Rear Suspension Drops - Sometimes
 

Every so often I will come out to my car and the right rear shock will have dropped. Sometimes after about a half hour. Sometimes not for a few days. Today both rears dropped. The car always lifts right back up again once the car is restarted.

If the shocks have leaks wouldn't they leak all the time?

What should I look for?

Thanks

Eric

I have an '03 E500 and my 2 rears do sag down occasionally. Sometimes after one night, and sometimes after a weekend of no driving. But yes I have the same situation, once I start the car up they rise back to normal ride height.


A few months ago they sagged down really bad, so I installed a new airmatic pump. Seems to be much better but I am guessing that is not a permanent fix.

With small leaks the compressor will keep lifting the car till it burns out.
You might want to take spray bottle with soapy water and test the accessible fittings for leaks.
Compressor rebuild kit cost about $40 and don't expect the compressor to last 20 years without service.
See my topic about compressor service.

I figure there has to be a leak but why does it happen only sometimes?

Thanks

Eric

Most likely internal leaks.
From what I figure out, the system beside electrovalves on the bags also has check valve on compressor.
So it takes combination of 2 leaks to drop the pressure.
Sometimes it happens more, sometimes less.

The rear air bags can crack where the rubber folds on the bottom. The crack will not let enough air out to sag when you drive it frequently because the compressor can keep up. The problem will become the cracks get so large the compressor can't keep up enough to raise it or it will cause the compressor to run full time and burn out the compressor. Don't wait to find this problem You might consider putting the car up on ramps then use soapy water squirt on the air bags paying attention to the bottoms for leaks but check the entire bag

Is Bagpipingdaddy on eBay the get to get the best rebuild kit from?

Thanks

Eric

I often think that a hypodermic needle filled with Slime and injected into the rear bags would solve this problem. At least until the crack gets really large and blows out completely.

I have not tried it because I don't know if the Slime could get into the air line/valve and cause a problem. But it would interesting to try on something that is going to get a rear airbag replacement anyway.

I did use slime a lot on trailer tires and it works well on something that turns. Sure it made very good job on wheelbarrow tire.
Don't think it would work on airbags, unless the leak is at the very bottom.
That beside having slime spitting back into air dryer and check valves.
I doubt those are air bags leaks.
I have over 20+ years old air bags on my 15 tons motorhome and they hold the air for weeks if not months.
Per my experience, once the rubber has a hole it goes very fast from there and is not intermittent. Putting some load on the hole might slow it down, but will not stop the leak.

Ok. So this really only happens when I drive to work early in the morning.

When I park the car in front of my house at night it doesn't drop but almost every afternoon after work the right rear has collapsed. I don't have time to soap and observe the right rear shock as I am at work.

Quite frankly I don't think it's the shock but I could be wrong.

Does this make sense or is there some other component that I should be looking at?

Thanks

Eric

How cold you get in the morning?
I had the situation with my wagon, when I pick it up on East Coast and drove home.
After very cold night (20'sF) the loaded wagon would stand up in the morning just fine, but few minutes later the rear dropped and I got red warning. I drove it few miles where I could get internet connections and in the mean time it got warmer, sun went up and after about 1/2hr the suspension pumped up.
The only explanation I could come up for it was that in freezing weather compressor would not move, or water froze in the lines and idiot-programmers made a program that in such situation would dump the air from the bags.
That is why I serviced the compressor lately and even after very dry summer the drier on it was soaked.
I made pictorial about compressor service and I would advise you to do it.
Cost $50 for rebuild kit and new filter and about 2 hr for the job and silicate baking.

It only gets down to around the mid forties so I don't think moisture is freezing in the lines.

Any other ideas?

Thanks

Eric