[DrivingPassion]

Hi there,

I had to replace a OEM Brembo brake caliper (blue color) on my F22 M235xi because of a corroded/broken bleeding nipple.
Not sure what happened, when I tried to screw in the hose into the new caliper, it started to tighten up ONLY after 2-3 turns. So, I used the 14mm spanner to tighten it because there were still a lot of visible threads.

When all was done, it started leaking only after 2 days. When I tried to unscrew it, I noticed the threads were pretty much messed up and it cannot hold the hose any more.

QUESTION:
How far do you tighten that hose to the caliper? I do not see any advice and instruction from the BMW technical service manual giving any instructions on that.

Do you hand-tighten it and stop even though there are a lot of visible threads?
How far do you go? I don't want to mess up another caliper.

I have ordered another caliper and I will be working on it this weekend.

[DrivingPassion]

Service Manual did say this:
--------
34 32 Brake Lines
Tightening Torques
Type Thread Tightening specifications. Torque
1AZ Brake line screw connection/union screws F22 M12x1/M10x1 17 Nm
2AZ Brake hose to brake caliper, front F22 24 Nm
3AZ Brake hose to brake caliper, rear F22 24 Nm


Looks like the recommended torque is the middle one, which is 24Nm (17.7015 lb ft).

So, I guess stop tightening when I hit the torque specs even though there are lots of visible threads?

[aerobod]

There shouldn’t be too much thread showing, I would look at the caliper on the other side to see how much. If the brake hose thread has been damaged or is not perfect, then the hose should be replaced.

The flare fitting on the brake hose to brake pipe end is easily cross threaded and should be finger tightened until almost fully seated. It is best to use a crow foot flare wrench suited to a 3/8” drive torque wrench to properly torque the hose and fittings.

[DrivingPassion]

Originally Posted by aerobod

There shouldn’t be too much thread showing, I would look at the caliper on the other side to see how much.

Excellent point. I will do that.

Originally Posted by aerobod

If the brake hose thread has been damaged or is not perfect, then it should be replaced.

I have actually ordered a new hose as well.

Originally Posted by aerobod

The flare fitting on the brake hose to brake pipe end is easily cross threaded and should be finger tightened until almost fully seated. It is best to use a crow foot flare wrench suited to a 3/8” drive torque wrench to properly torque the hose and fittings.

Haven't thought of these. Will look into them.

Thanks, man, for the tips. Really appreciate it.

[aerobod]

Here is a typical crow foot wrench that you use with an extension into the torque wrench to tighten brake pipes or similar flare fittings: https://www.canadiantire.ca/en/pdp/1...-0589832p.html

It is difficult to thread the hose into the caliper without cross threading it if the hose isn’t threaded into the caliper when it is off the car. Even finger tightening could cause cross threading of a couple of turns if the hose isn’t absolutely square to the caliper. The brake hose at the caliper end seals on the pipe end as opposed to the thread, so should screw in most of the way by hand, just needing wrench tighten for the last full turn or so.

The correct torque ensures the flare in the pipe end or fitting seals properly, but isn’t destroyed by over torquing.

[DrivingPassion]

Just got the crowfeet set from AMZN.

Come to think of it. I must have cross threaded the new caliper in my first attempt without removing the brake line completely, after following this stupid video.

I was naive enough to follow this short cut, which killed the threads of both the new caliper and existing brake line.

By the time I removed the brake line to retry, the thread on the new caliper were already cross threaded and the brake line threads were probably misaligned as well.

I should get both the new hose and caliper on Wed/Thurs and will hand screw it in very gently and slowly before I put the caliper back.

It was an expensive mistake but now I learn:
Always double-check with BMW tech service manual on the steps before I follow a YouTube video.

[DrivingPassion]

Installed new brake line into the new caliper very carefully by hand and tightened to specs using the Crowfoot wrench.

Slapped the pads back in and started up car after removing brake-pedal depressor. Pumped the brake a few times, pressure-tested it and no leaks.

Going to bleed it before I go out for test drive.

aerobod ,
Thanks for the helpful guidance. Much appreciated!

[Ajowhan]

Shit yeah, I was in similar situation but I got super lucky... I cross threaded mine when I swap to stainless line but for some reason, mine got pretty deep before it gets hard to turn.. so I force it a little and drove it and notice very very minimal leak after 2-3k miles.

I ended up switching that 1 corner back to the original line and luckily it went in fine..

[DrivingPassion]

Originally Posted by Ajowhan

Shit yeah, I was in similar situation but I got super lucky... I cross threaded mine when I swap to stainless line but for some reason, mine got pretty deep before it gets hard to turn.. so I force it a little and drove it and notice very very minimal leak after 2-3k miles.

I ended up switching that 1 corner back to the original line and luckily it went in fine..

If it is still leaking (even slowly) it meant that either the Brake Hose threads or the caliper threads are crossed or both are cross-threaded.

I have to say that even with the new caliper and the new hose both in my hands (off the car), I still had to be ultra careful to let the brake line sit absolutely square to the hole in order to get the screwing started.

Somehow, the threads are super weird and certainly not the regular threads we find elsewhere.

Once the turning starts, I turn it in by hand until tight.
Next, I used the crowfoot wrench to do wrenching.

Crowfoot wrench had to be introduced at about 3-4 inches above the screw point to allow the crowfoot to sit and wrap around the nut vertically. I set the torque to specs and stopped when it hits the specs.

I will NEVER install a caliper ever again without removing the brake hose.