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HEAD GASKET OR CRACKED BLOCK?

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by rh88k5, Mar 7, 2003.

  1. rh88k5

    rh88k5 Registered Member

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    Is there any way to tell if its a blown gasket or cracked block before teardown? White smoke,runs rough, smells like antifreeze! /forums/images/graemlins/mad.gif /forums/images/graemlins/mad.gif /forums/images/graemlins/mad.gif
     
  2. Blazer1970

    Blazer1970 1/2 ton status

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    Or just an intake gasket?
     
  3. ken

    ken 1/2 ton status

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    The head will crack 100 times faster than a block...more heat in the head region. As for white smoke and running rough...that sounds like a head gasket. Best way to check is to pull a compression check of the cylinders. If you have zero comp in one or more cylinders, then it's a head gasket. If all compression is good, then it is an intake gasket. Good luck.
     
  4. 4DiggerDan

    4DiggerDan 1/2 ton status

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    Agreed... A cracked block is unlikely. It may be a head gasket, it may be a crack in the chamber too. GM casting #426624 is about the worst head ever made for cracking, followed closely by anything that says "Hecho en Mexico" on it. '882's crack about 1 head in every 10 sets I see, but usually from an overheat or something else stupid. Both of these heads have a real habit of cracking in the center two exhaust valve seats out towards the spark plug. Lots of times it can only be seen with a Magna-flux and not with the naked eye. When you get the heads off, you'll know where the water trouble was. One or mores of the pistons will literally be steamed clean on top (they should be evenly carboned up over the top.) Once you peel the gasket off the head, look around the fire ring. You should see cast iron color there all around where the metal ring in the head gasket is, if its blacked up in a spot or two it was letting combustion gasses out.

    A compression test won't usually read ZERO. There will still be some compression in there, like 30-90 Lbs. I don't know what its supposed to be, I'm not a mechanic, I'm an engine machinist. My 400 cranks 130 Lbs, but its got issues, and more cam than stock.

    You should probably have the heads surface too... See what the engine machine shop sells a gasket set for when you're there too. I usually sell FULL Chevy sets 30 bucks cheaper than a NAPA HEADSET...

    An intake manifold gasket is unlikely. If you have water get out of there, it usually finds its way into the oil.

    Once you get everthing put back together, CHANGE YOUR OIL... You don't want to let all that antifreeze that gets in there go through your bearings... Very bad...
     
  5. smack

    smack 1/2 ton status

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    Well from what I know that's a tough one although likely your block is fine. The problem is likely the head gasket but you'll probably not know if your head is bad until after it's been removed and/or taken to a machine shop to have it fluxed. Depending on the miles of your motor you should seriously consider a whole rebuild. If the thing's fairly new 0-50k, then go for it. More than that, you should rebuild/replace the whole thing. There's no point in dumping money into getting your heads machined if you don't do it right and machine the lower end also. Sure, it could last a year or two, but eventually it's gonna go. My .02.
    The chevy dealerships here charge $35 for checking if it's a head or block using some special thingy I forget what -- not just a compression tester. If they say it's the head gasket they'll probably say there could be a problem with the head too but you won't know 'till it's off. So here's where you decide, rip it apart, take the heads in, spend the money, or just do it all the first time.
    smack
     
  6. Blazer1970

    Blazer1970 1/2 ton status

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    Have you done a compression test?
     
  7. rh88k5

    rh88k5 Registered Member

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    I just did a compr. test, well, half of it, driverside fine 165-175 psi, then I noticed coolant squirting out of #8 cylinder. Before I did compr.test, I pressurized the radiator and noticed coolant leaking from behind eng. near or above the starter, Im thinking that I sucked an intake gasket??
     
  8. Panther212

    Panther212 Registered Member

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    I have the same thing goin... crazy, because it's in the same exact spot. Will this be a head gasket or intake?
     
  9. rh88k5

    rh88k5 Registered Member

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    Thats what I was asking you!!!!!! /forums/images/graemlins/rotfl.gif
     
  10. Panther212

    Panther212 Registered Member

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    I know, I was asking too, since nobody has replied on both of your posts. I'm just excited to hear the answer cuz i'm burnin up soooo much coolant it's not funny...
     
  11. rh88k5

    rh88k5 Registered Member

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    Well I just finished the compression test on the pass. side of eng. and good compression in all cylinders, #8 had pegged the gauge, due to the coolant in the cylinder, but it did compress and very slowly leaked down like the other cylinders, so Im assuming its just an intake. Its cheap enough,just time consuming, Hope it works!
     
  12. Leadfoot

    Leadfoot 1/2 ton status Premium Member

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    You seem to think it's an intake gasket....so go for it.
    I replaced a cracked head and head gaskets on NoAngels 88 K5, due to poor compression and it fixed it. You seem to have good compression so I would just do the intake gasket for now (simple comparitively....the only hassle is the fuel lines for the TBI). If it works, you are set, if not your out $15 and some time.

    As someone stated depending on the mileage, it might be best just to pony up the $$ and do the heads as well. On Michelle's, buying a good "used" head to replaced the cracked one, Machine shop (did a valve job done on both heads, milled them flat, and installed valve seals), buy a head gasket kit (came with everything), new plugs, cap, rotor, wires, belts, hoses, waterpump, etc. etc. I think it was under $600 with fluid and misc items. Not a bad deal considering the "top end" is now all set for 100K or more.

    The machine shop did the heads, and I did the "labor" (R and R), and now no worries. Piece of mind is worth $$$

    Food for thought. Good luck /forums/images/graemlins/thumb.gif
     
  13. rh88k5

    rh88k5 Registered Member

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    Well Leadfoot, I swapped the intake gaskets and it still is leaking coolant into #8 cylinder, so Im going to do the heads, swap the cam, t chain,water pump and maybe a new intake as well, just to be sure.
     
  14. Leadfoot

    Leadfoot 1/2 ton status Premium Member

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    You probably already know this but......just in case. When you take the heads off, save the head gaskets and give them to the machine shop (they may or may not want them, but at least you'll have them), and have them magnaflux (or whatever convention they use now) the heads to check for cracks that the naked eye cannot see. No sense in paying $$$ for a cracked head to be machined. Some shops do it automatically, some don't.
     
  15. smack

    smack 1/2 ton status

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    Little hard to follow where you're at with your engine at this point, but I happen to have a set of heads I'm trying to get rid of -- rebuilt w/ 10k miles, 3-angle, new valves, springs,etc. Cost me $500, sell 'em for $200. They've been sitting in a bag for two years so they're a little discolored but they should be fine still. They were shaved twice I think so you might need to shave your intake a bit ( I didn't and had a slight oil leak ). The engine I had them on eventually started detonating and finally the lower end went kaput, but the heads should be fine. Don't know how much it would cost to have them checked but let me know since I'm only one state away.
    smack
     

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