Slow leak in struts? - Mercedes Forum - Mercedes Benz Enthusiast Forums

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Old 08-21-2007, 01:17 PM
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Join Date: Aug 2007
Posts: 5
Default Slow leak in struts?

2001......s430......44,000 miles....just had service B in shop (MB dealer) for non working fan sensor which caused overheat.

Dealer advised that front suspension struts have a slow leak and need to be repaired, which I assume is some type of a seal replacement ($600)

We are not too car repair savvy......questions:

Would it be unusual for the fan sensor and leaking struts both to be overlooked during the service B?
Should this strut issue occur at 44,000 miles?
Would it be dangerous to drive with a slow leak?
Can the leaking fluid be replenished?
MB dealer states that without repair, strut replacement would be forthcoming at $1200 per side, $2400 total....sound right?

Thanks in advance
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Old 08-22-2007, 09:28 PM
Join Date: Jan 2006
Posts: 76
Default RE: Slow leak in struts?

the struts leak down when the car is raised up on a lift. in some instances they will pump back up and hold- in others they wont. it's not a fluid leak it's air leaking out. wouldn't have been noticed during the b service because they probably weren't leaking at that time. it's one of those things that happens maybe 1 out of 30 times you raise an s class off the ground. as soon as the car is lifted you hear the air blow out.
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Old 08-24-2007, 02:38 AM
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Join Date: Dec 2004
Posts: 2,409
Default RE: Slow leak in struts?

Your S Class is not supported by conventional springs. You have cylinders which are pumped up with air.
Air is supplied by a pump located underthe RH front wheelarch liner. You may have heard this working and wondered what it is. If you move the HEIGHT switch on the dash this will cause the car to order to go through water etc...and operating this switch will cause the pump to work.

The pump is designed to add air to maintain the correct ride height as an automic process (Note. the car lowers itself on the highway at about 60 mph.) and once the car slows the suspension will rise once again to normal height.

Some air will leak from the system even when new and this is quite normal. For instance if the car is left in the garage for a week or so it may well be very low when you come back to it and require you to wait till the car reaches the correct height before driving away. A delay of 30 secs or so.

However the pump cannot cope with a BIG air leak and if called to do so wears out and requires to be replaced also.

UNFORTUNATELY the air struts are VERY expensive.

In some instances air leaks from a faulty "seal" at the top of the strut (common problem). This can be repaired without changing the strut.

Strut (spring) replacement depends on how often the pump runs and how often you get the "DO NOT DRIVE CAR TOO LOW WARNING.

The dealer may be correct that it is adviseable to replace the struts as a precaution BUT it all depends on who pays.

Suggest you get a quote for the job and then decide. I guess you will decide to let things continue for a little longer unless the requirement for change is Black and White.

My car has done 120k miles on original struts and pump although the pump did need to be cleaned because a one way valve was clogged with carbon dust. Low mileage/ infrequent use can be more demanding on the pneumatic seals in the strut (surfacerust removal) than high/frequent use mileage.

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Old 08-24-2007, 06:42 PM
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Join Date: Jul 2005
Posts: 146
Default RE: Slow leak in struts?

[sm=icon_cheers.gif]great explanation stuart.
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Old 09-04-2007, 10:13 PM
Join Date: Sep 2007
Posts: 6
Default RE: Slow leak in struts?

please take a visit here... may give little idea..
Despite their small package size and high force capability, one common fault with conventional pneumatic or gas (nitrogen-filled) struts is that they are susceptible to slow leaks or punctures during operation, resulting in a load loss over time. And they are not designed to withstand harsh environments such as dust and high temperature applications.
Most gas mercedes strut manufacturers offer various pressure ratings, forces, strokes and end fittings to meet certain applications within a small package design.
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