W126 - 1991 300SE Pros and Cons
 

Please enlist pros, cons and things to watch
Consider to switch it to the daily commuter after 3 years of parking

I've owned one for 21 years, so I've seen it all.
You might scan over my posts over the years - S-Class Guru - 90% of my posts relate directly to the 1991 300SE. I need to change my 'handle" though, since I've forgotten most of what I learned about it.

Number 1 con is the transmission gearing - the poor engine just screams at highway speeds. This wears out all the belt-driven accessories, so prepare for pulley/water pump/tensioner issues.
Number 1 pro is the overall durability of the chassis and body and general driveline - indestructable.

Details:
- tranny wears out the reverse clutch plates and starts clicking when moving in reverse. Pretty easy to fix if caught early.
- Head gasket scrubs itself to death every 100k and needs replacement.
- valve stem seals leak oil, but once replaced last a long time.
- upper timing cover leaks oil every 50k or so.
- rear main seal dies every 100k.
- injectors go bad every 100k or so.
- climate control vacuum system components go bad.
- Center driveshaft u-joint will eventually vibrate.
- front suspension ball joints, track rod joints, control arm bushings, not to mention tie rods and idler arm bushing kit. Rear subframe bushings bring the rear end back up.
- heap motor mounts do last too long.
- Belt tensioner damper starts clicking.
- brake rotors warp and wear out at 50K.
- Mufflers, mufflers, mufflers.

Anyway, check out all thse posts, makes interesting reading.

DG

I have an 89
 

They are not a bad daily driver. I have been using mine for about 3 years and its been good. It gets a rock steady 20MPG with a mix of ciy and highway driving. Power is an issue with these cars. Its quite quick on the freeway and mine runs at 3000+ rpm at 75mph. Off the line its not so quick and any request for a jack rabbit start will have it shift to first and spool up that M103 so it can deliver.

A few things that I think to watch for in addition to "Guru"s list:

1. Make sure it idles good! If it has low vacuum at idle and shakes a lot it gets annoying. If all the vacuum hoses are good then its a needle in a haystack to find the issue. You can throw $$$ at it and get minimal gains.

2. Air conditioning. If yours works that's great! If not then its expensive and labor intensive to fix. I fixed mine and its a job but nothing time and money cant handle.

3. Fan clutch. If you daily drive in the heat make sure you have a good fan clutch or cooling fan.

4. Parts. Locally sourcing parts is hard in my area. The local napa, autozone and schucks don't have much of anything for these in stock. Plan ahead and order parts from this site or another site and be willing to wait for a better price and better quality.

Pro's

1. Its very comfortable and easy to drive.
2. If you do your own work its not bad to work on. The fuel system needs reading and understanding.
3. Parts prices are not to bad if you order online and can wait a little extra time for them.
4. Has a great heater. It puts heat in the cabin on a frigid day before any vehicle I have driven in the past.

I owned an 89 for a few years. The High revving on the freeway really killed it for me.

If that car had one more gear, it would be the best all around car. Decent milage for the size, decent power. Not any more expensive to maintain than my 300e.

further clarification
 

300SE uses the same M103 engine 722.3 transmission combination as the W124 300e.
W124 260e uses a M103 engine with a 722.4 transmission.

As mentioned previously. The transmissions let these cars down in the comparison of modern vehicles. The transmission is a 4 speed albeit it's set up to start in 2nd gear.
4th gear is 1:1. To select first gear you either need to select it with the gear selector when stationary or give the accelerator the full boot at low speeds.

A 420 does not use much more fuel compared to the 3.0l engine - it doesn't need to work as hard to get the car moving.

Everything pertaining to the M103 engine and transmissions in the W124 300e and 260e are common with the 300SE.

Just go find a V8 powered W126 if you are wanting a gasoline powered W126. Diesel maybe, yet seeing how any of the gasoline ones burn 87 octane just fine (and is about 40-60¢ per gallon less currently)... it is somewhat pointless to go Diesel unless you do extreme freeway driving to potentially offset the cost. You would need to do the cost per mile to see if it is worth it to you...remember, fuel economy drops on the Diesel noticeably in winter due to the fuel blend.

The worst fuel economy I have seen city only is low teens in the summer on the 300SEL. Mid 13s to low 15s, yes that lame. Best freeway was 20-21 around 65mph. These are just poorly balanced, poorly geared cars. Too bad they were never imported with a five speed manual.

Make the V8s start out in first gear and fuel economy is a bit better, same with staying out of top gear (1:1) until on freeway as this just lugs the motor. Also mistimed camshafts are not helping fuel economy nor are vac leaks on the V8s either.

I am pretty sure the 300SE/L's cooling system is lacking... The radiator is smaller than any of the others (plus both hoses on the same side does not seem to help in heat dissipation) along with the clutch fan and I am sure this has to do with its higher temperatures in the summer. Not overheating, but hot enough which keeps that fan clutch locked basically all the time when the A/C is on. The car is absolute slug to drive in the summer. It is a so-so freeway car if you keep the speed moderate (60-65mph) so you keep the buzzing down. I would never buy another M103+W126 car.

Like 'S-class Guru', I have rebuilt or replaced just about everything on the car. It is pretty simple as it is an inline six. The only reason I still have it as everything works and starts every day. With nearly 300,000 on mine, cold compression on all six were between 160-170psi.



A better commute car is a 300SD.

I don't know if I could consider an engine that blows the head gasket every 100k reliable...

-J

Soo the bottom line
 

M103 W126 5 speed combo makes it perfect car.

There is no way to enforce first gear start on 722.3.

Fuel consumption never gets down from 21 mpg

75 mph not a valid speed for this car.

Back to W124???

Actually more W126 questions
 

Are there any 420 SE and 8 cyl cars without hydraulic suspension?

Only the 560's have the hydraulic suspension.

The 420s do not.

I really like the way my 560 rides. When I was looking at w126's, I looked at diesels first, then 420's then I found a 560 in great shape. It has turned out to be a great car. MPG is not that bad and with no car payments I really don't care much about MPG as long as it runs and drives nice. I looked at a lot of 126's and only one was worth buying. Keep looking, don't give up because the first dozen are shagged out. I love my 560.

I have been daily driving my 420SEL. The only issue I have run into was a sticking brake caliper. Gets about 400 to 430 miles per 20 gallon tank. Not too shabby for a 23 year old car with 131000 miles.

Interesting that I logon to this forum for the first time in I don't know when and see this thread.

I've owned a '91 300-SEL - long version - since 1997.

All of the aforementioned issues should be considered. Do you want to deal with these types of problems because sooner or later you will.

You're looking at a 21 year old car. I don't care how well it's been maintained, issues on M103(motor) equipped vehicles go in cycles...ie...valve stems-oil consumption - seal at front of motor-oil leak - worn out belt tensioner - blown/leaking head gasket, inadequate a/c cooling(you're in Canada-maybe not an issue).

It's one thing after another. In all but one case - I've always made my own repairs. Are you up for that?

If I had it to do over and REALLY wanted a 126 MB, I'd look for a 420SE/420SEL. Over the years on this forum, I've seen far fewer complaints about that model.

Just my 2 cents.

Thanks you all
 

I do consider one specific car.
Also consider importing 5 speed from Germany / Belgium / Finland, which is not financially sound, but fun option.

It is Canada, but summers are pretty hot and Toronto has traffic issues, so cooling capacity is important and I was my AC on in the traffic jam.

No winter driving.
During summer months covering 16K miles / year.
Can afford 21-23 MPG range on the highway, preferably not more.

So - back to 124 or Future is unknown country and it is W126?