You'll see the most miles on 617 turbo d's. I would argue this was the most indestructible engine Mercedes built for their consumer market. The amount of neglect and abuse these engines will take while continuing to run reasonably well is @ times utterly astounding.

Jonathan

 

I own many W126's and I can honestly say best car I have ever owned or driven,

If interior space a big plus, then look at the long wheelbase models, I had a 1985 500 SEL, with a 617 (5 cyl diesel in it) that I just sold, Space inside is excellent, no need to worry about moving your seat up or anything.

If fuel economy is a big plus look at the diesel models, typical milege of a 300 SD, 1982-1985 is 25 MPG, in my car over 2 years I averaged 28 MPG,

The best of the best in terms of the previous two conditions, is the 86 and 87 SDL. I have one with about 400K miles, on it, The engine must have been well taken care of, if it was overheated the original head will crack, the vacuum pump must be changed to the newer version or it could grenade the engine. the biggest downside to this model is desirablity, a good one will run you atleast $4000 or more.

A good SD can be had for between 2000 and 4000, with 4000 bringing a near perfect example.

These prices are relative to my area, and they do tend to differ accros the countries.

In terms of gassers, they are all good engines but do demand some preventitive maintence, timing chain tensioners and rails, They were to complicated for my simple mind so everytime i get a gasser i swap it out for a diesel,

Im building 2 diesel SEC's at present.

Oh and gassers are quieter and faster.

 

IMHO, those prices are quite cheap.. Any 3-4K examples of 300SD's I've seen come into the shop need on average 3K+ worth of work. The only one that came in that only needed minors (fluids etc..) cost 10.5K, had 90K on the clock/one owner etc, etc..

I've seen excellent examples of SDL's bring over 10K as well.

Jonathan

 

Well Maintained Late model 1989-1991 gas models are the way to go.
I have an 84 500SEC, euro of course, with over 400k miles on it and the head has never been off. It ia an all original valve train and it runs like a raped ape! Just keep the oil changed and the timing chain replaced every 100k.

Maintained though is the only way to buy these cars.
These cars are all expensive!
Just the beat up ones are just that beat up.
Bruce
BENZITCH
PS Look at the price of diesel, and the performance you get from it.
Gas all the way!

 

Hello All folks,
I have a W126 1990 300 SE having 200000 miles driven on it. I am facing some problems with this car.
First of all can some one tell me that how fast I can drive this car comfortably.
Secondly the car gains speed very difficultly, on a run of about 5 kms with full throttle the car can only gain a speed of 100 km/h. I have recently replaced the plugs and ignition wires as well but no use. Can any one guide me with the possible faults.
Thank you.

 

300sd hands down the best engine.