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On two of my vans I have the hit hill goes to defrost going on.. Before I get into it I was wondering if anyone has a most common leak area nailed down..
As far as I know there are no leaks at the engine as I just did intake gaskets on both engines.. Where might the leak be..?
99 F350 5.4 Lockers,Warn winch,Hubs..MDII Plow, 200 amp alt timbrens,Revo's.2 24 " LED bar lights THREE 96 aero*awd 4.0 ext. GREEN,BLUE,WHITE.Blue for parts//rust
2010 SUZUKI SX4 AWD CVT NICE USAF 76-80
CX500 TURBO ORIG OWNER
I'm dealing with the same issue right now. In my case, on a '97 Aerostar, the leak is where the EGR tube enters the manifold. Not looking forward to that one, though I should be able to do it without pulling the whole manifold.
Other common leak ares will be the PCV elbow, the vacuum line to the brake booster, and any of the lines that run to the controls. A faulty check valve can also cause these issues.
The fastest and easiest way I know to find the leaks is to have a pro with a smoke machine hook up to it.
If it's just the AC, it's probably a leak in one of those tiny plastic lines that run the AC controls. They get brittle and crack with heat and age. I would just replace all those lines in the engine compartment with rubber lines designed for under-hood use.
Regarding vacuum leaks i want to forward my expirience. When i was blowing and sucking for testing purpose through the tube that usually goes into the air inlet tube, i've noticed a hissing sound from the oil filler tube cap. This oil filler tube cap was "my" vaccum leak. By turning the cap with force into one or two full revolutions the cap and the vaccum becomes tight and close as it should.
Another leak i've suspected where the PCV is plugged into the rubber. The PCV was sitting loose there, much to easy to unplug. With some heat resistant tape around the PCV the connection is tight now.
That is, i belive, the way i've fixed the vaccum leak in different ways. As a side-effect, no engine-oil is dripping down anymore onto the starter motor..
DIY or die - btw: i'm trying to extract a faulty dent out of my mouth at the moment
I had this same problem. I found cracks in the hard lines that go from the "T" at the top of the blower housing, to inside the blower. The lines get very brittle, and snap and leak, but you may not see the crack. They also get a bunch of little hairline cracks that add up to a good size leak. I had the same issue with the vents switching to the defrost. My a/c was also not working well since it was not opening the recirc door, and was pulling in hot outside air all the time. You can get vacuum hose that fits over the hard lines, and just go right to the T fitting. They will probably break off right near where they enter the blower housing.
Sure, you should replace them all, but I could not see an easy way to get the two that enter the blower housing. I think they make some sharp turns, and cannot be replaced without taking the whole plenum apart.
The pieces of those plastic lines that are most vulnerable are those that are exposed in the engine compartment. Eventually, the heat gets to them. That one line that goes inside the air box should be fairly well protected, and not get as brittle as the others under the hood. What I did was pull a little of it out, slipped a rubber hose over it, then pushed it back through the little hole so that only rubber hose is exposed. It's been a few years, and it seems to be working OK still.
Got my leak fixed at the EGR, lean code came back, but vacuum was better, no obvious malfunctions like I had with the blend doors and stuff. Hooked it back up to a smoke machine, found a leak in the plastic hose that routes behind the engine that connects to the fuel pressure regulator. This would create a dual problem, a vacuum leak combined with constantly elevated fuel pressure. Anyway fixed. When inspecting the vacuum lines, make sure to check the tube inside the split loop tubing.
Now I am just waiting for my DPFE sensor to show up. My old one I guess failed because of the backpressure from the clogged cat I had. Ever since I replaced the cat the P0401 has been popping up.
I kept patching up my vacuum lines with electric tape because Auto-Zone did not carry replacements. Recently I went to a u-pull lot in PA, and got some better condition ones. Now that I replaced the bad ones under the dash, there is a hissing coming from the vent control switch when it is in the OFF position. Everything is working as it should, but I obviously have a vacuum leak somewhere.
Before I go pulling off the whole dash to get to the control switch, any other advice?
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