3.4 liter overheating

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Thread: 3.4 liter overheating

  1. #1
    Walking
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    3.4 liter overheating

    I have a 1999 Oldsmobile Alero with a 3.4 liter engine I believe. The cars catylst decal states a 3.4, and service manual shows a 3.4 as the only v6 option for a 99 Alero. However the upper intake manifold does have 3100 cast into the top of it. Anyways the car is overheating, and I have no heat in the cab when heater control is set to heat. have replaced thermostate, also made sure blend door actuator motor is working. pressure tested the cooling system over night and it dropped 2 psi. Not too worried about a 2psi drop overnight. Have not observed any external leaks. I have flushed water through the heater core, radiator, and engine. Have observed ther the t-state is opening as outlet rad hose is getting hot. the heater hoses are not getting warm. Did remove and inspect water pump, found no casue for concern. After last test drive had steam coming out surge tank overflow, and hooked up scan tool and found engine to be at 250 degrees. Also verified with Raytec temp gun. Was thinking of doing a cylinder leakage test next. Looking for any other thoughts.

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    R2-D2 Astromech Droid Smaart Aas Saabr's Avatar
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    Re: 3.4 liter overheating

    3100 and 3400 are essentially the same, maybe someone swapped engine or just changed intake manifold upper...

    is there an air pocket in the system / is it bled / burped right? If you have cold hoses and overheating there is something pretty basic happening (water not flowing...) if you kick it to 4000 rpm does it cool down quickly?

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    Walking
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    Re: 3.4 liter overheating

    removed valve covers, backed off valves, did cylinder leak test and am getting air into the cooling system..... heads coming off......

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    Re: 3.4 liter overheating

    No need to take off the heads. Its the lower intake manifold gasket. If you car has the 3100 upper manifold on it then its had it replaced before. Its possible that the original 3400 UIM was warped when the LIM gasket failed.

    Do you have dark stains on the heads? If so, its certain the LIM gaskets.

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    Re: 3.4 liter overheating

    How do I get compression into the cooling system from a lower intake gasket? Unless I am missing something when doing a cylinder leakage test and getting air into the cooling system. the only way that can happen is a bad head gasket, bad liner, or cracked head. I have done a few lower intake gaskets on 3.1 and 3.4 liter engines, have always had external leak, and never compression in the cooling system?

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    Re: 3.4 liter overheating

    Just replace them all then. Usually the 3400 heads are good unless there has been catastrophic overheating or very chronic overheating which it sounds like you haven't had.

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    Re: 3.4 liter overheating

    Quote Originally Posted by grandprixmark View Post
    How do I get compression into the cooling system from a lower intake gasket? Unless I am missing something when doing a cylinder leakage test and getting air into the cooling system. the only way that can happen is a bad head gasket, bad liner, or cracked head. I have done a few lower intake gaskets on 3.1 and 3.4 liter engines, have always had external leak, and never compression in the cooling system?
    what's the compression readings in all cylinders?

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