Dragging brake

[SeismicPumpkin]

Picked up my first e30, ‘88 325is, and have been working on catching up on some maintenance. Current issue is the front driver side brake is dragging. I don’t seem to notice it much while driving but can really smell it after it warms up. I thought it was a sticking caliper so I replaced the calipers and upgraded the rotors up front but still am having the same issue. The threads I’ve read on this don’t seem to focus on a single brake dragging but all brakes. Wondering if it’s a clogged hard line that’s preventing the caliper from returning after braking. The soft lines have been replaced. Not sure where to look next as I try to diagnose the cause. Any help is appreciated!

[82eye]

did you can trace the hard line back to check if it's pinched ?
how does the brake fluid look ?

an easy way to check to check for hanging caliper is get an ir thermometer. go for a drive then scan the suspect rotor and compare it to the other side and the two on the back. the two fronts and two back should have roughly the same temp, with the back being a little cooler. if there is a dragging caliper it will be noticeably hotter. sometimes you don't even need an ir therm to notice, you can feel the heat right from the wheel.

[SeismicPumpkin]

The fluid wasn’t terrible but I flushed it and filled the res with ATE SL fluid when I installed the new calipers. It’s definitely a lot hotter than the front passenger side. I can feel the heat from the wheel and smell it. I’ll trace the hard line to see if I can find a pinch. Am also curious if it could be a proportioning valve issue.

[82eye]

The fluid wasn’t terrible but I flushed it and filled the res with ATE SL fluid when I installed the new calipers. It’s definitely a lot hotter than the front passenger side. I can feel the heat from the wheel and smell it. I’ll trace the hard line to see if I can find a pinch. Am also curious if it could be a proportioning valve issue.

if the cailpers are new it could be a bad one from the box or install issue. proportioning valve is front to rear not side to side.

new calipers were bled correct ?

[SeismicPumpkin]

Calipers were bled until new fluid and no bubbles were coming through. They be done numerous brake jobs on my different vehicles over the years so I don’t think it’s an install issue. I suppose it could be a bad caliper but seems odd that the new caliper would be acting exactly as the old one with the cause being the calipers.

[82eye]

gotta be a pinched line not allowing the fluid to backflow.

[SeismicPumpkin]

Well, I can’t find a pinch in the hard line. I replaced the soft line with a new braided stainless line and still it continues to drag. Fluid flows out no problem when bleeding and no air comes out. Wondering now if the abs could be causing this. Anyone have experience with cleaning/flushing the abs units?

[iXBeater]

gotta be a pinched line not allowing the fluid to backflow.

Completely uninformed guy here - I might be getting ready to say something stupid: Possible that the master is deteriorating and a chunk of rubber (aka "brake turd") is stuck somewhere?

[82eye]

Completely uninformed guy here - I might be getting ready to say something stupid: Possible that the master is deteriorating and a chunk of rubber (aka "brake turd") is stuck somewhere?

only thing i can think of is a crappy caliper right from the box.