slow brake response when hauling any kind of weight

[kenman1717]

My truck 2003 Silverado 1500 ecsb 4.8l 4x4 4 wheel disc 287 000km. Every thing in the brake system is original except for pads and rotors that I know of. I bought it used in 2010 with 199 000kms. The brakes worked great up until last fall, aside from doing the automated bleed with the scan tool about once a year to get a solid pedal. Right now there is probably 80% pad left all the way around, the pins are free and so are the caliper pistons. I've been noticing more and more lately that when I have the box loaded or have a trailer on that it requires so much more to stop, and this is not going very fast either. I have noticed the pedal does feel lower and a bit spongey, but the fluid is still full and no leaks. Without a load it seems to stop on a dime. I myself am a licensed journeyman technician/mechanic, but have never run into this before. Given age/mileage I'm leaning toward master cylinder. But on the same token since I live in Canada where the rust is bad I'm thinking about getting one of those complete brake line kits for my truck as well as the 5 brake hoses and new calipers. Has anyone else ever ran into this before.

[Blue Bowtie]

Ceramic friction material? It wouldn't be a shock since they tend to fade more than carbon metallic, and with more weight/braking load that will occur even sooner.

[kenman1717]

Originally Posted by Blue Bowtie

Ceramic friction material? It wouldn't be a shock since they tend to fade more than carbon metallic, and with more weight/braking load that will occur even sooner.

Interesting, have never heard that before. I do believe that the fronts are ceramic, and the rears are semi metallic. But still the fronts do more work. Is it just age/mileage that this just seemed to happen now? like I said have owned truck for almost 8 years and have put almost 90 000kms on, never had this issue until recently. Because the brakes/abs work great with no load on the truck, but they fade out pretty quick with even a light load on the back.

[rhandwor]

Have you ever flushed the system with new fluid. Moisture can cause problems when hot. How long have these pads been on the truck?

[maxwedge]

I'd get it off the ground and see if the rear brakes are holding, engine running in neutral, gradually step down and with a helper see if the rear are holding.

[kenman1717]

The brake fluid has never been flushed as long as I've had the truck. Have just done the automated air bleed with the scan tool, but have never opened a bleeder screw. As for the pads, the rear pads have been on since july of 2010, but I have replaced the rotors a couple times do to rust. But as I said before everything moves freely, I take the brakes apart about once a year to clean and lube everything. The front pads are still probably 5 years old, but 80% left on all pads.
I have not lifted it up and tried to see if the hold while running in neutral, I will check that. But like I said before with no load in the box the truck stops on a dime, I suppose just the fronts could be working great.

[rhandwor]

Originally Posted by kenman1717

The brake fluid has never been flushed as long as I've had the truck. Have just done the automated air bleed with the scan tool, but have never opened a bleeder screw. As for the pads, the rear pads have been on since july of 2010, but I have replaced the rotors a couple times do to rust. But as I said before everything moves freely, I take the brakes apart about once a year to clean and lube everything. The front pads are still probably 5 years old, but 80% left on all pads.
I have not lifted it up and tried to see if the hold while running in neutral, I will check that. But like I said before with no load in the box the truck stops on a dime, I suppose just the fronts could be working great.

The idea with the fluid is it can draw moisture If the brakes are hot it can boil. You can compress steam but not liquid.

[j cAT]

never opened a bleed screw and you also say caliper pistons not binding ? does not compute probably why you have these braking problems with a load.

unbolt the front calipers , pads removed push down on brake pedal do both pistons pop out the same amount ? if not the piston binding it does happen on these. reason is calipers pistons bind up due to rust and other issues.

possible you can pop the pistons out and see if they are rusted or ? might work if you use silicone brake grease lube the piston exterior and piston boot after cleaning .

if you did lube the cal pins with petroleum grease that also will do it .. requires silicone brake grease only..

[kenman1717]

Originally Posted by j cAT

never opened a bleed screw and you also say caliper pistons not binding ? does not compute probably why you have these braking problems with a load.

unbolt the front calipers , pads removed push down on brake pedal do both pistons pop out the same amount ? if not the piston binding it does happen on these. reason is calipers pistons bind up due to rust and other issues.

possible you can pop the pistons out and see if they are rusted or ? might work if you use silicone brake grease lube the piston exterior and piston boot after cleaning .

if you did lube the cal pins with petroleum grease that also will do it .. requires silicone brake grease only..

when ever I do my yearly brake service I always push the pistons back in and there has never been any binding, yet. I did it last june, so I haven't done it yet this year, so I know it is a possibility they are bad. I only use Permatex extreme ceramic silicone lube on all the brake components.

I haven't had a chance to check anything as of yet, weather is kind of being weird here right now. and I don't have a heated garage. also just switched jobs, haven't started at the new shop yet, so not sure when I can bring my truck in to use a hoist.

also something I noticed, other than the pedal being a bit low, the pedal also seems hard, by that I mean when it goes down, about inline with the gas pedal, its feels like a lot of pressure. kind of like when you pump the brake pedal with ignition off and it gets hard. it never felt like this before, I mean you could feel normal brake pressure, but not to this degree.

[Blue Bowtie]

Does the truck have a vacuum power booster or a hydroboost unit?

[kenman1717]

Originally Posted by Blue Bowtie

Does the truck have a vacuum power booster or a hydroboost unit?

vacuum booster

[j cAT]

Originally Posted by kenman1717

vacuum booster

when I do the brake pads the bleeder screw is open after the C clamps are set in place .. with a clear plastic tubing and one end on bleeder the other in a can with brake fluid I push back the calipers pistons..

why ?????????????? because the brake fluid in the cal pistons is nasty sh*t . then the pistons binding and you may also mess up the ABS valve body valves..

[kenman1717]

I was able to put my truck on a hoist today. I put a brake pedal depressor on to lock the brakes and put the truck in neutral, and jacked up both ends of the truck. I was not able to move any of the 4 wheels. I then released the brakes and pulled the rear wheels off. both rear calipers moving freely, bleeder screw were seized in but I was able to push both pistons in with ease, no binding. I wasn't able to check the front, had to take my truck back out to do customer work. But I noticed that once I pumped the brakes back up, the when I backed off the hoist my brake pedal was a lot lower that it usually is. I'm wondering if I now have air in the abs module as well. this is starting to get really frustrating. I may end up buying another truck, the cost to fix this thing keeps rising. need like $4000 for body work, have to do rear springs, am rebuilding an engine to put in it, want to get a new transmission, with 287 000kms it might be time for something else, but I love this truck.

[j cAT]

you have to bleed the brakes . the bleed screws are rusted up because they were never opened . 1 ] replace the calipers 2] remove caliper try to drill out /replace the bleeder 3 ] what I have done on temp repair to bleed is use C clamp.. place C clamp on caliper not compressing the cal piston , then loosen the hose fitting bolt at the caliper .. crank the C clamp so all the brake fluid comes out of the caliper.. then tighten the hose bolt..repeat this until brake fluid is clear looks good .. fill the master cylinder with new fluid .. the front calipers will require 2 C clamps or use old brake pad backing plate.. also place the brake pedal down keep it down when you allow the brake fluid to flow out ... that will prevent air to get into the system when you open up the brake line/bleeder .

[rhandwor]

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