W124 400E rear hard brake line failure - PeachParts Mercedes-Benz Forum

moruzzi · #1 04-26-2008, 08:25 PM

Search of the archive showes some info on hard lines but I figure I'll start this thread.

Car is a 1992 400E with ASR

Realized I had a slowly sinking brake pedal and took a look under the car and saw fluid on the right rear (passenger side). Closer inspection showes it is the hard line that is leaking. Ordered a new hard line - wow this one goes from front of car (connection is under car roughly at firewall) all the way to the rear. I figure if you were to bring this in they would charge a fortune as they would probably drop the rear suspension etc. I plan on routing the line in place - it should prove interesting.

First problem is the hard line to flex fitting is frozen (started to round the 11mm nut). Soaked with PB and left it for now. I figure worst case I get another flex line and "brake hose holder" the U section that is above the hanger and next to the 11mm nut (see the picture). Again, worst case if it rounds after a soak in PB I'll just cut the sucker. I did check and free up the fitting in the front as well as the lower flex at the caliper.

Any words of wisdom? I may try some heat (note - that this should not be done on brake lines in general but I am replacing the line already) I'll try again later in the week as I need to do brakes on another car on Monday so don't want the garage spot taken with a dead car.

I figure the real challenge is going to be routing the line with the suspension in place. Anyone ever done this?

I'll try to take some pics and post the procedure for posterity.

deanyel · #2 04-26-2008, 09:15 PM

The CD has nothing which must mean they thought it was good for the life of the car. Just curious - how much does the hard brake line cost?

Arthur Dalton · #3 04-26-2008, 09:20 PM

You should use line wrenches , but if they fail........then you cut the line off clean at the fitting and then use a 6 point socket to break the fitting from the flex hose..........

moruzzi · #4 04-26-2008, 09:44 PM

Thanks for some quick replies - yes I have flare wrenches that is what I am using. Given I need to change the line anyway I will try to cut the line first and use the 6 point socket.

I also checked the CD - nothing, as you noted. The line was $25 from mercedes plus $10 shipping as it comes in a big box all by its lonesome. Its not prebent just one big loop.

Arthur Dalton · #5 04-26-2008, 09:49 PM

If you have a bubble flare tool and know how to use one [ they are a little tricky at first] you can cut the line back to a good spot and use a steel/bubble flare coupler kit and a standard Euro steel line available in any length from a regular Auto store.........

deanyel · #6 04-26-2008, 10:23 PM

That sounds good that it's not pre-bent - allows you to be a bit creative in the routing, if it's long enough - or do as Arthur suggests and not have to worry about it.

moruzzi · #7 04-26-2008, 10:25 PM

Thanks Arthur,

I tried a flare tool once and had a miserable failure. It was one of the cheap tools you can get at an auto parts store. The wing nuts clap the two bars on the tube, coud't get a decent flare and I tried a bunch, and the clamps chewed up the line if tightend enough to hold the line. I have seen better ones that are about $300 but while I do invest in tools, 300 for a flaring tool is a bit much. That time I brought the line to a local shop and they put the flare on for me.

Now maybe sometime I will look into making my own (I do have a lathe and a mill).

moruzzi · #8 06-02-2008, 11:49 AM

Got the job done - gawd what a PITA routing the line. I cut the hard line at the connection to the flex hose. That allowed me to get a 6 point socket on it and break it free. Either I need a better set of flare wrenches or I will pick up another one and grind the sides flat. The actual engagement surfaces of the wrenches are fine the issue seems to be that they are set in from the bottom surface - kind of like they are countersunk. This means that your engagement of the nut is not on the full height of the nut but only the upper part. Grinding away the countersink on the wrench would eliminate this. Incidentally sockets are this way as well but it is not nearly as pronounced. Removing the rest of the line was relatively easy as I was free to cut it and I toll it off in three pieces.

I would suspect that this job quoted at a dealer would be somewhere in the $2K range, I think they would drop the whole rear suspension - route the line then put the suspension back in.

Putting the new line in can be done without moving any of the suspension. Obviously my bends are no where near as crisp as the factory, but you can snake a single long line up over the rear suspension and follow essentially the same path as the factory. I was able to run from the right rear wheel past the transmission and engage two of the factory clips - this route was went very well with no contact points between the new line and any other hard points. Routing over the suspension was a major challenge and that is where you basically have no hope of following the exact factory route. Just keep working to minimize any contact points.

What I did do on any part I was worried about contacting a piece of metal or another hard point is slit some flexible tubing (I used clear tubing that I use for brake bleeding and running very low pressure CO2 for home brew because I had it around) and run it over the brake line. This is similar to what was on various parts of the original factory line. Low pressure rubber hose from the auto parts store may work better but I didn't have any handy.

Once over the suspension, routing to the front was really easy (its a straight run).

I think I will work on the homemade flare tool - I now have the die and tube holding blocks for 4.75mm din flares. I figure a small arbor press - one or two ton - to make the flare. Once I have that worked out I'll look at how to make one that can be used on the car.

Paul

Pete Geither · #9 06-02-2008, 12:08 PM

I am a bit puzzled,,,, I just did this exact job on the 400E, about 3 weeks ago. There was a distribution block on the rear crossmember where both rear lines tap in. Took about a 12 inch line on the left, and a 20 inch line to the right, not a big deal at all. If you didn't have that block and had to route all the way to the firewall,,, what a PITA.
BTW,,, that is exactly where my brake lines failed.

moruzzi · #10 06-02-2008, 12:19 PM

Well on a 92 400E with ASR there is no distribution block. Single line goes all the way from the front to the right rear and another one goes from the front to the left rear.

My assumption is this is necessary for the ASR as it needs to apply brakes to only one wheel.

Once I get tooled up to do flares properly I will probably use the Copper Nickel brake line on any issues in the future. It appears to eliminate the corrosion issue and looks to be more flexible than the usual stuff. Does seem to essentially be single sourced in the US.

mcguirjf · #11 11-14-2008, 01:19 PM

I bought all new lines, distribution block, hoses, and bleeders for front and rear. I'm suprised the lines don't come prebent. I would have went to autozoo or napo instead. Its good to know that I don't have to drop the rear subframe. I just got an alignment done at the dealer.

Pete Geither · #12 11-14-2008, 03:05 PM

Enjoy. Give us an update when it's done.

lkchris · #13 11-15-2008, 11:29 AM

Quote:

Originally Posted by deanyel

The CD has nothing which must mean they thought it was good for the life of the car. Just curious - how much does the hard brake line cost?

CD assumes mechanic is factory trained. This procedure is mechanics 101, i.e. a prerequisite for using the manual. If there were anything unusual about the job or if special tools were required, there would be a factory procedure.

mcguirjf · #14 11-21-2008, 12:03 PM

That sucked!

I finally had a chance to work on the car last night and finished 3:30 am. Trying to snake the "long" line between the subframe and body was the worst. 2nd most difficult was the passenger rear. I think they made the line way too long. I did a side by side and the new one had a good extra 3+ inches. I still have to change out the front hoses, and replace those plastic screws that hold the lines to the chassis. All of them broke off. I also finshed assembling my new power brake bleeder. I tested it up to 12 psi and it was fine.

Anyone know how much pressure I should use to bleed ABS brakes on a non-ASR W124?