Leak in front air suspention on 04 navigator

Try this.... My 2003 Lincoln Navigator was manufactured May 22, 2003 so it's the late model that came with the Intec 5.4 Liter DOHC V-8 (not the Triton engine). I replaced the two front ride height sensors (one for each air strut) and replaced the one rear ride height sensor (passenger side) that controls the ride height for BOTH rear air struts. That solved the problem for a few months during warm weather, until the weather started cooling off. Then back to the same issue. The front passenger air strut started releasing air from the solenoid (air block) making a "hissing sound." Replaced BOTH front air strut solenoids (connected at the top of each air strut). That also resolved the problem for a few days. After going all around the world, I discovered it's the Air Ride Control Module (ASM) that was the problem all along.

This is most likely the culprit for your air ride suspension problem.

there should never be a leak in the system at all when the car starts the compressor should run once about 5 to 15 second to check for leaks
if longer than that you are headed for bigger problems

leak at rear air ride shocks or bags.

there is a cap for the strut, the a/c condensation drips from the line and creates a pitting.

Air BAG oe Leaky fitting or hose

Remove battery, remove windshield washer bottle, remove air compressor and disconnect both air lines from the compressor dryer. Make sure compressor electrical wiring is plugged in, install battery, turn suspension switch to ON, turn ignition switch to the ON position, close all door and the compressor should come on and completely lower the whole truck. Once the truck is completely down, turn the ignition OFF, remove battery and connect both air lines. Install battery ensure electrical wiring is plugged in, turn ignition switch to ON, the compressor should come on and raise the vehicle to the correct ride height.

The compressor just could be damage internally .
I would just loose a line off the compressor . Then put power to the compressor again. You should feel air coming out the line.

So if the air is coming out of the line. The system has check valves through out , or the air suspension shocks are probably leaking . I would then take to the dealer for the repairs or your local shop

Good Luck

can you hear the pump come on when the vehicle starts? Check the rear height sensor at the rear axle it might have come off

if it makes the noise when you first start and then goes away It is probably the air suspension pump coming on like normal. These pumps have a tendency to be noisy. if there is no noticable problem with the suspension except for the noise I wouldn't worry about unless the noise bothers you.It is about a $500 repair

The air pump is located in front of the radiator reservoir on the passenger's side - with the power steering reservoir between the two.

The air ride is turned on in the truck. The panel in located on the opposite side from the gas tank input (inside the trunk) behind a door. It should be marked on the door.

Make sure the air ride is enabled. turn the ignition key on, You don't need to start the vehicle. After about 5 seconds the air compressor should engage. You don't always hear it when it's running well. Since the engine is off, you should be able to hear any leaks in the air system.

Possible causes:
Hole/crack is air spring
Hole or broken air line or coupling
Failed air compressor

The rear suspension should use the same air system. If the pump is 'out' then the rear will also fail to adjust, But since it is on a separate air-line and valve system, it will continue to operate when the front has air leaks. And vise versa.

One pump
Two suspension systems - Front/Rear
Four air springs - One for each wheel

Another possible problem:
Your front wheels have a censor to indicate the height of the vehicle from the ground (basically). If this come unclipped, your system will think It's too high and will not add air to bring it to normal height. This usually happens on ONE side causing the vehicle to 'lean' or seem to. One side will have the wheel up in the wheel well, and the other will be a bit more gap between the wheel and the wheel well, but may seem to be 'low' too. On the side which is lowest, turn the wheel that direction and look on the front of the suspension arm for the sensor. it should be attached top and bottom.

If the clips have failed, there are no replacements available from the dealer, and replacement of the sensor is required.