The largest online repair guide library for every car

About us
Contact support
FAQ
Sign up
Sign in

2018 F-150 Lariat running hot, coolant disappearing

0

Mike T. · rep 0 · May 24, 1:16 PM · 1 replies · solved · Question

Vehicle: 2018 Ford F-150 Lariat

Hey everyone,

I've got a 2018 Ford F-150 Lariat with the 3.5L EcoBoost, and lately, it's been acting up. The engine temperature gauge seems to be running higher than usual, sometimes even touching the red zone, especially in stop-and-go traffic.

I've noticed I'm having to top off the coolant reservoir pretty frequently, maybe once every week or two. The strange thing is, I don't see any obvious puddles or drips under the truck when it's parked overnight. I've peered under the hood, and while some areas look a bit crusty, I can't pinpoint a major leak.

Could this be a thermostat issue, or something more serious like a water pump? What are some common places to check for leaks on these trucks? Any DIY diagnostic steps I can take before bringing it to a shop? I'm trying to avoid a costly repair if it's something simple.

✓ Accepted solution

ClearTheCode Admin

ClearTheCode Team · rep 0 · May 24, 1:16 PM

0

ClearTheCode admin answer:

It sounds like you're dealing with a classic coolant system problem, John. A disappearing coolant without obvious puddles can be tricky, but it's often due to a slow leak or an internal issue. Here are some steps and potential causes:

  1. Check for External Leaks More Thoroughly: Even without puddles, small leaks can evaporate quickly on hot engine components. Inspect the radiator end tanks, all coolant hoses (upper, lower, heater core hoses), the thermostat housing, and the water pump weep hole. Use a flashlight and look for dried coolant residue, which often looks like a colored crust (pink, orange, green, or blue depending on your coolant type).
  2. Radiator Cap: A faulty radiator cap can prevent the system from holding pressure, leading to coolant loss through the overflow or evaporation. It's a cheap part to replace and a good starting point.
  3. Thermostat Issues: A failing thermostat can cause overheating by not opening fully, but it typically doesn't cause coolant loss directly. However, if the engine overheats severely, it can push coolant out through the overflow. A common OBD-II code for a stuck-open or slow-to-open thermostat is P0128 (Coolant Thermostat (Coolant Temp Below Thermostat Regulating Temperature)).
  4. Water Pump: The water pump is a common failure point. It has a weep hole designed to leak coolant when the internal seal begins to fail. This leak can be intermittent or evaporate before hitting the ground. Look for residue around the pump's pulley area.
  5. Heater Core: An internal leak in the heater core can cause coolant loss without external signs. You might notice a sweet smell inside the cabin, fogging windows, or a damp passenger-side floorboard.
  6. Head Gasket (Worst Case): While less common without other symptoms like white smoke from the exhaust, misfires, or oil in coolant, a failing head gasket can allow coolant to burn in the combustion chambers or mix with oil.

When to See a Shop:

  • If you can't locate an external leak after a thorough inspection.
  • If you suspect a water pump or heater core issue, as these repairs can be more involved.
  • If the engine continues to overheat despite your checks, as prolonged overheating can lead to severe engine damage.
  • If you notice any of the head gasket symptoms mentioned above. A shop can perform a pressure test on the cooling system, which is the most effective way to find elusive leaks, and also test for combustion gases in the coolant.
Menu

Help & account