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How to free up clogged brake system

2K views 10 replies 5 participants last post by  luke 
#1 ·
I have a 1991 Toyota Mr2 Turbo with 220k miles that I was rebuilding the rear brake calipers for. After install, I went to bleed the brakes and fluid wouldn't come out from either rear caliper bleeder valve. I built pressure from the reservoir using a Motiv brake system power bleeder and disconnected from where the brake line connects to the hard line and fluid wont come out the hard line either. I do however get fluid to come out from the front brake bleeder valves. The fluid is super old and hasn't been changed in a while as the fluid is pretty dark black. This leads me to believe the system is clogged somewhere after the front brake calipers and before where the hard lines connect to the rear brake lines. I have also built 35 psi of pressure from the reservoir to brake the clog loose to no avail. Any ideas on how to free up the system? I don't have an air compressor so 35 psi's is the limit of my power bleeder.

Also, if worse comes to worse, how involved is removing the brake line system if it comes to it and are there any other good diagrams than this one that shows the brake line system?
Slope Font Twig Circle Pattern


Source: Brake Tube & Clamp for 1990 - 1993 Toyota MR 2/ MR-S SW20 | Europe sales region, , 17929257-926532
 
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#5 ·
Might be time to use a thin flexible wire, possibly copper and fish from the rear forward. Disconnect the joints, tee-s etc. That might tell you where your plug is. Actually now that I'm typing this your stoppage is in a section common to both rear brakes, so it will be between the m/c and the last T.
 
#6 ·
Thank you so much for suggestion. I disconnected the T fitting and managed to stick a piece of thin copper wire into the line that routes up to the front where the front caliper lines connect to. After sticking the wire about 2 feet in (from the rear forward), it stops which is where I'm assuming the clog is. The end of the wire has traces of brake fluid which is a great sign. However, the line still appears clogged as I still cannot get fluid to come out when I build pressure. Any ideas on what could be going on? I would've thought a thin copper wire would be able to poke through any type of clog produced from old brake fluid. Another interesting thing to note is that the first half of my brake pedal feels operable (normal) but the second half feels pretty squishy.
 
#8 ·
I'll give the drill a shot. I don't think it's rust because the fluid was pretty dark with bits of black all over. I'm guessing that's the brake fluid eating away at the rubber/ non-metal components throughout the brake system? Is that a thing? Also, if the lines do need to be replaced, I would probably remake them since I have a roll of the line and a double flare kit.
 
#10 ·
The drill coiled the copper wire and snapped it. I did manage to attach a hose on this brake line with the vacuum pump but it wouldn't build pressure. So after having an exciting day breaking rusted bolts holding the plastic cover under the car to see if the line was broken somewhere, I decided to look at the lines in the frunk. Any idea what this line is supposed to be for circled in red?
 
#11 ·
There are two hydraulic lines going to the back, the rear brakes and the clutch. I imagine your problem is related to the stub of a hydraulic line directly above the battery's ground post in your pictures. That line should be connected to the block circled in red. If I understand the EPC correctly, that is the rear brake circuit and the line with the blue painter's tape is the clutch line:

This would seem to track, seeing as you're complaining of no rear brakes and not of no clutch actuation :p

Best,

Luke
 
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