P0128 on Chrysler: How to Diagnose & Fix

Water pumps fail prematurely due to bearing and seal wear. Air pockets frequently form in cooling system after repairs. The 300 is difficult to properly bleed air from cooling system.

PT Cruisers are extremely prone to overheating from multiple causes: radiator fan relay failure, fan motor failure, thermostat sticking closed, radiator clogging, and water pump failure. The high-speed fan relay is the most frequent single failure point. Overheating leads to head gasket failure. This is one of the most universally reported problems across all model years.

Head gasket failure is common, especially on turbo models. The aluminum cylinder head is susceptible to pitting from acidic coolant which compromises the gasket seal. Turbo models experience higher cylinder pressures that accelerate failure. Overheating from cooling system issues frequently triggers head gasket failure.

The turbocharger on GT and turbo models fails from oil starvation, wastegate actuator failure, and bearing wear. Failures reported as early as 60,000-78,000 miles. Turbo failure is often followed by head gasket failure within months due to changes in combustion pressure dynamics.

The 3.3L and 3.8L V6 engines suffer from water pump failures, thermostat failures, and radiator fan relay failures. The water pump weep hole is a common leak point. Overheating can cause head gasket failure. The cooling fan relay is a frequent failure point causing overheating at idle.

The 3.6L Pentastar's water pump is a recognized wear item on 2011-2016 vans. The internal shaft seal fails first and coolant escapes from the weep hole at the front of the pump; if it is ignored the bearing follows and the pump can shed its drive, producing rapid overheating. Owners report the leak between roughly 80,000 and 120,000 miles. A very common misdiagnosis on these vans is a leaking plastic thermostat housing, which drips into the same area and looks identical from above - replacing the pump without checking the housing leaves the van still leaking. Note this is the Pentastar pump; the 3.3L/3.8L vans have an entirely different cooling-system failure pattern.

The Cirrus equipped with the Mitsubishi-sourced 2.5L V6 is prone to head gasket failure, often caused by overheating episodes. The engine's aluminum heads warp easily when overheated, making a simple gasket replacement insufficient without machining the heads.

The 3.6L Pentastar V6 in Pacifica models suffers from engine stalling due to loose ground connections (recall NHTSA 19V348), crankshaft position sensor sync issues, and premature head gasket failures typically around 75,000-85,000 miles. Cooling system failures can lead to coolant entering the combustion chamber, requiring complete engine replacement.

The 3.5L V6 engine has common issues including leaky head gaskets, coolant leaks, and overheating. The water pump uses a molded plastic impeller that erodes from rust and sediment in the coolant, reducing cooling efficiency. These engines run hot and are prone to oil sludging, especially if oil is not changed every 3,000 miles.

The Chrysler 3.5L V6 engine in the Prowler uses aluminum coolant crossover tubes that develop leaks at the O-ring seals and crimped connections. The crossover tubes run across the top of the engine between the cylinder heads and are exposed to high heat. The O-rings harden and shrink, allowing coolant to seep. The Prowler's unique front-end design with exposed engine makes the leak visible but also means the engine compartment lacks the heat shielding of a conventional car.

The engine-driven water pump on the 3.6L Pentastar leaks from the mechanical shaft seal, venting coolant through the pump's weep hole onto the timing cover and front of the block. Chrysler acknowledged the pattern with STAR Online Publication S2307000002, 'Suspected Engine Coolant Leak', which mandates a specific inspection sequence before any water pump is replaced on 2016-2024MY 3.6L applications, and with dealer bulletin 9100212 covering the upgraded water pump part. Both bulletins are listed against the 2020 and 2021 Chrysler Voyager. Chrysler also published bulletin 0700723 warning that mixing coolant with tap water instead of distilled or pre-diluted coolant deposits minerals that abrade the pump's mechanical seal and cause exactly this leak — meaning some field failures are induced by prior service, not just by the part. Because the pump sits behind the front accessory drive and the leak path runs down the block, owners frequently misread it as an oil leak or as the separately documented oil filter housing failure; sweet smell and dropping coolant level distinguish it. Left alone, the loss progresses to bearing whine, coolant starvation and overheating, which on an aluminum-head V6 risks head gasket and head damage far more expensive than the pump.