6nz"d BXS Acert thumping noise

Discussion in 'Heavy Duty Diesel Truck Mechanics Forum' started by w9l, Jun 29, 2020.

  1. Guntoter

    Guntoter Road Train Member

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    I am in the shop now. 18:1 with twin 625 turbos (both the big ones) got 330K with 770HP and 2400Tq to the rear wheels. Never had any issues until last week, losing a gallon of water per day... Pulled the head, its junk, number one cylinder has been bouncing. I used all genuine Cat parts, updated head bolts etc... Im now learning that I should have gone with 16:1 pistons in the first place. Im a big fan of twin turbos because you get more volume with less pressure (pressure equals heat) I had 42 PSI all day long, never saw the pyro go over 900 (my powder coated hot sides look like new). All good, except that the head gasket will never survive that kind of cylinder pressure. Cat keeps recommending all sorts of band aids to "fix" the Acert head issue but bottom line, the high compression needed to meet EPA requirements is just too much for the technology they put into the head and head gasket design.
     
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  3. Shawn2130

    Shawn2130 Heavy Load Member

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    Guntoter: that’s a lot of twist power you got there.

    Yes I like having the 2 turbos.

    I’m not 100% sure what’s in the program I have but so far it wasn’t the reason for the failure as far as I can see.

    Last driver was hard on this BSX.

    He drove the truck back to the yard with a hole punched through the valve cover from the rocker studs breaking and the engine rattling. Not sure where he was when that happened.

    I haven’t got a chance to do much of anything with this engine when the head cracked.

    My boss said all 6 pistons showed overheating issues on the skirts and the sleeves.

    I’ll still try the 18:1 and see what happens.

    I’ve wondered what the guys did that made 3,000 horses out of the Cat engines for the truck rodeo up here in Ontario/Quebec.
     
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  4. w9l

    w9l Medium Load Member

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    My question on the rodeo trucks is how they keep a driveline in them...
     
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  5. w9l

    w9l Medium Load Member

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    My big Rodeo question is DRIVELINE???????
     
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  6. w9l

    w9l Medium Load Member

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    Starting to wonder if my thumping is a result of sucking air into fuel lines. Everyone that has tried to solve this for me has been asked could it be sucking air? One replaced the Cat primary screen canister and says all good. I get under truck to clean condensation drain for sleeper and notice splitter valve thing is dripping a tad and the fuel line out of top of pass side tank is covered in fuel saturated dust...... seems they all want to cure the problem with a few keystrokes on the laptop... Don't get hands dirty that way....
     
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  7. Guntoter

    Guntoter Road Train Member

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    Those 3000 hp motors run for about 15 seconds then shut down, they also have HUGE turbos and only 60-70 PSI so they don't heat the air too much. If you like the twins, I would recommend running the big pair instead of the stock staggered ones. Im going to drop mine to 35psi I think. I can still put 650+ to the ground and not be dumping that hot air and too much cylinder pressure on to those pistons.
     
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  8. Shawn2130

    Shawn2130 Heavy Load Member

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    Hot air is the big problem. I learned that right away when I mistakenly touched the pipe while looking for a leak.

    What 2 big turbos are those from that you’re running on your C15?

    I’ll consider checking them out. :cool:
     
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