jayedee

Here by chance? An I was getting lean codes a couple weeks back but my mpgs went down to 7 mpg and started doing some research and happened to find that leak.

jclark

That seems to be about where mine is leaking. I got a shop by my work that hooks us up and will check stuff out for free for us sometimes. Ill give them a call tomorrow

jayedee

Ya my lean code were showing up you can check for an intake leak by lettin it idle and spraying carb cleaner around the edge of the intake if it revs up you have an intake leak. Or you can see the antifreeze as well

jclark

Just tried carb cleaner. Didn't change the idle. But that doesn't surprise me because it only happens when the temps are cooler.

udderbrudder

I use a smoke machine to diagnose this. It's foolproof. If the manifold is leaking you WILL see it. I wouldn't start into the manifold until you're sure. There are other common places to leak vacuum also. Have you checked the PCV hose-particularly where it has a foam cover on it? The brake booster hose is suspect also. If you can hear the leak (hissing), try to home in on it.

jclark

I'm gonna look some more tomorrow on my day off. If I can't find it tomorrow I got a shop that will look at it for me

A7X

This is a common issue on this intake (the leak location in your pic) the plastic cracks in this area allowing coolant to pi$$ out...

A good fix is an intake manifold from a 99 (only) 5.4 which is aluminum with PI heads instead of plastic (97-98 were aluminum but non PI), or a replacement plastic intake which may or may not crack again while you own the truck... Either way the intake manifold should be replaced if this leak is present, otherwise it will only get worse and could cause other issues besides leaking coolant...

jclark

I'm not losing any coolant at all...

A7X

That's good!, you need to check for issues that are common to both cylinder banks...

PCV hose, (from pass side valve cover) known to crack and cause lean codes...
Clean MAF sensor
Check all around for vacuum leaks, all vac hoses etc...
Spray all around intake with carb cleaner or (a cleaner alternative) an UNLIT! propane torch and listen for change in idle...
Lean doesn't only mean too much air, could also mean not enough fuel,
When was the last time your fuel filter was replaced?

That should be a good start and get back to us

A7X

Plastic PCV elbow behind the throttle body