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Big Dog
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Everything posted by Macktech689

  1. What you are probably dealing with is high oil pressure in the rocker shaft causing low compression when the oil is cold, usually cause by running 15W40 instead of 10W30. Next time you check it cold install the gauge set on the front of the head. rocker pressure should be below 120 kPa, if the pressure goes to 150 kPa report results to tech support.
  2. Macktech689

    abs woes

    Any time a ABS fault is repaired the module will turn off the light if the repair was successful. If you are replacing a wheel speed sensor the truck will have to be driven for the light to go out. If it stays on you didn't fix it.
  3. Macktech689

    weird body code

    Not sure what you are using to read codes or the year model that has it. The only place I've seen a SIM card is in the telematics module.
  4. Macktech689

    Mp7 no fuel to head

    I totally agree but the reality is they sometimes get stuck during storage. I got burned by 1 in 2008 and have been checking them first since then. About half have been OK and the rest were stuck, only takes a minute to check the spool in the valve.
  5. Macktech689

    Mp7 no fuel to head

    New VCB control valves have done that for years, every time one is replaced the solenoid should be removed from the housing and checked to see if it is stuck, saves a lot of time. The valves work fine after they are freed up.
  6. Macktech689

    exhaust valve lash

    When I first read this post I cringed, it's so easy to bend and break the valve train parts if you don't adjust that engine exactly right. Won't be the first time!
  7. Macktech689

    presure in coolent tank

    The most likely cause of a MP-8 pushing coolant is the EGR cooler or injector sleeves. The first step is to perform a combustion leak test on the surge tank, if the test fluid turns green combustion gas is present in the cooling system. Check the cooler first by removing the hose and elbow and looking for coolant or chunks of soot in the cooler outlet. If your cooler looks OK you should get the sleeves replaced. I have never seen a head gasket failure on these engines. If the test fluid stays blue check your air drier for coolant.
  8. Macktech689

    Mack TRLR AUX

    The TRLR AUX switch operates the center pin hot system. It is used to supply 12V to the trailer center pin only when the key is off. It is used by gasoline tanker trucks to operate the over fill protection devices on the trailer when loading. The switch will not power the center pin with the key on or parking brake released. When the key is on the center pin is powered all the time to operate trailer ABS systems.
  9. Macktech689

    Turbo Actuator

    Replacing the actuator requires use of premium tech tool software. PTT has always had a operation to install and calibrate the actuator, if you put it on without doing it right the malfunction light will stay on and the turbo won't perform properly. You're dealer will have to do it, takes less than half an hour.
  10. Macktech689

    No throttle .Please help.

    Keep in mind any loss of voltage or ground to the control modules will log 6-4 also. The fault isn't always in the data link wiring. Fixed a 6-4 fault this week that was caused by engine harness wires rubbing on the block causing the engine module to lose power.
  11. Macktech689


    Blink code 6-4 is caused by a loss of communication between control modules on the J1939 data link.
  12. Macktech689

    Truck won't start 08 Granite

    Replace fuse F7 in the BEC.
  13. Macktech689

    Ground relay

    That is a circuit breaker that protects against system damage it there is a battery short to ground. Personally I would not bypass it.
  14. Macktech689

    A/C not working

    Fuse 41 is in the EPDM outside on the firewall, it's a mini fuse, right side 3rd from the top. Marked fan clutch 15a. If that is the fuse with no power, it comes off power relay #3 inside the cab behind the glove box area.
  15. Macktech689

    A/C not working

    Voltage to the APADS also comes from fuse 41 ( 15a ) down the red wire, but before it gets there it runs through the Freon high pressure switch connector. Also check the APADS ground.
  16. Macktech689

    2004 mack ch fan need help!!

    The only way to remove the password is to flash and program the control module.
  17. Macktech689

    Mac cxu613 fan clutch

    The easiest way to check to see if the fan is capable of engaging is to disconnect it from the engine harness and run the engine over 1000 rpm. The fan should fully engage in around 10 seconds, if it doesn't replace the fan drive. Loss of voltage triggers a limp home mode, keep in mind the fan drive will rarely fully engage during normal operation 75 to 80% is normal.
  18. Macktech689

    Mp8 code

    The only thing I get from what you posted is it a engine fault, you'll need to hook up with diagnostic software to get a better fault code description.
  19. Macktech689

    Bull gear on mp8 engines

    There was no change to the flywheel housing when the staked idler gears were installed, removing the housing is no small job the back and bottom of the engine needs to come off. You can check the idler gear through the PTO cover at the top of the housing on the right side to see if it is loose, if it is you will also see where it's rubbing on the housing. The video you mentioned may have been of a MP-7. A good picture of the top of the housing would be helpful, a pic of the bottom won't show anything.
  20. Macktech689

    Mp7 2007 04 EPA Harness

    The harness for that engine runs in the $600 range I think, I don't buy them I replace them. I've replaced dozens of engine harnesses, it's not a bad job as far as I'm concerned. The worst part of the job on a 04 emission's MP-7 is getting the harness disconnected from the mass flow tube module behind the alternator bracket.
  21. Macktech689

    Engine Code

    SPN 105 is the intake manifold temperature sensor, you didn't mention what year your truck is. The earlier engines used 2 sensors one for pressure the other for temperature, the sensor is capable of doing both so newer engines only had 1 sensor. Regardless the temperature sensor is located in the back of the intake manifold. If you have a older engine with 2 sensors switch them and see if the fault goes away.
  22. Macktech689

    Fast idle with cruise control

    If you are unable to adjust the engine speed using the speed control switches it's possible that the function is not enabled in the VECU. PTT will need to be used to make parameter changes in the control module.
  23. I would start with checking the sensor 5V. supply, ground and signal voltage. Do it first at the sensor and if everything is OK check at the ECM connector, may be a wiring problem.
  24. Macktech689

    Bull gear on mp8 engines

    I can't help with the VIN, the pinning campaign was PI0785 and was issued in May 2102. You can check your trucks build date it's on the decal inside the drivers door jamb, you could also contact Mack to see if your truck was part of this campaign and whether it was already done. Another thing to look at is to see if a plug is installed in the top of the flywheel housing next to the crank sensor, the plug is put in after the pinning is done.
  25. Macktech689

    Bull gear on mp8 engines

    Double idler gear failures are not uncommon. Starting in 2010 the oil temperature was raised to 238 degrees and the hotter oil was causing the retainers to loosen, originally the retainers were installed with Loctite and not staked in place. After a rash of failures staking the retainers was put into production can't remember exactly when. There was a campaign to "pin" the retainers for a while, haven't done it in years, You could ask your dealer about it and see if they would be willing to do it for you. It's possible the gear in your engine has a staked retainer already.

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