Ok, I'm new to this whole forum thing so be gentle, I have a 2000 excursion 4x4 v-10 with about 165k miles with locking front hubs, just purchased about 2 months ago.

When i first bought it, i noticed the ABS light would come on when i started the engine but once i would start driving the light would turn off. Well i recently had new tires and rims put on it and ever since, the ABS light constantly stays on. Ive done some research and people say to replace the sensor but where exactly is that located? oh ya, and when i am coming to a light and pressing the brake, sometimes the rpms will jump up a little bit and it feels like the truck is trying to move itself forward so i have to apply the brake harder for it not to move.

And another thing was the AC. It works perfectly fine cruising around town but when i get over 40 mph and accelerating, the ac will switch from the vents to the dash and will stay that way until i let off the gas or press the brake, in which then it will slowly come out of the vents. And when i sit at a stop light for a while, the ac will go from cold to blowing HOT air. Not very comfortable in these AZ summers of 110. Ive looked around under the hood and havent noticed any leaks or anything, but i do hear a whistling sound coming from under the serpentine belt (idk if that could be related)

Any help would be greatly appreciated. especially pictures =] thanks.

 

I think AC issue is strictly a vacuum problem. Probably related to your 4x4 front hub controls. Try finding the vacuum solenoid on passenger front inner fender. It may be leaking there, or it is leaking air at the hubs. On my 2003 4x4, this solenoid case was cracked open and leakng. In either event, you can plug off the vacuum lines from intake manifold to this solenoid. Then, see if the AC problem changes.

 

I think AC issue is strictly a vacuum problem. Probably related to your 4x4 front hub controls. Try finding the vacuum solenoid on passenger front inner fender. It may be leaking there, or it is leaking air at the hubs. On my 2003 4x4, this solenoid case was cracked open and leakng. In either event, you can plug off the vacuum lines from intake manifold to this solenoid. Then, see if the AC problem changes.

 

Is there any easier way of looking for leaks rather then just feeling around and trying to listen for them? because when i have the truck on and the air running to try and find the leaks, its so lout and windy down there i cant get a good feel for anything? i checked the solenoid and it checked out ok. i undid the red line and it had suction, and i also unhooked the other end after and it had suction as well. i also took a glance around the hubs and the wheels to see if maybe there could be a leak there, but nothing. im kinda stumped.

 

Try plugging the 2 lines going to the hubs.

Another quiet technique is to use a hand vacuum pump or a small vacuum pump you could build from an old refrigerator compressor. Disconnect the main supply line coming from the manifold. If you can pull and hold a vacuum, then there are no leaks. If you cannot hold a vacuum, then you have to go looking for it.

On a diesel it is a bit easier as we have to have vacuum pumps built in. We can look for leaks by turning on the key and listening if the pump cycles or not. Mine ran continuously because of the massive leak I had at 4x4 solenoid (not correct name, I know).