Torque for brake hose into caliper

[JHZR2]

As many know I refurbished my calipers on my 1982 MB 300CD. Brake job went well, greased the bearings and all that as well. Drove the car maybe 50 miles and the pedal starts to feel soft. I immediately start to think master cylinder. The fluid level was a bit low, but didn't have time to investigate, so I'm thinking it went to the booster. Had a better look this am, in the course of 12 hours I gravity bled my caliper from the caliper to hose joint. It does NOT use a banjo bolt, it just threads in. I tightened it with a wrench, same as I had when installing the refurbished caliper... and the time before I had removed the caliper (as a I had replaced the hoses due to age and drove thousands of miles on the refurbished hoses). So I'm a bit concerned that the hose backed out under reasonable torque. Certainly don't want to loctite it. Are brake hose threads single use only?

 

[andyd]

Are brake hose threads single use only? On a Mercedes, no way! Just like plumbing in the house, , I fit stuff together hand tight only. Then final tighten as necessary. Using a 6" wrench as a lever prevents me from shearing the fitting. So far even using 25 yr old ATE hoses I've never had a hose fail. I don't have any crowsfoot wrenches or a 3/8 torque wrench. Even if I had them It would be a clumsy tool . Your front brakes sound similar to the 528e set up. Straight coupling M/F. I recommend tightening the Caliper first, then the hard line connection. I'm pretty sure a copper washer was used. Final torque was snug with a 14mm open end. I had fluid loss due to an overlooked loose bleeder once. Mechanicus interruptus ? When a new symptom arises after working on or near something. I have learned to suppress ego and check stuff again, several times if necessary. Doesn't do much for self image but saves time. And money

 

[JHZR2]

I don't recall a Cu washer when I did hoses. These hoses thread into the caliper with an M10x1.0 fine thread connection. My greater concern is that I tightened the hoses, then one backed out. That's a fluid (paint and wheels) issue, but more concerning, a safety issue. I'll be the first to claim mechanic errror. No ego. But I did torque those down so I'm more concerned from safety and mess than anything.

 

[atikovi]

Even if you only finger tightened it, I can't see it loosening even a half turn since the other end would prevent that. Is it leaking?

 

[slo town]

OP, both our BMW use calipers with tapered threaded connections. I tighten those fittings with a small combination wrench. I don't tighten them to a specific torque, I just snug them up firmly. "Firmly snugging" them up is far less than actually "tightening" them. You know what I mean. Even if they were just "lightly snugged", I cannot imagine the fitting backing out. Did you somehow twist the flexible brake hose so that it was putting a loosening pressure onto fitting? Scott

 

[bdcardinal]

Originally Posted by SLO_Town

OP, both our BMW use calipers with tapered threaded connections. I tighten those fittings with a small combination wrench. I don't tighten them to a specific torque, I just snug them up firmly. "Firmly snugging" them up is far less than actually "tightening" them. You know what I mean. Even if they were just "lightly snugged", I cannot imagine the fitting backing out. Did you somehow twist the flexible brake hose so that it was putting a loosening pressure onto fitting? Scott

It took me a second, then I remembered the hoses on my S60R were like that on the caliper side. Hand thread in until it stops and then use a flare nut wrench and go "snug" should be enough. You should be able to feel it.

 

[Rollins]

You will find some torque values here for w201 and w124 series: https://www.startekinfo.com/StarTek/outside/11832/Resources/201Create/PDF/10009.pdf I would not expect the w123 to be any different regarding the torque spec of the flex hose. Other manufacturers also use similar type of connection , for example Peugeot (15Nm again here,floating caliper ): https://www.qclt.com/html/%E6%A0%87%E8%87%B4307_607%E7%BB%B4%E4%BF%AE%E6%89%8B%E5%86%8C/307/info/gb/b3fg2pk3.htm No washers used on these. Yep, multiple use allowed . You can also check some other manufacturers' torque specs for reference but I would not expect them to be very different...

 

[vavavroom]

You must be talking about the front brakes. Check if the threaded connector on the hose is tapered with conical threads. If so, it doesn't need a washer. Parallel/cylindrical threads require a copper or aluminum washer. My old Benz had conical threads on the front calipers.

 

[andyd]

I mis remembered about the washers.

 

[JHZR2]

Originally Posted by SLO_Town

OP, both our BMW use calipers with tapered threaded connections. I tighten those fittings with a small combination wrench. I don't tighten them to a specific torque, I just snug them up firmly. "Firmly snugging" them up is far less than actually "tightening" them. You know what I mean. Even if they were just "lightly snugged", I cannot imagine the fitting backing out. Did you somehow twist the flexible brake hose so that it was putting a loosening pressure onto fitting? Scott

I tightened the caliper to the hose, before I bolted it in. So any twist should have been taken out. This why I was confused. I'm going to chalk it up to mechanic error and monitor it.