1999 Ford Ranger (107,000 mi.): 4X4 worked good a couple of months ago, with a slight squeak in the front appropriate axle (when engaged). Now that it’s 10 degrees outside, the 4X4 won’t engage. The light come on, I believe I have the right to hear the engagement motor turning, but the prior axles just won’t turn. The 4X4 Low also engages usually in Neutral, yet only spins the rears. It warmed up for a few days last week, and also presto – it operated again. Appears to it is in a cold weather symptom. Any kind of suggestions? It would be pretty if I could use 4X4 in the snow.

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The Concept:

Ranger Pulse Vacuum Hublock (or PVH) 4×4 system. This part-time 4×4 device with wheel-end disconnect offers optimized fuel economic climate in a robust style that needs no on regular basis scheduled maintain under common driving conditions. The system allows silent 4WD transition on the paris at any type of speed or temperature and also does not call for reversing the automobile to disengage the hublocks.

The Weaknesses:

The device depends on vacuum. Vacuum is provided through tubing come an electrically controlled valve come actuators in the hubs that engage and also disengage the front wheels. If vacuum is lost because of a leak, the mechanism cannot operate. You could also have an electrical failure of the 4×4 transition solenoid valve the controls the applications of vacuum come the hublocks.


The electrical solenoid valve is placed in the right front wheelwell, in between the bumper and inner fender liner. The front part of the wheel well splash safety liner have the right to be eliminated for access.

The PVH solenoid is regulated by a computer system called the GEM (Generic digital Module). The GEM look at the 4×4 switch as an input, along with the automobile speed. When vehicle speed is right and also 4HI is commanded, GEM pulses the solenoid. The solenoid applies and releases vacuum to the hubs. The GEM inputs and outputs have the right to be monitored through the Ford NGS scantool. However you probably have an issue with something besides the GEM (since it is additionally controlling the carry case, an interpretation it is acquiring inputs and commanding outputs appropriately), and also the NGS is not an absolute necessity once you recognize the system.

Here is a vacuum schematic:


Here is a snapshot showing a vacuum pump linked at the wheel finish (also referred to as actuator, hublock above). The vacuum pump is pumped up to 20 in Hg, climate monitored to watch if that holds vacuum. Shot rolling the car a small in neutral to watch if vacuum holds if rotating.


If vacuum can not be held, the hublock (wheel end) must be replaced. Or it could be modified in a few different methods as explained in the pages below. One means is come install hand-operated hubs. The other involves modifying the existing parts slightly for hand-operated operation, by removing a display screen to provide a finger hole so the hublock can be operated in a press on/push turn off fashion. If you are wanting to change it, make sure it is actually poor first. The hublocks can be fine and the PVH solenoid valve might be the fault. PVH solenoid have the right to be experiment to watch if it is qualified of switching vacuum on and also off when the 4wd switch is switched in between 4hi and also 2wd.


Yes, excessive cold can affect the hardness the the seals, make them much less pliable. Extreme cold can additionally cause electrical difficulties if there room cracked solder joints or loosened connections anywhere, the steel contracting once cold can reason an open circuit. This has actually the same impact as a broken wire. This type of phenomena is possible where relationships are made too. If a woman terminal that a link becomes spread out apart as well far, the masculine terminal have the right to lose call if the is a borderline type situation. Every the terminals of the relays, module, and change motor need to be good. In general, a fault like this only strikes one or two terminals, not all of them in ~ once. The terminal fit deserve to be checked by seeing exactly how tightly every individual terminal fits that is mate. It should require significant force to pull the link apart. The catch is when you have a multi-pin connector (as virtually all automobile connectors space made). If one terminal is loose, the others still make it tough to pull apart a connection. So, the surest examine is come visually examine them all, and either remove suspect terminals indigenous the key plastic hardshell and fit them into their mates to check individual fit. If you have actually a sample of the proper size mating terminal, you have the right to use it as a tester through seeing how well each female grips the “tester” masculine sample. Do sense?

You really should verify what is happening when the fault is present. Get under the truck and feel ~ above the change motor, make the efforts to identify if it sounds like it is going with the complete sweep. There are some faults that can take place with the shift motor, so simply hearing it is no enough, it might be running, yet shutting off too soon. Read much more about the shift motor and also how to rebuild it because that some common failures here:

Rebuilding A transport Case transition Motor

For the prior hublock system, you require to connect a vacuum gauge to check out if something is happening when you have the problem. If the is inconvenient, what I imply is to acquire a size of rubber tubing of the appropriate size to affix to the nipples in ~ the hublocks. Get some 3-port vacuum tees. Cut a 2 inch piece of tubing and also attach one end to the tee and also the various other to the share vacuum line. Operation the middle leg of the tee to the cab and attach come a vacuum gauge. This is a temporary setup that will enable monitoring that the vacuum in the PVH lines. It will permit the hubs to continue working while wait for the difficulty to happen. As soon as you an alert 4×4 not engaging, watch the vacuum gauge and also see what happens as soon as you switch the 4×4 switch. If no vacuum pulse is seen, climate you must do the hublock leak test, test the vacuum lines because that leaks by plugging one end and pumping vacuum top top the various other end–seeing if that holds. Track with the vacuum system, connect the vacuum gauge directly to the solenoid and the vacuum source, and also see if you have the right to catch any type of vacuum problems.

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At the solenoid, friend should have the ability to hear that click on and also off once the hubs engage. Acquire a listen to this if the system is working and then hear for it when the system is not working. If there is no solenoid click, climate no vacuum pulse deserve to be sent to the hublocks. This can be a problem of the solenoid obtaining water into it and also freezing, since it is placed ahead of the best front wheel area. The could likewise be water in the vacuum present freezing, a an easy fix that disconnecting, blowing castle dry with compressed air. Dry out the solenoid might aid it too.