Hydroboost problems

Pulling my hair out trying to get the brakes to work.

Have a Mustang Master Cylinder, manual steering and a LS Power Steering pump.

One line from PS to MC. Two lines from MC on a "T" fitting back to Power Steering reservoir.

Power bled lines, bench bled MC and power bled MC while in the car.

First push on the brake pedal is stiff, second is mush and straight to the floor.

Let the car sit overnight, and the break pedal stiffens up again for the first push, but mush on the following applications.

Anyone have any ideal or advice?

I'm not completely sure but maybe that tee is messing things up for you. The two return lines might need there own nipples on the reservoir. The HB line that normally goes to the P.S. valve, will be higher pressure than the return hose. From what I've been reading, back pressure on the return hose, is bad.

I ran mine setup without the power steering rack as you describe. Temps were a bit hot so i put a cooler inline from the high pressure return from the hydraboost, then T'ed into the low pressure line and back to the PS pump. Sounds like you either have air in the line or a defective HB.

Thanks for replies! It's very frustrating not knowing exactly how to fix the issue. I will power bleed the Master Cylinder again tonight and keep my fingers crossed that does the trick.

I have two lines coming out of the MC going to a 3 way "T" fitting for the two brake lines to the front brake calipers, and one that runs to the back calipers and then "T" off at the back end.

The pedal is also very slow to return after the initial push and almost feels like there is a vacuum with a reverse pedal feel.

It's a 1984 EURO spec car so I don't know if that makes any sort of difference?

Don't forget to bleed the two side ports on the mustang MC.

I too thought the brake pedal was a bit slow to return with the hydraboost. That may be a function of not having the power steering rack in place.

Thanks for all the advice and help with all of this Tim.

Where did you purchase your cooler and fittings from?

I would like to replace the fitting I have on the bottom of the MC that connects the 12mm outlet to the 10mm brake line, as well as the high pressure outlet on the MC to the power steering line that I have "T" off back into the reservoir.

See pics below for cooler placement.  I'll make you a good deal on it if you are interested.

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Will you sell it complete with all the fittings and lines?

Do you have the fitting for the lower front brake line on the MC?

wanczykj wrote:Will you sell it complete with all the fittings and lines?

Do you have the fitting for the lower front brake line on the MC?

Yes, send me a PM.

I'll have to look for the MC fitting, not sure what I did with it.

Just sent you a PM

Lemming,
You mentioned bleeding the 2 side ports on the mustang hydroboost. What exactly do you mean?

C4924S wrote:Lemming,
You mentioned bleeding the 2 side ports on the mustang hydroboost. What exactly do you mean?

He was talking about bleeding the mustang master cylinder. It has two bleed ports.

Hotrodz of Dallas wrote:Lemming,
You mentioned bleeding the 2 side ports on the mustang hydroboost. What exactly do you mean?

He was talking about bleeding the mustang master cylinder. It has two bleed ports.

Ahh he wasn’t talking about the mustang Hydroboost unit then?

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Yeah, some people use the mustang master cylinder as well as the mustang HB. I always use the Porsche master cylinder. Mush easier to hook up and the brake bias stays correct.