Bad Head Gasket

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Colorado Yeti

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So here is the story....

Bought a 1999 Tahoe Z-71 with 52,000 miles. It is a beautiful truck that looks brand new. I have put approximately 7,000 miles on it since I bought it. I did notice that the antifreeze looked quite dirty when I bought it but it drove perfectly and the oil was clean.

I flushed the coolant after I bought it and put in brand new coolant. Approximately one month ago I noted bubbling that came from the coolant overflow tank when it was warm. No bid deal I thought, just a bad radiator cap. I replaced it but it did not fix the issue of bubbling. That when I started worrying. I then blew a heater core last week and replaced it. Now I am noticing more and more bubbling noises, especially when I am accelerating. The brand new coolant is now dirty again with a thin film of oil when I put it in a pan.

Okay, so now I am really worried. The truck drives perfectly fine, no smoking, no misfires, no overheating. The oil still looks pristine. But what else besides a head gasket could explain the symptoms that I am experiencing as illustrated above? I thought perhaps a leaking intake manifold gasket, but the intake manifold is a negative pressure system, not positive pressure so it should not cause bubbling with acceleration. And I should see coolant in the oil.

I have not had time to do a compression test but that is my next step. Then I guess I will tear it apart this weekend. Not looking forward to that job but I have done them before on a small block Chevy. I'm just worried about getting the intake to seal properly as I have heard that it is a horrible design on the Vortec and virtually impossible to get to seal properly.
 

BG1988

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So here is the story....

Bought a 1999 Tahoe Z-71 with 52,000 miles. It is a beautiful truck that looks brand new. I have put approximately 7,000 miles on it since I bought it. I did notice that the antifreeze looked quite dirty when I bought it but it drove perfectly and the oil was clean.

I flushed the coolant after I bought it and put in brand new coolant. Approximately one month ago I noted bubbling that came from the coolant overflow tank when it was warm. No bid deal I thought, just a bad radiator cap. I replaced it but it did not fix the issue of bubbling. That when I started worrying. I then blew a heater core last week and replaced it. Now I am noticing more and more bubbling noises, especially when I am accelerating. The brand new coolant is now dirty again with a thin film of oil when I put it in a pan.

Okay, so now I am really worried. The truck drives perfectly fine, no smoking, no misfires, no overheating. The oil still looks pristine. But what else besides a head gasket could explain the symptoms that I am experiencing as illustrated above? I thought perhaps a leaking intake manifold gasket, but the intake manifold is a negative pressure system, not positive pressure so it should not cause bubbling with acceleration. And I should see coolant in the oil.

I have not had time to do a compression test but that is my next step. Then I guess I will tear it apart this weekend. Not looking forward to that job but I have done them before on a small block Chevy. I'm just worried about getting the intake to seal properly as I have heard that it is a horrible design on the Vortec and virtually impossible to get to seal properly.
The easiest way to check is look in the cylinder with a camera (via the spark plug hole)and see if one cylinder is clean OR much cleaner then the others....


there is also a test kit as well
 
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willxfs

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Good luck and keep us posted on what you find. I changed the lower intake gasket on my old 350 and on the new 383 in there now. Have had good luck with the improved design of the felpro gaskets.
 
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Colorado Yeti

Colorado Yeti

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Good luck and keep us posted on what you find. I changed the lower intake gasket on my old 350 and on the new 383 in there now. Have had good luck with the improved design of the felpro gaskets.
That is what i bought. Thank you.
Good luck and keep us posted on what you find. I changed the lower intake gasket on my old 350 and on the new 383 in there now. Have had good luck with the improved design of the felpro gaskets.
 
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Colorado Yeti

Colorado Yeti

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So, after talking to some guys who are very familiar with Vortec motors, they say this is a classic presentation of a bad intake manifold gasket which is a very common problem on this engine. They said this because I have oil in my coolant but no coolant in my oil. Of course, I don't know until I do a compression test and I haven't had time to do this yet. I'll let you guys know what I find. I sure hope it's an intake manifold gasket problem.
 

HiHoeSilver

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So, after talking to some guys who are very familiar with Vortec motors, they say this is a classic presentation of a bad intake manifold gasket which is a very common problem on this engine. They said this because I have oil in my coolant but no coolant in my oil. Of course, I don't know until I do a compression test and I haven't had time to do this yet. I'll let you guys know what I find. I sure hope it's an intake manifold gasket problem.

Happened to my OBS.
 
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