ABC Suspension

SLINFL

MEMBER
2008 MERCEDES BENZ SL500
5.5L
V8
2WD
AUTOMATIC
140,000 MILES

I replaced a weeping hydraulic hose and on restart the rear (left and right) bottomed out. I have flushed and bled the system. Front bleeders produce a spray and rear valve block line produces fluid at valve block, however when bleeder screws on LR and RR are opened, only a drop or so of fluid comes out. Flushed again while performing a rodeo with no change. I have used a Foxwell 510 elite to scan the suspension module and the results show that there is a "critical vehicle level" for both LR and RR. No other codes besides low voltage from battery Intermittent It shows that all four abc valve locks are open during live data scan. Sensors for both left and right font show voltage and bar measurements to be well within tolerance but the LR and RR show.56v-1.3v and 0-2 bars consistently from idle to rodeo. The ABC pressure shows 180-195 bar during all situations and never below 178. During rodeo the rear does attempt to move up but only about 1/2 inch. Measurements from ground to apex of wheel well LF 28.5 in. RF 28 in. LR 25.5 in. RR 25.75 in. Please help me. The men with the nets and funny jacket are already here for me.

3 Replies

KASEKENNY

MECHANIC
18,907 POSTS

I suspect this is one of two things. Either you have a leak or there is air in the lines. Basically this is a sealed system and when pressure is sent through the system it will move the actuator and the springs will raise. However, if there is a leak it cannot build pressure. Or when there is air in the system the pressure will build but the spring will not move because air will compress but the fluid will not which is how it gets the movement from the spring.

So adding in the fact that you have almost 2700 PSI of pressure in the system but not getting much of any fluid out of the spring and the front seems to operate just fine then I suspect you have air in the lines.

If you had a pump issue then the front would not work properly so again, I suspect you need to bleed the system until you have a good amount of fluid coming out of the bleeder.

I attached some info below. Basically you need to get the motor to run and open the bleeders one at a time.

Please review this material and let us know what questions you have. Thanks

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Sunday, April 18th, 2021 AT 7:08 AM

SLINFL

MEMBER
2 POSTS

Thanks for a very informative answer. I proceeded as instructed and I think I am getting somewhere. After the first bleed the pressure went to 4 bar, which is a lot better than 0 where it was. About the 5th bleed I began to get a steady stream, small stream but still a stream. However after 6 bleed offs the pressure has not gone above 12 bar and. 62 ma I am going to begin anew in the morning as I have read that this can be a very time consuming process.
If you feel I am heading the wrong direction please let me know.
Again thank you for the answer. I did not expect a fast reply on a Sat/Sun nor did I expect an answer that educated me so much. Thank you

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Sunday, April 18th, 2021 AT 4:32 PM

KASEKENNY

MECHANIC
18,907 POSTS

Thanks for the kind words. The fact that you are making progress, I would continue with what you are doing. If you got no results then we could rethink this but that is not the case.

Just be sure to keep the reservoir full or you are going to be back to the beginning.

Thanks for the update and let us know how you make out. Thanks

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Sunday, April 18th, 2021 AT 6:57 PM