P1299: How to Diagnose & Fix — Cylinder Head Over-Temperature Protection Active (manufacturer-specific, Ford)

2019-2020 Nautilus models with the base 2.0L EcoBoost (non-hybrid) suffer unexplained coolant loss, white tailpipe smoke, an overheat warning, and sometimes coolant intrusion into the cylinders. Ford TSB 20-2234 traces the most common cause to a failing exhaust gas recirculation (EGR) cooler that leaks coolant internally; the related design also has a known coolant-intrusion weakness (narrow coolant slit between cylinders compromising the head-gasket seal). Owners report repeated coolant top-offs with no visible external leak, then misfires as coolant fouls the plugs. A June 2025 Ford EcoBoost coolant-intrusion class action covers 1.5L-2.0L engines; the most severe Nautilus cases require engine replacement with the redesigned block.

Early 1.6L EcoBoost Fusions can suffer a localized lack of coolant circulation that overheats one corner of the cylinder head; the head cracks and pushes oil/coolant onto the hot exhaust, and vehicle fires occurred while driving or after shutdown. Ford recall 14V437 covers 2013 Fusion 1.6L vehicles built in a defined window; the failure mode is distinct from the 1.5L coolant-into-cylinder intrusion issue.

The 4.0L SOHC V6 used in 2005-2010 Mustangs commonly develops coolant leaks from the composite thermostat housing and related seals. The plastic housing can warp or crack with age and heat cycling, causing external coolant seepage and sometimes overheating if the leak worsens. This is a well-known issue across Ford applications using the same 4.0L engine and is frequently documented in owner forums and repair databases.

On the 3.5L and 3.7L Duratec V6 the water pump is driven off the timing chain and lives INSIDE the oil-lubricated front timing cover, not bolted to the outside of the block. When the pump's shaft seal and bearing wear out (commonly 90k-130k miles), coolant does not drip onto the driveway - it runs down the weep passage and, once the passage plugs or the seal fully lets go, straight into the crankcase. Owners report the first sign is a slowly dropping coolant reservoir with no visible external leak, then milky residue on the dipstick and oil cap. Coolant-contaminated oil destroys rod and main bearings and scores cylinder walls, which is why so many of these turn into engine replacements rather than pump jobs. A class-action suit was filed against Ford over this design. The labor is brutal because the front cover, timing chains and often the engine's front accessory drive must come off, and many shops quote the job with the engine partially lifted.