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Blown headgasket or cracked block?

Discussion in 'The Hokey Ass Message Board' started by So-cal Tex, Oct 4, 2010.

  1. So-cal Tex
    Joined: Aug 24, 2005
    Posts: 1,376

    So-cal Tex
    Member

    Guys,

    How can you tell whether a engine has a blown headgasket or crack in a water passage?

    I am looking a '51 Chevy with a 216 inline 6 and the oil is real milky and the radiator is empty ( was full and I was told did not leak, so water went somewhere).

    Any advice or ways to diagnosis without pulling the engine apart?

    Is thier a really good stop leak that will seal small cracks?

    Thanks,

    Tex
     
  2. squirrel
    Joined: Sep 23, 2004
    Posts: 48,668

    squirrel
    Member

    Take the head off, see if you can find the leak. The heads crack around the exhaust valve. Sometimes they crack on the outside if it freezes and no anti-freeze in it. Head gasket leaks are usually visible, look for a line across the gasket or missing piece.
     
  3. RichFox
    Joined: Dec 3, 2006
    Posts: 10,017

    RichFox
    ALLIANCE MEMBER

    Most GMC heads I have seen are cracked inside the one of the siamiesed exhaust ports. I wouldn't be surprised to find 216s do the same thing. When they are dead, they stay dead.
     
  4. Little Terry
    Joined: Oct 17, 2007
    Posts: 504

    Little Terry
    Member

    Is there any water coming out the exhaust? Take the plugs out one by one with the motor running and check for water coming out the bores - should locate the site of the problem if so.

    Could just be a head gasket - I have had them go on 235's between number 2 and 3 cylinders and also right at the front of the motor, behind the water pump.

    The heads are prone to cracking though - only real way to tell is to get the head off (not a big job when you get stuck in), get it crack tested and skimmed then refit with a new gasket.

    Quick fixes are no good in my experience.

    Hope you get it sorted out.

    Alternative is find a decent 235 and drop that in :cool:
     

  5. Oil is milky? Do you mean the oil in the crankcase, or is there a milky film on the inside of the valve cover?

    If you have a film on the inside of the valve cover, you have poor/no crankcase ventilation.

    If the oil in the crankcase is milky, how much oil you got? Did you drain the oil and take a look at it? Does the water seperate from the oil?

    Did you try a radiator leak down test? If the radiator will not hold pressure, then you have a leak. Could be the radiator, heater core, hose, freeze plug, head. Any fluid on the ground?
     
  6. Squablow
    Joined: Apr 26, 2005
    Posts: 15,034

    Squablow
    Member

    My dad went through 2 cracked blocks before he found a good one for his '54. They are very prone to cracking water jackets. The good news is that good running 235's are pretty cheap and a good upgrade from the babbited 216.
     
  7. Little Terry
    Joined: Oct 17, 2007
    Posts: 504

    Little Terry
    Member

    [​IMG]

    this is what happened to my last 235 block...and the heads are even more susceptible to cracking.
     
  8. Mr48chev
    Joined: Dec 28, 2007
    Posts: 29,058

    Mr48chev
    ALLIANCE MEMBER

    I'm with Squablo in that I'd figure on replacing the engine from the get go. If the rest of the car is in good shape make an offer that reflects having to replace or rebuild the engine. If you luck out and it has a blown head gasket you can get the head surfaced and put on a new gasket and put it back together if that is what you want to do or do a valve and ring job on it along with replacing the gasket and have it ready for another few years of running. I'd probably be looking for a 235 or 261 to rebuild and install from the start to have a rig that I could get out and drive at highway speeds for hours on end without too much worry.

    The one Little Terry showed above shows what happens a lot when one forgets to put antifreeze in the vehicle. They will also split on the inside filling the crankcase with coolant.
     
  9. tommy
    Joined: Mar 3, 2001
    Posts: 14,757

    tommy
    Member Emeritus

    2 weeks before the 1978 Nationals in Columbus, I bought a 47 Chevy woody wagon with intentions of driving it there. It ended up with a crack in the side behind the lifter gallery plate. I had a certified welder experienced in welding cast iron try to fix it in the car but it was asking too much.

    I can't remember how I found it without pulling the head but I did and found a cheap 216 to swap in later.

    I'd pull the head and hope to find a clean cylinder where the coolant has steam cleaned the combustion chamber. If so then it could be a gasket and further investigation is needed. If they all look the same then a replacement engine is most likely in your future.
     
  10. Bluetick
    Joined: Jul 16, 2010
    Posts: 17

    Bluetick
    Member
    from USA

    I've seen this product used with success on cracked blocks. Just depends where the crack is, welding unless done right will leave stress that will cause a new crack.

    http://www.locknstitch.com/
     
  11. So-cal Tex
    Joined: Aug 24, 2005
    Posts: 1,376

    So-cal Tex
    Member

    Guys,

    Thanks for the advice..........I have not bought the truck yet because I needed to figure out if the motor had problems. The old man ( honest guy) said he parked in April with Anit-freeze in it. When he started it again 6 months later it did not have any water in the radiator and engine oil was WAY full of milky oil on dip stick. I figured the water drained into the oil??

    Anyways I have a buddy with a good running GMC 226ci (?)inline six out of the similar year GMC 3100 truck. Are these an easy swap or do they mount differently chevy vs. GMC?

    I really like the truck and I think this might be an option if the price comes down a bit.
     
  12. RichFox
    Joined: Dec 3, 2006
    Posts: 10,017

    RichFox
    ALLIANCE MEMBER

    About the GMC, look at the pad where the distributer mounts. You will see the engine number there. The first three numbers are the size. 270 - 248 and so on. If it has the front mount and your Chevy also has a similar front mount your in business. Only the GMC is longer so you need to drill new holes and move your radiator to the front side of it's mount. The Chevy bellhousing will fit the GMC block. If the GMC has a big truck flywheel you will need to find a pickup flywheel that fits the bellhousing. Chevy will not work.
     
  13. Sounds like what happened to my 235. You can change the oil about 8 times and get the water out and it might then be okay if you run it like every day, but left to sit and get cold enough and the water will drain back in the oil.

    These blocks to drain properly you need to remove a plug in the bottom of the water jacket, and a lot of people didn't. Hell I didn't even know about it until after the fact, but I think mine was already ruined anyhow.
     

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