Cat C15 Jake Brake Question

Discussion in 'Heavy Duty Diesel Truck Mechanics Forum' started by High Stepping, Oct 29, 2020.

  1. High Stepping

    High Stepping Bobtail Member

    Oct 29, 2020
    I'm working on a 2004 Cat MBN C15. The jake brake has always given the driver trouble. After closer inspection of the assemblies, I found one of them cracked. It has the Pac Brake brand on it. For some odd reason I was told that only the MBN engines used this particular jake brake assembly. I was told, as with any C15, you can change out all of the jake brake assemblies, if you can't find that particular one. It's been like pulling teeth trying to find a good used one. Which model or particular year jake brakes are you partial to? Is there a particular set that works better than the others? Thanks in advance!
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  3. blairandgretchen

    blairandgretchen Road Train Member

    Dec 9, 2011
    South west Missouri
    Well, it’s a S60, but I’ve had issues lately too.

    I should’ve left them alone, but the mechanic was in the head anyway, so I had him rebuild the PAC brakes. He wound up machining off a few parts, for some reason - messed them up, they were really weak.

    So he swapped them all out with Jacobs. Which are as weak as his rebuild job on the Pac.

    Now he wants to try adjusting them down further, as a last resort.

    Last heard he was searching for plungers and parts for the PAC brakes to try and get them right, parts were difficult to find.

    He hasn’t charged me anything - and it puzzles me because he and his Dad have extensive mechanical knowledge, he cuts counter bores round town as well. But he can’t get these darn jakes right.

    Part of the problem is - the truck was in the shop for a month, and after all the back and forth, I think I’ve forgotten how good/bad they operated before - but we all agree they’re weak now.

    Sorry for the ramble, but that’s all I got.

    Oh - his Dad said they used to be a dealer installed option - at one point, even wiring and switches. That was his explanation to my question of why they weren’t Jacobs brand initially. It’s a Pete 379, 1995.
  4. If you come across a set of 340c jakes, use them. They work better than the pac brakes. Even a set of 340A's will work also.
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