Community Forums

BigSkyBob · 08-20-2008, 06:43 PM

I have discovered my Pacbrake exhaust brake is inadequate on the mountain grades I face a lot of the time. I've considered the PRXB and will probably run with that option failing everything else. My question is, does anyone know if a 2006 ISL 400 with a factory installed Pacbrake can be retrofitted with a Jacobs engine compression brake? And, could the internal components for the engine brake be in this engine without me knowing it only to be "hooked up" at a later date?

BigSkyBob · 08-20-2008, 06:43 PM

I have discovered my Pacbrake exhaust brake is inadequate on the mountain grades I face a lot of the time. I've considered the PRXB and will probably run with that option failing everything else. My question is, does anyone know if a 2006 ISL 400 with a factory installed Pacbrake can be retrofitted with a Jacobs engine compression brake? And, could the internal components for the engine brake be in this engine without me knowing it only to be "hooked up" at a later date?

Route 66 · 08-21-2008, 03:50 AM

I'm quite sure the compression brake components are not installed if not being used.

I believe an engine brake can be installed, but I suspect it would cost several thousand dollars.

A call to your Cummins distributor would answer the questions.

Happycarz · 08-21-2008, 07:17 PM

Bob,
Do you have a PacBrake exhaust brake or a Jacobs exhaust brake, not to be confused with the Jacobs engine brake. My 08 Camelot (built June 07) came with a Jacobs brake. Me, not knowing, assumed it was an engine compression brake, like the first ISL's had. While driving back to Az from the factory delivery, I soon found out that the Jacobs was not holding me back, like the last two Monacos had. Same roads/same mountains. When I looked at the engine, I was surprised to see an exhaust brake, and even more surprised that it was a Jacobs and not a PacBrake. Cummins road tested it and agreed it was marginal. Thinking it was not working, they took it off and bench tested it to make sure it was capable of closing all the way. It was working as designed, poorly. And, there was no way to adjust it. Plus, the plate had a 1/2' hole drilled in it to limit the back pressure. I talked to one shop and the were putting a bolt and nut in the hole toraise the back pressure. I didn't agree with that method. The early PacBrakes were adjustable. And, PacBrakes have a 1/8" pipe port to screw a liquid filled guage into test the back pressure. The Jocobs do not.
So, I bought a PRXB and installed it. A lot better, but not as good as the last two Monacos. I then took a back pressure reading, which was 48 psi and spec is 60. When they build the PRXB, cross drill the adjusting stud and insert a roll pin to secure it. The cross drilled hole is a blind hole, so once it is in, it in not removable. I called PacBrake, told them my story and they sent me another. Then, before it arrived, they said not to use it, as they were sending one that was adjustable and not pinned yet. That one tested at 52 psi and I adjusted it up to 60 psi back pressure and now it works super. PacBrake is waiting to get another ISL 400 in the shop for more testing. Meanwhile, our next step is increasing the spring size, so the adjustment stud doesn't have to be screwed out so far. They are absolutely great to work with and they appreciate the real world feedback. I asked if they wanted me to send the other units back and they said when we finish with every thing, they would issue a pick up ticket. Every time they said they would do something, they did. They wanted to solve the problem. They are one of the few that do care, and a pleasure to do business with.

BigSkyBob · 08-22-2008, 02:57 PM

Harry, you opened my eyes with your information. I had assumed my exhaust brake was a Pacbrake so I never did more than look at it in general as I lubed it and did a visual check. My exhaust brake is also a Jacobs and works about as good as dragging my foot on the road. You did a lot of real world testing and adjusting on yours and this information is excellent. I was hot to order a PRXB and install it but now I have a question. Is the center to center distance the same on the Jacobs as the Pacbrake? I would assume the Marmon clamps securing the Jacobs will work on the PRXB. If I ordered a new PRXB now do you know if it would come with a stronger control spring or is that really necessary? I also discovered Pacbrake offers an engine compression brake kit with 3 stages but it's about $1700 and I don't know if that includes the operating controls. I'm pretty sure Cummins would have to install this as it's pretty technical. Thanks for the information.

Route 66 · 08-22-2008, 03:18 PM

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">I'm pretty sure Cummins would have to install this as it's pretty technical. </div></BLOCKQUOTE>

Be sure to check with Cummins before purchasing.

Your engine is still under warranty, and I wouldn't think Cummins would install a non Cummins part.

BigSkyBob · 08-22-2008, 04:07 PM

Dirk, I'll certainly check with Cummins before doing any major mods. Thank you for the heads up.

Happycarz · 08-22-2008, 08:58 PM

Bob,
PacBrake is a direct replacement. Romove the bands, pull on the exhaust pipe to get 1/2" gap, and pul ut out. You will have to get a brass adapter from the hardware store. The ones in the kit wont work. I'm down to tewnty minutes on changing it out. Of course, after it has cooled down.
Mine was in warranty, but the safety and peace of mind were well worth the $950 that I spent on the problem.
I'll call PacBrake Monday and see what the current status is.

Happycarz · 08-22-2008, 09:05 PM

Dirk,
Jacobs engine compression brake has been an factory option for many years. Monaco ordered them on the fisrt ISL 370's. That is why I thought when Monaco listed Jacobs brake, I thought is was an engine brake and not an exhaust brake. But, I am repeating myself.

Route 66 · 08-23-2008, 04:21 AM

I have the Jacobs engine compression brake on my ISL. Cummins calls it the C-Brake, licensed from Jacobs.

I was referring to the installation of Pac Brake's version of the engine brake.

I'm sure Cummins would install their own C-Brake, but not Pac Brake's version.

For you trivia buffs, Clessie Cummins perfected the diesel engine for use in vehicles. Before that, diesels were only used in stationary applications.

Clessie went on to found the Cummins company.

Sometime later he left the company, and invented the engine compression brake.

He offered it to the Cummins Co., but they were not interested.

He then sold his invention to Jacobs.

BigSkyBob · 08-23-2008, 01:08 PM

Harry, what is the brass adapter that won't work that you speak of? Also what did you use for a gauge to set the 60 PSI back pressure? I assume it would have to be something that would survive the heat generated at the turbo. Cummins informed me that I have a Variable Geometry Turbocharger on my engine which I didn't know. I sent them my serial number and received an email back with this information. My interest was piqued because I read somewhere that the VGT can also be used as a very efficient exhaust brake but I don't have a clue how this works. If I can achieve 60 PSI back pressure I guess it doesn't matter how and the PRXB seems to be the least expensive route.

Sixpack98 · 08-23-2008, 02:47 PM

Harry,
It's interesting that Monaco/Cummins installed the Jacobs exhaust brake. Our '06 ISL 400 has the PacBrake (not PRXB) exhaust brake. '07 ISL 400's also have the PacBrake so it sounds like the Jacobs was installed '08 model year and later.

mark

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Happycarz:
Bob,
Do you have a PacBrake exhaust brake or a Jacobs exhaust brake, not to be confused with the Jacobs engine brake. My 08 Camelot (built June 07) came with a Jacobs brake. Me, not knowing, assumed it was an engine compression brake, like the first ISL's had. While driving back to Az from the factory delivery, I soon found out that the Jacobs was not holding me back, like the last two Monacos had. Same roads/same mountains. When I looked at the engine, I was surprised to see an exhaust brake, and even more surprised that it was a Jacobs and not a PacBrake. Cummins road tested it and agreed it was marginal. Thinking it was not working, they took it off and bench tested it to make sure it was capable of closing all the way. It was working as designed, poorly. And, there was no way to adjust it. Plus, the plate had a 1/2' hole drilled in it to limit the back pressure. I talked to one shop and the were putting a bolt and nut in the hole toraise the back pressure. I didn't agree with that method. The early PacBrakes were adjustable. And, PacBrakes have a 1/8" pipe port to screw a liquid filled guage into test the back pressure. The Jocobs do not.
So, I bought a PRXB and installed it. A lot better, but not as good as the last two Monacos. I then took a back pressure reading, which was 48 psi and spec is 60. When they build the PRXB, cross drill the adjusting stud and insert a roll pin to secure it. The cross drilled hole is a blind hole, so once it is in, it in not removable. I called PacBrake, told them my story and they sent me another. Then, before it arrived, they said not to use it, as they were sending one that was adjustable and not pinned yet. That one tested at 52 psi and I adjusted it up to 60 psi back pressure and now it works super. PacBrake is waiting to get another ISL 400 in the shop for more testing. Meanwhile, our next step is increasing the spring size, so the adjustment stud doesn't have to be screwed out so far. They are absolutely great to work with and they appreciate the real world feedback. I asked if they wanted me to send the other units back and they said when we finish with every thing, they would issue a pick up ticket. Every time they said they would do something, they did. They wanted to solve the problem. They are one of the few that do care, and a pleasure to do business with. </div></BLOCKQUOTE>

Happycarz · 08-24-2008, 12:38 PM

I hate it when I type a long response and then hit the wrong buttom and delete it all. I think I'll type in Word and paste here in the future. ARRRG
Bob, I'll get back to the forum later tonight.

Sixpack98 · 08-24-2008, 05:10 PM

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Happycarz:
I hate it when I type a long response and then hit the wrong buttom and delete it all. I think I'll type in Word and paste here in the future. ARRRG
Bob, I'll get back to the forum later tonight. </div></BLOCKQUOTE>

That's called hitting the "AWE shucks key"