82 300DT SLS question? - PeachParts Mercedes-Benz Forum

ngarover · #1 02-05-2012, 08:30 AM

I replaced the Hydraulic shocks, I put in the pair that I got from Vstech, it did make a huge difference on the ride, and the "clucking" sound is now gone when you hit bumps.

But, I sounds like the rear tire in the drivers side is rubbing at low speeds *under 40 At interstate speed the sound is gone. slow back down and it's back.

My wife mentioned that when she followed me into the shop the drivers rear was 6 inches lower than the the pass side... she tends to over estimate, but it would account for the scraping sound I'm hearing from the wheel.

I'm picking up the car from the body shop in the morning and just would like an idea of what to look at to fix the issue before I put the new tires on the car.

locry · #2 02-05-2012, 09:56 AM

Maybe the driver side struts need burping?

ngarover · #3 02-05-2012, 11:03 AM

Quote:

Originally Posted by locry

Maybe the driver side struts need burping?

That was my first guess, but I thought the system was self purging?

Biodiesel300TD · #4 02-05-2012, 11:21 AM

It is self purging, but did you load down the rear a couple times with the car running, to make sure they system has moved through it's range?

locry · #5 02-05-2012, 11:26 AM

I read that indeed they were self purging... but when I had my spheres/accumulators replaced that didn't seem to be the case... It apparently did not self purge, I even tried bleeding it through the nipple at the leveling valve... no dice. What did eventually get the fluid circulating was bleeding through the banjo bolt AT the pump. Weird I know, but that did it for me. My guess is not enough fluid was in the system such that there was no fluid at the impeller at the pump, maybe it was pushing air or something. Anyway, just throwing it in as a possibility if it doesn't self purge.

ngarover · #6 02-05-2012, 12:17 PM

Quote:

Originally Posted by locry

I read that indeed they were self purging... but when I had my spheres/accumulators replaced that didn't seem to be the case... It apparently did not self purge, I even tried bleeding it through the nipple at the leveling valve... no dice. What did eventually get the fluid circulating was bleeding through the banjo bolt AT the pump. Weird I know, but that did it for me. My guess is not enough fluid was in the system such that there was no fluid at the impeller at the pump, maybe it was pushing air or something. Anyway, just throwing it in as a possibility if it doesn't self purge.

I'll give this a shot when I get it home. After putting the parts in I ran the car and bounced up and down on the rear, you could feel them getting tighter. But the system took about a quart less fluid then when I stared....

Biodiesel300TD · #7 02-05-2012, 01:00 PM

Bouncing the rear won't let the system run through it's whole motion. It's kind of a slow reacting system. If you have two adults sit in the way back with they're feet on the ground you should be able to feel the rear lift and it take a few seconds to lift up to proper height.

bamba · #8 02-05-2012, 01:37 PM

I've found that actually driving it helps. After recently replacing my accumulators, rebuilding my pump and valve, and flushing the system, I didn't get it to completely bleed until I drove it for a mile or two.

ngarover · #9 02-05-2012, 02:01 PM

Quote:

Originally Posted by bamba

I've found that actually driving it helps. After recently replacing my accumulators, rebuilding my pump and valve, and flushing the system, I didn't get it to completely bleed until I drove it for a mile or two.

I drove it 30 miles to the body shop... I figured it should have been fine by then.

Biodiesel300TD · #10 02-05-2012, 03:20 PM

Quote:

Originally Posted by ngarover

I drove it 30 miles to the body shop... I figured it should have been fine by then.

There is no flow through the rear parts(accumulators and struts) when the car is being held at height. The way the system works is that the pump is always pumping fluid to the valve. If the system is sitting level the fluid just goes back to the res. When you load the rear the valve then open the port to supply the rear parts with more pressure and fluid. Which raises the rear, until it's level again and then it cuts off the flow and maintains the pressure in the rear. Then when you unload it the valve allows the pressure and fluid to flow back out until it's level again. So if you have air in the accumulators or struts and you simply drive it. You're not actually running fluid through the struts or accumulators. To get all that air out you need to weight the rear down a few times. This will push fluid through the whole system and purge air out.

ngarover · #11 02-05-2012, 04:37 PM

Quote:

Originally Posted by Biodiesel300TD

There is no flow through the rear parts(accumulators and struts) when the car is being held at height. The way the system works is that the pump is always pumping fluid to the valve. If the system is sitting level the fluid just goes back to the res. When you load the rear the valve then open the port to supply the rear parts with more pressure and fluid. Which raises the rear, until it's level again and then it cuts off the flow and maintains the pressure in the rear. Then when you unload it the valve allows the pressure and fluid to flow back out until it's level again. So if you have air in the accumulators or struts and you simply drive it. You're not actually running fluid through the struts or accumulators. To get all that air out you need to weight the rear down a few times. This will push fluid through the whole system and purge air out.

Thanks! When I get it home I'll load it down with some bricks and see how it does.

bamba · #12 02-06-2012, 12:11 AM

Quote:

Originally Posted by Biodiesel300TD

There is no flow through the rear parts(accumulators and struts) when the car is being held at height. The way the system works is that the pump is always pumping fluid to the valve. If the system is sitting level the fluid just goes back to the res. When you load the rear the valve then open the port to supply the rear parts with more pressure and fluid. Which raises the rear, until it's level again and then it cuts off the flow and maintains the pressure in the rear. Then when you unload it the valve allows the pressure and fluid to flow back out until it's level again. So if you have air in the accumulators or struts and you simply drive it. You're not actually running fluid through the struts or accumulators. To get all that air out you need to weight the rear down a few times. This will push fluid through the whole system and purge air out.

That's an excellent explanation of how the system works. I don't disagree with you. In my situation, for whatever reason, I could not get the system to bleed by running the motor and adding weight to the rear. I tried adding weight, manually moving the arm, bouncing on the end, etc., and it wouldn't seem to work. I finally took it for a ride, and the rear finally rose a bit and held pressure. I wonder if there was some residual air in the valve assembly or accumulators that just needed to be jostled out by hitting a few bumps. It sounds like my experience is atypical, but I'm happy that it finally worked for me.

kerry · #13 02-06-2012, 12:50 AM

My intuitive response is that instead of adding bricks, jacking up the back bumper to force the height adjustment level up would be easier. It would open the valve to bleed off pressure in order the drop the back of the car down and allow the air trapped in the ram to exit out into the system. If you put bricks in the back, the system will operate the reverse way and try to force more fluid into the ram instead of letting the fluid/air inside escape. I'd jack it up with the engine off to bleed it down, lower the car back down, start up the engine to pressurize the ram, shut off engine, jack up the car again to bleed off pressure. Do this a number of times.

Orv · #14 02-06-2012, 06:09 PM

The rear tires shouldn't rub, even if the system is at its lowest point. I drove around with the struts totally collapsed for a while and I didn't have tire rubbing. (I'm using stock-sized tires, though; if yours are wider that might change things.)

Can you actually see where the tire has rubbed against the body? It's possible you're hearing something else, like the rear brake pads scrubbing against surface rust on the rotors. Very common in the winter in northern climates, where salt spray gets on the rotors -- they will get a patina of surface rust overnight.

I don't know if your model year had stamped-steel lower control arms in the rear, but if so, look them over carefully. Some people have had them crack from rust and allow the wheel to tilt in. Very dangerous if they decide to let go.

ngarover · #15 02-06-2012, 06:16 PM

Not getting the rubbing sound anymore. Seems to level out fine after you drive it. It a 100% rust free car top and bottom. Stock tires on it.

Quote:

Originally Posted by Orv

The rear tires shouldn't rub, even if the system is at its lowest point. I drove around with the struts totally collapsed for a while and I didn't have tire rubbing. (I'm using stock-sized tires, though; if yours are wider that might change things.)

Can you actually see where the tire has rubbed against the body? It's possible you're hearing something else, like the rear brake pads scrubbing against surface rust on the rotors. Very common in the winter in northern climates, where salt spray gets on the rotors -- they will get a patina of surface rust overnight.

I don't know if your model year had stamped-steel lower control arms in the rear, but if so, look them over carefully. Some people have had them crack from rust and allow the wheel to tilt in. Very dangerous if they decide to let go.