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6.2 Questions

Discussion in '1982-Present GM Diesel' started by daleearnhardt01, Apr 11, 2004.

  1. daleearnhardt01

    daleearnhardt01 1/2 ton status

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    Hey guys posting this up for a friend who just purchased a CUCV Thanks for helpin him out.......

    I just bought a CUCV truck (1 tons with 4.56 gears on stock size tires) and drove it home for 7 hours going 75mph. The engine didnt seem to mind, and I had more power to keep going but didnt want to as it had been sitting for awhile before I bought it. My Q is that now there is a slight knocking on the inside of the block, like a spinning piece continually hitting the block. (although it might not be spinning, just that constant). Could this be from the possibility of over-revving the engine or could it be a mixutre of low oil and coolant that was in it when it first started. Thanks for your input, I can try to get a sound file/video of the noise if that might help diagnose this problem. THanks again,

    Leach
     
  2. azblazor

    azblazor 1/2 ton status Premium Member

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    It could be an injector, or could be a bearing associated with the rod or crank. You can check if it's an injector by cracking the inlet to the injector 1 at a time and see if the noise stops. Just make sure you get them tightened back up good. If it's a minor bearing knock, it sould not be there when its cold and/or go away with oil thickening agents/products.

    Running these engines at or near the governed speed won't normally affect anything but the MPG.
     
  3. tRustyK5

    tRustyK5 Big meanie Staff Member Super Moderator GMOTM Winner Author

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    7 hours at redline...I'd be a little worried. 3600 is redline for a 6.2 and 75 mph with even 32" tires is 3800. probably comparable to running a small block at 5500 for 7 hours...pretty dumb IMO.

    Rene
     
  4. daleearnhardt01

    daleearnhardt01 1/2 ton status

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    I knew that it was fast in the rpms, the engine just didnt disagree with it. It started making the knocking noise about 5 hours into it, and when we put coolant in and more oil the noise stopped for the rest of the ride. Now its doing it again, but I havent had the chance to drive it because its still not tagged and I dont want to take anymore chances about getting a ticket. I appreciate the help though guys. Anything else I should look out for? Or does it just sound like a bad bearing like AZBLAZOR stated? Thanks again,
    Leach
     
  5. rjfguitar

    rjfguitar 3/4 ton status GMOTM Winner

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    I'm with TrustyK5, You shouldn't have ran it for 7 hrs at redline. As for "it didn't disagree" My 406 doesn't "disagree" with 5,500-5,700RPM's but it doesn't mean that I can just hold it there, it would probably blow up after a few minutes. Why would you want to go 75MPH anyway? /forums/images/graemlins/yikes.gif /forums/images/graemlins/dunno.gif
    Basically this....31" tires+ 4.56's+ no OD+ low revving diesel+ 75mph = probably knocking rod and in need of a short block rebuild. /forums/images/graemlins/shame.gif bummer. /forums/images/graemlins/frown.gif
     
  6. daleearnhardt01

    daleearnhardt01 1/2 ton status

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    I am not sure if I stated this or you are aware of it, but as soon as oil was added after the knocking first started, it stopped for the remaining drive home (couple hours). It started up again the day after I got home, but then I added oil and for another drive around for an hour I didnt hear it once. It only came and went during those times. Its not near me so I am not sure if it is leaking or burning lots of oil, I will know as soon as I get the chance to go back out there and check it out. And the 75mph was a little cushion to what my speedo said, which stayed between 65 and 70 the whole time. If it is only a come and go problem as I desribed, could that still be a knocking rod? Or does the added oil just help that out. And if it is a knocking rod, what kind of money is gonna be needed to fix this from a shop or should I just look into swapping in another engine? Thanks for your help.

    Thanks again for helping my buddy out yall. Me and him really apprectiate it......
     
  7. tRustyK5

    tRustyK5 Big meanie Staff Member Super Moderator GMOTM Winner Author

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    I'd do a compression test and get an accurate oil prseeure guage on it before committing any money or looking for another motor. It could be a lot of things...

    Has the oil and filter been changed since you got it home? Perhaps it's just really overdue for a change and the quality of the oil is poor. You add a quart and things improve a bit at least for a little while...

    Might consider doing all the filters, air, fuel and oil. Also make sure to run the stanadyne fuel additive if you haven't been.

    Any smoke?
    How does it start hot and cold?

    Rene
     
  8. daleearnhardt01

    daleearnhardt01 1/2 ton status

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    I am registering it this week and gonna switch out all the fluids with Chris (daleearndhardt01, the man) and then take it up to autozone/whatever and run a compression test and possibly other diagnostic tests and I am gonna install a bunch of guages in it because I dont have the money for all the rebuilding and stuff right now. Im think tach and oil pressure and temp. Any other recommendations? It starts up like a charm and has never given me a single problem starting it, hot or cold, never a complaint. Coldest its been when starting was maybe around 40 something, but still fired right up every time.

    Is it possible the knocking and what we have been talking about is just due to lack of oil in quantity and condition or something similar to that? Thanks again for all your help and hopefully I'll be able to point you pros in the right direction one day. Thanks again. Leach
     
  9. tRustyK5

    tRustyK5 Big meanie Staff Member Super Moderator GMOTM Winner Author

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    An intermittant knock is pretty weird...could maybe be an injector knock too. I'm certainly no diesel pro, but there are quite a few guys here that will likely have some better input.

    Starting easy is a good sign, usually if compression isn't great they are pigs to start.

    For guages I'd stick with the basic three, oil, temp and volts. A tach can be a bit spendy for a diesel, and it really isn't necessary if you know where the limts are as far as your speed goes. With the stock tires on it I'd keep to 60 or under on the freeway...for any other driving either the tranny will shift up or you'll find the govenor.

    I'd do the fluids and filters, maybe add the 3 basic guages and see where you're at.

    Hopefully arveetek or BlueBlazer62 or one of the other 'guru's' here sees this and has some further input for you.

    Rene
     
  10. arveetek

    arveetek 1/2 ton status

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    First of all, stay away from Autozone unless you're just buying basic parts. They will not be able to help you at all with any engine diagnostics concerning the 6.2L diesel. In fact, they can't help with ANY diesel. I tried to get codes read on my '96 Ford, and their scanner said everything was okay, despite the fact the CEL was on. You'll need to search for someone familiar with the 6.2L.

    Secondly, I doubt you did any harm driving the way you did. The 6.2L can run all day long at it's governed limit. The so-called "redline" on the 6.2L isn't the point at which it's about to explode, but the point at which the governor quits delivering fuel, simply because it no longer makes any more power. I know of guys who have 'adjusted' their governors to be running nearly 5000 rpm on their 6.2L's. A lot of 6.2L's are used in marine applications, and many times they run at governed speed all day long. So I wouldn't worry about that.

    Thirdly, the knocking could be a sticking lifter. I get a knock in mine occasionaly. Since you said adding the oil made the noise go away, this could be a possibilty. Here's what I would do: add a quart of ATF to the engine oil (don't overfill, drain some oil if needed), run it for a few hundred miles, then change the oil and filter. The detergents in the ATF help loosen sticky lifters. I've done it twice to my engine, and it helps get rid of the knock or tick.

    As was mentioned, the knock could also be from an injector. Here's how to determine that: start it up, and loosen one injection line at a time with the engine running. Just back it off enough to make the engine run rough. This is just like pulling a spark plug wire off of a gasser....it kills that cylinder. If the knock goes away on one cylinder when you do this, then that probably means that injector is bad. Try swapping that injector with one on the other side of the engine. If the knock moves to the other cylinder, then you know for sure it is the injector.

    Of course, it could be a main or rod bearing going out, but I'd start with the above first.

    BTW...I'm by no means a diesel guru, but just an avid 6.2L enthusiast with many hours of wrenching and getting to know the 6.2L even better! /forums/images/graemlins/crazy.gif

    Casey
     
  11. tRustyK5

    tRustyK5 Big meanie Staff Member Super Moderator GMOTM Winner Author

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    [ QUOTE ]
    BTW...I'm by no means a diesel guru, but just an avid 6.2L enthusiast with many hours of wrenching and getting to know the 6.2L even better!

    [/ QUOTE ]

    Much too modest...thnaks for chiming in Casey.

    Rene
     
  12. BlueBlazer

    BlueBlazer 1/2 ton status

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    Another thing I think that can cause an intermittent knock (although I cant tell for sure) is the drive pulley on the front of the crank. On my 87, its a two piece design that isolate the pulley grooves from the part that bolts to the front of the damper. What I found after I removed it is the rubber that isolates the two pieces was in bad shape and allowing the two pieces of the pulley to hit each other (if you saw one it would be obvious what I am talking about). I do not know if your buddies rig has this or not, but if it does it would be worth checking out.
     
  13. daleearnhardt01

    daleearnhardt01 1/2 ton status

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    Alright guys THANKS for helping my buddy out..I know nothing about 6.2s so Im in the dark without yall..We're gonna look at it soon and Ill let yall know what the prob is/was. Thanks again
     

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