Mike Romain

I would guess you have power brake booster issues or MC issues. The
booster is the unit between the master and the firewall.

I also have seen rebuilt masters go 'hard' too. An internal seal or
something went strange. The one I saw recently was standard brakes, so
there was no power or vacuum issues, others I have seen in the past had
a vacuum issue of some sorts that affected the idle if you pumped on the
'hard' pedal.

Mike
86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00
88 Cherokee 235 BFG AT's



Paul wrote:
>
> Attention all you amateur and pro jeep mechanics out there...I have a
> problem for ya
>
> I have a 1995 Jeep Wrangler, 5 speed, 4.0L engine.
> The jeep is totally stock with P21575R15 tires (Goodyear Wrangler
> Radials)
> The jeep developed a problem last summer which has appeared again this
> summer. After work, when the temperature is 88 or better, I jump in
> the jeep to start the trek home. After I start up the jeep the brake
> pedal feels hard to push. I still have very good brakes and it stops
> ok, it's just that the pedal feels much stiffer. When this happens, on
> the way home I have very little power going up hills. I usually have
> to downshift to 3rd to make hills that I could normally make in 4th
> gear. In the morning on my trip into work the jeep seems to run fine.
> When the temperature is below 80 the Jeep seems to run fine. Before
> you answer..here are some of the things I have already done:
>
> new spark plugs, distributor cap and rotor
>
> new ignition wires
>
> new oxygen sensor
>
> Jeep dealer put the scan tool on the computer and said I needed a new
> crankshaft position sensor which he replaced. He also put fuel
> injector cleaner in fuel rail and some other cleaner in gas tank.
> He also set the timing to chrysler specs using the scan tool.
>
> Mechanic sprayed Gumout carb cleaner all over the vaccuum lines to see
> if any were leaking. Found no leaks. Sprayed around the power brake
> unit..no leaks.
>
> I had the brakes bled twice (I thought trapped air was expanding and
> causing the brakes to drag)
>
> I adjusted the rear brakes with brake calipers and they are not
> dragging. The parking brake appears to work ok.
>
> Both rear wheel cylinders new last year
>
> Rebuilt master brake cylinder put on last year..
>
> New Clutch master/slave linkage installed
> New clutch installed, but this was just done a month ago, long after
> the problem had been noticed. Same for the clutch linkage.
>
> The fuel filter is less than a year old and the air cleaner is new.
>
> I'm out of ideas and I'm thinking of trading my beloved YJ in for a
> (excuse the expression) rice box.
>
> My theories, none of which have been tested...........
>
> 1. A front brake caliper piston is sticking and causing a front brake
> to drag. I smell no brake smell and the vehicle stops arrow straight.
> Would a sticking piston cause a hard brake pedal? I dont think so.
> Loss of manifold vaccuum causes the hard pedal.
>
> 2. The power brake booster is leaking internally when the temperature
> gets really hot. I can jump into my jeep after work and press the
> brake pedal in 2 or 3 times before I run out of stored vaccuum. Thus
> the booster has stored this vaccuum for 9 hours...could the brake
> power booster still be bad?
>
> What do you think??? Got any ideas??
>
> Thanks in advance
>
> Paul