Has anyone done this GM vacuum pump delete?

KARNUT · October 25, 2020

Then they’d be admitting to lots more oil related design screwups, wouldn’t you agree?

When it’s all said and done, it’s all about greed!

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There’s ways around that. I have one vehicle they advise extreme service schedule. That made my oil change at 3400 miles. I’d purchase extended warranty and didn’t want excuses, so I followed the recommended service.

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imiller1974 · October 25, 2020

I deleted mine a couple of years ago. AFM is turned off. I put a vacuum canister Tee'd off and I'm running an extra check valve inline from the supercharger snout 1/2" port to the brake booster. Had some work done by a dealership a couple months ago. They saw what I did and how well it worked, some of the employees copied it for their trucks. In fact one of them still has AFM and with the vacuum canister, it works as well as stock. Checked with a vacuum gauge.

James Dink · October 25, 2020

I deleted mine, brakes feel better afterwards

rav3 · October 25, 2020

10 minutes ago, imiller1974 said:

I deleted mine a couple of years ago. AFM is turned off. I put a vacuum canister Tee'd off and I'm running an extra check valve inline from the supercharger snout 1/2" port to the brake booster. Had some work done by a dealership a couple months ago. They saw what I did and how well it worked, some of the employees copied it for their trucks. In fact one of them still has AFM and with the vacuum canister, it works as well as stock. Checked with a vacuum gauge.

Good information. thanks for posting

Grumpy Bear · October 26, 2020

9 hours ago, TXGREEK said:

Then they’d be admitting to lots more oil related design screwups, wouldn’t you agree?

When it’s all said and done, it’s all about greed!

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They have shorted the OCI..in a memo.

M1ck3y · October 27, 2020

I'm keeping mine, although I would like to install the improved version.

When does a Vacuum Pump benefit an engine?

A vacuum pump, in general, is an added benefit to any engine that is high performance enough to create a significant amount of blow-by. A vacuum pump will, in general, add some horse power, increase engine life, keep oil cleaner for longer.

How do Vacuum Pumps work?

A vacuum pump has the inlet hooked up to one or both valve covers, sometimes the valley pan. It SUCKS the air from the engine, thus reducing the air pressure build up created by blow due to combustion gases going past the piston rings into the pan. Vacuum pumps vary in the amount of air volume (CFM) they can suck so the potential VACUUM a pump can create is LIMITED by the amount of air it can flow (CFM). The exhaust from the vacuum pump is sent to a BREATHER tank with a filter on the top, which is intended to retain any fluids (moisture, unspent fuel, air born oil) sucked from the engine. Exhaust air goes to the atmosphere thru the air filter.

So what actually happens at high RPM during the combustion process, and how does a Vacuum Pump change that?

As RPM increases the rings start to get pushed upward on the outer ring edge due to the pressure behind them due to the blow-by build up in the pan, this causes a reduction in ring seal to the cylinder walls, this causes more blow-by. It also causes the rings to "flutter" which further increases blow-by.

The increased pressure in the pan (due to the fact that in a higher performance engine you cannot get all the excess air pressure out of the engine with just breathers (much less engines with PVC systems that are sealed) then PUSHES oil entrained in the air past the rings on the intakes stroke when the engine is SUCKING in air. During the intake stroke oil is also SUCKED past the valve guides. The net result is oil contamination of the fuel (the same way a PCV system contaminate the fuel by sucking oil into the intake), which effectively reduces the octane rating of the fuel. This reduces HORSEPOWER, and on a nitrous or power adder engine can actually burn a hole in the pistons from the increased heat in the chamber due to the faster flame front.

The vacuum pump can reverse every one of these problems by reducing, eliminating or even putting a negative pressure on the engine. The net result is better ring seal, less or no oil contamination, less oil leaks, cleaner oil, longer engine life and MORE HORSEPOWER. An added advantage is your engine builder can use lower friction ring packages because the resulting blow-by is mitigated by the Vacuum pump.

rav3 · October 27, 2020

1 hour ago, M1ck3y said:

I'm keeping mine, although I would like to install the improved version.

When does a Vacuum Pump benefit an engine?

A vacuum pump, in general, is an added benefit to any engine that is high performance enough to create a significant amount of blow-by. A vacuum pump will, in general, add some horse power, increase engine life, keep oil cleaner for longer.

How do Vacuum Pumps work?

A vacuum pump has the inlet hooked up to one or both valve covers, sometimes the valley pan. It SUCKS the air from the engine, thus reducing the air pressure build up created by blow due to combustion gases going past the piston rings into the pan. Vacuum pumps vary in the amount of air volume (CFM) they can suck so the potential VACUUM a pump can create is LIMITED by the amount of air it can flow (CFM). The exhaust from the vacuum pump is sent to a BREATHER tank with a filter on the top, which is intended to retain any fluids (moisture, unspent fuel, air born oil) sucked from the engine. Exhaust air goes to the atmosphere thru the air filter.

So what actually happens at high RPM during the combustion process, and how does a Vacuum Pump change that?

As RPM increases the rings start to get pushed upward on the outer ring edge due to the pressure behind them due to the blow-by build up in the pan, this causes a reduction in ring seal to the cylinder walls, this causes more blow-by. It also causes the rings to "flutter" which further increases blow-by.

The increased pressure in the pan (due to the fact that in a higher performance engine you cannot get all the excess air pressure out of the engine with just breathers (much less engines with PVC systems that are sealed) then PUSHES oil entrained in the air past the rings on the intakes stroke when the engine is SUCKING in air. During the intake stroke oil is also SUCKED past the valve guides. The net result is oil contamination of the fuel (the same way a PCV system contaminate the fuel by sucking oil into the intake), which effectively reduces the octane rating of the fuel. This reduces HORSEPOWER, and on a nitrous or power adder engine can actually burn a hole in the pistons from the increased heat in the chamber due to the faster flame front.

The vacuum pump can reverse every one of these problems by reducing, eliminating or even putting a negative pressure on the engine. The net result is better ring seal, less or no oil contamination, less oil leaks, cleaner oil, longer engine life and MORE HORSEPOWER. An added advantage is your engine builder can use lower friction ring packages because the resulting blow-by is mitigated by the Vacuum pump.

Thanks Mickey......interesting article. I wonder if this also applies to the GM Silverado vacuum pump?

Grumpy Bear · October 27, 2020

2 hours ago, rav3 said:

Thanks Mickey......interesting article. I wonder if this also applies to the GM Silverado vacuum pump?

Nope. The one under discussion draws vacuum on the power brake booster. One he's talking about draws vacuum on the crankcase.

M1ck3y · October 27, 2020

9 hours ago, Grumpy Bear said:

Nope. The one under discussion draws vacuum on the power brake booster. One he's talking about draws vacuum on the crankcase.

I'm confused now. Where would the brake booster draw power if not from the crankcase?

Ah, the manifold... so these engines don't even have a pump to create a vacuum in the crankcase... just ventilation.

Edited October 27, 2020 by M1ck3y

rav3 · October 27, 2020

4 minutes ago, M1ck3y said:

I'm confused now. Where would the brake booster draw power if not from the crankcase?

The GM Silverado vacuum pump pulls a vacuum on the brake booster because AFM system, when in V4, doesn't pull enough vacuum from the engine, so GM added the vacuum pump to give the power brakes it's supplied vacuum. When this pump goes bad, your booster doesn't get enough supplied vacuum from the pump and you will have a hard brake pedal. Basically, that's what this thread is about. This pump has a history of going bad, some early in their life. When that happens, you will have a hard time stopping. Two solutions; either replace the pump or do a delete which requires adding a device to stop the AFM so that the engine only runs in V8 mode, which will be able to supply enough vacuum for the booster. If you do the delete, as described in the video I linked in the original post, you do NOT need to replace the vacuum pump every time it goes bad. Hope this helps explain it.

M1ck3y · October 27, 2020

22 minutes ago, rav3 said:

The GM Silverado vacuum pump pulls a vacuum on the brake booster because AFM system, when in V4, doesn't pull enough vacuum from the engine, so GM added the vacuum pump to give the power brakes it's supplied vacuum. When this pump goes bad, your booster doesn't get enough supplied vacuum from the pump and you will have a hard brake pedal. Basically, that's what this thread is about. This pump has a history of going bad, some early in their life. When that happens, you will have a hard time stopping. Two solutions; either replace the pump or do a delete which requires adding a device to stop the AFM so that the engine only runs in V8 mode, which will be able to supply enough vacuum for the booster. If you do the delete, as described in the video I linked in the original post, you do NOT need to replace the vacuum pump every time it goes bad. Hope this helps explain it.

Thanks, yeah I know the pumps have had problems. But I thought most of the problems were from extended drain intervals. Seems like a really back asswards way of doing things on gm's part...

I watched the video you posted. Did he change the way the pcv system will operate? The vapor canister and valve cover oil/air separator still works?

Edited October 27, 2020 by M1ck3y

rav3 · October 27, 2020

9 minutes ago, M1ck3y said:

Thanks, yeah I know the pumps have had problems. But I thought most of the problems were from extended drain intervals. Seems like a really back asswards way of doing things on gm's part...

Well, with the EPA pressure for more MPG & fewer emissions, they are forced to find ways to meet these requirement. Hence, the AFM on K2XX models & DFM on the new Silverado's. These engines don't produce enough manifold vacuum to keep the brake booster up to where it needs to be, so to solve that issue, GM added the infamous vacuum pump. Thank the EPA for this. It saves fuel up front but passes that cost on to the consumer via more frequent repairs.

mookdoc6 · October 27, 2020

34 minutes ago, M1ck3y said:

Thanks, yeah I know the pumps have had problems. But I thought most of the problems were from extended drain intervals. Seems like a really back asswards way of doing things on gm's part...

I watched the video you posted. Did he change the way the pcv system will operate? The vapor canister and valve cover oil/air separator still works?

That is memo from GM to save face most likely? Look, I got bored decided to replace mine. The main culprit is the microscreen which invariably will become restricted, restricted until failure!

Edited October 27, 2020 by mookdoc6

M1ck3y · October 27, 2020

I'm not doubting guys, just trying to get a picture of how the brake booster works, along with the pcv system. And what's affected, if anything by introducing the brake booster to the pcv system.

rav3 · October 27, 2020

2 minutes ago, mookdoc6 said:

That is memo from GM to save face most likely? Look, I got bored decided to replace mine. The main culprit is the microscreen which invariably will become restricted, restricted until failure!

Where is the "micro screen" that you referenced? in the PUMP? I have searched several GM online parts sources and most come back: "ON back order". this is the P/N i've searched for: GM GENUINE 12696313. Is there a newer version of this one? I noticed that GM just did a recent recall on the 2018 trucks for the "hard brake issue". October 1, 2020 NHTSA CAMPAIGN NUMBER: 20V603000