hi this is the first time iv,e used this site.
wounded if anyone could help me?a freind of mine has bought a cadillac allante 1990!!!.and this is first time i,ve worked on this type of car.the brakes have failed,the pedal is rock hard!!!! no assistance.i had a breif look on the net and found a couple of trouble shooting methods.
i have cheked for fault codes and it gave me.E0521 history,R051 history,B448 history,and B552 history.this is all could get out of the diagnotics via the a/c contol unit? i tied bridging pins A+H on the diagnostic plug but the brake light on the dash would not flash it stays on constantly?also on the dash it tells me the abs and the traction is disabled? i think i disabled it by carring out checks i found on the the net!!! it told me to disable the pressure by pumping the brake pedeal 25 times wih ignition off then to check how long the pump runs for?this was suppose to only run fot about 30 seconds but it runs constantly until igniton is switched off?after i did this i found the brakes worked fine for about 30 seconds but then failed again!!! would be gratefull if anyone could help me out!!!!

going by your post, it sounds like the ac***ulator has failed.
not uncommon after 15+ years. about $200 for a retro.
then again, is the high pressure hose connected and in
working condition? if that hose fails, you also get the same
problem as the ac***ulator doesnt get pressurized.

i directed someone here and hopefully will come
and provide more detailed diagnostics.

hopefully the master cyl is ok. a bit more expensive.

regardless of the outcome, you need to flush out the whole system
and get fresh DOT3 brake fluid in there.

===============

edit ....

i see Dick (allantesource) has arrived .. go with his diag below but DO FLUSH the system ....

When the pump runs all the time when the ignition is on, the pedal remains hard, and the red brake warning light stays on, the pump is not generating pressure. It must be replaced. We have rebuilt ones in stock. New ones are over $2000 list.

ORIGINAL: dave

hi this is the first time iv,e used this site.
wounded if anyone could help me?a freind of mine has bought a cadillac allante 1990!!!.and this is first time i,ve worked on this type of car.the brakes have failed,the pedal is rock hard!!!! no assistance.i had a breif look on the net and found a couple of trouble shooting methods.
i have cheked for fault codes and it gave me.E0521 history,R051 history,B448 history,and B552 history.this is all could get out of the diagnotics via the a/c contol unit? i tied bridging pins A+H on the diagnostic plug but the brake light on the dash would not flash it stays on constantly?also on the dash it tells me the abs and the traction is disabled? i think i disabled it by carring out checks i found on the the net!!! it told me to disable the pressure by pumping the brake pedeal 25 times wih ignition off then to check how long the pump runs for?this was suppose to only run fot about 30 seconds but it runs constantly until igniton is switched off?after i did this i found the brakes worked fine for about 30 seconds but then failed again!!! would be gratefull if anyone could help me out!!!!


I doubt that you disabled traction contol by doing checks. You CAN disable traction control for 11 ignition cycles on the 93, not positive about the 90. Your brake situation makes the auto unsafe to drive. Resident expert D. hussey is the best source I am aware of regarding the brakes on pre '93's. Good luck.

G.A.R.Y.

i see Dick (allantesource) has arrived.
go with his diag.

but FLUSH the system no matter what...