When checking the solenoid, I assume it should hold vacuum when closed and vacuum should pass through when open? I have tested mine and when in the normally closed position it will not hold vacuum. Also when apply voltage to activate the solenoid it is very intermittent in engaging. I am sure it is bad, just verifying my test procedure.
Yes, when the truck is running and you check the vacuum on the side of the solenoid that the actuators are are on, you should get a constant stead vacuum. If you dont the solenoid could be bad if it completely drops off to nothing and then back up.
I'm back with more of the same. My truck has been in the shop 3 times over the last month - They have replaced the solinoid twice, put all new vac lines and check valves on both wheels, and I still have this problem. My mechanic finally said "Sorry I am out of ideas". When he put the new lines on I drove the truck about 100 miles before the noise came back, so he did something right, it just did not stick.
What do you mean by check valves at the wheels? There are two check valves but they are not at the wheels. The IWE actuators are at the wheels. If he has only replaced the check valves maybe he doesn't even know the actuators are there and one if not both of those could be bad.
Ya have them check the actuators cause if everything else was replace and you still have the problem you probably have a leaky actuator. If you have or can get a vacuum guage (about $60 at a auto store) you can check the actuators yourself. Hook you guage up to the large vacuum port on the actuator (after you pull the stock vacuum hose off the actuator) pump up the vacuum and see how each side holds vacuum. If one or both sides doesn't hold vacuum or it drops off more than 5 psi in a minute (ithink that's the spec if I can remeber) than it needs replaced. If your a little mechanic you might be better off checking the whole system with a guage yourself and then you will know what isa good and what isn't. But if not maybe you could be there while your mechanic does it. It really sounds like you got a vacuum leak somewhere. Good luck. Let us know if you need something else.
The problem was the check valve in the vac line running between the Intake Manifold and the reserve cannister. It had not been replaced, and apparently not checked.
Does anyone know why there is so much dirt in the vac system? I thought it was a closed system.
I was going to tell you to look at the check valves again next, but you beat me to it. Those stupid little check valves cause more problems. Well the dirt in the vac system could be from any little leak in the system (even one that is too small to affect the system). Because if there is any leak in the system, that leak is constantly sucking in whatever is outside of it. So if you drive down a dusty road, or through a big mud puddle and dust and dirt or water gets around that leak, its going to get sucked in. Even more so if you had all the lines replaced because of what im assuming could have been a leak.
I just came across this little write up a few weeks ago. A contractor friend has a 2006 f150 whose 4wd system is driving him nuts. The last straw was when he had to have his son pull him out of a real muddy patch of ground with his 2wd GMC. The Shame! Any way I printed out the write up and gave it to him. I am no mechanic and didn't really know if the information related to 2006's, but they got everything squared away and now I am his new best friend and hero.
Still, I feel more confident with my real old school manual hubs and manual transfer case. Very nice job on this write up, would like to see more of the same around here.