Dsc/abs Part 3

[srein1]

Well, I replaced the DSC/ABS control module and the lights went out and everything was fine for about a month and a half -- now the ABS and DTC lights are back on and the car does not drive well. I took it to the dealer and now they diagnose it as the HYDRO UNIT, the box the DSC module mounts to. The repair cost by the dealer is $3500-- WOW!! So the question is, can I do this myself? Does anyone have any experience with replacing this unit? If I can't do it myself I may just have to retire this car and go to one of those small, high gas mileage boxes ----- JUST KIDDING - you can't go back again. Any opinions or help appreciated.

[crewdog843]

Navigate to the following site, maybe this will help: http://www.e34.org/forums/posts/392851 There are several other posts accessed on Google by searching for "e38 hydro unit".

Back in the day, long before sensors on cars, I owned a '62 3.8 litre e-type Jag. One day, while driving at a normal rate of speed on a city street, the rear brakes completely locked up. I found the cause to be small flakes of aluminum from the float inside the brake fluid reservoir had migrated through the system and blocked a return valve.

Brake fluid is hygroscopic and will absorb water (one of the reasons BMW advocates changing the fluid every couple of years). This dilution of the fluid can have a deleterious effect on your system.

I cannot help you with the ASC hydro unit itself, but it may not be a bad idea to look around for some decent BMW factory trained independent mechanics with experience in this area. Richmond is a fairly good sized town, so there should be more than a few in the area. Is it possible that the cause could be the module which controls the ABS system?

Good luck.

jake

[srein1]

I guess the new module can fail after a month and a half but I don't get any codes when I scan with the code scanner. I may just start with flushing the brake system, then if that does not work replace the wheel sensors. Then I may consider replacing the hydro unit - unless someone out there has done it and thinks it can be a DIY.

[srein1]

Finally figured it all out. I replaced the hydro unit and it was a snap. You just unbolt the lines, take the unit loose and slide in the new one. (Thanks to Scubaa Steve in Tampa for for helping and supplying the hydro unit at a very resonable cost!) If you replace the hydro unit you have to have the brake bleed done by a computer at the dealers. Of course the same fault kept coming up _"left front wheel inlet valve" on the hydro unit. So I took it back to the dealer and said how could the same fault occur on a different hydro unit. The young BMW mechanic said "we only change out the entire unit" meaning the hydro and the control module (for around $4000.00!!) - like that was going to fix everything. So I took off my rebuilt contol module and put on the module that came with the hydro unit I got from Scubaa Steve. I took it back to the BMW dealer and stayed there and made a general pain of myself until the service manager agreed to recode the ABS control module with the codes for my car. The mechanic (like a young stuttering peacock--maybe 30 yrs old) was angry and said "this'll never work" and stomped out of the service rep area to the shop without so much as a "well we tried everything else" or even a look at me. An hour later the service rep called me and said sheepishly "your car is all fixed and ready and the codes have all cleared." It cost me $400 more but it was worth every penny (priceless in fact) when I got to tell the service rep and the mechanic to their faces "don't you just hate it when the old guy is right." The service rep. had a good laugh but the mechanic was pissed. Guess I'll have to request one of the other mechanics at the dealers.

Turns out the rebuilt control module (rebuilt in Feb 08) had failed in the meantime with the same failure code as it did when I originally sent it for rebuild in Jan 08. That caused the hydro unit to show as a Hard Fault eventhough the hydro unit itself was OK. So the rebuilt control unit was still in warranty and has been sent back for a re-repair so I will have a spare. The extra hydo unit I'll put on e38.org in the for sale area -- someone needs one. But as that BMW mechanic told me when I originally took it to the dealer in Dec. 07 -- "I don't understand it, the hydro units never fail." All told, spent about $1200 total - not too bad - and learned tons about the electronics on the e38. And I learned that just like everything else, if you do the thinking for yourself you will eventually come out to the good. Now that the antilock brakes and the dynamic traction control are working fine, I can once again delude myself into thinking that I am somewhat safe at 90 or 100 mph.

I thought you might enjoy how the story turned out.

[srein1]

Hope my 7 - Blue picture uploads