Detroit Diesel stripped thread question
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  1. #1
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    Default Detroit Diesel stripped thread question

    Anyone have any experience with thread repair on diesel engines, specifically a 1996 12.7 not that it matters but truck is a Peter-built
    18 wheeler.

    I was asked if I could do this onsite so the motor would not have to be removed again. Is this a job that could be done in the field so to say.

    What I have learned is at least one hole maybe more has been repaired already, the head was put back on and one or more threads stripped out
    while being (impacted on with an air powered device) is this how big trucks are worked on ? using an impact on cylinder head bolts.

    Would it be best to do all of them or go thru the time and torque all of them and see if any others fail.

    I count 38 holes as far as I can tell, with at least one repaired, & another failed.

    Any particular insert better for this job ?

    That is as much as I know at this point, the guy is supposed to call me later.

    Thanks again guys

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    Impacts are ok for taking stuff apart but to put it back on you are asking for trouble if you hold the trigger to tighten up the bolt or nut. You can run the nut up but a torque wrench should be used to tighten the bolts. I have repaired many turrets for tool holders that have been stripped by impact wrenches. I bet that many of those bolt holes are damaged from overtorqueing.

    John

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    This happens often. Those bolts are fine thread and torqued to around 200 ft-lbs. They usually strip on the way out, not in. The issue just shows up when you put it together. The coolant leaks around the bolts and they get rusted in.

    You can fix it on site. Take an old head bolt (I'm sure they have one) and cut it off. Turn a diameter on the bolt shank that is true to the threads. Thread it into what is left of the original threads (should be something left at the bottom). Set up a mag drill and indicate to the tool you just threaded in. Drill and tap for a helicoil.

    I would not do them all. It will take forever.

    Don't drill too big or too deep. There are oil, coolant, and god knows what else passages cast in the blocks all over.

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    Use a torque wrench to assemble. And I am betting the threads are metric. I think 60 series are metric engines.

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    Why would you use an air impact???

    Well after 6 valve jobs on D343 Cat engines..

    ~36 head bolts, getting first of three torque sequences down, with a 3/8ths impact saves time...

    I think you end up at 325 or 375 ft lbs, last go round. I do look at the manual first

    There are also torque limiting extensions, that are used on impacts to limit torque.. Odd looking link, but it is OK Unusual Activity Detected - Free Shipping on Orders Over $99 at Summit Racing

    Sometimes you just don't have time to Di&* around, Drag strip for example... Save the dial or click torque wrench for final round of head bolt torque.



    Fine threads in a softer material, are not the greatest way to go..

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    What does it is the hydraulic action when the fail to blow the water/oil out of the hole first.

    Block will be broken and junk.

    Do a mag particle inspection.

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    Check out KENTMOORE or lock n stitch full torque bolt hole inserts, they probably make an insert and installation kit. Ive done alot of 855 cummins and KT cummins with these and had good luck. NOT!!! cheap, but they work good

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    Still, if the book states 220 pounds I don't think you can be spot on with using an air torque wrench.

    It is not uncommon for a 3/8 air wrench to go 250 or 300lbs

    6. Diesel ARP Head Stud Torque - YouTube


    Cummins N855 Big Cam engine specs, bolt torques and manuals

    I suppose one could do the pattern going to one click with a 3/8 drive and even a 1/2 drive if being at least a little sure of the torque to save time. Then finish up with a proper wrench. I have had good success with gas engines but have yet to do a diesel. The torque is such that it can stretch the bolts and then a little more can pull the thread.

    *Yes, I think a good mechanic can repair a pulled thread in the field.

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    You might be shocked how many of these engines are running around with stripped head bolts that are never fixed...

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    Quote Originally Posted by Heavey Metal View Post
    What does it is the hydraulic action when the fail to blow the water/oil out of the hole first.

    Block will be broken and junk.

    Do a mag particle inspection.
    What are you trying to say ?

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    Quote Originally Posted by vonleyser View Post
    What are you trying to say ?
    He doesn't know what he's talking about.

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    Quote Originally Posted by ewlsey View Post
    He doesn't know what he's talking about.
    One day you will have to make a decision

    Are you going to keep fucking people's shit up or are you going to fix it.

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    Quote Originally Posted by vonleyser View Post
    What are you trying to say ?
    Either you stand behind your work or you do presidential work.

    Do a mag particle inspection.

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    Back in the day I was taught to put Permatex on coolant through threads. My son is a diesel mechanic trained at UTI.
    I will ask him what is the current correct procedure.

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    I think id have a go with a solid type insert rather than a coil, stronger and better chance of a result.
    Would also torque bolts to see which ones want doing.

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    Quote Originally Posted by Heavey Metal View Post
    One day you will have to make a decision

    Are you going to keep fucking people's shit up or are you going to fix it.
    How many series 60 Detroits have you rebuilt?

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    Quote Originally Posted by michiganbuck View Post
    Back in the day I was taught to put Permatex on coolant through threads. My son is a diesel mechanic trained at UTI.
    I will ask him what is the current correct procedure.
    There are no head bolts that pass though to coolant. Sometimes you see it on a thermostat or waterpump. It that case you would be right.

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    Quote Originally Posted by ewlsey View Post
    How many series 60 Detroits have you rebuilt?

    You don't have to build that POS to know how to do quality work. Torque is a very crude method of tensioning a fastener. Using an impact wrench makes it laughable.
    Helicoil is the best repair. There is a reason that a 747 comes new with over a quarter million of them. There is no room here for the huge other types of thread inserts.
    Sounds like this shop could be a goldmine.

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    He had some crackpot theory about the head bolts hydraulically breaking the engine block because no one blew out the holes. I'd pay to see that happen.


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