Vacuum jake brake??

[Philip Saran]

I was talking with a guy who has been a Cummins mechanic for 18 years and he says to leave
the vacuum jake brake switched on all the time so that it will clean air going into the turbo.

Anyone have experience with this?

Also what is the plus/minus switch on the auto shifter arm do? Is it to make the auto trans downshift
more or less?

Mine is a 2012 3500 - 6.7 diesel

 

[jhenderson]

On 3rd gen trucks a Jacobs exhaust brake was available through Mopar. It was powered by a belt driven vacuum pump. I have no idea what he’s talking about with clean air through the turbo. I’d bet a farm out west he doesn’t either. Especially since these trucks have had an electrically operated exhaust brake, controlled by the ECM starting in the 2007.5 model year. The + and - on the shifter allow you to select the highest gear the trans will shift to. It will not allow you up shift before the pcm wants the truck to but it will within reason allow you to downshift to the gear you’ve selected. It maydownshift below the pre selected gear if conditions warrant it.​

 

[ScottLewis]

When I bought my '06, a vacuum operated Jacobs was an extra cost option. Other than an on/off switch, it is fully controlled by the ECM. The vacuum pumps were problematic and I replaced the brake with an air operated PacBrake at about 70K miles. I know little about the brake system on the 6.7s but believe they are incorporated with the turbo.

 

[jelag]

I had a group of trucks that used the same style of vacuum pump... we found that if once a year.... for us.... it was in the winter(when we winterized the truck) and we would pull the vacuum line from the pump and let it slurp up 2-3 oz's of light oil.... We'd put a rag over the discharge of the pump and let the pump, sort of clean and lubricate it self... You would be surprised how nasty the discharge would be....

We found that on the pumps we were using.. (Delco) would easily last 2-3 times longer... Just my thoughts...

 

[petersonj]

I was talking with a guy who has been a Cummins mechanic for 18 years and he says to leave the vacuum jake brake switched on all the time so that it will clean air going into the turbo.

Since the 6.7 liter engine was introduced in 07.5, a variable geometry turbo (VGT) was introduced along with the it. Sliding vanes were incorporated into the exhaust housing of the turbo to improve the turbo's boost performance throughout the operating rpm range of the engine.

A computer controls the operation of the sliding vanes located in the exhaust housing and determines the size of the opening feeding exhaust gases to the turbine wheel. A restricted opening at low engine rpm's while accelerating the vehicle will increase the velocity of the gases contacting the turbine wheel, consequently improving spool up under those conditions. As the engine rpm's increase and /or engine load changes, the size of the opening will change correspondingly.

An added benefit of the VGT is that by almost closing the variable vanes, the turbo can be used as an exhaust brake. A win, win situation.

With the more restricted emissions that came with this technology, problems were encountered involving the VGT - mainly that the turbine housing easily became contaminated with soot and the variable part became sticky. I really think this is what the mechanic was trying to portray - operating the exhaust brake frequently will make it more reliable.

- John

 

[cerberusiam]

A Jake Brake is completely different than the exhaust brakes our truck use, it depends on what the mechanic was really referencing. Not going to force clean air into the turbo but rather forces more thru the turbine side of the housing to keep the sooting form causing issues, on the VGT turbos anyway.

 

[KATOOM]

I was talking with a guy who has been a Cummins mechanic for 18 years and he says to leave
the vacuum jake brake switched on all the time so that it will clean air going into the turbo.

Wut...?

 

[Hoefler]

He works on the Ford owned Cummings

 

[NIsaacs]

I was talking with a guy who has been a Cummins mechanic for 18 years and he says to leave
the vacuum jake brake switched on all the time so that it will clean air going into the turbo.

The wordage might be the OP's interpretation of what the mechanic said....

 

[mfurrh55]

When I bought my '06, a vacuum operated Jacobs was an extra cost option. Other than an on/off switch, it is fully controlled by the ECM. The vacuum pumps were problematic and I replaced the brake with an air operated PacBrake at about 70K miles. I know little about the brake system on the 6.7s but believe they are incorporated with the turbo.

i took the vacuum pump off my jacobs and put an electric thomas air pump on mine and hooked it up backwards so that i used vacuum side instead of discharge side and it has worked great for 15 yrs. so far