Overheating at Idle and Lost A/C Performance After Collision Repair

A 17°F drop across the radiator (225°F in, 208°F out) is far too small. A healthy radiator at a 232°F engine temperature should show roughly a 25–45°F drop.

Reasoning from the physics:

• Small ΔT across the core plus a hot lower hose means the coolant leaving the radiator is nearly as hot as the coolant entering it - heat is not being rejected. The engine is being fed hot coolant back, which is exactly why it climbs only when there is no ram air.
• If the coolant circuit were the problem, the opposite pattern appears: a restricted radiator or a weak pump reduces flow, so the coolant spends longer in the core and the outlet temperature drops (a large ΔT) even though total heat rejection falls. Low flow shows up as a big spread, not a small one.
• Combined with the fact that the symptom is idle-only and clears completely at 45 mph, the fault is on the air side, not the coolant side. That also explains the A/C degradation: the same air stream that cools the radiator cools the condenser, so condenser capacity collapses at idle and vent temperature rises to 62°F.
• The small ΔT rules out an air pocket and a combustion leak as primary causes, but confirm cheaply with a block test and by checking for a coolant level that drops after a drive.

Fan current proves the motor is energized - nothing else. It does not prove which direction the blade turns, whether the blade pitch is correct, whether the blade is cracked or slipping on the hub, whether the fan is sealed to the shroud, or whether the shroud and air seals are still on the truck.

Inspect and measure, in this order:

1. Airflow direction: hold a sheet of paper at the grille of each fan and confirm it is pulled toward the engine bay. Reversed polarity or a fan assembly swapped side to side will spin and draw normal current while pushing air forward.
2. Shroud and seals: the fan must sit in a sealed shroud with a close blade-tip clearance. After a front-end repair, missing or unclipped shrouds, radiator-to-condenser foam seals, and the lower air dam/valance are common. A missing air dam alone can cause idle overheating and lost A/C performance because air recirculates instead of being drawn through the cores.
3. Core faces: look through the grille with a light for debris, plastic bagging, or bent fins, and scan the radiator and condenser with an infrared thermometer row by row. Uniform temperature across the core means air is moving; cold bands or a cold lower third mean blocked tubes or blocked airflow.
4. Condenser-to-radiator gap: a large gap with no seal lets the fan pull engine-bay air around the condenser instead of through it.
5. Only after airflow is proven should the coolant circuit be revisited with a flow test.

Those parts all live on the coolant side, and the measurements show the coolant side is moving heat but the air side is not removing it.

• The thermostat, cap, and pump cannot help if the heat cannot leave the radiator. A 17°F drop across the core says the radiator is receiving hot coolant, passing it, and returning it almost as hot.
• The pump replacement would have addressed low flow - but low flow produces a large radiator ΔT and a cold lower tank, the opposite of what this truck shows.
• Idle-only symptoms with normal highway temperatures are the classic signature of an airflow defect, and the collision repair six months ago gives a concrete mechanism - missing shroud, air dam, seals, or a fan installed so it blows the wrong way.

Frame the next step as verification, not parts: airflow and seal inspection plus an infrared scan of the core. If those check out, then and only then move to a coolant flow test. Keep the explanation symptom-based - the gauge number at idle versus at 45 mph, and the vent temperature drop from 44°F to 62°F - because that is what the customer can see and what the data shows.