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

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.

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Current
1989 300SE - Siegfried
2010 Toyota Tundra Crewmax
2005 Honda CRV

Gone but not forgotten
2001 F150 Supercrew - The Screw
1966 Ford LTD 390 - The Big G!
1995 Mercury sable
1986 Subaru DL
1982 Ford EXP - my first car

After owning a 300SEL for a couple months now I thought I would chime in on this.

Yep, no doubt.

One little trick that I use occasionally regarding the 2nd gear takeoff is to lightly ride the brake pedal with the left foot when needing to coax a downshift to first. Not recommended as a regular procedure of course, but handy in certain situations.

I would think that the MB engineers would have solved this with simple adjustments in pulley diameters. For example, if the alternator is the same as other models that run at lower rpm, just making the M103's pulley circumference larger (to the same degree as the difference in rpm between the two) should have the alternator spinning at the same speed on both models. If this is not the case, is there a pulley swap and longer belt mod that can be done?

Much of the above also applies across the W126 line, no? Apart from engine/model specific items like head gasket, valve seals, mufflers, etc. of course. My old 300SD had the reverse clicking issue, front suspension & brake rotor problems, climate control gremlins, and so on...

Nevertheless a nice writeup that has been helpful. Many thanks for the tips.

Just out of curiosity, if the biggest issue with 300SE's is the rear axel ratio would it not be possible to swap the axel for one from a V8 if those are different ratios?

- Peter.

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2021 Chevrolet Spark
Formerly...
2000 GMC Sonoma
1981 240D 4spd stick. 347000 miles. Deceased Feb 14 2021
2002 Kia Rio. Worst crap on four wheels
1981 240D 4spd stick. 389000 miles.
1984 123 200
1979 116 280S
1972 Cadillac Sedan DeVille
1971 108 280S

A nicely sorted w124 sedan with the 420 engine is great!

I have had no problems worth mentioning in my 1995 e420.

The mechanic calls it a "stealth" car because it's about 75-80% of what you'd get in an e500/500e with the bulletproof 420 engine (which has a much shorter than the 560 timing chain, so it's not as critical to change out the 420 timing chain every 100 miles as it would be in the 560.)

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1991 560 SEC AMG, 199k <---- 300 hp 10:1 ECE euro HV ...

1995 E 420, 170k "The Red Plum" (sold)

2015 BMW 535i xdrive awd Stage 1 DINAN, 6k, <----364 hp

1967 Mercury Cougar, 49k

2013 Jaguar XF, 20k <----340 hp Supercharged, All Wheel Drive (sold)

Every 100 miles?!? I hope that the fact that it's April 1st has something to do with that statement... ;-)

Bc did that with the 300se that I sold him. I don't remember exactly but I got the impression that the power is a bit too low on the m103 to handle the 2.88? Diff I think he installed. Just required a different driving style and a bit of manual downshifting.

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Eugene

10 E63 AMG
93 300te 4matic
07 BMW X3
14 Ford F-150 Fx2

Could one not adjust the kickdown functions on the tranny to compensate?

Also curious to know what rpm this delivers at freeway speeds, and if there is an online list of ratios used on the various models.

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.

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Eugene

10 E63 AMG
93 300te 4matic
07 BMW X3
14 Ford F-150 Fx2

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.

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I'm not a doctor, but I'll have a look.

'85 300SD 245k
'87 300SDL 251k
'90 300SEL 326k

Six others from BMW, GM, and Ford.

Liberty will not descend to a people; a people must raise themselves to liberty.[/IMG]

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

-J

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1991 350SDL. 230,000 miles (new motor @ 150,000). Blown head gasket

Tesla Model 3. 205,000 miles. Been to 48 states!
Past: A fleet of VW TDIs.... including a V10,a Dieselgate Passat, and 2 ECOdiesels.
2014 Cadillac ELR
2013 Fiat 500E.

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???