SabrToothSqrl

Is there anyway to tell if these are wearing out? It still stops fine, just feels like it takes a lot of foot force. And wow do I miss the dead pedal for my left foot from my other car.

I had the brake booster go out while going down a huge hill in my 1995 Tahoe. Almost wrecked into a parked car. ended up in a lawn.

I'd rather just replace it before that occurs. I did the one in my 95 Tahoe without issue myself at 18 or 19.

Anyone else had to do this? Do they sell any that are more powerful? I thought some had hydro boost from years ago, but I'm not ready to upgrade to that ($$$).

thanks!

I guess I could also replace all the brake fluid. Its also 9 years old... so I'll do that too. Check the manual or fluid cap for type, then buy some.

oilcanhenry

With a 4X4 if you need to change out the brake fluid after three years. Five is maximum so you need to do that now. Brake boosters are easy to change, compared to the clutch master cylinder on a manual transmission, IME. Nothing wrong with the stock unit IMO.

SabrToothSqrl

I looked under the hood, says DOT3. I believe DOT3/4 are compatible, so I'll get some tonight and replace it within the week.
Then I'll see how the pedal feels (not expecting it to be better though) and revisit the booster.

http://www.stoptech.com/technical-su...rs/brake-fluid

Looks like I will go DOT3, as indicated on the fill cap.

DOT 3 fluids are usually glycol ether based, but as stated earlier, that is not because they are required to be. The brake fluid industry has determined by consensus that glycol ether fluids are the most economical way to meet the requirements.

By definition, DOT 3 fluids must have a minimum dry boiling point (measured with 0 percent water by volume) of 401°F and a minimum wet boiling point (measured with 3.7 percent water by volume) of 284°F. The specification says little more as far as the performance enthusiast is concerned.



DOT 4 fluids are also glycol ether based, but have a measure of borate esters added for improved properties including increased dry and wet boiling points. A seldom talked about characteristic is that because of this chemistry, the DOT 4 fluid will have a more stable and higher boiling point during the early portion of its life, but ironically once the fluid does actually begin to absorb water its boiling point will typically fall off more rapidly than a typical DOT 3. By FMVSS116 standards, DOT 4 fluids must have a minimum dry boiling point of 446°F and a minimum wet boiling point of 311°F.

DOT 4 is the grade applicable to most race engineered brake fluid in the world today, especially with regard to viscosity limit. Note that although the DOT 4 designation has a minimum dry and wet boiling point, a DOT 4 racing brake fluid may have a dry boiling point over 600F. Its viscosity is challenged, however, to be under the viscosity limit of 1,800 mm2/sec. Some claimed racing brake fluids exceed this important limit. Caution should be exercised if these fluids are used in race cars with ABS systems. This does not mean that DOT 4 fluids are necessarily better than DOT 3 fluids. Remember, the boiling points listed are minimums. There are certain DOT 3 fluids with higher boiling points than some DOT 4 fluids. The real differentiating factor is that DOT 4 fluid should be changed more often than a DOT 3 fluid, because of the effects and rates of water absorption.

tech2

fluid...doubt it.. Spongy pedal yes but poor assist have not seen it. Fluid...maybe if its leaking all over the pads!

does the truck use variable valve timing? Some may use a electric vac pump to supply the booster.
some have a vac sensor which you can read with a scan tool....see if the vacuum reading is bleeding off after shut down.

there are booster tests but need to know if this is intermittent or all the time type of problem.

co-efficient of friction....when its poor...you can push as hard as you want and get no braking. like someone put grease on your brakes. inspect your brake rotor drum surfaces and brake linings

oilcanhenry

Yeah DOT 3 or 4 are both okay to use.

SabrToothSqrl

Finally had some time, bled all the brakes. the rear two, fluid came out grey, watery and nasty. Fronts were both fairly clean looking. I drained the tank first, then filled with new and bled from farthest to closest in order. Might do it again in a few months, I want to be sure I got all the nastyness out.
The truck seems to stop flatter than it did before with less nose dive, but maybe I'm just being hopeful.

73shark

If you didn't activate the ABS system while bleeding, there will still be contaminated fluid within it.

SabrToothSqrl

I did not. awesome.