Quick question about 1990 300SEL - PeachParts Mercedes-Benz Forum

Hit Man X · #1 06-08-2009, 01:08 AM

Quote:

Originally Posted by nickofoxford

Thanks Hitman,

Great, a gas powered 240D!

The guy says it needs the transmission rebuilt, but I was thinking something along the lines of adjusting the vacuum and cable, because I've done both countless times between the 240D and my friends 300D.

..BUT, now I have my eyes on a beautiful 420SEL to flat out trade the 240D for! (well maybe 500 on top of it, who knows) My main goal is to get something that can handle taking me to collage every day for the next two years on the hilliest damn roads possible without lugging like crazy like good 'ol Betsy does. I mean it gets great mileage until you're climbing hill after hill with a parade of mad cow disease office workers. Not to mention passing amish horse drawn parephenalia left and right ..uphill

I wanted to do the whole biodiesel thing, but will collage, work, homework, and SWMBO.. time's going to be limited. Biodiesel can wait until after collage.. And I gotta say these w126's are pretty slick

.

Collectively I've figured out that the timing chain is the "achiles heel" of the w126, especially the V8's. The 420SEL has 260,000 or so miles so should I be concerned? What other major problems or little petpeeves should I look out for in a 126? Anyone feel free to chime in.

Never drove the 240D I bought, just lost interest. At least you know what to expect with it and has more torque at 2000rpm than the M103 does. AND in a much lighter car. The 300sel is just a turd for the US market as delivered, with a five speed it'd be great and better yet in the SWB. Should have been 300se or 300e only here. The damned thing @ 70mph is around 3500-3600rpm buzzing along to keep the car going.

Bottom end on the V8s pretty much lasts and lasts, well the top end does too if maintained. From what I gather not until into the 300k area do you have oil consumption issues. I'd roll a chain into it and swap the guides, that's the key as OE guides get brittle with age. MEYLE makes aluminum backed guides for the M116s so they never fail again and of course the chain will be stretched by this point in time... chain failure is due to guide failure. Also do the cam oiler plastic retainer stuff. Peek the front main, if it leaks swap it when you have time. Oil leaks are just a pain and can/do create vac leaks.

V8s need specific plugs, non Resistor. BP5ES NGK or W8DC Bosch from memory. And of course quality cap/rotor.

V8s like to leak oil from the oil level sender, $2 for the o-rings on the next oil change as you have to drop the lower pan. They like a heavier oil too like a 5/50, 15/50, whatever.

They start in second gear, but for a few hundred you can get a box to be rid of that nonsense. Trans is the same autos as the others, 722.3 Just service it on a regular basis and make sure it shifts crisply but not harsh.

They don't get 100% WOT stock, the rod in the back has some spring in it to prevent it. Just squish it in a vice for 100%.

1985+ cars have more efficient A/C condensers already which is good and bigger aux fan for better cooling, the '89+ cars had dual fans and updated interiors.

The auto climate can be a pain until you fix it, it's easy. Usually the car needs a new climate head (just get a Programma reman used from ebay) and you usually have three pods that'll leak. They're behind the glove box and take maybe an hour your first time... these are the dual diaphragm units.

The CIS injected cars do not like vac leaks (well what cars do?), as much of the rubber is very brittle after 20 years or more. To check easily, see if the ECONOMY gauge is pegged left at hot idle in P/N... it should be. Also, put it in B and FLOOR it from a dead stop. It should just take off without hesitation.

W126 LWB cars love rear sag, this is due to tired springs, old shocks, old rubber. Just do it all at once and motor on. Brakes are the same as on your W123 basically (style/function just bigger/more efficient on 126). Front end is the same setup, hard to align if rear sags and front is old.

The 300sel/420sel/560sel are all about the same in economy as pointed out. The 300sel buzzes and lugs, the 560 has enough torque to stay under 2k most of the time, and the 420 is like the 560 but about 50lb-ft less... plus less crap to fail.

All I got for now.

nickofoxford · #2 06-08-2009, 02:16 AM

Quote:

Originally Posted by Hit Man X

Never drove the 240D I bought, just lost interest. At least you know what to expect with it and has more torque at 2000rpm than the M103 does. AND in a much lighter car. The 300sel is just a turd for the US market as delivered, with a five speed it'd be great and better yet in the SWB. Should have been 300se or 300e only here. The damned thing @ 70mph is around 3500-3600rpm buzzing along to keep the car going.

Bottom end on the V8s pretty much lasts and lasts, well the top end does too if maintained. From what I gather not until into the 300k area do you have oil consumption issues. I'd roll a chain into it and swap the guides, that's the key as OE guides get brittle with age. MEYLE makes aluminum backed guides for the M116s so they never fail again and of course the chain will be stretched by this point in time... chain failure is due to guide failure. Also do the cam oiler plastic retainer stuff. Peek the front main, if it leaks swap it when you have time. Oil leaks are just a pain and can/do create vac leaks.

V8s need specific plugs, non Resistor. BP5ES NGK or W8DC Bosch from memory. And of course quality cap/rotor.

V8s like to leak oil from the oil level sender, $2 for the o-rings on the next oil change as you have to drop the lower pan. They like a heavier oil too like a 5/50, 15/50, whatever.

They start in second gear, but for a few hundred you can get a box to be rid of that nonsense. Trans is the same autos as the others, 722.3 Just service it on a regular basis and make sure it shifts crisply but not harsh.

They don't get 100% WOT stock, the rod in the back has some spring in it to prevent it. Just squish it in a vice for 100%.

1985+ cars have more efficient A/C condensers already which is good and bigger aux fan for better cooling, the '89+ cars had dual fans and updated interiors.

The auto climate can be a pain until you fix it, it's easy. Usually the car needs a new climate head (just get a Programma reman used from ebay) and you usually have three pods that'll leak. They're behind the glove box and take maybe an hour your first time... these are the dual diaphragm units.

The CIS injected cars do not like vac leaks (well what cars do?), as much of the rubber is very brittle after 20 years or more. To check easily, see if the ECONOMY gauge is pegged left at hot idle in P/N... it should be. Also, put it in B and FLOOR it from a dead stop. It should just take off without hesitation.

W126 LWB cars love rear sag, this is due to tired springs, old shocks, old rubber. Just do it all at once and motor on. Brakes are the same as on your W123 basically (style/function just bigger/more efficient on 126). Front end is the same setup, hard to align if rear sags and front is old.

The 300sel/420sel/560sel are all about the same in economy as pointed out. The 300sel buzzes and lugs, the 560 has enough torque to stay under 2k most of the time, and the 420 is like the 560 but about 50lb-ft less... plus less crap to fail.

All I got for now.

Shopping list so far: non resistor plugs, fluids, timing chain and guides, more R-12 (just in case).

What does this majestic tranny box do? A few hundred bucks can be bypassed if it's electronic im good with that stuff

86560SEL · #3 06-10-2009, 01:23 AM

Quote:

Originally Posted by Hit Man X

W126 LWB cars love rear sag, this is due to tired springs, old shocks, old rubber...

I have noticed this too on alot of the W126s, even the SWB models. My '85 380SE sagged a little and I am not sure, but my '88 300SEL looks like it does too... especially a certain way its parked. It dont look as saggy in this photo, but it does appear to be sagging dont it?

Mid May

Mid April