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crankshaft bearings

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by newyorkin, Jul 10, 2001.

  1. newyorkin

    newyorkin 1 ton status

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    I actually have two completely different questions for two completely differnet vehicles...

    1. I'm going to drop my oil pan and swap out the pump soon. A B tech (or even A by now, I forget) I know said if I have the pan off, I'd be a fool not to change the rod, thrust, and main bearings while I have the pan off. Another mechanic I know, not necessarily a "tech" but wrenches for a living and has been all his life, said not to mess with them unless I have to, cause of scratch risk and potentially lethal bolt torque issues. What do y'all think? To furthur my fear of messing up the bearings, here's my second question:

    2. I've been looking for another K5 in trade for my Heep, and someone just offered me one. '78, d44/12b, 4bbl edelbrock, new fenders, blah blah blah, 350 with loose rod cap. Should I stay away and consider that crank and motor junk? Or is that an easily fixable problem that should not have lasting effects?

    opinions?

    Ratch
    <A target="_blank" HREF=http://k5.8m.com>http://k5.8m.com</A>
    **K5 - What more is there to life?**
     
  2. Emmettology 101

    Emmettology 101 3/4 ton status

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    1. I wouldn't mess with them unless you have the engine out or you have a problem...

    2. Deosn'tsound bad. You will probably have to yank the engine and have it rebuilt. How is the body?

    <font color=green>MIKE</font color=green> - "Hukd on fawnics,werkd fer me!"
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  3. wayne

    wayne 3/4 ton status

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    1. If it aint knockin, don't mess with it.
    2. Trade a Heep for a K5 and you have to think about it. As far as the moter goes it sounds like it could use a rebuild and chances are you can turn the crank down if it has scars that are not to deep.

    <font color=blue>Wayne<font color=blue>
     
  4. newyorkin

    newyorkin 1 ton status

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    Thanks for the opinions. Just want to top this and get some more, but it looks unlikely that I'll mess with them if they're not making noise.

    Not trading for that K5. It has way too much rot, not much truck left... If I had to yank and rebuild the motor, it wouldn't be worth it (if basically nothing is in good shape but the tires). Putting the heep back on the road as a daily driver (v6, drinks less gas) and to get it seen to get cash for it. Oh well.

    Ratch
    <A target="_blank" HREF=http://k5.8m.com>http://k5.8m.com</A>
    **K5 - What more is there to life?**
     
  5. K5RON

    K5RON 1/2 ton status

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    'nother point of view.............If ya had low oil pressure as the pump change suggests, maybe it's due to excessive clearance at the bearings and not a worn out pump! Jus' summizing though!
     
  6. 84_Chevy_K10

    84_Chevy_K10 Banned

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    I agree. You need a complete rebuild if your motor is worn out. A high volume pump isn't going to make your bearings new when they're worn out.

    Tim
    '84 Chevy K10, lifted, loud, fast, and 3/4 ton axles
     
  7. 90K5

    90K5 1/2 ton status

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    My buddy had the exact same problem. The oil pump went out in his S10 while driving, and the pressure got really low. So probably some damage happened to the engine. Why spend all the time changing the oil pump on an engine that has a questionable life span? Needless to say, I've spent the last 2 days pulling that beast out...by the way, GM engineers are retarded!!! To take the engine out of an S-10 you have to jack up the body and take off the bumper....what a joke!! anyway, just my $.02

    90K5

    See my truck at <A target="_blank" HREF=http://albums.photopoint.com/j/Albumindex?u=1329584&a=9886502>http://albums.photopoint.com/j/Albumindex?u=1329584&a=9886502</A>
     
  8. newyorkin

    newyorkin 1 ton status

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    I don't think the motor needs a complete rebuild yet. It has great compression, doesn't burn any oil, no noises (even when oil PSI reads 0), and runs great. If I hadn't seen it on 3 different guages, and the same thing on a dozen prior vehicles, I wouldn't believe it had zero oil pressure. The symptoms I'm having are high/normal pressure at startup, gradually getting lower as I drive, and eventually ending up as zero while in gear, maybe one psi in nuetral.
    I think my friend was telling me to change the bearings out of convenience and preventive maint. He's got a cushy dealership job (just bustin your chops al), so major delicate procedures are pie to him...
    But looking at the TBI for something else tonight, I noticed some real clean spots and various stuff on the motor, so I'm starting to doubt this is even the original motor, which means it has less then the 115k on the clock. The rockers are clean as a whistle, 2k old oil still looks and smells new (it's synthetic, though, and probably not even pumping through the motor, lol), and previous oil changes showed the waste oil looking and smelling very clean. I wouldn't even think the pump is bad, since it seems like the oil is thinning out too much after heating up.
    Maybe I'll do the bearings then, if wear in them can cause low pressure like that. I'm just ascared that during a procedue to extend her life, I stand the chance of prematurely ending it!!!

    Thanks all!



    Ratch
    <A target="_blank" HREF=http://k5.8m.com>http://k5.8m.com</A>
    **K5 - What more is there to life?**
     
  9. newyorkin

    newyorkin 1 ton status

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    Yeah, I remember swapping the tranny in my old S10 took forever. Then a few weeks later, I found out about lifting the body for major work like that... It would've saved me time and misery in the worst winter in years up here if it wasn't designed to have 300lbs of crap in a 30lb bag!

    Good luck on the motor!! I was going to say why the heck would you need to pull the front bumper, but then I started thinking about how I had to change the plugs on my S10, and figured the answer would equally not make sense.

    Ratch
    <A target="_blank" HREF=http://k5.8m.com>http://k5.8m.com</A>
    **K5 - What more is there to life?**
     
  10. 84_Chevy_K10

    84_Chevy_K10 Banned

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    If I were you I'd be running 50 weight or 20W-50 and praying. You're not going to save that thing with that low of oil pressure with a 20 dollar oil pump. If it really has no pressure, ditch it.

    Tim
    '84 Chevy K10, lifted, loud, fast, and 3/4 ton axles
     
  11. mpascino

    mpascino 1/2 ton status

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    Do you have oil pressure when you rev the motor up. I have never seen an oil pump have such high pressure when cold and then drop to zero. The problem you describe sounds like a bearing problem to me. You can always hear a problem like that. One thing you might try to test this theroy is one at a time pull the plug wires off whille the engine is running, or pull them off and then start it. Listen for and noise changes in the motor. If it is something in the low end it might start knocking real bad. I just went thru this whole deal with the motor I just built, turns out I had a bad crank. Good luck, let us know what happens.
    Mike

    You call that dirty!?
     
  12. newyorkin

    newyorkin 1 ton status

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    Yes, there's pressure when I rev it, and the pressure's ok while driving, only bad when idling hot in gear at a stop. I've walked around the motor with a pipe to my ear, but hear nothing out of the ordinary. Even when the pressure's reading 0, motor still sounds and runs perfect. I've seen pumps do this on previous vehicles, and as I research this, I'm starting to think that's how they're designed, to wear out and not just let go without warning. I'd think the pump is always pushing about the same, though, the oil just thins out more once warmed up and the wear-creating low presure is noticable.

    I will change the pump and the bearings together. Hopefully it will be the pump, but I'll know when I get the old bearings out... Too bad it's such a PIA, or I'd just do the pump and see if it's fixed before buying and doing the bearings.

    I can't afford an entire rebuild or new motor right now, and I really don't think it needs a complete rebuild right yet, maybe in a year or so, though.
    My intention is always to have a spare motor, but I haven't been able to find exactly what I want for this truck yet or a block worth rebuilding at what I can afford.

    My Camaro had the same symptoms, but I had a spare motor for it, so I ignored it for 150k miles, and ended up never having a problem.

    BTW, a couple years ago, a buddy of mine tried thicker oil in his low-pressure, but otherwise fine 2.8, and it blew the motor on him. His pressure went from consistent low to spiking up and down randomly. The guy that rebuilt his engine told us thicker oil can kill a good late model engine because it won't flow through all clearances as it's supposed to. He said thick oil is fine if the motor is truly worn out, but bad if it's not. I noticed the same thing when I was in a bind with my camaro and did an oil change with 10w instead of 5w oil. The needle looked like a mexican jumping bean at idle, and when I revved it it spiked over the guage limit... Needless to say, I did two oil changes that day, and always think twice about thicker oil...

    I've never done bearings in a vehicle before, only when on a stand, so I'm worried about a cruddy work environment leading to shoddy work, I.E. scratches or nicks, which will lead to death.

    Ratch
    <A target="_blank" HREF=http://k5.8m.com>http://k5.8m.com</A>
    **K5 - What more is there to life?**
     
  13. 84_Chevy_K10

    84_Chevy_K10 Banned

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    If my motor was that worn out and I couldn't afford a re-ring and head rebuild, I'd at least take the crank out and get it polished.

    Tim
    '84 Chevy K10, lifted, loud, fast, and 3/4 ton axles
     
  14. newyorkin

    newyorkin 1 ton status

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    Tim,
    I still have to insist that we don't yet have enough facts to say the motor is worn enough for major overhaul or job such as removal of the crank. I don't know that polishing the crank would be any help for my current problem (heh heh, he said polishing the crank), especially if
    A. it's not a worn out motor
    B. it's a daily driver
    C. there's a greater likelihood of damaging it by removing it from the truck than there is by leaving it in and swapping the bearings with it in the vehicle

    I think if there was enough wear present to warrant removal of the shaft, then removal of the engine would also be required to equally bore the block, at which point I'm back at rebuilding it, which I can't do because of the down time and cost involved. If I had a spare motor, I'd say ok, maybe I will just yank the motor and rebuild it, but I don't, which means a rebuild costs much more than money; downtime.

    Don't take this as offensive or questioning your knowledge, but there is more to rebuilding a motor than new rings, bearings and heads, and more to the signs of it being required than low oil pressure (although I admit that's a big one). If you're to go far enough as to remove the pistons because of wear on the motor, then it's pretty likely that the cylinders would need to be honed, most likely to the point of requiring new, oversized pistons, I.E. .002, .010, .020, .030 (personally, when someone tells me a motor's bored to .030 over I mentally note "ok, that motor has had it's last real rebuild").

    Not intending to argue, I just think calling rebuild is a little premature.

    Ratch
    <A target="_blank" HREF=http://k5.8m.com>http://k5.8m.com</A>
    **K5 - What more is there to life?**
     

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