5.7 L Vortec, intake manifold??

Discussion in 'GM Powertrain' started by fierodough, Aug 9, 2007.

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  1. fierodough

    fierodough New Member

    Please let me know if the intake manifold is a good candidate for the problems I'm having.

    Truck: 1997 suburban K1500 4X4, engine: 5.7L Vortec

    First off, NO coolant leaks. NO Loss of coolant!
    I do have oil consumption, Plugg #3 fouls constantly.
    High idle, idles at 1K

    Huge amout of vacuum at the breater (hose that goes from intake tube to valve cover) Way too much vacuum for the crank case in my opinion.

    No oil mixing with coolant ect..

    Engine seems to ping inder hisgh load at 2K rpm. (ok after that)

    getting code 507, IAC, high idle. (iac is fine)

    Thanks in advance! hope it's not intake gasket.. :p However I'm worried about an internal vacuum leak.
    Last edited: Aug 9, 2007
  2. GaryL

    GaryL New Member Platinum Contributor 1000 Posts 100 Posts

    Have you replaced the pcv? Might be plugged up and not allowing air to flow through properly.
  3. Cableguy

    Cableguy New Member 1000 Posts 100 Posts

    Hi Eric. What was your mileage again?
  4. fierodough

    fierodough New Member


    220K now. :(
  5. fierodough

    fierodough New Member

    Ahh crap!

    Found out how to test the intake for a vacuum leak... Just for further reference in case someone has the same problem...

    Disconnect the breather and disconnect the pcv. cover both valve cover holse with your thumbs. Feel some vacuum? not good.. .

    I was quoted a 7 hours job to change the lower intake gasket. I think I may attempt to do this one myself.

    Cheers!
    Eric
  6. GaryL

    GaryL New Member Platinum Contributor 1000 Posts 100 Posts

    The intake gaskets are not too tough to do on your own. Just take your time and bag all of your bolts and nuts so you know where they go back.
  7. MrShorty

    MrShorty Moderator 1000 Posts 100 Posts

    I did my intake manifold gaskets last fall on my '98 5.7. It wasn't too difficult, but it took some time (spread out over three days for me). I don't remember where, but I know there is at least one good write up on the internet that I found that really helped, in addition to the information I got from the Haynes, Mitchell, and Motor repair manuals.

    I would recommend the FelPro gasket set (98000T I think).

    I think the hardest part for me was getting the manifold back on. The manifold was heavier than I expected and, with wires and such in the way, I had a hard time setting the manifold straight down so as to properly set on the RTV along the valley ends. Other than that, it was mostly the painstaking process of removing everything.

    The only question I still have on the job involves disconnecting the fuel lines. I disconnected them on top of the intake manifold, but the o-rings that came with the gasket kit didn't fit those fittings. I wonder if they intended you to disconnect the fuel lines farther back.

    Anyway, as noted, take your time, pay atttention to where things came off, and you should do fine.

    Oh, one other thing: The seals in the heater hose quick disconnect fitting broke when I disconnected the fitting, so I had to replace that fitting. A lot of people report breaking this fitting off whenever they take it apart, I guess I got lucky because the fitting didn't break on me. So it was pretty easy for me to replace, but be aware that you may not be so lucky, if you end up needing to replace that fitting.

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