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Weird braking help please

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AlanMcR
Posts: 7729

Re: Weird braking help please

Post#31 » Thu Jul 26, 2018 12:47 pm

hummermaniac88 wrote:I changed the lines before changing the portioning valve. After driving a while the problem reappeared I changed the porportioning valve. No mix up.

You lost me here. The 1997 doesn't have a proportioning valve. The ABS/EBV does that in software.
...Alan

blueg
Posts: 2318

Re: Weird braking help please

Post#32 » Thu Jul 26, 2018 1:28 pm

Software has to physically move something to regulate fluid pressure.
I thought we were dealing with older vehicle until thread entered ABS. Right out of my ballpark.

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cal_w460
Posts: 2205

Re: Weird braking help please

Post#33 » Thu Jul 26, 2018 2:00 pm

blueg wrote:I thought we were dealing with older vehicle until thread entered ABS. Right out of my ballpark.


X2
w460.333 1982 Colorado Beige 300 GD OM617.931

hummermaniac88
Posts: 721

Re: Weird braking help please

Post#34 » Thu Jul 26, 2018 2:26 pm

cal_w460 wrote:Are you guys talking about the same "proportioning valve"?

What valve have you replaced hummermaniac88?
The rear proportioning valve (load compensation valve) above the rear axle?

image.jpeg


Yes, replaced this valve right above the rear axle.

hummermaniac88
Posts: 721

Re: Weird braking help please

Post#35 » Thu Jul 26, 2018 2:26 pm

AlanMcR wrote:
hummermaniac88 wrote:I changed the lines before changing the portioning valve. After driving a while the problem reappeared I changed the porportioning valve. No mix up.

You lost me here. The 1997 doesn't have a proportioning valve. The ABS/EBV does that in software.



I found one on mine, perhaps a products 1996?

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AlanMcR
Posts: 7729

Re: Weird braking help please

Post#36 » Thu Jul 26, 2018 3:10 pm

MB dropped the proportioning valve on 1997 gas and 1996 diesel. Lots of systems changed along with that: ECU, transmission, instruments, ABS, all integrated with a CAN bus. You need to figure out exactly what year/model you have.
...Alan

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kafkaonwheels
Posts: 438

Re: Weird braking help please

Post#37 » Thu Jul 26, 2018 3:20 pm

rpanter wrote:No great way of trouble shooting it due to lack of manuals with good wiring diagrams (1992 300GE).


I think the 90s manuals are very good at explaining how system works, it's components, how it was intended to use and how to troubleshoot problems. On newer vehicles the workshop programs (like WIS) often only consist warning messages and just step-by-step instructions (to replace component).

42.53 - Anti-lock braking system (ABS)
1985 300 GD Turbo (Everlasting project)

goat
Posts: 1794

Re: Weird braking help please

Post#38 » Thu Jul 26, 2018 3:42 pm

blueg wrote:Metering valve is downline between master and front calipers.
It slows the pressure to front discs long enough for rear drums to engage. Balancing front to rear braking.


I modified your quote because I have the inline valve on the left front shock tower.

1. Why does the metering valve go bad?

2. Can I clean it and restore it to correct operation.
G less
2008 Lexus GX470
2015 BMW X-5 35D

blueg
Posts: 2318

Re: Weird braking help please

Post#39 » Thu Jul 26, 2018 4:07 pm

I think they just gunk up.
I would remove and thoroughly clean and put it back.
Once removed you should be able to investigate what it is made of.
I suspect a metering jet or restrictive orifice that gets worn larger with time or clogs up in same time.
Clogs are easily fixed but worn is a little more tricky to find tolerance and figure how to get that back.

goat
Posts: 1794

Re: Weird braking help please

Post#40 » Thu Jul 26, 2018 4:17 pm

Thanks BlueG...

I'll pull it and clean it and check for orifice wear.
G less
2008 Lexus GX470
2015 BMW X-5 35D

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