Head problem chevy impala

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  #1  
Old 10-01-05, 01:41 PM
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Head problem chevy impala

2000 chevy impala 3.4L auto ac.My sisters car over heated.IT was driven a few miles.Checked oil and it had coolant in it.Took heads off engine and when a straight edge is held on there is a .002 gap on one head. No gap on the other.Is this enough of a gap to cause a problem?Thankyou for the help.Posted another question a couple weeks ago and got real good advise.Thankyou.
 
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  #2  
Old 10-01-05, 06:50 PM
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I would say that the head needs to be machined. Out of flatness should not exceed 0.001", from what I understand. Was this the rear head by chance? On these engines, the rear head gasket is prone to leaks for some odd reason. We do a ton of lower intake gaskets on these for oil and coolant leaks, with the occasional rear head gasket. In my time as a tech, I have never replace a front cylinder head on this engine style unless there was a severe overheating issue, and those were the 2.8 and the 3.1 engine. The 3.4 is pretty much identical to the ones mentioned.

You may want to call the local machine shop to verify machining is needed. I cannot access the shop's service info specs from home to back up my statement. Let us know how everything goes.
 
  #3  
Old 10-01-05, 07:37 PM
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It was the front head but the rear head gasket looks like it may have been leaking.When it got low on coolant and heated up front head may have warped.I am taking the heads to machine shop monday. Thanks for info.
 
  #4  
Old 10-02-05, 12:48 AM
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You should be good at .002"


Check this out http://www.federal-mogul.com/cda/con...9_7519,00.html
 

Last edited by toyotaman11769; 10-02-05 at 01:01 AM.
  #5  
Old 10-02-05, 07:50 AM
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We did a compression check before taking off heads.Readings on front head where #2 cyl 180, #4 cyl 120, #6 cyl 220.Head gasket looked okay.If the .002 is okay maybe there is another problem?When engine over heated no coolant was showing in oil.Aftet water pump and themostat where changed coolant started showing up in oil.Original problem may have been bad lower intake gasket.
 
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Old 10-03-05, 04:22 AM
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Nobody asked the most important question; how accurate is your straight edge? You could be off by more than .002 unless you have a high-quality (read "expensive") straight edge. One of our favorite garages has one that they use specifically for this purpose and it cost a couple of hundred bucks.

Safest thing, knowing it was overheated to some extent, is to have it machined. Why risk having to do it over for the relatively small expense?
 
  #7  
Old 10-03-05, 05:53 AM
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Going to take it to machine shop today. Checked it again and a .003 gauge fits under.Could be straight edge is off.
 
  #8  
Old 10-03-05, 07:54 AM
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Even at .003 I would have no question about using it. Some times machine shops can cause more problems by milling. There is a spec for the finish, if too coarse when the head expands it can't move on the gasket and can damage it (gasket).
 
  #9  
Old 10-04-05, 06:14 AM
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If head being warped wasn't the problem I don't know how the coolant got into the oil.The head gasket looked okay.
 
  #10  
Old 10-04-05, 09:06 AM
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The gasket would have to show where it leaked. I would look at the intake gasket. Your local chev dealer most likely does more of them than tune-ups.
 
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