Hydroboost question

[Blackdog3]

Hey Gang, i am not familiar with hydroboost all that much. I know my brake petal was hard as steel and now it goes to the floor. The rear portion of the master cylinder was empty. I filled it up and i have to bleed the brakes now. But where did the fluid go? I am baffled. Is my hydroboost bad>?

Chris

 

[Mr Clean]

sounds like you have a rear brake cylinder leaking. I had hydro-boost on my short bed, gas engine and loved it. If your hydro-boost goes bad you will see power steering fluid all over it, and your power steering pump will whine like it is out of fluid. I would check all of your brake lines, while someone steps on the peddle.

 

[crazy4offroad]

X2 I've busted several wheel cylinders, poorly designed in my opinion. Look at the inside sidewalls of your rear tires. If it looks like one has been slinging fluid, you've found which wheel cylinder blew. They would usually do that if I had to slam on the brakes, like an emergency braking situation. I just figured I would always have to check my wheel cylinders when I got home if that happened.

 

[bucket]

Exact same thing happened to me over the weekend, but the master cylinder was low, not empty. It started off on Sat with the pedal a little low compared to normal, then today, the brakes turned to crap in a hurry. If you pump the pedal a couple times, the brakes work great.

There is no signs of leakage under the truck. I'm betting on a failed master cylinder. The fluid could have seeped out the rear cylinder seal over the winter, explaining the low fluid.

 

[oneluckypops]

He said the rear chamber was out of fluid, That would indicate the FRONT brakes NOT the rear. The Big chamber is for front and the smaller chamber is for the Rear brakes.

As your Pads wear the pistons in the calipers extend out further which takes fluid from the resevoir, so your master cylinder will be low on fluid, BUT it shouldnt be completely empty because of worn out pads. Like others have said Inspect all your Brake Lines, Master cylinder, Proportioning valve, Ect. ect. If you dont find any leaks then suspect the master cylinder.

 

[HotRodPC]

Yes, the larger resevoir is for the front. My smaller resevoir is in the back. I'd have to go with he lost a wheel cylinder too. If you'll look behind the tire into the wheel, you are likley to find its very wet on one side or the other. That is where your fluid is going. Unless of course it was a slow gradual leak, then it can actually be absorbed in the brake dust, but even then usually you can see a drip or something or fluid. I've had the same issue on a 14b FF rear axle.

The Repair and good as New !!!

 

[HotRodPC]

BTW, I have no fear of rebuilding wheel cylinders whatsover. Do keep in mind, if you do not have a brake hone to get all the rust out where the piston seals slide, you're wasting your time. When I did mine, I expected the wheel cylinder rebuild kit to be about $5 each and they were. Just for giggles, I also asked about price for NEW wheel cylinders which came with lifetime warranty and they were $11.99. So it was double the price, but I didn't have to question the bore size, didn't have to hone the cylinder, got a full warranty for as long as I own the truck and it was a no brainer. If that is the case with yours, just buy new wheel cylinders. There does come a point where you can hone them, and of course it takes a lot, but you hone them to much then your pistons and pistons seals will leak much sooner than later. Just consider it insurance and buy new wheel cylinders if they're under $15 each. Also get a new inner hub seal. That will help keep gear oil off your brake pads on the Full Floaters. Got any questions just ask !!!

Also notice how much meat was left on my brake shoes. I didn't replace those. I cleaned them good with brake clean as I did the brake hardware. Also lubed the adjuster with white lithium grease and made sure it moved freely throughout the whole threads. After the cleaning and dry, hit the brake shoe material with some medium to course sandpaper to sand off a layer of material giving a new surface of brake shoe. Don't breathe that dust. I also didn't see the need to have the drums turned since I didn't do a shoe replacement and they looked good with no hot spots, or grooves. I did also hit the drums with medium sandpaper too just to break down any glaze even though it didn't appear to have any. With seals, new wheel cylinders and 2 cans of break clean, back brakes were good as new for about $45 and no more adding brake fluid.

 

[RetroC10Sport]

wise to replace wheel cylinders in pairs...When one goes, the other will soon.

 

[HotRodPC]

wise to replace wheel cylinders in pairs...When one goes, the other will soon.

Absolutley !!! In fact, I have pictured above the worst side that let go. When I did the other side too, it was not as bad as this yet, but you could tell, it certainly had seeping leaking just not as bad just yet. What pissed me off was, by looking at those pads you can tell, they had been replaced not long ago before I bought the truck. You can get a good 40,000-60,000 miles out of those biggo rear brake shoes. In my mind, that is like 5 years worth of brake shoes, and knowing brake rubber parts get hard, I'd have replaced those wheel cylinders when I did the shoes just because, chances of them starting to leak inside of 5 years would be good, so do it right and replace the ****. DUHH !!!

 

[Blackdog3]

Thanks for all responses. I cant find any leaks in the system. I crawled all over the place while my buddy pumped the brakes. I guess i will replace the master cylinder.

Chris

 

[HotRodPC]

If it were master cylinder, you should lose fluid in both resevoirs. Of course the smaller one will run out quicker, so the small be out, and the big one be low. But the fluid would be laking between master and the hyrdoboost so you should be able to see the brake fluid in he engine compatment.

 

[bucket]

Not really. The master cylinder can fail in a way that it just bleeds off pressure internally. When they do leak, it comes out the seal at the rear and you might not notice evidence of a leak. Brake fluid evaporates, so if it's just seeping, it may never be seen. It often just leaks into the vacuum booster or hydroboost unit too, also making it difficult to spot a leak.

 

[crazy4offroad]

If you have carpet/rubber mat in your cab pull it back on the driver's side and see if the fluid has been running down on the inside of the cab. Also if the rear reservoir was completely empty, the master cylinder will need bench bled to get the air pocket out, otherwise the fluid may never make it down into the lines. You can bench bleed the MS on the truck, I take the line off from the reservoir you want to bleed, place your finger over the hole and have someone apply the brakes very slowly. Allow the fluid to come out but once they let off the pedal you have to seal the port off real tight with your finger. This purges the air and makes the MS draw fluid into the chamber. Do this 3 or 4 times then put the line back on, then I usually gravity bleed it for a half hour or more before trying to pressure bleed it.

 

[HotRodPC]

Not really. The master cylinder can fail in a way that it just bleeds off pressure internally. When they do leak, it comes out the seal at the rear and you might not notice evidence of a leak. Brake fluid evaporates, so if it's just seeping, it may never be seen. It often just leaks into the vacuum booster or hydroboost unit too, also making it difficult to spot a leak.

Yep, the fluid can stay in the MC and the piston just go right past the fluid and not compress or push it, but he mentioned he lost fluid. Depending on how fast he loses it, it many times will be obvious.

How fast are you losing the fluid Bdog?

 

[Blackdog3]

I haven't lost any fluid in a day or so..... but i also haven't driven it.

Chris