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Old 08-20-2017, 11:53 AM
1970 Merceds 300SEL 6.3
Join Date: Aug 2017
Location: Boston, MA
Posts: 2
1970 Mercedes 300SEL 6.3 need help

We would like to ask your group to help to find out why our 1970 Mercedes 300sel 6.3 is suddenly having problems after a tune-up.
Our nonprofit organization has a donated 1970 Mercedes 300 SEL 6.3 that has run well for 4 years except for two things:
1. a very slow leak in the air suspension. After the car runs for about 20 minutes it is raised up fully, and it takes about 5 days for the air ride to deflate.
2. After driving for about 2 hours, it has always stalled out. We then could put the gas pedal to the floor and restart it, blowing smoky exhaust out the back for about 15 seconds then drive it again for 2 hours.
We have been using it for four years as our showcase car for our Cars4Kidneys program. It looks great and had no need to put a lot of money into it
Last week we brought it to our local mechanic to tune it up to solve the stalling problem.
After the tune up, it drove great, and we drove it back to our location about 1 mile away. Again, after about 5 days the air ride deflated – as expected. So we started the car and ran it – after about 2 hours the car did not raise up and there were other problems that did not exist before.
1. The car doesn’t rise up and it seems the compressor does not run.
2. The engine runs very hot now
3. The vacuum door locks now do not work
4. The electric fan in front of the radiator now does not run,
5. The battery is now reading 17 volts on a digital voltmeter.
I just talked to the mechanic and he said he did nothing electrical and he did the following for the tune up
1. Replaced the distributor cap
2. Checked the points and condenser
3. Replaced the distributor rotor
4. Repaired three ignition wires from distributor cap to the spark plugs
5. Retapped the sparkplug on the second or third cylinder on the passenger side
6. Replaced all the sparkplugs
7. Cleaned the throttle body
8. Put duct tape around the air intake boot that was torn
I talked to a great gentleman, Martin Werminghausen, who is an expert on the air suspension of the Mercedes 300 , 600 and 109. He told us to first drain out the air tank then pump up the air suspension with a compressor to see if there were any new serious leaks.
We did and the car went up great and is still up after 24 hours. Which rules out any new leaks.

Can you help us with this question or put it out to your group to see if they have an answer? Thank you for your help.


Paul Dooley
766 Turnpike Street
Canton, MA 02021

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Old 08-20-2017, 07:43 PM
Registered User
Join Date: Dec 2002
Location: New Castle County, DE
Posts: 1,041
Paul, go here for help: Site dedicated to Mercedes 600, 6.3, and 6.9 (all have M-100 engine designation).

'79 6.9 Sold (after 27 years of ownership)
'83 280SL, 5 spd.
'94 E320 Sdn. 5 spd conversion
'95 E320 sedan
'02 E320 Sdn.(on loan to mom!)
'87 300E (5 spd. conversion) Sold
'05 E500 Wagon
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