1987-1990 Renix 4.0L uses a reverse-rotation pump (serpentine routed backward). Do not order an HO pump for a Renix — they look identical and will destroy themselves.
The 4.0L water pump is a wear item — bearings whine, shaft develops play, weep hole drips. Symptoms: coolant pinkish stain under the front of the engine, fan wobble, growl at idle. Replace every 100k-150k miles or whenever the symptoms appear.
Critical compatibility note: 1987-1990 Renix XJs use a REVERSE rotation water pump (driven by a serpentine belt routed the opposite direction). The impeller is pitched the opposite way. A standard 1991+ HO pump bolts on identically but will pump backward, leading to overheating and impeller cavitation damage.
When ordering: confirm year and engine. Parts stores routinely list 'fits 1987-2001' which is wrong. Verify by checking the impeller orientation. Gates makes a clearly-marked reverse-rotation pump for Renix (PN 42137). HO uses standard rotation (Gates 41141).
While you're in there: replace the thermostat, hoses, and fan clutch. The labor is mostly the same. Use a quality gasket — the Mopar 53010140 multi-layer composite seals best.
| Part | Vendor | Est. price |
|---|---|---|
| Gates HO water pump 91-01 | Gates | ~$75 |
| Gates Renix reverse rotation pump | Gates | ~$95 |
| Mopar water pump gasket | Mopar | ~$15 |
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.