1997 GMC Suburban Owner's Manual - Page 232

Trailer Brakes loaded, then it needs its own brakes -- and they must be adequate. Be sure to read and follow the instructions for install, adjust and the trailer brakes so you'll be able to maintain them properly. Your trailer brake system can tap into the vehicle's hydraulic brake system only if: 0 Driving with a Trailer If your trailer weighs more than 1,000 lbs. (450 kg) The trailer parts can withstand 3,000 psi (20 650 kPa) of pressure. The trailer's brake system will use less than 0.02 cubic inch (0.3 cc) of fluid from your vehicle's master cylinder. Otherwise, both braking systems won't work well. You could even lose your brakes. 0 If everything checks out this far, make the brake tap at the port on the master cylinder that sends the fluid to the rear brakes. But don't use copper tubing for this. If you do, it will bend and finally break off. Use steel brake tubing. If you have a rear-most window open and you pull a trailerwith your vehicle, carbon monoxide (CO) could come into your vehicle. You can't see or smell CO. It can cause unconsciousness or death. (See "Engine Exhaust'' in the Index.) To maximize your safety when towing a trailer: 0 Have your exhaust system inspected for leaks, and make necessary repairs before starting on your trip. Keep the rear-most windows closed. If exhaust does come into your vehicle through a window in the rear or another opening, drivewith your front, main heating or cooling system on and the with fan on any speed. This bring fresh, will outside air into your vehicle. Do not use the recirculation button orMAX because it only recirculates theair inside yourvehicle. (See "Comfort Controls'' in the Index.) 4-50