Air ssuspension lines
Thread Starter
Junior Member
Joined: Apr 2022
Posts: 36
Likes: 11
From: michigan
S550
Air ssuspension lines
Two part question:
For those who replace air struts (especially mechanics who do this often)
1. Do you simply disconnect the air line from old strut and reconnect by just screwing it on or do you cut the line perfectly straight and use a new ferrrel?
2. If you have replaced the valve block and unscrewed the brass connecters, do you put pipe sealant on the NPT threads when you screw therm back in?
How critical are the above and will this eliminate any very slow leaks?
For those who replace air struts (especially mechanics who do this often)
1. Do you simply disconnect the air line from old strut and reconnect by just screwing it on or do you cut the line perfectly straight and use a new ferrrel?
2. If you have replaced the valve block and unscrewed the brass connecters, do you put pipe sealant on the NPT threads when you screw therm back in?
How critical are the above and will this eliminate any very slow leaks?
MBWorld Fanatic!
Joined: Aug 2014
Posts: 5,322
Likes: 1,678
S500
if it looks stressed about to snap and you have the olive change it ?
early cars had a damaged pipe on the rear from bad build - scored as they dragged it through - merc say never do a bodge inline repair
and many seem to find issues around the valve block
and recent post one guy found some strange valve that doesn't work on the new units he was fitting
20 years of under bonnet heat ought to give a clue as whether its time for replacement
early cars had a damaged pipe on the rear from bad build - scored as they dragged it through - merc say never do a bodge inline repair
and many seem to find issues around the valve block
and recent post one guy found some strange valve that doesn't work on the new units he was fitting
20 years of under bonnet heat ought to give a clue as whether its time for replacement
Super Member
Joined: Jun 2025
Posts: 784
Likes: 249
From: USA
Two part question:
For those who replace air struts (especially mechanics who do this often)
1. Do you simply disconnect the air line from old strut and reconnect by just screwing it on or do you cut the line perfectly straight and use a new ferrrel?
2. If you have replaced the valve block and unscrewed the brass connecters, do you put pipe sealant on the NPT threads when you screw therm back in?
How critical are the above and will this eliminate any very slow leaks?
For those who replace air struts (especially mechanics who do this often)
1. Do you simply disconnect the air line from old strut and reconnect by just screwing it on or do you cut the line perfectly straight and use a new ferrrel?
2. If you have replaced the valve block and unscrewed the brass connecters, do you put pipe sealant on the NPT threads when you screw therm back in?
How critical are the above and will this eliminate any very slow leaks?
Yes, use PTFE tape on the brass NPT threads.
This is critical to eliminate slow leaks.
MBWorld Fanatic!
Joined: Oct 2010
Posts: 5,142
Likes: 1,293
From: Southern US
2010 E550, 273 Engine: 2012 S550, 278 Engine
I checked all connections with soap water spray and found no leaks.
I did not use any tape in the threads as there is no need for it. The connection seals with the end of the brass "nut" you turn so pressurized air never sees the thread.
The air tube cannot be cut forever as it does not have extra length so the best thing to do in my opinion is to use the old nut and ferrule and do the tube cutting for the new connection if it is needed. I have not seen a leak on any of the connections with my two cars and I even changed the valve block on the E550 while troubleshooting the problem with the car rear lowering down before I bought ne new air springs for it.
My advice is to use the old connectors and go with new when necessary after soapy water spray test so indicates.. Chances are the old ones are just fine.
