← Coolant loss on all engines

Symptoms · ProMaster 3.6 (gas)

ProMaster 3.6 (gas): losing coolant

2 documented failures on this engine list this among their signs. They are ordered from the most widespread down. Each one shows the signs in its record's own words, how to tell it from the others, the usual fix and any recall or bulletin.

1. Plastic oil filter/coolant housing-adapter leak (the signature Pentastar leak) Very common · 3 complaints
2. Cooling: water pump, thermostat housing and coolant bottle leaks Common · 38 complaints

Not sure which engine you have, or want the recalls for your exact truck? Check your VIN: it names the engine and lists the campaigns for that model year. Whether a recall is still open on your VIN: nhtsa.gov/recalls.

1 Plastic oil filter/coolant housing-adapter leak (the signature Pentastar leak)

aggregated How widespread: Very common 3 NHTSA owner complaints match it, out of 459 checked

How it shows up

• coolant loss alongside the oil leak (the housing carries both circuits)

Its other signs

• oil film tracking down the back of the engine onto the transmission bellhousing (routinely misdiagnosed as a rear main seal)
• oil level drops between services with no obvious pan drip

How to tell it apart

• degrease and observe: oil tracked to the bellhousing from the valley = the housing, not the rear main
• pressurize the cooling system and watch for coolant weep at the housing
• on replacement: correct torque and alignment - installation errors restart the leak

Usual fix

housing-adapter replacement (updated/aluminum housing) with gaskets and o-rings

Root cause, parts and sources →

2 Cooling: water pump, thermostat housing and coolant bottle leaks

aggregated How widespread: Common 38 NHTSA owner complaints match it, out of 459 checked

How it shows up

• coolant smell/weep at the water pump weep hole
• coolant loss with visible crust at the thermostat housing
• overheat episodes after level loss

How to tell it apart

• pressure-test the system; inspect weep hole, housing, bottle and hoses in order
• check the coolant bottle for hairline cracks at the seams
• replace the failed item; refill and bleed per procedure

Usual fix

water pump / thermostat housing / coolant bottle replacement per findings

Root cause, parts and sources →

Other symptoms on the ProMaster 3.6 (gas)

Hard start, long crank or no-startStalls or dies while drivingLoss of power, limp mode or derateMisfire, rough idle, hesitation or surging

Everything on the ProMaster 3.6 (gas)Its recalls and bulletins

Order: how widespread each failure is in its record (near-universal, very common, common, occasional, rare), then the number of NHTSA owner complaints that match its keywords. Complaint counts are keyword matches, not a manual review of each complaint. A symptom listed here means the failure is documented with that sign; it is not a diagnosis of your truck. Tiers: verified, aggregated, contested, data-gap. How we tier and source facts.