jake brake vacuum pump

[TFaucette]

the vacuum pump that operates my Jacob's Jake Brake is making a very loud ticking and is not creating enough vacuum to operate the canister, has anyone had any experience with a vacuum pump failure? it only has 50,000mi onit, is it the same pump (pulley and mounting, i'm sure the diaphram is) as used on the powerstrokes where i can find a used one? and the ticking can i just replace the diaphram or do i probably need the whole thing?

 

[CSkal]

Take a look at the new Geno's catalog. They just started offering a replacement vacuum pump for the Jacobs brake, as well as just the replacement POD for the pump.

I just bought and replaced my vacuum pump with a new one from Cummins (not Dodge) for about $249. I was a little bit surprised by the price of the pump from Geno's being more than the Cummins unit.

Anyway, my pump just started grinding one morning on the way to work. It would still operate the brake but just barely. 105K+ on the original pump that came with the kit. I can't really complain.

I don't know about the Fords, but I am sure that someone will chime in if they know something.

 

[meanmatt]

The new Geno's catalog shows just a diafram kit and the complete unit . Probably price is competitive with your local Cummins dealer

 

[CKelley1]

now is a good time to junk the jake and install a bd. no more pump problems and a huge increase in braking power

 

[Okie-Go]

Mu pump went out at about 125k. Went to the pars housse to get a new one. It came in but the shaft was a different length. the nice fellow changed the diaphram and oil and put it back together. I think it was 126. 00. He did say to keep an eye on it. the bearing usually goes out as well according to him

okie

 

[nunya]

Just had mine replaced @ 49K by the dealer under warranty. It just quit workin while pullin my 38` 5th wheel, nice ticking noise, easy to figure out the problem for sure. I was glad it didn`t come apart, just broke internal. I sure missed havin it, what a difference with it. Thanks for the info on the Geno`s parts, hadn`t seen that one.

 

[HBarlow]

The Jacobs E-Brake vacuum pump on my '01 Ram failed at somewhere around 200k miles.

I was extremely satisfied with the Jacobs brake on my '01 and '06 Rams. They gave me about 550,000 miles of service between the two trucks.

I have always been a bit skeptical about the claimed great advantages of a PacBrake. No exhaust brake can do anything more than completely block the exhaust. The Cummins ISB5. 9 has the same displacement, same exhaust valves, same cylinder head, same exhaust manifold, and same amount of exhaust flow and pressure discharged regardless of what exhaust brake is hung on the discharge side of the turbocharger.

We each pay our money and take our chances. I have always been happy with the Jacobs brand but have never used any other brand so I don't make bold comparisons.

 

[CKelley1]

harvey it is the way the back pressure is held that makes the difference. the bd completly blocks the exhaust with a butterfly valve by way of a air cylinder who's pressure is regulated to keep exactly 65 psi back pressure on the exhaust. this is the maximum you can have because of the exhaust valve springs. the pac uses a slightly different version for patient infringement reasons in there butterfly valve there is a small hole in it. when it closes there is a ball with a spring that covers the hole, the spring is calibraded to hold 65 psi back pressure. the jake and banks just have a small hole in the butterfly valve. the hole is calculated to hold 60 psi at 3200 rpm at sea level. at 1000 rpm you do not have very much stoping power and for every 1000 feet in elevation you loose 2. 7% more. i am at 7000 feet and at 2000 rpm there is one gear difference between a bd and a jake

 

[HBarlow]

I've read the explanations of how PacBrake exhaust brakes increase exhaust back pressure before but I remain skeptical.

It sounds like marketing hype to me but as I posted earlier, I've never used one so won't state that the claims are false.

 

[CDonaldson]

I run a PacBrake, have an exhaust back pressure gauge, it sits right at 60 when I engage the brake, so it does the back pressure they claim it does. I have been very pleased with my PacBrakes performance, not one problem with it, works perfectly. I also like having the air compressor to run my wireless air controlled air bags, air horn, and having some air when needed for tire inflations or other air related stuff.





CD

 

[CKelley1]

you explained it better than i did. the pac and bd hold 60 psi through out the rpm and at any altitude where the jake is 60 psi at max rpm at sea level and go's to near zero at low rpm and high altitude. harvey i can send you a pix of one of the jake's we removed to replace with a bd if you need to see how it works

 

[HBarlow]

I may be stupid or stubborn . . . or both, but simply don't see how a PacBrake can create more back pressure at lower engine rpm than a Jacobs brake. If the engine is not running fast enough to create a steady 60psi of exhaust brake pressure with a Jacobs brake how does PacBrake create that much back pressure?

Sure, please post or pm me the pictures/diagrams/etc. I promise to examine them with an open mind. I can (on rare occasions) be convinced of something that initially appears to violate what I perceive to be common sense or the laws of physics even though I am a stubborn and opinionated old man.

I am most skeptical of amazing claims made by the marketing departments of manufacturing firms selling products very similar to those of other companies who cannot and do not make such claims.

If I can believe the advertising claims I will back down and admit it publicly.

 

[BrianJ]

if I understand this correctly... the jacobs has a "FIXED" hole in the butterfly valve to assure a maximum back pressure of 60psi at maximum RPM. The BD and Pac have a "VARIABLE" hole in the butterfly so they can maximize back pressure as RPM's and exhaust pressure decrease, i. e. as RPM's drop the hole closes up and blocks more exhaust.



That being said, I am still not sold on it making that big of a difference in real life application.

 

[HBarlow]

if I understand this correctly... the jacobs has a "FIXED" hole in the butterfly valve to assure a maximum back pressure of 60psi at maximum RPM. The BD and Pac have a "VARIABLE" hole in the butterfly so they can maximize back pressure as RPM's and exhaust pressure decrease, i. e. as RPM's drop the hole closes up and blocks more exhaust.

That being said, I am still not sold on it making that big of a difference in real life application.

My thoughts exactly.

But perhaps you explained it in your brief paragraph above.

 

[TCDiesel]

The Ball is Spring applied in the PAC it will close completely at low RPMs,when the pressure over comes the spring it will open,the less pressure the longer the ball closes the hole, the greater Pressure / volume it will stay open. This cannot be achieved with a fixed orifice. My experience with Pac and Jake is the PRXB has 10% better holding pressure under 1500rpms. Its not a Big difference but is noticeable. At Idle/Ramp the PRXB will warm your engine twice as fast as Jake or fixed orifice design.

 

[HBarlow]

That sounds reasonable and I can accept the theory. I do wonder how much true difference in braking actually results from the PacBrake design and how much is, shall we say, optimistic.

I would like to see actual recorded back pressure at each 100 rpm increment from about 2900 to 1000 rpm with each exhaust brake.

If engine rpm is down below about 1800 rpm I wonder how much exhaust back pressure is generated with either brake.

I guess what I'm wondering is if engine rpm is low does brake pressure with the butterfly valve fully closed exceed 60 psi with either style.

I also wonder how effective either brake is from 1500 rpm down to 1000.

 

[ENafziger]

That sounds reasonable and I can accept the theory. I do wonder how much true difference in braking actually results from the PacBrake design and how much is, shall we say, optimistic.

I would like to see actual recorded back pressure at each 100 rpm increment from about 2900 to 1000 rpm with each exhaust brake.

If engine rpm is down below about 1800 rpm I wonder how much exhaust back pressure is generated with either brake.

I guess what I'm wondering is if engine rpm is low does brake pressure with the butterfly valve fully closed exceed 60 psi with either style.

I also wonder how effective either brake is from 1500 rpm down to 1000. <!-- google_ad_section_end --> <!-- / message --><!-- sig -->

I may have some answers for you soon.

I had the Jacobs Exhaust brake installed by the dealer when I bought the truck new in '06. I had a vacuum pump failure at 35k miles, and another at 71k miles. In one instance, it also snapped the belt, broke the tensioner and sent it into the back of the radiator, and broke the fan shroud. All pulley grooves were filled with melted rubber.

I opted to remove the Jacobs, and install a 5" inline PXRB PacBrake.

I have a 0 - 100 psi drive pressure gauge in the cab, so I was able to monitor performance of the Jacobs brake (well, at least some of the time... the gauge was quick to "soot up" and quit responding).

I should have the PacBrake installed within the next week, and can give a real-life comparison. Just from looking at the two brakes, it looks like the variable orifice on the Pac is promising. It's a little hard to see from pictures, but makes sense when you hold one in your hands.

A spring sets tension on the ball lever that pushes against the orifice slide. The spring tension is adjustable with a set screw... although for the ISB applications, it is set at 60 psi... a limit I understand is imposed due to exhaust valve spring rates.

I did do some adjusting on the Jacobs brake I had to achieve a full 60 psi backpressure. I expect to monitor and adjust if needed on the PacBrake to achieve the same. With the Jacobs, the 60 psi was only attained at 3200+ rpm. As rpm came down, so did backpressure. While I don't have a data logger or imperical data, it appeared to be a linear relationship. Thus, by about 1500 rpm, backpressure was down to around 25 psi or so.

The amount of braking (retarding horsepower) achieved, is directly related to the amount of pressure acting on the piston during compression. The intent of the PacBrake's sliding orifice, is to keep a full 60 psi backpressure throughout the rpm range. I'll be anxious to see if this is realized on the Drive Pressure gauge in the cab.

My initial thought, is maintaining constant backpressure will help alot. However, as rpm comes down, you have fewer compressive piston strokes available to do the braking "work". Thus, retarding horsepower will decrease even if drive pressure remains constant. In order for braking power to remain constant, drive pressure would have increase as rpm decreases... at least that's the way it makes sense in my head!

I'll report actual findings later...

--Eric

 

[HBarlow]

Your findings will be of interest to me even though my current Ram uses a VGT to provide the exhaust brake function.

 

[CDonaldson]

I may have some answers for you soon.



I had the Jacobs Exhaust brake installed by the dealer when I bought the truck new in '06. I had a vacuum pump failure at 35k miles, and another at 71k miles. In one instance, it also snapped the belt, broke the tensioner and sent it into the back of the radiator, and broke the fan shroud. All pulley grooves were filled with melted rubber.



I opted to remove the Jacobs, and install a 5" inline PXRB PacBrake.



I have a 0 - 100 psi drive pressure gauge in the cab, so I was able to monitor performance of the Jacobs brake (well, at least some of the time... the gauge was quick to "soot up" and quit responding).



I should have the PacBrake installed within the next week, and can give a real-life comparison. Just from looking at the two brakes, it looks like the variable orifice on the Pac is promising. It's a little hard to see from pictures, but makes sense when you hold one in your hands.



A spring sets tension on the ball lever that pushes against the orifice slide. The spring tension is adjustable with a set screw... although for the ISB applications, it is set at 60 psi... a limit I understand is imposed due to exhaust valve spring rates.



I did do some adjusting on the Jacobs brake I had to achieve a full 60 psi backpressure. I expect to monitor and adjust if needed on the PacBrake to achieve the same. With the Jacobs, the 60 psi was only attained at 3200+ rpm. As rpm came down, so did backpressure. While I don't have a data logger or imperical data, it appeared to be a linear relationship. Thus, by about 1500 rpm, backpressure was down to around 25 psi or so.



The amount of braking (retarding horsepower) achieved, is directly related to the amount of pressure acting on the piston during compression. The intent of the PacBrake's sliding orifice, is to keep a full 60 psi backpressure throughout the rpm range. I'll be anxious to see if this is realized on the Drive Pressure gauge in the cab.



My initial thought, is maintaining constant backpressure will help alot. However, as rpm comes down, you have fewer compressive piston strokes available to do the braking "work". Thus, retarding horsepower will decrease even if drive pressure remains constant. In order for braking power to remain constant, drive pressure would have increase as rpm decreases... at least that's the way it makes sense in my head!



I'll report actual findings later...



--Eric

Pretty good assessment Eric. The back pressure does stay pretty solid, but it is also relative to what gear you are in as well. You DO have to downshift on steep grades sometimes to hold a particular speed, which in turn increases rpm's and compression (per se) and that does maintain the pressure.





CD

 

[CKelley1]

eric i have had the same problems you have had with the jake and it allways happens at the most inconvient time and place. we also observed the same back pressure readings. the bd is a little easier to adjust to set the 60 psi than the pac but neither the pac or bd seem to drift once set.