Vacuum pump going out

FL335i · September 5, 2017

Well when it rains it pours. My truck turned 3yrs old in mid-August and it's at 69k miles. A/C condenser is leaking and now the brake pedal is going. It was only doing it during heavy traffic commutes home and now it's doing it almost all of the time. Pedal effort is very inconsistent and at times i loose all power assist. Feels like the booster is going out. But I did a booster check upon startup and it works. So I'm betting it's a vacuum pump going out. Why can't I just hook the booster up to the intake manifold like my older trucks? The vacuum pump lasted 69k and 3yrs. So in 69k more miles I'll be doing it again. That's a maintenance items with that interval. I don't feel like having a vacuum pump on my 3yr maintenance schedule. The Vac pump has a dedicated belt, so I was looking at just taking the belt off it. Disappointing to have these issues at 3yrs/69k.

Edited September 5, 2017 by FL335i

LongrangeLauber · September 5, 2017

I know the feeling. Month ago I had my fuel tank replaced bc it wasn't filling up. 3 weeks ago my condenser went out and I got it replaced. Friday night I noticed torque converter shudder so it's going in the shop this week

newdude · September 5, 2017

I would be cautious on just cutting the belt. That pump has a dedicated lube feed off of an engine oil gallery, which I assume is an in and out. If you got oil going in and wont come out...boom goes the engine. Same goes for if the pump fails fails.

As for the poor brake assist, check inside the vacuum lines from the pump to the booster. If they have oil dripping/running in there, it can cause poor brake assist. You will need a new pump, hoses and booster if that's the case.

Colossus · September 6, 2017

I know the feeling. Month ago I had my fuel tank replaced bc it wasn't filling up. 3 weeks ago my condenser went out and I got it replaced. Friday night I noticed torque converter shudder so it's going in the shop this week

that's what I call a real lemon. I'd be ticked big time.

FL335i · September 6, 2017

I would be cautious on just cutting the belt. That pump has a dedicated lube feed off of an engine oil gallery, which I assume is an in and out. If you got oil going in and wont come out...boom goes the engine. Same goes for if the pump fails fails.

As for the poor brake assist, check inside the vacuum lines from the pump to the booster. If they have oil dripping/running in there, it can cause poor brake assist. You will need a new pump, hoses and booster if that's the case.

And let me guess, all out of warranty right? What kind of coverage is GM giving on this vac pump?

LongrangeLauber · September 6, 2017

that's what I call a real lemon. I'd be ticked big time.

I'm lucky I invested in an extended warranty. As long as it works out all the kinks before 100k miles id be happy. Think I'm gonna invest in a commuter car to keep the miles and wear off the truck here soon though

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Arth · September 6, 2017

I feel like that's the game today.

Newer trucks make us feel like we should invest in a cheap commuter car because when our trucks are working they're great. When they break.. man do they break.

Just hoping for more use out of my 06 Avalanche.

I'm lucky I invested in an extended warranty. As long as it works out all the kinks before 100k miles id be happy. Think I'm gonna invest in a commuter car to keep the miles and wear off the truck here soon though

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LongrangeLauber · September 6, 2017

I feel like that's the game today.

Newer trucks make us feel like we should invest in a cheap commuter car because when our trucks are working they're great. When they break.. man do they break.

Just hoping for more use out of my 06 Avalanche.

If it's a 1500 avalanche with a 4l60e that's the only thing you need to worry about, and the 8.6 rear end. But, as long as you don't abuse it like I use to in my old truck you'll be fine lol

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newdude · September 6, 2017

And let me guess, all out of warranty right? What kind of coverage is GM giving on this vac pump?

Falls under the 3yr/36k. Not a powertrain item.

Thomcat · September 6, 2017

Anybody on the OP's original question. Why do we need a vacuum pump instead of a direct takeoff from the intake manifold? I can only assume it has something to do with not disrupting the air flow in the manifold downstream of the MAF sensor and somehow screwing up emissions.

.02 What happened to the abandoned "high tech" solution used primarily by Fords in the late 60s - instead of a vacuum booster pump they added a vacuum reservoir with a slow draw check valve in line with the vacuum takeoff from the manifold used primarily to power the vacuum operated HVAC damper servo. Concept should also work for vacuum assist braking which could draw from the reservoir instead of disruption of airflow in the intake manifold. Guess the idea of a reservoir which was nothing more than an empty #10 size "food" can isn't high tech enough for them over a guaranteed maintenance item costing hundreds to service.

KARNUT · September 6, 2017

From what I read on this site, you need the vacuum pump for when your truck is in V4 and not making enough vacuum.

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newdude · September 6, 2017

Anybody on the OP's original question. Why do we need a vacuum pump instead of a direct takeoff from the intake manifold? I can only assume it has something to do with not disrupting the air flow in the manifold downstream of the MAF sensor and somehow screwing up emissions.

.02 What happened to the abandoned "high tech" solution used primarily by Fords in the late 60s - instead of a vacuum booster pump they added a vacuum reservoir with a slow draw check valve in line with the vacuum takeoff from the manifold used primarily to power the vacuum operated HVAC damper servo. Concept should also work for vacuum assist braking which could draw from the reservoir instead of disruption of airflow in the intake manifold. Guess the idea of a reservoir which was nothing more than an empty #10 size "food" can isn't high tech enough for them over a guaranteed maintenance item costing hundreds to service.

See below

From what I read on this site, you need the vacuum pump for when your truck is in V4 and not making enough vacuum.

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Correct. And with the Gen V engines, GM wanted to push more run time for V4 mode. Gives a better vacuum reserve at all times, and in low vacuum situations (V4 mode).

Edited September 6, 2017 by 15HDriver

Paintor · September 6, 2017

If you delete the vacuum pump, this is the plug kit to plug the oil ports on the block.

GM part #11546665

I'm at 12,000 miles....its on my to do list.

Edited September 6, 2017 by Paintor

FL335i · September 7, 2017

If you delete the vacuum pump, this is the plug kit to plug the oil ports on the block.

GM part #11546665

I'm at 12,000 miles....its on my to do list.

Thank you so much!! I'm probably going to delete it, plumb it into the intake manifold and get a AFM delete plug-in module. V4 mode sucks anyway. Now, where to get vacuum from the intake manifold??? I know there is a port for the PCV, only one I have seen. Tee it into the PCV suction hose?

Edited September 7, 2017 by FL335i

LongrangeLauber · September 7, 2017

Too bad you can't do hydraboost like in the gmt800 trucks. Man, did that improve my pedal feel and stopping power tremendously over the vacuum type brakes

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