A 302 cooling system holds about 14 quarts. A 351W with auto trans and standard cooling holds 16 quarts (17 with super-cool or A/C). Run a 50/50 mix of concentrate and distilled water, and don't skip the block drains — they hold 4–5 quarts of old fluid even after the radiator is empty.
The Windsor cooling system on a full-size Bronco is straightforward, but it has two traps that catch first-timers. Trap one: there are two block drain plugs (one on each side of the block, near the back), and if you don't open them the system stays half-dirty. Trap two: the heater core can hide air pockets that overheat the engine on the first hot afternoon after a flush. Backflushing the heater core during the flush is the difference between a clean job and an overheating cycle.
If the existing coolant looks brown, oily, or full of suspended brown flakes, this is a flush-and-fill job, not a drain-and-fill. The 351W in particular runs hot and the iron block sheds rust scale into old coolant. Pull a few ounces into a clear jar before you start — clear green or pink fluid means a basic drain-and-fill is enough; opaque brown means you need to flush with water two or three times before the new coolant goes in.
Use a 50/50 mix of coolant concentrate and distilled water. Tap water in Phoenix or anywhere with hard water leaves scale in the water jackets. The 50/50 ratio is the freeze/boil sweet spot — going richer than 60% concentrate actually reduces heat transfer.
The block drain plugs are 1/4" NPT brass and they sometimes round off when you turn them after 30 years untouched. Hit them with PB Blaster the night before and use a 6-point socket, not a 12-point. If one snaps, you can swap to a replacement plug from any hardware store NPT bin.
After refill, leave the radiator cap off, set the heater to max heat / max fan, and idle the engine until the upper hose gets hot. Top off as the air burps out of the thermostat housing. If the truck has the bleed screw at the thermostat housing (later 351W trucks), crack it until coolant streams out without bubbles.
| Part | Vendor | Est. price |
|---|---|---|
| Prestone DEX-COOL / All-Makes coolant concentrate, 1 gallon | Prestone | ~$22 |
| Motorcraft Gold concentrate, 1 gallon | Motorcraft | ~$26 |
| Distilled water — 4 gallons | Grocery store | ~$6 |
| Replacement upper radiator hose (if cracked) | Gates / Dayco | ~$22 |
| Block drain plug (brass, 1/4 NPT) | Dorman | ~$4 |
Written and maintained by an AZ wheeler and driveway wrencher. Always cross-reference your factory service manual — modifications affect vehicle safety and warranty. Work at your own risk.