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  1. #1
    Join Date
    Jan 2016
    Posts
    25

    Default 07 Replacing Head Gasket - Send Head to Machine Shop?

    My 2007 XC70 had what I think is a small head gasket leak. Combustion gases were pressurizing the overflow tank, pushing the fluid level down. Opening the cap allowed the level to return. I used a combustion gas tester to make sure that was what was happening. The engine never overheated.
    The head is off the car now, and Iím trying to decide whether to send it to a machine shop or not.

    About 30k miles ago, something got into a cylinder and damaged one or more valves. I now think that the ďsomethingĒ may have been a part of a banjo bolt in the PVC system. As a result, a shop pulled the head and sent it out for a valve job. Since it has had this recent valve job, is it needed to send again to a machine shop? The valves look fine to me. Should I just clean it up and put it back together?

    Iím not very familiar with what machine shops do. If it is recommended that I take it to one, what would I ask them to do, besides cleaning? Pressure test? Check the valves?
    Also, if so, does anyone recommend a shop in the NW Chicago suburbs?

    Thanks!
    BrickDriver

  2. #2
    Join Date
    Nov 2012
    Location
    Pacific NW
    Posts
    364

    Default

    You have to ask, what caused the head gasket to leak after the previous repair. Something was not right. I think the head should at least be checked by a shop for flatness, pretty easy to do. There could also be a crack somewhere. There may a shop that specializes in head work locally. Perhaps google will turn up something.
    PDX-Vancouver, USA

    2005 XC70 140,000

  3. #3
    Join Date
    Dec 2009
    Location
    GA
    Posts
    1,410

    Default

    Quote Originally Posted by BrickDriver View Post
    Combustion gases were pressurizing the overflow tank, pushing the fluid level down.
    The head is off the car now, and I’m trying to decide whether to send it to a machine shop or not.
    The valves look fine to me. Should I just clean it up and put it back together?
    I’m not very familiar with what machine shops do.
    Pressure test? Check the valves?
    I would find where the combustion gasses were getting into the cooling system before putting the head back on. A head gasket breach is always obvious, one or more of the metal rings outlining the cylinder bore could be damaged. If so from what - perhaps a previous poor installation or poor quality head gasket, or a warped head from overheating. If warped straightening is called for, (because the cam journals would be warped also) which requires a valve job afterward.

    The head should be perfectly flat and clean - easy to do that at a machine shop, and a pressure test is a common way to check for cracks in the head. (but out of maybe 100 Volvo 4, 5 and 6 cylinder aluminum head valve jobs I never had a cracked Volvo head report from the machine shop)

    A third possibility is a cracked cylinder liner. Allegedly the 04-07 R engines have that happen to them and I've seen it once on the 1.9 4 cylinder in the early S40. (4 cyl version of same block)

  4. #4
    Join Date
    Jan 2016
    Posts
    25

    Default

    Thanks hoonk and Scopeman. Good points. A local Volvo expert has recommended a machine shop. I'll take it in for cleaning and test.

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