07 Sierra brake booster problem

[Chuck Youngblood]

I have an '07 Sierra w/ 5.3 4WD. 183,000 + I had what I believe was the original brake booster go bad by applying the brakes itself. I replaced the booster but about 3 months later it happened again. NAPA stood behind the booster so I put another one on it. Now it's about 2-3 months later and it is starting to do the same thing. We checked the 2nd booster for any oil residue inside from the engine and found none. What is causing this?

[Doug_Scott]

If it was me I would have taken a look at the brake pedal hanging up under the dash, or the adjustable length drive pin that goes between the brake pedal and the brake booster being adjusted too long in length and not allowing the master cylinder to fully release.  I have seen that happen, but even then it was not the original problem, original problem was some weird issue with the bushing on the brake pedal rotating.

Maybe I have lived a sheltered life, but I have never heard of a brake booster ever actually failing, and now you apparently have seen two, on the same vehicle no less.  I have seen brake booster diaphragm (when the hell did spell check start sticking a "g" in diaphram) leaking so bad you could hear the vacuum leak in the passenger compartment, and still give what appeared to be full assist on braking.  Car was a two stepper at idle though. 

[Chuck Youngblood]

I had never heard of it either but when the first NAPA unit failed they called the factory and the tech verified that it really does happen but it happens occasionally when the engine oil is getting sucked in through the vacuum hose. This is not the case, the hose was dry inside. I suppose it could be two bad ones in a row but I really don't think that at all. When the booster(s) were new the truck rolled as free as can be so that rulles out brake pedal adjustment.

[Jsdirt]

If the rear seal of the master is leaking brake fluid, that'll destroy a booster diaphragm pretty quick. Only other cause would be the great 21st Century parts cheapout that's been plaguing auto techs for nearly 10 years now.

 

Ahh, reread and noticed this isn't a typical failure. Why am I not shocked? I have heard of this only with the 900 series trucks and newer - I'll get back to you on that - I have to do some digging ...

Edited October 13, 2019 by Jsdirt

[Chuck Youngblood]

I sure hope you find something.

[Doug_Scott]

15 hours ago, Chuck Youngblood said:

I had never heard of it either but when the first NAPA unit failed they called the factory and the tech verified that it really does happen but it happens occasionally when the engine oil is getting sucked in through the vacuum hose. This is not the case, the hose was dry inside. I suppose it could be two bad ones in a row but I really don't think that at all. When the booster(s) were new the truck rolled as free as can be so that rulles out brake pedal adjustment.

 You won't get engine oil pulled in simply because it is the engine creating the vacuum.  You can get brake fluid pulled in, and it is usually very easy to see, it will usually leave a trail down the front of the booster as long as the booster/master are somewhat level.  I have not seen brake fluid hurt a booster though.  I have far more Chrysler experience than GM, that maybe why. 

[Chuck Youngblood]

The master was new when I got the truck last year. I just picked it up because it was 4WD and it was priced right. The master has never went down one bit  I'm going to get hold of the maker and talk to them. The booster has a lifetime warranty but I am 70 years old and do my own work and I am not going to change it again. Might be an easy job for a young guy but I'm far from that.

[Doug_Scott]

When you say "applying the brakes itself" exactly what do you mean? 

[Jsdirt]

Now that I've had time to reread everything, I don't think the booster is the issue.

 

Is it all 4 brakes , or just the fronts?

 

There's a few things that will cause the brakes to start applying themselves (dragging) (will get progressively worse with heat). Brake hoses can fail internally, and act like one-way check valves. Fluid will enter the caliper, but won't return to the master (or will very slowly). Considering the quality control of that model year, and the mileage, there is a good chance of this being the issue.

 

A faulty proportioning valve can do this too.

 

If memory serves correctly, I thought I read of the newer trucks ABS units failing internally and causing this issue - this is another possibility. Also read of the newer truck's boosters causing this, but I don't see how that's possible. Knowing GM, they reengineered something to make it cheaper (for THEM), so this is the way they may fail now.

 

Best thing to do is drive around staying near where you'll be working on the truck. When the brakes start to drag, feel which discs/drums are warm. If the fronts, get the front in the air on jack stands - verify that the wheels are hard to turn by hand. Crack a bleeder and see if you can now spin the wheel - if you can, it's the brake hose. If not, you may have a bad caliper, bad master, or something else preventing the master from retracting properly (bad check valve in ABS unit, or ???). 

Edited October 14, 2019 by Jsdirt

[Chuck Youngblood]

I was starting to think you were on to something with the hoses deteriorating but the darn thing will get to where they are dragging very noticeably and I stop, pull the vacuum line off the booster and the truck rolls free as can be. However, it just starts all over again in a very short time.

[Chuck Youngblood]

29 minutes ago, Doug_Scott said:

When you say "applying the brakes itself" exactly what do you mean? 

Just that, the brakes will start gradually dragging. They will actually hold the truck in gear, if I give it just enough throttle to let it roll then let off it stops immediately, no gradual slow down. 

[Jsdirt]

11 hours ago, Chuck Youngblood said:

I was starting to think you were on to something with the hoses deteriorating but the darn thing will get to where they are dragging very noticeably and I stop, pull the vacuum line off the booster and the truck rolls free as can be. However, it just starts all over again in a very short time.

Yep, that's a friggin strange one right there! Something GM has engineered in that I'm not familiar with. I'll keep digging - not having much luck finding a solution - everyone wants money for the answers (And guess where that comes from? GM of course! Crap rolls downhill, as they say ...). 

 

EDIT: Just found something that said to pull over and do exactly what you did - if it now rolls free with the vacuum line disconnected, you need a new booster. Ain't that grand?  $50-LARGE for a truck isn't enough - they have to build cheap crap poorly engineered parts that fail long before they're supposed to ... then, never fix the problem - just keep selling parts! These people should be in jail ...

Edited October 14, 2019 by Jsdirt

[Chuck Youngblood]

I had forgot to tell you that it is the front wheels that are the tightest but with the percentage of braking done by the front I would venture to say it is affecting all 4 corners. I agree about the cheap parts I just had to R&R 3 alternators on another car of mine to get one that worked. I have about had it with this booster b.s. but I could never sell it like it is so I guess as long as NAPA keeps replacing them I'll have to keep changing them, that's the part that pisses me off. I sent an email to the company that puts them out so I'll (hopefully) see what they have to say.

I see you have a Yamaha RD 350, I had one of those back when I was riding that little sob is FAST!

[Jsdirt]

Yeah, that sucks. Very familiar with the aggravation!

 

 If that doesn't work out, you could try buying an OE one, or AC Delco on RockAuto - will be cheaper than any dealer, and might be the fix (at least until that one does the same thing down the road a bit).

 

Nice! Yeah I love this bike. I did ALOT of work to it - it's putting out at least double the power it did stock. It's alot of fun. SIMPLE, too! No stupid electronics to break or get buggy. Still has the OE dual-points ignition, and the alternator with brushes. I did upgrade the regulator and rectifier to a combined modern unit. That's the only electronic thing it has, but it was hand built by a retired guy in his shop out in OR somewhere. Hasn't given me any grief in 10 years so far. 

 

[txab]

On 10/12/2019 at 10:28 PM, Doug_Scott said:

If it was me I would have taken a look at the brake pedal hanging up under the dash, or the adjustable length drive pin that goes between the brake pedal and the brake booster being adjusted too long in length and not allowing the master cylinder to fully release.  I have seen that happen, but even then it was not the original problem, original problem was some weird issue with the bushing on the brake pedal rotating.

Maybe I have lived a sheltered life, but I have never heard of a brake booster ever actually failing, and now you apparently have seen two, on the same vehicle no less.  I have seen brake booster diaphragm (when the hell did spell check start sticking a "g" in diaphram) leaking so bad you could hear the vacuum leak in the passenger compartment, and still give what appeared to be full assist on braking.  Car was a two stepper at idle though. 

I would pay more attention to this suggestion.

 

Of course see what the manufacturer has to say. I've only ever had one booster go bad in all my years and never exhibiting itself in the manner you've described. 

 

You bought this truck used? Did the issue present itself in the same time frame that these boosters have failed?  I would make sure, if you haven't already, that I was getting the correct part #. IIRC, 3 different part #s for the new body style 2007 and don't forget about the 2007 "classic". As noted on a vacuum booster, engine oil would not be drawn into it, If there is fluid it would be brake fluid.

 

When this appears, does it do it every time your out for a drive? Does it when fluidi is cold or hot?

[Chuck Youngblood]

1 hour ago, txab said:

I would pay more attention to this suggestion.

 

Of course see what the manufacturer has to say. I've only ever had one booster go bad in all my years and never exhibiting itself in the manner you've described. 

 

You bought this truck used? Did the issue present itself in the same time frame that these boosters have failed?  I would make sure, if you haven't already, that I was getting the correct part #. IIRC, 3 different part #s for the new body style 2007 and don't forget about the 2007 "classic". As noted on a vacuum booster, engine oil would not be drawn into it, If there is fluid it would be brake fluid.

 

When this appears, does it do it every time your out for a drive? Does it when fluidi is cold or hot?

There is nothing in that suggestion that is valid in this case, sorry not being an ass but if ny of that was the problem it would be worse cold (?) and the problem would not go away when I remove the vacuum line. I am 70 and I have never had a bad booster and I have had many cars. I did buy it used but no problems for at least 5-6 months. It does do it every time I drive it unless it is a very short trip so yes, the fluid would be warm at least.