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Anti-lock (ABS) : Brake line blocked. My dissaembly.
Hello everyone,
(I try to write english as weel I can )
My 86 Vette had front left brake blocked. I bought front brake caliper kit, and hoses.
After that, the wheel was permanently braked and... absolutly no fluid was coming out at this front left.
I thought ABS system. Anti-lock light was good at start, then switched off.
I tested all 3 relays, everyone one switched ok with good continuity resistance.
I finally disassemblied the system.
First, disconnet electric relays, lines, and 3 silentoblocks, and remove it from the car. Master cylinder won't probably be empty while disassebly ABS.
Remove 2 bolts on the top (allen wrench).
The two 24mm bolts with springs on the underside. Use only 6-point wrench. 12-point wrench risk to spoil the bolt (like one of mine).
Remove 2 slides, wash & blow them. During all disassembly, be really careful with little parts, or gaskets, not to loose them !
Open the central cap. There's a big bolt under it (allen 12mm). This maintains 3 solenoids.
After removed the bolts about the electric block, we can separate elements.
We pull the 3 solenoids from the up casing.
The line blocked is front left. Solenoid on right on picture is the answer to my problem. We recognize it with its dark filter.
We clean upper and lower filter. I personally removed lower filter, by simply pulling them. You'll find little spring and ball under each, be carefull !
And of course, clean & blow interior solenoid. I used "brake cleaner".
II inverted darker filter (even if it's good now) with other solenoid (rear line, less important).
While cleaning & blowing, we verify/activate each solenoid, by short circuit 12V one after the other, several times (3 yellow wires, and each solenoid ground black wire).
Cleaning & blowing again, and all lines inside the ABS system.
Re-assembly all parts like disassembly.
Fluid comes easily at all purge screws ! Yes !
Vette is braking correctly now.
Hard braking activates ABS !
All seems to be good now !
Before changing anti-lock system, maybe watch them !
Last edited by Tof; 12-23-2020 at 05:43 PM.
Reason: Error translation.
my 86 had the exact same issue. i knew it was in the abs but didnt have the time to disassemble and clean. I replaced with one from wrecker for $500 (yesss!!!) and now that you have posted i see how easy it is. very nice work.
I have a locked right front wheel despite installing an new caliper and flex hose. Likely same issue as yours but mine is a 90 so I don't know if the pump will be the same. Its also a convertible so from what I've read the pump is under the back panel by the speaker which will probably be tougher to access. The place that's going to look at it is a vette specialist but they are talking replacing with good used one but I will definitely ask them about cleaning instead. The used pumps run 600 bucks so that would pay for a lot of labor.
Thanks for your post. I don't think I'll tackle it myself but it will give me some insight into the repair.
I will flush brake fluid more often after seeing this. If you are going to put a fine screen/filter in the brake system why not put it where people like me can replace it easily. That way everyone on this site can remind people to flush your brake fluid and make sure you change the filter. Dan
I hope the mechanic I'm going to see is into cleaning the abs pump rather than replacing with a used one. I'd rather start out with the original pump cleaned than getting a used one which could already be ready to block.
Yes of course ! But remember ABS system may have other problem than this. Electricity/eletronic, solenoids, module... ?
If brake line is blocked, this will be probably like my problem.
Yes I posted earlier that my right front is locked even after a flex hose and caliper change. Releases on its own after a relatively short time period. I'm guessing a blockage in the abs pump which is acting like a check valve.
I have a quick question. I saw the clogged screen filter like everyone else. Is there a way to backwash this screen without removal and disassembly? Like pushing fluid from each wheel backwards. Dan
Thank you so much for posting this. I am going thru a brake problem with my 88, the rear will not bleed, with vacum or with a reverse (push) pump. The front brakes have been reverse bled, just can't get the rear to bleed. I am going to use my reverse pump on the rear and check at each connection. I have bought new rubber brake lines for the rear in case they have collapsed on the inside and are blocking the fluid. After seeing this post, I will bet the screen in the ABS unit, is blocked and will not let fluid pass thru it, causing the blockage. Thanks !!!!!
I have a quick question. I saw the clogged screen filter like everyone else. Is there a way to backwash this screen without removal and disassembly? Like pushing fluid from each wheel backwards. Dan
It's better to remove one of the 2 filters of each solenoid, to let dirty go out. One of these is easy to remove. Just pull it with pliers.
You'll be serene.
Well my locked wheel will bleed but won't release for awhile afterwards. Makes me think its not the screen but rather a blockage in one of the passages but who knows.
Fluid comes easily at all purge screws ! Yes !
Vette is braking correctly now.
Hard braking activates ABS !
All seems to be good now !
Hello !
I update this topic 1- When I looked closer (and later), my car had trouble braking well. The fluid came in fine, but eventually there was a restriction in the ABS circuit. There was always a delay to the left, compared to the right side, just as I pressed the pedal. During pressing brake pedal, the car turned on the right. When the pedal was finally pressed, it turned straight good. Difference was just on every first impulse (purge was good, but fluid has difficulties to go out by the purge bolt).
2- I thought anti-lock was working, but that was only its electric motor !
I bought antoher anti-lock system. Its brake circuit very dirty with rust, but was in "good condition", but anti-lock system was all rusted and electric motor seized ! (Money was refund due to seller lies, and anyway I kept this unit )
I decided to make 1 with 2, the second unit will be the master.
Electric motor from the last unit ("100% checked" by seller lol) :
Anti-lock pistons, welcome to rust. All is seized.
First, I remove the external screws holding these pistons.
With a pin punch, take out the pistons.
Hum.....
For each, take out the grille, by pulling it and o-rings.
We have this now.
Take out the aluminum lower end. Be really careful ! Take rags and a clamp, in a vice.
Be careful, there are small ***** and spring, don't loose them ! Just take your time to do it.
Then, find a pin (or pin punch) which fits into the piston.
In the vice, hammer on the pin punch.
The internal piston is out ! Just pull it after.
Be careful not to loose small parts !
Clean and rub with a light abrasive (don't know the tehcnical word in english, just show you a picture), the parts which need it.
Clean it, blow it.
Averything is ready for reassembly.
Really take time to look where is everything. For exemple, I think this spring is lightly conic. If yes, the larger side is ball side.
Pistons will look like this, in place.
BUT, you have to reassembly the electric motor first, and THEN reassembly the pistons. (I took my old electric motor, which was is good condition).
Don't forget external bolt, on each side.
Other thing, i forgot to talk about those big screws. (24mm).
Clean and blow the interior before reassembly.
Anti lock works perfectly now. Braking is satisfying
Hope this will help someone ! Sorry is english is not good
12-23-2020, 04:29 PM
Anti-lock (ABS) : Brake line blocked. My dissaembly.
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Sorry is english is not good 
