Need advice on brake work
Posted 09 June 2019 - 09:41 PM
With that said.. ive never messed with this hub bearing style brake setup with disc.. ive done plenty of re-packing bearings.. had a 65 mustang with drum..
Anyway ive ordered all around pads and rotors (went with titanium drilled rotors)
As of now the brakes suck.. as in car requires alot of pedal to slow down. And i feel like only right front is really doing anything.. rotors are original (116k)
Im assuming i may have to replace some lines and calipers.. hope not but it really doesnt stop well.
My reason for the thread... any tips? Will i expose any bearings and need to replace or repack them?
Side note: this is an 89 TSI SHP 5spd im going to be picking up 4 (full set) of of used SHP struts Wednesday seller claims they are in good shape... someone replaced my rears with bs struts and lowering springs and they torched the front shp springs... last owners were idiots. So should i wait to do brakes/struts/bearings at same time? Id rather piece it together as im driving it daily.. not because its my daily driver... because its fkin awesome and i cant believe i own one!
Thanks any tips/advice appreciated!
Posted 09 June 2019 - 10:04 PM
Edited by markhansenconquest, 09 June 2019 - 10:09 PM.
Posted 10 June 2019 - 04:42 AM
If the brake pedal travel is large before much of any braking action happens I'd look towards the master cylinder. Under normal operation, when you press the brake pedal the sequence is:
1: power brake booster helps push on the master cylinder. If the booster is bad, the brake pedal is much harder to press.
2: the brake master cylinder has two pistons. The one closest to the booster is for the rear brakes; it gets the initial push from the brake pedal As the rear piston moves, brake fluid pressure builds up in the rear brakes. Once the rear brake pistons and calipers move enough to start applying the brakes, the pressure in the rear hydraulic line jumps up.
3: that higher rear hydraulic pressure THEN pushes on the front piston in the master cylinder. The front piston starts shoving brake fluid to the front calipers.
4: if there is an issue with the rear brakes - e.g. a leak in the hydraulic lines or rear master cylinder piston itself then the rear hydraulic lines (and the region between the front and rear piston which is where the rear hydraulic hose connects) then no significant pressure ever builds up in the rear brake lines. Ergo the brake pedal moves a fair bit but no braking action is felt. Eventually the rear master cylinder piston moves enough to physically touch the front piston... further pushing of the brake pedal then makes the rear piston push on the front piston so you start getting front brake action.
A very common failure is for the seals around the master cylinder pistons to fail, especially the rear piston. When this happens, brake fluid leaks past the seals rather than getting pushed into the brake lines so no pressure ever builds up. Old brake fluid collects a fine silt from the atmosphere... this silt is like sandpaper to those seals.
If the car is driveable: on an empty road or just up and down your local street, get to 20 to 30 mph and apply the brakes trying to decelerate as you normally would coming to a stop sign or red light. Don't stomp on the brakes, don't baby them either. Accelerate again, stop again. Do this 5 to 10 times. Then park the car. With your hand, see if you feel any temperature radiating from the brake rotors - BUT DO NOT TOUCH THEM OR THE WHEEL RIMS in case they are hot. Just see if there is any heat evident. If you have one of those temperature guns (with the red dots cats love to chase) use that to measure the rotor temps. Ideally the two front rotors will be warm/hot and similar temperatures and the rear rotors will also be similar temps. If one rotor is much colder than its twin on the other side of the car that's a bad sign - that brake isn't functioning. If one rotor is much hotter than the other three then that brake is probably dragging - also bad. No real temp in the rear rotors? Think master cylinder.
When the master cylinder fails (those piston seals inside it) brake fluid will leak out, dribbling down the front of the power brake booster. If you see wet/bubbled paint on the booster below the master cylinder then this is the first part of your bug. You need a new/re manufactured master cylinder.
Other common problems - not unique to StarQuests: old brake fluid also absorbs moisture from the air. Fresh brake fluid is a light brown color, almost clear. Old and contaminated fluid is dark brown. The moisture leads to rust forming on the caliper pistons at each wheel; that rust jams the piston so that brake doesn't work at all... but if you stomp on the brake pedal you might be able to get the piston to move and apply the brakes... but now the rust will jam the piston in this position so the brakes on that wheel stay applied even when your foot is off the brake pedal. Rust also forms if the rubber seal between the outside of the caliper and the lip of the piston (this seal is a round bellows, similar to a CV boot would look like if you compressed it) gets old and rips/tears, letting water and road crud into the very tight gap between the caliper body and caliper piston. Caliper rebuild kits include this seal plus the square cross-sectioned o-ring that seals the piston to the caliper bore against brake fluid pressure. Not a difficult job to install. You'll need a lot of spray brake cleaner too. And emory paper to polish the caliper bore and piston surface to remove rust. Don't grind away - just a light wiping should be enough. If not, replace the caliper and piston.
If in doubt, whenever acquiring an older used car, I think it's smart to completely re-do the brakes. Flush the brake lines, inspect the innards of the calipers and rebuild them (kits are cheap), replace the pads, resurface the rotors, and I'd even swap out the master cylinder or at least get a rebuild kit. None of this stuff is expensive... and the brake system is critical to safety... and the brake system does not respond well to neglected maintenance nor a car parked for extended time. Stuff rusts.
When removing the calipers, you'll notice the bolts that attach the calipers to the frames supporting the pads have rubber seals around them and there should be high-temp brake grease on those bolts. The calipers actually slide on those bolts... so if they're rusted the caliper gets jammed. Typically that results in one of the two brake pads wearing out rapidly rather than the pads wearing evenly.
The brake bleeding process similar to how most import cars are bled: start with "bench bleeding" the master cylinder before installing it onto the car. I.e. fill it with brake fluid while it's gently held in a vice, use temporary tubes (included with most master cylinder rebuild kits or with re-manufactured units) to connect the output ports to the brake fluid reservoirs... then slowly push on the rear piston with a screwdriver until no bubbles come from the temporary hoses. Install the master cylinder into the car. Bleed the rear passenger side first (furthest from the master cylinder), then the rear driver side, then the antilock assembly, then the front passenger side caliper, and finally front driver side caliper.
Brake pedal adjustments: the pushrod connecting the brake pedal arm to the master cylinder is a long screw with a jam nut to lock it into position. With the system bled and otherwise working properly, engine OFF, use one fingertip to gently push on the brake pedal There should be a little pedal motion (a quarter to half inch pedal travel) before the pushrod even touches the master cylinder's rear piston - this "gap" allows parts to expand without applying the brakes as under-hood temperatures rise. When the master cylinder is installed, there should be 1 millimeter gap between the rear of the piston and the end of the pushrod. Measuring this fun... you can't do it with the master cylinder installed obviously as this stuff ends up inside it. So you have to measure from the machined surface by the mounting bolts to the dimple in the piston, then compare that measurement to its counterpart on the power booster where the master cylinder bolts too (i.e. what the machined surfaces end up touching) and the tip of the pushrod.
Posted 10 June 2019 - 04:50 AM
Posted 10 June 2019 - 06:19 AM
I recommend deleting the rear ABS. Doesn't really work half the time and when I deleted mine I took it apart. The gunk and corrosion inside was insane. Made a big difference in pedal feel/stopping ability.
Re packing the bearings isn't hard to do and it would also be a good time to maybe throw a tack weld or two on the back of the front wheel studs as those are prone to slipping in their bores.
Edited by Turbo Cary, 10 June 2019 - 07:18 AM.
Posted 10 June 2019 - 08:12 PM
Posted 10 June 2019 - 09:13 PM
Posted 10 June 2019 - 10:02 PM
Posted 11 June 2019 - 07:30 AM
Posted 11 June 2019 - 08:59 AM
I would do full compression test to eliminate big stuff.
Next I would check for vacuum leaks all over.
Next check the timing
Throttle body rebuild.injectors cleaned and tested nose switch cleaned and lubed tps isc re set is a must.New plugs wires rotor and cap.
Fuel pressure test.
The basics to start with.
Posted 11 June 2019 - 11:44 AM
Vac leaks cause all sorts of problems too. A can of spray carb cleaner sprayed at EVERY vac hose and air hose (including the fat ones from the air filter all the way to the throttle body) will help identify leaks. Also spray around the intake manifold gasket, the base of the throttle body, etc. StarQuests measure the airflow using the stuff inside the air filter... and air leaks after that Mass Air Sensor (MAS) confuses the ECU. Even leaks around the lip of the air filter canister or where the MAS bolts to the canister lid cause problems. Sloppy clips/clamps on the canister lid will cause problems.
Posted 11 June 2019 - 06:48 PM
I should start a new thread... bwaah
But ive replaced plugs with cold ac delco. Im going to source the ngk 7031's asap.
I did run a compression test. Conditions were.. 80 ded f. Eng temp. Injectors unplugged (thoes have new connectors btw) unplugged coil wire. Throttle to the floor. I got 133-136 on all 4. (Is that good or bad? Ive not looked up the spec yet) consistancy is good.
Fuel pressure is right at 38-39 at idle.. no idea at revs. Idle is the issue.
The air box... yeeaaaaa.. rednecks cut a giant hole in the side.. A N D the lid does not fit well.. its canted off a bit with a tiny tiny gap all around. Clips do not seem to line up well with the corresponding latch..
Ive picked up the throttle pedal with my foot during idle and no change. I will check cable slack
I just sold a 95 suzuki sidekick that had all of the same issues and same idiot type if owners.. im very familiar with all of the sensors used back then.. had to replace almost all of then on the kick. AND the idiots adjusted the throttle plate STOP screw!! Hope this didnt happen on the quest!!!
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