Replacing rear brakes

[dseretakis]

I replaced the L rear caliper today on my 71 280SL but ran into some trouble.  The brake line that screws into the caliper is rigid.  I've never seen this before.  Anyway, the nut/fitting that screws into the top of the caliper did not turn independently of the brake line over which it lies.  This meant that in order to separate it from the caliper I had to unbolt the caliper and then twist the caliper while holding the rigid line in place.  Is this the proper procedure or is the nut/fitting supposed to turn independently of the brake line?  Anyway, I removed and re-installed the new caliper in this fashion by rotating the caliper to thread it onto the brake line fitting.  Once it was nice and tight, the caliper was now not properly oriented with respect to the rotor so I had to bend the rigid line to get it to fit right.  I'm not sure if this is correct procedure. 

[tel76]

I would suggest that your best plan of action would be to remove the brake line and make a new one,it may be a good time to replace your obviously corroded brake lines fitted to the rear axle,not a very expensive operation.

[dseretakis]

Well the problem just got more complicated.  I just tried to bleed the brakes and no fluid would come out and as would logically follow the new pads would not move to seat against the rotor.  Logically there is an obstruction somewhere.  Perhaps my manipulating the rigid line caused some blockage?  The next step would be to remove the caliper and pump the brake pedal to see if fluid comes out of the line but I know that it won't.  I know that I should replace the rigid line and the flexible line that goes to the proportioning valve.  Could the proportioning valve have gone bad and would it cause this symptom.  Funny thing is that I can still drive the car and it brakes OK.

[dseretakis]

Here's my progress.  I went "all out" and replaced both the steel and rubber brake lines.  Forming the steel line from the OEM Mercedes line with both fittings already in place wasn't as bad as I thought.  Check out the swollen from the inside rubber line!  The lumen diameter is almost as tight as a pinhole.  Now all I have to do is get my girlfriend to help me bleed the brakes and I should be set for the 500 mile trip to Boston from DC.

[ja17]

Sounds like you have your problem under control. Yes, rubber brake hoses are the most common problem with the brakes.  Replacing them every 10-15 years is important, especially if the car is not used.

[dseretakis]

I'm actually having trouble purging out the air from the left rear circuit where I did the work.  I keep getting air bubbles no matter how long I bleed. I tried to start at the right rear caliper but the bleeder screw is very rusty and won't budge. I know that if I apply any more torque it'll shear off.  So what are my options here?

[menesesjesse]

Give me a call and I can help you.  I have avacume bleeder at my house.  I just had my car up in old towne today. 
Jesse

[jacovdw]

...Replacing them every 10-15 years is important, especially if the car is not used.

Even though the BBB calls for the flexhoses to be replaced every 5 years, I tend to think that this interval might be a bit overkill.
I do agree with Joe that 10 years would be a better choice.

[jameshoward]

I think that key to maintaining the servicabilty of the system is to replace the brake fluid regularly also, especially if the car isn't driven. Doing every 3 years or so will prevent the lines and hoses decaying from the inside. Good external care should prevent the outside of the hoses getting too bad.

As for the situation with the bleed valve, you could try soaking it with decent penetrating fluid, but at some point I think you're going to have to bite the bullet and risk it coming off. Brakes are fairly fundamental in the stop/go equation, and you'll want to ensure they're properly bled and safe.

A gunson easibleed is a good enough device to aid bleeding. I've used mine quite a bit and, whilst not brilliant, it does the job.

[RickM]

A gunson easibleed is a good enough device to aid bleeding. I've used mine quite a bit and, whilst not brilliant, it does the job.

I have the Motive Power bleeder and it works well for solo bleeding. No tire pressure needed    http://www.amazon.com/s/ref=pd_lpo_k2_dp_sr_sq_top?ie=UTF8&cloe_id=4a6c149f-9c24-4645-9e56-948903497bc7&attrMsgId=LPWidget-A1&keywords=motive%20pressure%20bleeder&index=blended&pf_rd_p=486539851&pf_rd_s=lpo-top-stripe-1&pf_rd_t=201&pf_rd_i=B0002KM5M4&pf_rd_m=ATVPDKIKX0DER&pf_rd_r=0DW6D3APE4KETDA9A6VD.

A less expensive alternative is assembling a pressure bleeder from a garden sprayer and a few other bits...it's quite kit. http://www.bmw-m.net/TechProc/bleeder.htm

[graphic66]

I couldn't get my homemade bleeder to work on the newer style master cylinder with the floats inside. The pressure and brake fluid escapes out the places where the rods go from the floats through the top to the electrical contacts. The older style master cylinder without the floats would pressurize fine. Has anybody got the bleeder to work on the master cylinder with floats without spewing brake fluid out the top of the master cylinder?
  I do really like the homemade bleeder and it has worked on everything so far except for the float style master cylinder.  I had the older style on my 230SL, but when I put in a disc brake rear end I had to upgrade to the proper master cylinder with the floats. That is when I found out about the leaks around the top.

[dseretakis]

But how do I bleed a brake with a frozen caliper bleed screw short of replacing the caliper or drilling out and tapping for a new bleeder screw?

[RickM]

But how do I bleed a brake with a frozen caliper bleed screw short of replacing the caliper or drilling out and tapping for a new bleeder screw?

Unfortunately, you can't.

Are you using the proper wrench, clean around threads and soak with PB Blaster or similar (many times if needed)?

Some tap very lightly around the bleed "screw" or lightly work it left to right. Obviously you need to be very careful.

[Witt]

.....this will probably help in the interim.....if the nut the holds the solid brake fluid line to the caliper is not frozen, loosen it instead of the bleeder nipple, enough to let fluid and air escape during the bleeding process........ I have used this method often when working on older cars in general...  

CHEERS !
WITT !  

PS: with your new lines the nut will be free of course,  BEWARE THIS METHOD IS VERY MESSY, BEST TO HAVE  LOTS OF RAGS HANDY TO CATCH THE SQUIRTING FLUID !

[jacovdw]

I have the Motive Power bleeder and it works well for solo bleeding...

Rick,

I'm also wondering about the possibility of a leak when using the pressure bleeder with the later style 2 float reservoir.
I take it that you have no leaks when using the Motive bleeder?

The reason I ask is that I'm looking at ordering one from Motive Products as it looks like a very good tool to add to the collection, but my W114 has the later style reservoir.

[graphic66]

You will have leaks with the Motive bleeder. It is exactly like the homemade bleeder I have. There is no way I can see the little rubber seals around the float stems holding any pressure. You need 10-15 PSI to bleed your brakes and it spews everywhere around those seals. I tried it with no success. You even need to get the cap incredibly tight to not get leaks when doing this method. I use big channellock pliers to tighten the cap just a little tighter than you can get with your hands to avoid seepage.
   I am going to miss being able to flush my brake lines so easily. With the old style master cylinder you just put on the bleeder, pumped to 15 PSI and went around with a tube and a jar bleeding until nice clean fluid came out. Now with the float style master cylinder I am back to finding a pedal pusher. It seems to be particularly irritating to women having to "push down "let up" over and over.
   I was bleeding my girlfriends front brakes on here Toyota Tacoma once and they just wouldn't do anything, no fluid no pressure or anything. I had just put on all new calipers so I kept thinking maybe the master cylinder had an air lock. I did find the air lock eventually, it was in my girlfriends head, she was pushing the clutch in and out!

[RickM]

I have not yet used the Motive on my 280.
On 911s there's a vent hose that needs to be clamped or plugged in order to prevent fluid from spewing out. Another trick is to put a square piece of ziplock plastic bag material between the pressure bleeder cap/adapter and the reservoir neck when screwing on to seal.
The goal is to somehow seal or plug any orifice that may allow leakage.

[jacovdw]

Thanks for the replies guys.

I thought as much. At least it can be used on the pagoda, but for the W114, I'm afraid that I have to assign my wife to "pedal duty"... 

[RickM]

I couldn't get my homemade bleeder to work on the newer style master cylinder with the floats inside. The pressure and brake fluid escapes out the places where the rods go from the floats through the top to the electrical contacts.

I'm working with Motive and ATE for a possible solution. I will likely start a new thread when appropriate.

[Witt]

.....I had good success with a plain old hand operated vacuum pump by sucking the brakefluid through a clear plastic hose from the bleeding nipple, cracked open a bit.
The old fluid would collect in a small container attached to the hand pump. The clear plastic tube helps monitor the flow of the fluid and air bubbles. As soon as no more bubbles appear, close the bleeding nipple, replenish the mastercylinder reservoir and move on to the next wheel....

CHEERS !
WITT !