Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
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HOMESERVICE MANUALSGMC1999FORWARD CONTROL 5.7 R, AUTOMATICREPAIR AND DIAGNOSISEXTERNAL PAGESDIFFERENT CARSECTION 67 (AUTOMATIC TRANSMISSION SERVICING)LUBRICATIONOIL COOLER FLUSHINGBACK FLUSH
1999 GMC Forward Control 5.7 R, Automatic
Back Flush
1999 GMC Forward Control 5.7 R, AutomaticSECTION Back Flush
WARNING: This page is about a different car, the 2002 GMC Sonoma, 2002 GMC Jimmy, 2002 Chevrolet S10 Pickup, and 2002 Chevrolet Blazer. However, it is still accessible from the selected car via links, so may be relevant.
- Disconnect both hoses from the oil cooler pipes and then connect them to the opposite oil cooler pipe. This will allow the oil cooler and pipes to be back flushed. Repeat steps 2 and 3 of the INITIAL FLUSH procedure. Release the trigger (8) of the flusher and allow water only to rinse the oil cooler and pipes for one minute.
- Turn the flusher water supply valve (1) to the OFF position and turn OFF the water supply at the faucet. Attach the shop air supply to the flushing system feed air valve (2) on the flusher, and blow out the water from the oil cooler and pipes. Continue until no water comes out of the discharge hose (5).
RENDER: 1.0x
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.