: Intake manifold crack?

12-21-07, 01:40 PM
I had my 99 eldorado at the shop getting some new exhaust put on and they noticed a whistling noise that they beleive is from the intake manifold. He said that the manifold was too old and brittle to torque it down much more and suggested replacing it quite soon. I didn't get a complete story yet as whether they believe there is an actual crack in yet, or if its just a seal leak. I haven't heard about a crack issue before on these forums, only people who need to replace the gasket.
If it was a cracked intake manifold, is it possible to buy that alone and repalce it or do I need to repalce the whole assembly. On Gm parts direct it seems to be onyl sold as the whole assembly.
I will know a lot more tomorow when I pick the car up.

12-21-07, 02:52 PM
Take a look in the search ^^function for ...plenum, vacuum leak, like that.

Start the car, remove the beauty cover. Take a spray can of choke cleaner and carefully spray a bit in the area just under and between the throttlebody/crossover base and the intake manifold. (You should be able to see a black rubber "grommet-gasket" between the manifold and throttlebody/crossover. If the idle characteristic changes, it's a plenum leak.

All in the search area ^^^......

12-21-07, 05:41 PM
I think only the 2000+ have the rubber coupler (plenum) between the TB and intake manifold, if that is what you are talking about. I think the '99 and earlier TB's mount directly to the manifold, if I am not mistaken.

Never heard of a cracked manifold either. or a gasket for that matter. Not sure if the gasket is separate or molded into the manifold base though, if that is what you are asking.

12-21-07, 05:58 PM
I heard cracked manifold more correctly been there but haven't heard of it for a Caddy

12-21-07, 09:28 PM

12-21-07, 11:09 PM
If there was oil on any of the intake manifold bolt threads, it would be very easy to overtorque the bolts and crack the manifold. I've done it.

12-21-07, 11:39 PM
There is a backfire valve, basically a little spring loaded door, on the intake. They can stick or the grommet can leak. Check that.

12-22-07, 12:35 AM
These manifolds do not torque down far. Your mechanic may have overtightened it and said this to cover himself.