300TD Rear Suspension - wondering about mine - PeachParts Mercedes-Benz Forum

tfrain · #1 11-23-2006, 04:23 AM

I bought the 81 wagon about 3 months ago and am slowly working on it. The gentleman I bought it from said the rear suspension had been "worked on" or "fixed" before he bought it. I don't think he knew about the SLS system. I checked the fluid reservoir and it appears near empty. The car rides great with no bouncing or bottoming out or firmness, but I don't think the rear leveling suspension is working. It doesn't seem to sit up any when you crank the car, and when you put a load on it (my 220 lb carcass sitting on the threshold) it just seems to sag like regular shocks. It doesn't really sit too low I don't think, but I don't know how it should really look. Does anyone think the shocks were just replaced with regular shocks? They don't look new by any stretch. Would they act like regular shocks like this if the fluid was low or would they be bouncy and/or hard? Should I just try putting fluid in to see if that changes anything? I'm assuming once you start the car, the rear should raise up some. Please let me know if this is correct and if anyone has a picture of the rear of a car with a working SLS if you could send it to me for me to compare that would be great. I have done searches on here about the SLS already on here, but wanted to throw out this question.

Thanks,
Tom

MarkM · #2 11-23-2006, 08:04 AM

No, when you start the car, the rear end should not move up.....if it does (like mine), the suspension control valve is leaking, losing pressure, and allowing the rear to slowly sag when the car is not running. This system should "hold pressure" overnight so that the car should still sit properly. I have a rebuild kit and I will be rebuilding susp. valve soon to correct this. (It is cool to see the car sit up when I start it though!)

You should put in some fluid into the susp. reservoir (use OE susp. fluid- Febi), and then get under the rear of the car (with the rear on ramps or stands) and disconnect the lever that connects the susp. control valve to the torsion bar. Disconnect it at the torsion bar leaving the other end connected to the shaft of the control valve. Then, while the car is running, crawl under there and rotate the lever up and down by hand. If the system is working, you will see the car move up and down. If not, then you have other problems that need to be sorted out.

When you rotate the lever by hand, you will also get a feel for how smooth or rough this thing moves. On my car, the lever did not rotate very smoothly...there seemed to be "rough spots" ...variations in resistance as I moved the lever. I think this was the reason that I would not see the rear move up when I was sitting on the rear bumper....the pressure from the flexible torsion bar was not enough to overcome a "rough spot". Only when I really loaded down the rear would I see the rear come up. I am hoping with the rebuild of the control valve that the lever will move much more smoothly, making the system more responsive light loads in the rear.

Good luck,

Mark

Biodiesel300TD · #3 11-23-2006, 12:17 PM

Here is a write up I did on another forum. It might help you figure out whats not functioning.
http://schumanautomotive.com/forums/showthread.php?t=2226
It sounds like you have a leaky system. Your rear end shouldn't bump up when you start the car. It should stay at the same height. I would fill the reservoir up. Then clean all the lines and the suspension valve in the rear, and watch for leak. I bet you sus. valve is leaking. Like stated before there is a rebuild kit for it. Which is much cheaper than a new valve. If/when you rebuild it make sure you take it a part very carefully, and pay VERY close attention to how things come apart. There are a few parts that can go back together in several ways.

Mismost · #4 11-23-2006, 12:27 PM

You gotta fill the reservior with fluid so you can see what is going on. I got semi-lucky and my leak was in the low pressure fluid return line...about a 9 dollar fix. Worked great for a couple of months, then the high pressure line developed a leak.

Just hope it isn't the pump!

JimmyL · #5 11-23-2006, 10:07 PM

I would do a quick exploratory before you fill it with fluid, just to make sure somebody didn't remove the rear SLS struts in favor of some type of shock. Put rear of wagon on ramps and crawl under there. You want to make sure that the rear shocks/struts have hydraulic lines going into them. It won't do any good to dump 15-20 bucks of fluid in there if hyd. struts have been removed.
If the struts are still there, then you may have a leak somewhere.

I have had leaks in the hyd. pump itself (on the head), I've had the low pressure hose leak, I've had the high pressure hose explode,

I've had a drippy valve, no real leak, and I've heard of the rear struts leaking. The fluid has to go somewhere in a closed system. There is also a bleed nipple on the rear valve that you don't really need to use, but just make sure it doesn't leak too....
Check back after checking this, and after doing what my informative forum buddies have said.

tfrain · #6 11-24-2006, 10:15 AM

Thanks everyone. I'll try to crawl under there today and check it out. I need to clean it off so I can get a good look. Not real familiar with the rear end of this particular car so I'll have to really investigate better.

Hopefully I'll have some time after getting all the Christmas stuff out.

Hope everyone had a safe and happy thanksgiving and hope your significant others survive the insane shopping day (if anybody was brave enough to venture out)

JimmyL · #7 11-24-2006, 12:38 PM

Quote:

Originally Posted by tfrain

Hope everyone had a safe and happy thanksgiving and hope your significant others survive the insane shopping day (if anybody was brave enough to venture out)

I was startled awake at 4:00a.m. this morning (

) to find the wife already dressed and fixing to head out! Good grief...
Alas, that is the only way I am startled awake by her anymore........