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MtylerAZ · 08-31-2020, 10:48 AM

I have a 91 Damon, F53 460 motor. MH been sitting for 5+ years, trying to resurrect it

Working on getting brakes to work properly this last weekend. Pedal goes to the floor with no resistance. I first flushed out all the brake lines with new DOT3 fluid, used almost 2 gallons getting the old fluid out in order to run clear. Did the farthest rears first, then moved to the front. Yet pedal still has no brakes. PR - DR - PF - DR...

I attempted to flush out the power steering system, but not 100% the proper effective method on it. It might still have some air or old fluid in it. This system has the remote tank mounted up on the firewall, with 2 hosed going into it, large hose goes down towards the cooler for it, and cooler seems to go back towards the hydro boost, and then has a hose going back to the steering box, and then back to the pump?

At first flush, the pump whined for a while while i was turning wheels back and forth, then it cleared up after about 10-15 minutes of doing that, now turning is easy again and no PS whine...seems ok..

Yet not sure if no brake issue is the hydroboost or aMaster cylinder issue. I am not 100% I have the Hydro bleed right. I was pulling the PS hose off the lower cooler and running it for a bit, and refilling, ran again, filled it.. did this about 4 times....fluid was coming out nice and clean again. BTW I was using red ATF fluid, as that was what was in it prior.

After all this, brake pedal still goes to floor and no stopping. Its not from hot fluid as its not being driven...cold sitting in lot.

Anyone have this issues? Is there a better way to bleed/flush the PS/HYDRO system? Any good methods to test to see whats the issue?

I do have a hunch the MC is shot...it was barely pumping anything out when bleeding brakes.

Thanks again for any help.

R Bob · 08-31-2020, 11:00 AM

Drum brakes? The shoes may need adjusting. There may be a way to check the MC with a bleeder hose setup, from the outlet back up into the reservoir. That's the way MC's are bench bled.

MtylerAZ · 08-31-2020, 11:52 AM

They are all disk brakes, not drums.

GypsyR · 08-31-2020, 12:35 PM

Sounds like you're going to have to get a master cylinder. The hydroboost is just "power assist" to make it easier for you to press the pedal hard enough to brake effectively. Your brakes would still be fully functional without the boost, you just have to be King Kong to press the pedal hard enough to panic stop.

twinboat · 08-31-2020, 01:39 PM

If the caliper bleeder valves are on top ( Check that ), like they should be, i would suspect the master cylinder bypassing.

Time for a new one.

MtylerAZ · 08-31-2020, 04:22 PM

Quote:

Originally Posted by twinboat

If the caliper bleeder valves are on top ( Check that ), like they should be, i would suspect the master cylinder bypassing.

Time for a new one.

Yea bleeder valves are pretty much on top of the caliper, on the side but about an inch or so from the top.

im going to try a new MC this weekend, bench bleed it and reburp the lines to see if it fixes it.

MtylerAZ · 08-31-2020, 04:24 PM

Quote:

Originally Posted by GypsyR

Sounds like you're going to have to get a master cylinder. The hydroboost is just "power assist" to make it easier for you to press the pedal hard enough to brake effectively. Your brakes would still be fully functional without the boost, you just have to be King Kong to press the pedal hard enough to panic stop.

Gotcha.

Based on how i flushed out the PS and hydroboost, was that the proper way to do that?
Ive read that if there is still air in the HB, it will act up as well.

GypsyR · 08-31-2020, 05:36 PM

Quote:

Originally Posted by MtylerAZ

Gotcha.

Based on how i flushed out the PS and hydroboost, was that the proper way to do that?
Ive read that if there is still air in the HB, it will act up as well.

Sounds good to me. Some power steering systems need a flush once in a while. If/when there is air in the system you will be like" Holy cow, this brake pedal is hard to press!" Since the master cylinder is just letting it drop to the floor we can't really say if your hydroboost is good. But odds are if there's no power steering type whining noise then it's OK.

I drove a Chevy chassis the other day that had pump problems and the hydroboost was kind of intermittent. That'll start your heart. All normal and then "Whoa! I said whoa!". Happily it was just a truck instead of an RV but I still barely got it to stop when it went flaky.