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Brake line advice

Started by hamidagha, 12 July 2021, 02:00 PM

hamidagha

Hi all. So I decided to take a look at the brakes on my 1979 280 SE which I have been working on for past 18 months.
The brakes look like they were last done some time ago and the car must have been sat for a long time. Long story short I have sent all calipers to be refurnished but I am having a tough time getting the brake hoses off the brake line. So I think I need to cut the brake line and renew a section. My question: is it ok to let the brake oil drain off or should I avoid the brake cylinder getting drained? My idea is to take the cut off brake lines to a local shop so the can make me new ones.
Thanks 

daantjie

You have to bleed the brakes regardless after any brake work, so letting fluid out the line is no biggie.
Daniel
1977 450 SEL 6.9 - Astralsilber

Alec300SD

No need to cut the brake line.
Spray the union with your favorite penetrant, and let it sit overnight.
On the next day, only use the pair of right sized metric flare wrenches to break the clamping torque of the flare fitting.
Have the wrenches  offset by an angle of about 30 degrees on each side of the fitting, and then squeeze the wrench handles together.

78 W116 300SD 'Desert Rose' new as of 01/26/2014
79 W116 300SD 'Stormcloud' RIP 04/11/2022

hamidagha

Quote from: Alec300SD on 12 July 2021, 02:27 PM
No need to cut the brake line.
Spray the union with your favorite penetrant, and let it sit overnight.
On the next day, only use the pair of right sized metric flare wrenches to break the clamping torque of the flare fitting.
Have the wrenches  offset by an angle of about 30 degrees on each side of the fitting, and then squeeze the wrench handles together.

Hi Alec
I did that and no joy! I mean really solid and actually looking at the lines, I should replace them! Looking at buying my own flaring kit! Hey what could go wrong?

Alec300SD

Next step, apply some heat (propane torch) to the union.
Have a fire extinguisher handy. :)

If you must replace the brake line, go with Cunifer alloy brake line material(copper/nickel/iron alloy) if permitted by your local regulations.
78 W116 300SD 'Desert Rose' new as of 01/26/2014
79 W116 300SD 'Stormcloud' RIP 04/11/2022

Jed

If the line is rough, rusty and needs replacement don't waste any more time trying to free up the fitting.  Just cut it out. 
Two options:  if you can readily access the 'other' end of the line removed t and source another line of nearly the same length and with some very inexpensive bending tools you can replace the entire line without having to do any flaring.

On the other hand if it is a very long inaccessible line then resort to plan B: you can cut out the bad section and flare in a new one.  There are 'portable' flaring tools you can use under the car 'in situ.' i have found them to be a little finicky and difficult but doable. Follow the directions, and check your work, because after all, you are working on the braking system!  Also, don't skimp on this tool.  Buy the best set you can.  Lastly, if you plan on doing any significant amount of flaring consider getting a vise mounted set with a 'pull down' arm on the flaring tool (like a slot machine). I bought one of these sets from eastwood tools and I love it! It makes flaring brake lines a piece of cake and fun! I have used it on my 6.9 hydraulic suspension lines as well as many brake lines.

https://www.eastwood.com/professional-brake-tubing-flaring-tool.html

Of course you can have someone make you the lines too...

good luck!
Jed
1979 Mercedes 6.9 #5206 - restored
1979 Mercedes 6.9 #6424 - ongoing restoration
1976 Mercedes 6.9 #484 - restoration?

ptashek

The route I'd also recommend would be going for new cunifer /cupronickel lines, with stainless or brass fittings. It'll cost more to do, but it won't have to be done ever again.

And they look great too :)

If you drain the system fully for an extended time, you may need to replace the master cylinder. If exposed to air, It will rust internally like there's no tomorrow.
1993 "Pearl Blue" W124 280TE
1988 "Arctic White" W124 200T
1979 "Icon Gold" W116 450SE

Engineerd3d

I would cut off the lines and clamp the chassis side shut and keep the fluid in there. It will be a pain to bleed manually if you let it all drain and it will cause rust issues.

Also for the bleeding, use a vacuum pump of some sort to flush the system. If you try to manually bleed via pedal you may cause issue with the master cylinder or the vacuum assist.

Start right rear, then left rear, then right front and then finally left front. Providing this is a left hand drive car.

Jed

The motive pressure bleeder has worked great for me for years and very reasonably priced. 
1979 Mercedes 6.9 #5206 - restored
1979 Mercedes 6.9 #6424 - ongoing restoration
1976 Mercedes 6.9 #484 - restoration?

raueda1

Quote from: ptashek on 13 July 2021, 02:51 AM
The route I'd also recommend would be going for new cunifer /cupronickel lines, with stainless or brass fittings. It'll cost more to do, but it won't have to be done ever again.

And they look great too :)


If you drain the system fully for an extended time, you may need to replace the master cylinder. If exposed to air, It will rust internally like there's no tomorrow.
Another vote for ^^^this.  The tubing is easy to form.  And the flaring kits aren't very expensive.  Make sure it's the kind that makes a double flare.
-Dave
Now:  1976 6.9 Euro, 2015 GL550
Before that:  1966 230S, 1964 220SE coupe, 1977 Carrera 3.0

hamidagha

I have started this. Interesting enough it appears to be a bubble flare!
The heating trick worked but I still plan to change the lines now that I have started. Thank you all for the tips