Hydroboost question..

[diesel4me]

Yesterday I went to drive my '82 GMC diesel ,and when I went to stop at the end of my driveway,I almost went in the street--the brake pedal was firm,but it acted like it had no power assist,or not the usual amount..I had to really press hard to stop it..the pedal felt like it may have a bit more travel than before too..

The brake fluid is full,the master cylinder was replaced about a year ago,power steering was full too,no apparent leaks on any steel brake lines or P/S lines..
The P/S feels normal,so I assume the pump is OK..

It acts as if it has seized calipers or wheel cylinders,or a pinched line or bad rubber brake hose--but all those were replaced in recent years ,with low miles since,and the truck seemed normal last wednesday when I drove it..the calipers aren't dragging either,nor does it pull to one side when braking..

The only other thing I can think of,is it was only 6 above Friday night and almost as cold the night before,and it was maybe 30 degrees when I started it up...

A friend suggested maybe the brake fluid got water in it and it froze,but it looks clean in the master cylinder,and I've bled it enough times in recent years (along with new steel lines in 2012),so I kind of doubt it is moisture..

I drove the truck about 10 miles (5 each way),and on the way back,the brakes felt like they had a bit more power assist than right after the cold start..

Has anyone else with a hydroboost setup experienced a hard pedal in frigid weather ?.. I have not had to touch a hydroboost unit ever,so I'm not very experienced as far as how they work,or if thick cold fluid can affect them,etc..

I prefer a good old vacuum booster myself--I think it is kind of dangerous trusting a 3/4 or 1 ton truck to have power brakes when if a P/S belt or hose fails,now you have NO power brakes OR steering!..

I've come close to crashing my truck after the P/S belt got wet going thru deep puddles on a highway,and having the P/S suddenly "go away",and the brakes felt like a block of wood was under the pedal,I had to stand up off the seat and it barely slowed it down..

So,anyone else have any hydroboost experience ?..

 

[Fordum]

The only boost experience I have had was on an 80s or 90s model Lincoln Town Car. For a year or so, they came stock with hydroboost brakes.
One day I was driving it, came to a stop sign, and had the block of wood sensation.
Power steering was fine, and, being young, strong, and slightly panicked, I got it stopped.
Eased forward, touched the brakes, and they were fine.
Drove a little farther, and it happened again. Naturally I had to be driving in a neighborhood with lots of stop signs. Once I was used to it, I didn't have a lot of trouble. I just made sure I started braking farther away from where I needed to stop.
If the pedal felt normal, I just eased on up. If it felt hard, I started cranking on it sooner.

Figured I could get home on it, and take it to the dealer next day. It was still in warranty. Then, the other shoe dropped. Rolled up to a stop sign, fortunately no one behind me. Went to stop, block of wood.
Braced, stepped down hard as I could on the brake, and the boost kicked in!
Not fun.
Left black skid marks from all four wheels. That started happening a little more often as I went on.

I got home with it, called the dealer's wrecker to come get it next day.
Went by the shop that afternoon, they said it was ready. Tech who did the first test drive to figure out what was wrong, just said WOW. He still had a steering wheel shaped bruise on his forehead.
I asked what was wrong, they said since it was warranty, they just replaced the whole boost unit and sent the old one back to Ford.
Not a lot of help for you, I'm afraid.

As far as I know, they did not use that on many years of those cars. Either because of problems like that, or the whole PS belt breakage/ no boost situation.

Pretty sure it was not the same car, but it was a Town Car that had the horn as a rubber ring all the way around the inside of the steering wheel. I loved that idea. To blow the horn, you just squeezed the steering wheel where ever you happened to be holding it.
But, there was a downside. If you lost power steering, like that car did a couple of times before we got it fixed, you started constantly blowing the horn as you were wrestling that boat to the curb. No way to turn the wheel without squeezing it hard enough to blow the horn.
Of course, since you had just lost most of your maneuverability, maybe that was a good thing........

 

[campfire]

Yesterday I went to drive my '82 GMC diesel ,and when I went to stop at the end of my driveway,I almost went in the street--the brake pedal was firm,but it acted like it had no power assist,or not the usual amount..I had to really press hard to stop it..the pedal felt like it may have a bit more travel than before too..

If it felt very solid and it did stop, it sounds like a lack of boost, not a brake issue. Even the feeling that the pedal travel had increased

Did the power steering function during this episode? Water contamination in the P/S system could have frozen, or you could be looking at a hydroboost repair.

 

[campfire]

I think it is kind of dangerous trusting a 3/4 or 1 ton truck to have power brakes when if a P/S belt or hose fails,now you have NO power brakes OR steering!..

Is it significantly different from the ever-cracking vacuum lines that render vacuum boosters useless? I'd think keeping it simple (with one boost system instead of two) is a good thing.

 

[diesel4me]

The P/S acted "normal" during the ride..the belt has squealed a bit at times after I put on new tie rod ends that are still "stiff",and had the plow on it--it could probably stand to be tightened up a bit more,but I doubt its loose enough to be causing the braking issue..
I can turn the wheel and apply the brakes to make a corner and not feel any loss of P/S assist..

The only trouble I've had with vacuum power brakes is the diaphram going south in very old or high mileage vehicles I've owned--I only had to replace two of them,and good used ones were plentiful at salvage yards,for under $50...cant find a good used hydroboost around here for that--if your lucky enough to see a truck with an unmolested unit around here,chances are good it has sat so long it'll be junk once you get it all installed and go to use it..
I'm in no condition to be doing a hydroboost R&R now either...if its "bad",the truck may end up being retired to "yard truck" status..
I have no desire to strip parts off the Suburban either,then I'll have 2 useless hulks in the yard..

My G-10 van has manual brakes--it never bothered me either,the pedal effort is greater,yes,but at least there's nothing to fail between my foot and the master cylinder..I learned on that thing never use mettalic brake pads on manual brakes,only organics...
My first ride with the mettalic pads resulted in it having almost no braking power after a long downgrade in NY state..at the advice of the Bendix rep at work,I put organic pads back in it,and the difference was amazing..
I could actually lock up the front tires,something that was impossible with mettalics,it acted much like a vehicle with power brakes with no vacuum would..

 

[sweetk30]

sometimes if steering and braking at the same time it can cause 1 or the other to not assist .

 

[Magikal]

I live in north Idaho with plenty of cold temps and I run hydro boost with no issues, so is not the temperature. I had a similar issue before. Check the hose plumbing, be sure return line from gear box and hydro boost are correct and one isn't backwards. I ended up replacing my pump in my case

 

[Blue85]

Water is heavier than brake fluid, so it tends to end up in the calipers. Braking should thaw it, which would restore braking, at least until the calipers/cylinders rust. It would be weird for all 4 wheels to have the problem, which does make it sound more like a booster or master problem. The normal test for the booster is to press the pedal with the engine off and on to compare. That little cylinder on the HB stores some charge, so it takes a few pumps of the pedal to bleed that off. You could disconnect the return line and have it dump into a container or something to prove the fluid is flowing (wouldn't want to run the pump with a pressure line loose). You can also crack the bleeders to ensure fluid comes out with pressure and see if the pedal stiffness changes.

 

[sweetk30]

also hydroboost test is this .

pump brakes 10x with engine off to drain the storage can .

then with foot pressing on brake pedal start engine . pedal should drop then come back .

 

[diesel4me]

All the OEM hoses are still intact and it has always stopped and steered OK previously,so I assume the pump is OK,no leaks and the fluid is up to the correct level,and it steers OK,though I have noticed its been a bit stiffer feeling after replacing all the tie rod ends a few months ago--they might have got even tighter due to the extreme cold too..

But its the brakes that aren't acting right,not the steering..

It was too dam cold to be outside for long yesterday to do much diagnosis,I just checked all the fluid levels (and had to add a bit of coolant for the first time in a long time),everything else was full..

I did notice the P/S v-belt is kind of on the loose side,so I am hoping tightening it might help the issue,I'm going to wait for a warmer day to do that,tomorrow may hit 45 here,and I'll try that and report back and tell you guys if any improvement was noted..

I noticed the P/S has double pulleys but only one crank pulley--I'd think having two v-belts (matched pair) would have been a good idea for safety's sake,seeing losing the one belt would leave you with no power steering OR brakes..(hate to be towing if that happened,you'd be dead !)..

I'll try the test Sweet K30 mentioned after I get it started and warmed up..its always a crap shoot whether it'll even fire up below 25 degrees,with old batteries and thick 15W-40 oil in it..

The more I look at the truck,the more things I see I do not like..and am amazed I've been lucky to drive it in this shape so far and long,without having a breakdown..

Rotted inner fenders for one,the drivers side is barely attached, and I've added a few pieces of sheet metal to it just keep the plow control valve from ripping off (again) and the battery trays are about all that's keeping them bolted on up front..the fenders themselves have some rot too,and I'm pretty sure the body mounts up front have the frame brackets rotted enough to let the rubber cushions pull through..
Long story short--it could use a whole nose,really..

The tank heater in the heater hoses looks like it may be leaking,the plow pump has been leaking fluid too,radiator is showing signs of old age and potential failure,and I have no clue if the engine will go another 100,000 or 10 miles,so I'm not very enthused about fixing it up,even if my physical condition would allow me too..

I know there will be some issues on the frame in the rear,though very minor,and a rear spring mount is starting to crumble in one spot--its highly discouraging the more I look at it overall--the step side bed is pretty much roached now too..truck has shocks so old on it they probably do nothing,and it will likely need axle u-joints again soon,rotors are rusting away inside too,brake pads are about due,and the calipers were Autozone ones I put on it probably 10 years ago..

The '85 Suburban isn't much better off either,the ailing 700R4 is the worst part of that thing,and the rockers rotted off it--it'll be another headache with brake problems and various other things from sitting too long,if I were to swap the plates to that thing and try using it as a daily driver..It will need all the steel lines,brake hoses,calipers,and the 6.2 in it will likely need glow plugs and maybe more..

I'm getting to the point I may just sell everything off,and get something else to plow my driveway,like a farm tractor/loader,then I will not have to register a truck just to plow with,and buy something else to daily drive..

It wouldn't be a big deal for me to fix the truck(s) up if I felt better,but I dont...if I did,I'd have the truck in my garage all apart,in hopes of fixing everything at once,instead of having one failure after another..

I have been keeping an eye out for a better later model truck,but every one I've seen around here is a worse P-O-S than mine is--rotted frames,bodies,blown transmissions,engines that rap,etc,are all I've seen in my price range..the few old square bodies I came across were still in better shape underneath than every 1995 or later truck I looked at..mine still is too..even those,no better off than what my truck is now,are priced at 2500+ bucks..