Air bag suspension info

1965 - 1972: 250S, 250SE, 300SEb, 280S, 280SE, 280SEL, 280SE 3.5, 280SEL 3.5, 280SE 4.5, 280SEL 4.5, 300SEL, 300SEL 6.3, 300SEL 3.5, 300SEL 4.5
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Simon Dove
170s
Posts: 175
Joined: Tue 20 Dec, 2005 10:49 pm
Model you own: w126
Location: Kensington Grove, QLD

Air bag suspension info

Post by Simon Dove » Tue 27 Dec, 2005 11:27 am

Air bag saga.......

The front air bag suspension on my 71 300sel drops down to the stops (more left than right) overnight and takes a fair while to regain height when i start the engine. The warning light in the cabin remains on nearly all the time.

I removed the hose from the engine driven compressor to check its out put and it seems to be low considering the operating system pressure is somewhere in the 130psi mark and i get a greasy residue in the storage tank.

As far as i see im up for a new/reco air pump and a master air valve to stop the air leaking overnight, i accept that it will drop some height overnight but what is acceptable? Would it be fair to assume that both front sides going down would point to the master valve than the levelling valves?

Any input from anyone who has had a similiar problem would be great.

Cheers,

Simon (air bag learner)

:?
71 W109 300SEL 3.5
78 W123 300D
88 W126 420SEL

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bahnstormer109
C 111
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Joined: Thu 23 Jun, 2005 7:01 pm
Model you own: w109
Location: Brisbane

sinking ship

Post by bahnstormer109 » Tue 27 Dec, 2005 12:19 pm

Hi Simon,

ive had my 300SEL 3.5 for 3 years now and so far ive replaced all 4 airbags and the pressure sensor under the bonnet.

my car seems to sink erratically, whereby it has had periods when the front would sink in a few hours to it would stay up for a couple of days.

for a time both the front and the back would sink after about a week.

at the moment, though ive been checking on it every weekend and taking it for a run around the block and it hasnt sunk AT ALL in a couple of months with it only being started once a week.

the only thing i can attribute this to is keeping the air tank in front of the front pass. wheel empty of oil and condensation, and keeping the little tank under the bonnet full of metho and a good, fast long run. i topped up the metho bottle and took the car for a great long run a couple of months ago and its been fine ever since.

try this first and see if theres any improvement in how long it stays up then go searching for leaks. they all take a while to pump up, mine takes about 10 mins. i just let it idle until the engine starts to warm up a bit then ill raise the revs and it pumps up much faster then.

also replace your rubber airbags if they are looking really cracked, because they can burst. one popped on mine when it was sitting in the driveway and im glad it didnt happen while i was driving!

a lot of people complain about the air system but ive been happy with mine. be patient with it, and give it lots of love and excercise and get to know how it works and what its quirks are before you panick and start spending heaps of money on it.

how long have you had the car? and was it sitting idle for a time before you got it? if its been sitting around not being used its not surprising its being tempremental. these cars really need to be used regularly.
Paolo
Brisbane

72 300SEL 3.5
82 380SEL
84 280CE
86 560SEL
86 230TE
A good Benz these days is hard to find, so please be gentle with this Benz of mine.

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Simon Dove
170s
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Joined: Tue 20 Dec, 2005 10:49 pm
Model you own: w126
Location: Kensington Grove, QLD

Post by Simon Dove » Tue 27 Dec, 2005 5:47 pm

Hi Paolo,

Thanks for the info, its good to hear that the sel has a mind of its own regarding the suspension, gives it a tad more character! Ive only had mine about 6 weeks and as you stated nothing is normal, sometimes it works as advertised and sometimes not.

I will take your advice onboard and try the metho and take it on a decent run.

Once again thanks for the info.

Cheers,

Simon (air bag provisional)
71 W109 300SEL 3.5
78 W123 300D
88 W126 420SEL

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bahnstormer109
C 111
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Model you own: w109
Location: Brisbane

metho in the suspension

Post by bahnstormer109 » Tue 27 Dec, 2005 9:34 pm

by the way, does anyone know what the metho in the air suspension actually does???

i assume its some sort of antifreeze to stop the condensation in the system freezing, but does it have another purpose?

keep the system clean?
keep seals soft?
Paolo
Brisbane

72 300SEL 3.5
82 380SEL
84 280CE
86 560SEL
86 230TE
A good Benz these days is hard to find, so please be gentle with this Benz of mine.

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OzBenzHead
300 SLR
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Joined: Mon 22 Aug, 2005 10:11 am
Model you own: w126
Location: Byron Shire, Northern NSW, Australia

Re: metho in the suspension

Post by OzBenzHead » Wed 28 Dec, 2005 12:18 am

bahnstormer109 wrote:by the way, does anyone know what the metho in the air suspension actually does???
i assume its some sort of antifreeze to stop the condensation in the system freezing ...
My understanding is that it does just that - by absorbing any moisture that gets into the system, thereby keeping it "dry" and free from freezing (fat chance here in 40 degree summer!).

I also think that it ought to be something more like isopropyl alcohol rather than metho.

The airbag suspension on my '65 300SEC can sag if not cranked over weekly, but it really shouldn't drop noticeably inside of a week; it will, however, just now and then sag in a couple of hours if the car is parked on an unusual angle on a slope (even if that slope is just a steep kerb).
OzBenzHead
Currently owned:
1965 W112 300 SE/C
1983 C126 380 SEC

and formerly:
1955 W180 220a
1965 W111 220 S
1970 W108 280 SE (my first Benz)
1973 W116 280 SE Crayford Estate (previously owned by Rolf Harris)
1980 W116 280 SE
1989 W124 300 E
1992 W201 180 E
1992 W201 190 E 2.0
+ numerous W108 and W116 rolling spares

and prior to my M-B enlightenment:
53 other cars of many nations, but mostly British oil-leakers (including 14 Rovers of the 50s and 60s) cursed by Lucas the Prince of Darkness. First car owned (at age 13): 1953 Fiat. Learned to drive in: 1927 Nash utility paddock-basher & Grey Fergie tractor. Driven distance (logged as at 30 June 2016): 4.6 million km.

CraigB
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Post by CraigB » Tue 03 Jan, 2006 11:08 am

Don't know if this helps, but if you get water in your fuel tank, adding metho to the tank will fix it. I assume the metho combines with the water and makes something that is combustible. Maybe it also makes something that is less compressable? I am sure there are some chemists on here that can describe the process and maybe if there are better products for absorbing water. While working in the UK my car started misbehaving with the onset of winter. I went to a car parts place Halfords and bought new ignition bits and noticed a product there to use if you had water in the tank. I stupidly didn't take note of what was in it but it certainly worked fast with me pouring it into the tank in the carpark and then drove home without a problem.

Just a couple of points on water in fuel that may be of interest to readers(from hard learnt experience!), which often isn't the first thing you think of when having problems. If you get petrol on your hands it evaporates fast and leaves your hands feeling quite cold whereas water doesnt have this same effect. Not that I suggest you dip your hands in that nasty carcinogenic stuff too much but if you get it on your hands in the process of chasing a fault, this effect might be apparent. Also if you are able to look into your carby bowl, water doesn't mix with the fuel and often is quite visible as droplets and 'blobs' in the fuel. Also if you get it in your tank, the water will sit on the bottom (where the outlet is!) and not mix with the fuel. If you have a drain plug and you drain it off into say a large ice cream container, the water will drain off first and you will see a line form when the fuel starts draining off. I did this and then chucked the metho in to fix anything left in a low spot or nook.
Craig Baulderstone
Lurch
280s's
280SE3.5
280SL
350SL
500SEC's
560SEL's

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Hendrik
Mercedes Demigod
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Post by Hendrik » Tue 03 Jan, 2006 1:45 pm

Found this article in regards to metho in the fuel system
http://www.users.bigpond.com/INTERJECT/kcase.htm
Something to think about before stealing the local deros metho.
Just having some leberkaesse and sauerkraut for lunch.

CraigB
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Post by CraigB » Wed 04 Jan, 2006 3:02 pm

wow! Thanks for that Hendrik. I had never used the metho trick on a fuel injected car. I wonder if that product I used in the UK also had lubrication in it? A great article but they didn't address what you should do if you do have water in your fuel in an injected car.
Craig Baulderstone
Lurch
280s's
280SE3.5
280SL
350SL
500SEC's
560SEL's

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Simon Dove
170s
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Joined: Tue 20 Dec, 2005 10:49 pm
Model you own: w126
Location: Kensington Grove, QLD

Post by Simon Dove » Fri 13 Jan, 2006 2:17 pm

The old girl has been off the road for the last 3 weeks because of a terminal radiator failure which gave me the opportunity to have a good look at the suspension. I cleaned and leak tested all of the lines, filled up the "metho bottle" and screwed up the pressure 1.5 turns on the main valve and its going like a beauty!!! It only takes about 2 min to raise to ride height and the pressure warning light now goes off after about 5 min or so. To say the least im wrapped.

Touch wood it seems to be fixed for the total cost of $2 for the metho, free download of the suspension guide from 300sel.com, about 10 manhours and a heap of swearing, cuts and bruises (my garage is small)

Simon :D :D

(air bag P plater)
71 W109 300SEL 3.5
78 W123 300D
88 W126 420SEL

MBChris
B Class
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Joined: Sat 11 Feb, 2006 8:24 pm
Model you own: w901-905
Location: Cranbourne, Vic

Post by MBChris » Sat 11 Feb, 2006 9:00 pm

Welcome to the wonderful world of Air Suspension...

On your car, there is a steel pipe that goes across the front of the engine from the compressor to the air valve assembly. This gets hot, and if the compressor is pumping oil, it will burn the oil, and block the pipe. This is where I would look.

The car should not go down AT ALL. It should not matter where it is parked, of whether it is run or not. They don't go down if there is nothing wrong with them. I have a 1964 300SE LWB, that is now off the road pending a small rust repair and repaint.

It has not been run for nearly 6 MONTHS!

It has not gone down. One of the tyres has....but the suspension hasn't. It will go on blocks when it goes down: I just want to see how long it takes.

By the way, it still has the original rear valve, and John Green rebuilt the front two.

The metho (or any alcohol) is there to absorb moisture. This is not to prevent freezing, it is to prevent rust in the steel valves. It is VERY important, especially if you live in a humid environment that you CHANGE IT REGULARLY! it will only absorb a certain amount of moisture. The receiver under the front left guard should be drained for the same reason once a week, and if it comes up with a fair bit of water, the alcohol should be changed.

Again, not for antifreeze, for rust prevention.

If you do these simple things, and have the valves rebuilt, you shouldhave a wonderfult ime driving in one of the best riding cars of the 70's (or 60's if you have a W112).

Remeber: if the car does sink regularly, you should park it where it will sit on blocks. If you allow it to sink at the front to the bump stops, the leverage that the car puts on the pivots will eventually break the front inner of the lower control arm, with potentially disastrous results if you happen to be braking when it goes. Besides, the lower control arms are now VERY expensive and rare..because they break!

Chris

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