1973 cadillac eldoradeo , brake problem no back brakes and booster problem

[34858]

Hi i'm have problems with brakes had the master cylinder changed still had a soft brake.had it checked and there are no rear brakes and the front disk hardly work ,they belive its the booster?? need help
?what does the vacuum control?? thanks kenny

[TJ Hopland]

A booster problem isn't going to cause a soft pedal unless for some reason its not allowing the master cylinder to fully retract to its rest position.   There really isn't anything in the booster itself that would cause that.  When it happens its usually due to the wrong booster / mc combination.

Does the pedal start out firm after bleeding or can you just never get it firm?  Have we talked about this issue with this car before?

Lack of back brakes with multiple masters assuming they are properly assembled and reasonably well adjusted would just about have to be an issue with the proportioning valve unless its a bad hose?  Has the rear hose been changed recently?  They can have internal failures and plug up.  Usually a hose failure keeps the brakes from releasing but they can also keep it from applying.

[Jeff Rosansky CLC #28373]

My 70 Deville had no rear brakes when we got it. I bled them and had issues getting the fluid to flow. When it finally did, it was absolutely filthy.
If the old master really failed, there could be debris in the lines too.
I know that some Eldorado brakes are different, and I don't know about yours. But there may be a way to bleed the brakes by inserting a fitting in the proportioning valve to allow bleeding.
So, unless something is showing that the master is really bad, I would start with a line flush. Do the fronts too. How are the rubber hoses?

Good luck,
Jeff R

[34858]

Hi had the brake changed, the master cyl,rear wheel cyl, bake hose rear, and 2 brake lines, brake pads and brake booster.The pedel is firm  when. Will check with the mech, thanks Kenny

[TJ Hopland]

So if I am reading correctly pedal starts out firm but with no rear brakes then the pedal gets soft.   How many applications are we talking before it gets soft?   And then what do you have to do to get it firm again?

It could be that maybe the prop valve is mostly stuck and eventually some fluid makes it past it to the rear which isn't bleed or adjusted so pedal goes soft.....   I think I would try bleeding the fittings under the hood.   Try and the rear output and input lines on the prop valve.  You should be able to figure out if that is where its getting stopped. 


I'm not sure the Eldo's are really different than the other cars when it comes to brakes at this point.  Front single piston calipers and the rear is drums with the single line/hose to the T on the solid axle and hard lines out out the wheel cylinders.  76-78 rear disc was standard and that came with hydro booster that ran off power steering pump.  79-85 went back to vacuum booster unless it was a diesel but stayed disc and independent suspension so 2 hoses.   

[34858]

Hi no the mech told me it is a hard pedel no brake in rear and front hardly no brakes, he also told me that he tried the brake with and without the booster and there was no difference.thank kenny

[TJ Hopland]

Does this thing have the track master ABS?  I think the brake pedal had some sort of logo on it and all the dodads are kinda tucked in the drivers side fender area under the hood.

IF it doesn't have the track master then I think you need to tow it to a different shop.  This car doesn't really have any unique features, other than rear drums its not even that much different than a modern car.   

[34858]

Hi problem solved he changed the booster, this time they put the correct booster and it worked.
thanks for all the info kenny

[The Tassie Devil(le)]

Does this thing have the track master ABS?  I think the brake pedal had some sort of logo on it and all the dodads are kinda tucked in the drivers side fender area under the hood.   

Not all cars fitted with Track Master have the added attachment to the brake pedal.

My '72 came with all the options, including Track Master, but the brake pedal was plain.   I managed to locate a proper pedal rubber with the Track Master logo on it.

Bruce.

[34858]

hi thanks kenny