Where is the brake fluid reservoir for a 1988 Chevrolet 1500 pick truck 4WD?

The fact that the service 4wd light comes on is good. That gives us something to go on. Did you have the 4wd trouble codes retreaved? If you tell us what the codes are we can go from there

Have you checked the fluid level in the master cylinder reservoir.. There is a float in there that is connected electronically to let you know when the fluid is low.

Loosen the bleed ******* off 1 at a time , if no fluid comes out the nipple is blocked clean them or change them .

If there's no pedal pressure, you've still got air in the brake pipes or you've got an open fluid circuit. Look for leaks, if none they need bleeding again.

power steering is at the front of the engine and runs on the belt. The reservoir cap looks like this:
To top off steering fluid, use standard steering fluid.

The reservoir in front of the brake booster is the brake master cylinder reservoir. To refill, use standard brake fluid. If it the truck is using brake fluid, check for leaks at the back of the master cylinder and at all wheels.

Please let us know if you have more questions.

You may have disconnected / or moved a broken wire to the ABS wheel sensor during the brake job. Also taking the brake fluid cap off and checking the fluid level, and just reseating the cap may turn off the code. Check these things first, check the wires to the wheel sensors check the fluid in the reservoir, reservoir top fit, and any wires / plugs at the brake ABS master cylinder. If all else fails have some one read the code.

It will be under the hood, on the driver's side, mounted on the brake booster, mounted on firewall. The master cylinder is usually silver with a plastic reservoir on top with a black plasic cap, there should be 4 steel lines coming out of it. Remove the cap and fill up to the "FULL" level on the reservoir.

Have you checked the break fluid ?

Or could be the master..

run to autozone and buy a hayes muanual for your truck. i got one for every vehicle i own, they're great! (please rate my answer)

There's a switch on your emergency brake that the indicator (on your dashlight) operates from. Sometimes it slips in its bracket and gets out of adjustment causing your dash light to stay on. Its located on the upper part of your emergency brake pedal. Hope this works for you. Goodluck.