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Blown head gasket?

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by Sparky87k5, Mar 5, 2002.

  1. Sparky87k5

    Sparky87k5 1/2 ton status

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    Isn't air bubbles in the radiator and steam coming from the exhaust pipe a sign of a head gasket leaking or a cracked head? Please tell me this isn't.
     
  2. dogman

    dogman 1/2 ton status

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    steam that doesn't go away, is.
    carbon monoxide in the radiator, is. radiator shop can test for it.
    and water in your cylinder, pull out the plugs and see whats coming out; when turning the engine over.
    starting with a cylinder full of water, won't start very easy; and may show up like a starter or battery problem.

    good luck on that gasket change, you may think about a valve job now.


    77 k10 350 4sp < because I ordered it new that way!
     
  3. Grim-Reaper

    Grim-Reaper 3/4 ton status Author

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    Sounds like it. Sometimes bubbles will come up into the radiator from the water pump cavitating. Also the cooling systems is designed to run pressurized. The pressure raises the boiling point of the coolant. Running the engine with the cap off long enough and it will boil over so don't confuse a start of a boil over with exhaust in the coolant.
    Here is the sure test. NAPA sells a tester that checks for Exhuast in the coolant. You stick it over the radiator fill for a minute or two and if there is exhaust coming through the cooling system it will change colors.
    Another way to check is to pressurize each cylinder with compressed air. If your having a leak from cylinder to cooling system then you will get bubbles in the radiator.
    On cold mornings some steam coming from the exhaust is normal. If you smell that sweet burnt coolant smell near the tail pipe thats also a sign (now don't go sticking your face up against the tail pipe here and gassing yourself, just sniff and see if you smell it).
    If the NAPA tester comes up negative and eventually the steam goes away after full operating temp is reached it may be a mixture problem.
    On your FI truck a few things can cause a mixture problem. Most common is a bad O2 Sensor. Another problem is the temp sensor for the computer is not telling the comuter that the engine is at operating temp so the computer never switches to closed loop operations (where it uses the O2 sensor to calculate fuel mixtrue). LOTS of people have made the mistake of putting 180 or lower thermostats in FI engines and the temperature in the engine will not get high enough to go closed loop. Stuck open thermostat again can cause the issue. FI trucsk are designed to run 195deg thermostats. It helps with emmisions and the computer is calibrated to the higher temp.
     
  4. tRustyK5

    tRustyK5 Big meanie Staff Member Super Moderator GMOTM Winner Author

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    Bill has a carbed 427...

    The leak down test is the best way to confirm a head gasket problem.

    Rene
     
  5. Sparky87k5

    Sparky87k5 1/2 ton status

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    I've got 2358 miles on this 427 BBC carb'd engine. NEW everything except block, crank, rods and head castings. Built with heavy duty use in mind. If I have to pull heads, I'll just pull engine as heads are on loc-tighted studs rather then head bolts. A real pain to pull heads only with brake booster and A/C unit blocking head removal w/o pulling all studs. Was planning on leaving for California with the truck 12noon Thursday. Looks like I need to head for NAPA for one of those testers. I don't want to leave town towing my trailer if I have slightest doubt this engine will cause problems. If need be, I could swap my old 350/300hp back in. Never sold it and it's still got everything needed to run on it. Was figuring on selling it this summer. Glad it's still here now. Hope this isn't going to be a long night.
     
  6. Sparky87k5

    Sparky87k5 1/2 ton status

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    Well, 427 sitting on engine stand ready to be torn down looking for water leak. 350/300 going back in tomorrow for trip south on Thursday. Man, what a way to ruin a week. Will need to pull 350 back out when I repair 427. Right now I'm trying to remind myself how much I love my K5.
     
  7. BurbinOR

    BurbinOR 3/4 ton status

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    Aw, that really sucks. Very sorry to hear.............but you are amazingly resilient, not only having a motor laying around but dropping it in like that on NO notice. *bowing to the master*
     
  8. gokartergo

    gokartergo 3/4 ton status Staff Member Moderator

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    Were are you heading to in Calif??????????
     
  9. Sparky87k5

    Sparky87k5 1/2 ton status

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    Heading for Milpitas to visit my daughter. She's a first year teacher and just started teaching 5th graders this year. After the weekend there, will head up to Sonoma Beach and park my trailer on the beach, crack open something cold, throw my line in the water and relax. I'll try not to think about what went wrong on the 427 and how much money it'll cost me. 350 is back in and I just need to hook everything up. Glad I took the whole week off from work.
     

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