Vacuum pump & mechanics

Adam Leinss · November 11, 2016

I have a 2014 Silverado with 42K miles. On Sunday, I was pulling into the garage after a short errand and I lost most of the braking power. I was able to stop the truck by pressing the brake pedal hard. I immediately drove backwards and it did the same thing. I had it towed to a local mechanic on Monday to have the braking system checked out. They had it for about 4 hours and could not find anything wrong. They showed me an article how the ABS system can kick in if the system is over worked due to hot weather, driving up hills, frequent stops, etc. However, I just was away for 15 minutes: it's in lower 60s and I wasn't doing hills or frequent stops. The mechanic did 2 test drives and he told me the braking system was fine.

I carefully drove it to the GM dealership for a 2nd opinion and within 15 minutes they diagnosed it as a weak vacuum pump. It was only doing 10 in Hg and it should be doing 27 in Hg. My question is having a vacuum pump as part of a braking system exotic? Is this something a normal mechanic should have been able to diagnose? I found the TSB here by Googling vacuum and 12669488 as the part # which describes the problem perfectly: http://m.gm.oemdtc.com/TSB/SB-10081053-2280.pdf

I guess my worry is that this mechanic gave me a clean bill of health on the braking system which shakes my confidence in any future work he may do for me. Are these 2014+ Silverados just too new or specialized to be worked on by normal mechanics?

GsBowtie · November 11, 2016

Short answer, no. You're local tech should have been able to check vaccum. However, these new trucks are very complex so it takes some understanding of how everything is integrated.

It's not getting any easier by any means

newdude · November 11, 2016

Hopefully they checked for oil/fluids in the vacuum pump lines...

#PIT5361B: Diagnostic Tip - Additional Brake Pedal Effort - (Jun 28, 2016)

The following diagnosis might be helpful if the vehicle exhibits the symptom(s) described in this PI.

Condition/Concern

In some rare situations, a customer may comment on a hard brake pedal or that increased effort is needed to depress the brake pedal. Also, in some cases a tick or ticking noise may be heard, which may sound like an exhaust manifold leak. While performing normal diagnostics, fluid may be found in the brake booster and/or the booster vacuum line.

Important: Pay close attention to the fluid and if it is determined to be engine oil, it could be coming from the vacuum pump. The vacuum pump is belt-driven and mounted to the side of the engine block. It is lubricated by pressurized engine oil.

Recommendation/Instructions

If engine oil is found, it is important the following parts are replaced. If not, the condition will return.

Vacuum Pump

Vacuum Line between the booster and the pump

Brake Booster

Master Cylinder

Vacuum Pump Belt

Edited November 11, 2016 by 15HDriver

Adam Leinss · November 12, 2016

Yeah, I hope so too. I was reading one story where a guy's vacuum pump was defective and pushed back bits of metal back into the engine block and toasted it. Since the dealer did the repair they should be responsible if anything like that should happen.

Nathan79 · November 12, 2016

Did you report this as a safety issue?

https://www-odi.nhtsa.dot.gov/VehicleComplaint/

2016 Sierra Owner · November 13, 2016

Did you report this as a safety issue?

https://www-odi.nhtsa.dot.gov/VehicleComplaint/

Why would he need to do this? It's no different than losing the power steering pump and you have to actually use some muscle to steer. The vacuum pump just assists the breaks in that you don't have to push so hard on the pedal to apply the breaks. He never lost breaking just had to push the pedal harder to stop. Would it be surprising to be in this condition. Absolutely Yes however he has done the right thing and had it towed to the repair shop. Try letting your truck roll in neutral with the engine off. You have to press the breaks hard but, it will stop.

kstruckcountry · November 13, 2016

Vacuum pumps were on the earlier 2000 pickups IIRC... not really a rare system, or very complicated to check vacuum.

Sent from my SM-G920V using Tapatalk

Nathan79 · November 13, 2016

Why would he need to do this? It's no different than losing the power steering pump and you have to actually use some muscle to steer. The vacuum pump just assists the breaks in that you don't have to push so hard on the pedal to apply the breaks. He never lost breaking just had to push the pedal harder to stop. Would it be surprising to be in this condition. Absolutely Yes however he has done the right thing and had it towed to the repair shop. Try letting your truck roll in neutral with the engine off. You have to press the breaks hard but, it will stop.

Doesn't matter that you can figure out how to stop in this situation. It is a safety issue and if systematic should be a safety recall. Reporting the issue to NHTSA can help force an investigation.

last truck · November 13, 2016

what series is this truck?

OldBlue61 · November 13, 2016

I hope this doesn't sidetrack this thread, but I was unaware that these trucks had a vacuum pump. The engine doesn't develop enough vacuum on it's own?

newdude · November 13, 2016

I hope this doesn't sidetrack this thread, but I was unaware that these trucks had a vacuum pump. The engine doesn't develop enough vacuum on it's own?

AFM is why. It allowed them to change the AFM so it runs more with low/no load. When you drop 4 cylinders, you drop your vacuum supply. Helps for added brake assist to increase pedal feel over the last gen as well.

2016 Sierra Owner · November 14, 2016

Doesn't matter that you can figure out how to stop in this situation. It is a safety issue and if systematic should be a safety recall. Reporting the issue to NHTSA can help force an investigation.

I fail to see is why it's a safety issue. The breaking system Never failed. You just have to press the pedal harder. When the power steering pump goes out it's a safety issue to? You don't lose steering just the assistance to turn the wheel easier.

Adam Leinss · November 14, 2016

The series is 1500.

montytx · May 8, 2017

This happened to me today. Ordering a new pump. I can tell you this, you have to push down really hard to bring these to a stop. I assume they included them in the engine because they drop to 4 cyl. What a pain, 43K miles and my brakes go out, I wonder how many lawsuits they are going to get from this? Also, the power steering is mentioned as a defense. Big difference, braking is way above PS in importance. I litterally braked, turned and then barely stopped before hitting a car. I had no warning, and I am a big guy.

Edited May 8, 2017 by montytx

bgmartin · July 12, 2017

Same thing happened to me yesterday. Very heavy and hard pedal when parking or applying brakes several times at low speed. 2014 Chev Silverado, 5.3 V8, 42K miles. Chev dealership diagnosed it today, vacuum pump not pulling enough vacuum. Seems a common fault...