New member 2003 Z71 with brake issue

[MOZ2121]

Hey guys new member here just wanted to say hello and pick your brains on something.
I picked up this tahoe a few years ago and the brakes were horrible, I tow very frequently and under load the brakes are down right scary. Now I've read up on the hydroboost upgrade and the 07+ front caliper upgrade, but I'm wondering, why can't the old vacuum system be repaired or diagnosed? I've been to about 4 mechanics and all say everything looks good, but I know how these cars are supposed to performed I've owned one since 2004. I was going to throw some money at a new booster and master cylinder but I've also read that some get no improvement after the replacement. Let me know what you fellas think.

 

[Bill 1960]

Welcome. You’re going to have to tell us as much as you can since we can’t see it or take a test drive.

What symptoms specifically are you having? Soft pedal, lack of booster assist & hard pedal?

Is the braking proportional front and rear as far as you can tell, or is one end not contributing?

Can you get ABS engagement with an emergency stop?

Have the brake pads and calipers been inspected for wear and contamination? Have they been changed?

 

[Big Mama]

Welcome to the forum from Virginia. Lots of knowledgeable folks here that’ll help with your brakes.

 

[George B]

I owned an 03 Suburban Z71 for 5 years that had crappy brakes. They just felt spongy and didn’t inspire confidence. They stopped it but not as good as I liked. I did end up with a new master cylinder that didn’t help and bled about a gallon through the system. Some have had good luck with the NNBS brake upgrade and I have read about a larger bore master cylinder too.

Try a couple stops in gravel that get the ABS to actuate and see if the brakes get better.

 

[MOZ2121]

Welcome. You’re going to have to tell us as much as you can since we can’t see it or take a test drive.

What symptoms specifically are you having? Soft pedal, lack of booster assist & hard pedal?

Is the braking proportional front and rear as far as you can tell, or is one end not contributing?

Can you get ABS engagement with an emergency stop?

Have the brake pads and calipers been inspected for wear and contamination? Have they been changed?

very soft and spongy, going down a mountain pass once was scary as hell , wouldn't stop for beans luckily I made it out ok. I've had other tahoes with vacuum assist and their brakes were perfect, even my dads 2001 tahoe with 250k miles brakes 1000 times better.
I've never had the ABS engage at any speed , if I slam the brakes at any speed they will not lock just eventually comes to a stop .

the braking seems proportional as far as I can tell, although sometimes when I really slam on them I can feel a slight throbbing on the pedal.

the calipers, rotors and pads are new and were installed about 3 years ago by previous owner.

system was bled twice.

 

[OR VietVet]

Welcome to the forum from Oregon. Fortunately my 05 Z71 has the hydro boost brakes. They work great. If the brakes are that bad and you likely have heated them up a few times just trying to stop. The pads may be baked enough that they should be replaced. How much vacuum are you making with the engine? Air bleed at booster?

Upgraded brake system, options at RA. There are a few threads here about the hydro boost changeover that has been done here.

 

[Dantheman1540]

I feel the trucks with the vacuum booster come with very poor brakes from the factory. The hydro-boost upgrade is the single best upgrade I've done to brakes on anything I've ever owned. It's actually a significant difference where SS lines and new pads/rotors have never made much difference to me. If you are considering dumping money into replacing the vacuum booster I'd recommend just getting the hydro-boost. I don't think the money difference would be much if any and the improvement will be drastic.

 

[Joseph Garcia]

Welcome to the Forum from NH.

Lots of knowledgeable folks here who freely share their knowledge, experiences, and perspectives. Knowledge is power.

I hope that you will become a participating member in the Forum's discussions.

You are already receiving sage advice from the knowledgeable folks on this Forum.

 

[Tonyrodz]

I feel the trucks with the vacuum booster come with very poor brakes from the factory. The hydro-boost upgrade is the single best upgrade I've done to brakes on anything I've ever owned. It's actually a significant difference where SS lines and new pads/rotors have never made much difference to me. If you are considering dumping money into replacing the vacuum booster I'd recommend just getting the hydro-boost. I don't think the money difference would be much if any and the improvement will be drastic.

The pwr steering pump needs to be changed for hydroboost?

 

[MOZ2121]

The pwr steering pump needs to be changed for hydroboost?

I've read that you should , to one that has two outlets , new hydraulic booster ,new master cylinder , 3 new lines , and new brake pedal. at least from the quick research I've done

 

[OR VietVet]

The pwr steering pump needs to be changed for hydroboost?

I've read that you should , to one that has two outlets , new hydraulic booster ,new master cylinder , 3 new lines , and new brake pedal. at least from the quick research I've done

Yea, @Tonyrodz, everyone knows that. Just remember, it is not your money you are spending, it is HIS MONEY you are spending.

 

[Bill 1960]

Sounds like air, or possibly soft brake hoses which can swell under pressure. When they bled it, did they have the tool to activate and bleed the ABS pump? Was a power bleeder used?

Some vehicles bleed ok using just the old school method with pumping the pedal, others I’ve had in the shop that require all the tech tools (bidirectional ABS scanner and power bleeder) to get the residual air out.

Some people swap in stainless brake hoses to replace the rubber but that’s usually to get some minor improvement in pedal feel. Based on the severity of your symptoms I’ll place my bet on air that’s never been chased out.

And, sounds stupid, but did they put any calipers on upside down? I have seen left /right get mixed up and the bleeder is not on top.

 

[MOZ2121]

Sounds like air, or possibly soft brake hoses which can swell under pressure. When they bled it, did they have the tool to activate and bleed the ABS pump? Was a power bleeder used?

Some vehicles bleed ok using just the old school method with pumping the pedal, others I’ve had in the shop that require all the tech tools (bidirectional ABS scanner and power bleeder) to get the residual air out.

Some people swap in stainless brake hoses to replace the rubber but that’s usually to get some minor improvement in pedal feel. Based on the severity of your symptoms I’ll place my bet on air that’s never been chased out.

And, sounds stupid, but did they put any calipers on upside down? I have seen left /right get mixed up and the bleeder is not on top.

Calipers are oriented correctly, I bled them myself using the old school method, pumped most of the old fluid out, didn't see much air come out , worked my way from the rear passenger forward. The previous owner mentioned they bled them but I doubt they used any tools to bleed em out.

I'm not so much worried about the costs of doing the conversion, I have just heard mixed results, and have also read that the old vacuum system were repaired to original feel, but also heard of guys throw so much money at parts but never get them to work properly.

 

[MOZ2121]

Update...so I decided to give the gravel road hard brake deal a try...I definitely, definitely increased stopping power. I'm able to actually stop and lock the brakes a bit. It did not give me a firmer brake pedal, and it still feels spongy a sinks , but I can actually stop now...so what does this tell me? bad ABS ? when I was braking on dirt, felt all kinds things going on with the pedal, so I am getting some ABS action, but the ABS lights did not come on.
I recall on my 05 z71 suburban, the ABS lights came one once in the rain when I hit some pot holes.

 

[Bill 1960]

Sounds like you have air in the system near the ABS pump and it expelled some when you forced the pump to activate on the gravel.

If it were mine, I’d take it to a shop with the right tools to force the pump on and power bleed it. Maybe even the dealer if there’s one you trust.

I am a hard core DIY guy however sometimes the pros have tools I can’t or won’t buy.

 

[George B]

Update...so I decided to give the gravel road hard brake deal a try...I definitely, definitely increased stopping power. I'm able to actually stop and lock the brakes a bit. It did not give me a firmer brake pedal, and it still feels spongy a sinks , but I can actually stop now...so what does this tell me? bad ABS ? when I was braking on dirt, felt all kinds things going on with the pedal, so I am getting some ABS action, but the ABS lights did not come on.
I recall on my 05 z71 suburban, the ABS lights came one once in the rain when I hit some pot holes.

Same results as me with my 03. I ended up with a new master and several bleeding events while cycling the ABS in between. Autel makes a handheld that will do the ABS cycle for you and a Chinese TechII will do it too. The motive Power bleeder is a great tool as well.

In the end my brakes still sucked. I don't have any more data since I traded that truck for my 13 Burb.

 

[MOZ2121]

So sitting over night, the brakes reverted back to horrible. The frustrating part is every shop I got too, they seem not to want to touch this thing, there are no codes being thrown. So my only option seems to be to tell Them what I want done.

 

[ThisIsLivin]

I had the same thing happen over time on my 03 Suburban. I am sure it's either air in the ABS or the ABS itself. Mine has 360k on it and the lines are rusted so I am planning on a complete replacement of everything from the master cylinder out. I've already replaced the master cylinder twice and pumped a gallon of fluid through the lines. I plan on plumbing around the ABS as it's not worth replacing.

 

[shegarty]

So sitting over night, the brakes reverted back to horrible. The frustrating part is every shop I got too, they seem not to want to touch this thing, there are no codes being thrown. So my only option seems to be to tell Them what I want done.

If the shops you are taking it to don't want to do what you are asking I wouldn't trust them to change my oil. Find a reputable shop that will listen to an educated owner. My 2c's ... it sounds like you definitely have air trapped in the system, likely in the ABS module loops. The only way to get this out is with the scanner tool that can activate the bleed cycle function. I would try to find a shop that will do this first before going to all the trouble of replacing the booster. If it doesn't work you're not going to be out much and you've also found the shop to do a full system bleed after you replace all the hydroboost components.

 

[exp500]

From what I've seen, bleeding antilock on gm takes 2 qts. or way more than 1 qt. Everybody stops early, so air still in there. ( it takes about 3 brake pushes to get a known bubble out back, so a little insurance is alot of pumping).
The other thing that helps, 2 man bleeding or pressure bleeding is to cycle the key on off several times with foot on pedal(2man) . Done that a few times now and bleeding finishes faster (activates ABS solenoid self test). I don't remember who on this board suggested that, but it works well and I thank you. Newer models may not work cycling key. Using Tech2 (vxdiag)now.
Also mentioned above is caliper hoses, They are cheap and not a bad Idea every 100K.