Toyota 4.7 plenum/intake leak?

[D60]

2008 Tundra 4.7 with 283k miles.

I smoked this 4.7 today and finally started see light traces of smoke coming from the area circled in red, ie rising up from under the plenum.

I understand this is limited info, but based upon this is this likely plenum gaskets? Are there are other usual suspects for intake leaks under there?

I'm not asking for guarantees but asking for the experience(s) of those who have seen this before.

 

[paulo57509]

I'm not going to be much help. A high confidence confirmation is necessary because this can be a time consuming job to replace that gasket.

My experience is with the 4.0L 1UZ; I have yet to hear about plenum leaks (doesn't mean it doesn't happen). I believe that the 4.0L and 4.7L use the same steel plenum gasket, FWIW.

Because of the ACIS diaphragm and linkage and lack of firewall clearance, the manifold needs to be removed on order to get the plenum off the lower manifold. You probably need to remove the lower and upper as a unit and replace the gasket on the bench.

1UZ Intake manifold (inverted); ACIS diaphragm and linkage

 

[cptbarkey]

Try tightening the bolts a little bit and see if it goes away. There should be some give. Will confirm gaskets.

 

[D60]

So apparently the "air intake pump" lives under there. I've heard these fail but I wonder if they ever develop vacuum leaks? I suppose the hoses running to it could

Maybe I'll try to poke around with a borescope, although I have low confidence of being able to spot smoke slowly escaping with a scope. Might get lucky, though

 

[paulo57509]

So apparently the "air intake pump" lives under there. I've heard these fail but I wonder if they ever develop vacuum leaks? I suppose the hoses running to it could

Maybe I'll try to poke around with a borescope, although I have low confidence of being able to spot smoke slowly escaping with a scope. Might get lucky, though

On the LS, it's just a plastic vacuum reservoir tank and hoses. I'm sure these aren't immune to leaks.

If you do end up removing the manifold, you may want to replace anything underneath to avoid having to remove the manifold in the near future. I replaced the vacuum hoses with OEM Toyota because I didn't want to remove the manifold in the future. I should have replaced the starter too - 28 months later, off came the manifold again. I took a risk and left the knock sensors alone.

The hose ID is between 1/8"-9/64" and comes in several lengths. All the small vacuum hoses around the engine should be the same diameter.