If you are experiencing a loud noisy fan sound on your late model Ford F150, do not fret! This is quite a common problem and many F150 owners have reported and solved this issue on forums across the internet. The good news is there is a very logical answer and an easy fix.
So, what causes your F150 to sound so noisy even after you’ve shut off the engine?
The Ford F150 trucks are equipped with an auxiliary fan which is designed to engage and keep running until the engine temperature drops down safe operational degrees. It is programmed to keep running even after you’ve shut off the engine.
Below are a few common causes for the auxiliary fan to engage:
- Low Coolant levels
- Leaking Water Pump
- Faulty Thermostat
- Misaligned Fan assembly
Let’s now take a detailed look at a few common reasons why your F150 sounds so noisy. If you’re unable to diagnose and resolve the issue yourself, it’s advised to have your F-150 inspected by a qualified mechanic who can pinpoint the exact cause of the noise and carry out the repairs professionally.
Table of Contents
Why Does My F150 Fan Keep Running – (AFTER CAR TURNED OFF)
AC Expansion Valve
Firstly, what is the AC Expansion valve and how can it cause the Auxiliary fan to engage? The (AC) Air Conditioning Expansion valve is designed to receive the refrigerated air-con fluid and then reduce the liquid pressure before it gets sent through the evaporator. This drop in pressure is what cools the fluid and then sprays it into the evaporator thus sending cool, clean, air into the cabin. Fantastic!
Okay, great, now that we know what its designed to do, what happens when it fails? Basically, if the AC Expansion valve is stuck in either open or closed position, the AC system will not cool sufficiently. A clogged valve will lead to too little refrigerant, increasing the pressure in the system and causing the AC compressor to overheat.
Below is a DIY fix on how to strip and replace your AC Expansion valve with some basic tools. IF you are not a DIY person or you don’t have the required tools, rather send your vehicle to a reputable dealership to have a qualified technician sort it out.
Be warned, if your truck is out of warranty, this can turn out to be quite an expensive repair.
Another reason why your F150 might sound noisy is related to the water pump. Let’s take a look at that next.
Faulty Water Pump
The water pump is another cause for your F150 to make strange loud noises. When functioning properly the water pump is designed to keep the engine cool. Its primary function is to circulate coolant, also known as antifreeze, throughout the engine to maintain optimal operating temperatures.
If you have a leak in your water pump, it results in your truck losing anti-freeze and thus causing the engine temperatures to run hot. This in turn causes the auxiliary fan to engage sooner and keep running for longer to compensate for that loss in coolant.
A quick check would mean crawling underneath your truck to inspect for water leaks or green coloured water, also known as anti-freeze, dripping slowly.
First thing to check is coolant level, if it’s low on coolant the computer will default to high speed fans. If your levels are low, top-up immediately with the correct coolant to the full level if necessary.
Low Coolant Levels
This is directly related to the above section. Low coolant will mean the engine is running hot and the aux fan will engage more frequently, thus causing the loud fan noises even after you’ve shut off the engine. When the outside temps are high the fans will cycle to high speed for a while with the A/C on. Also when driving in stop-start slow-moving traffic.
On F150’s if the A/C is on the fans will always come on at low speed.
A faulty thermo is directly related to engine overheating issues and one of the first components to inspect. The thermostat is responsible for regulating the flow of coolant through the engine. If the thermostat is stuck closed or partially closed, it restricts the flow of coolant, leading to inadequate cooling. This will result in the aux fans to engage and blow at max speed in an attempt to prevent the engine from overheating. If the aux fans do not engage, the engine may overheat, which can cause damage to engine components and potentially lead to engine failure.
Why Does My F150 Sound Like a Diesel
Does your F150 exhibit a loud rattling noise that makes it sound like a diesel engine? Is the rattling sound more audible when you raise the RPM or when starting up in extremely cold weather? Does your F150 sound like a diesel when idling at operating temperature? Does this mean that the motor is not good anymore and for how long is it safe to drive it in this condition?
Certain model F150s were reported to emit a diesel-like rattle at idle. The rattling noise could be caused by a loose heat shield, contaminated injectors, or the infamous Cam Phasers and VCT phenomenon which causes the Ford F150 to rattle at start-up.
In most cases, the truck isn’t throwing out any codes but just sounds like a loud, rattling diesel engine. Many owners have taken their trucks to the dealership for a diagnosis only to be told, everything was normal and the noise will eventually go away. If you’re not satisfied with that diagnosis, as many aren’t, then read this article further to determine the possible cause(s) and the solutions available.
F150 Rattling Noise when accelerating.
Does your Ford F150 emit a very annoying rattling noise when driving between 20-35 mph or accelerating at low speeds? Is the rattling sound audible at the very first part of the throttle or does it occur at any time irrespective if the engine temperature is at operational level or cold? Does the rattling noise come from the engine bay or can it be heard from the driver-side closer to the catalytic converter or transmission area?
Most Ford F150 trucks that experience these rattles are caused by a loose heat shield or loose heat shield clamps. The clamps become corroded over time and once the clamp breaks it simply hangs on the exhaust pipe causing a rattling noise under acceleration.
Many F150 owners report the noise to occur under any driving conditions and at any engine operating temperature. Whether your transmission is in (D)drive, (R)reverse, (N)neutral, (P)park, or even when accelerating from a stop, the rattle can be heard. LOVELY!!!!
Read the full article below for a more detail and a solution to this rattling noise.
User Experience & Feedback
User Experience #1
After 75 mile highway run, I pulled off and heard a loud fan sound coming from under the hood. I turned off the heater/fan and listened. All i could think was its the auxiliary radiator fan? But i was hearing it on the cab?https://www.f150forum.com/f38/what-fan-noise-always-loud-408108/
I turned off the truck and it stopped. In my experience most the auxiliary run even when the engine is off (runs until it reaches the appropriate coolant temp) So, i came to place where i could investigate further. Dummy gauge reading upper range of normal operating temp and loud fan sound.
I went to the front of the truck and sure enough it was the auxiliary fan blowing like a SOB (or is that sucking?) Once it cooled down a little it shut off.
User Experience #2
I have a 2016 f150 / 5.0 with 36k on it. Recently my auxiliary fan started running all the time. Coolant level is fine. Ford dealer is NO HELP…surprise. have heard ac pressure switch may be the answer. Any help is appreciated. Read in a older model about fuse 27…but in this one..that is for power seat. HELP please.https://www.f150forum.com/f38/what-fan-noise-always-loud-408108/
User Experience #3
My truck fans were coming on like that after 15 mins and were loud too. After some back and forth with the dealer, it turned out that my water pump was bad, making me loose coolant, thus making my fans turn on.https://www.f150forum.com/f118/engine-fan-really-loud-439509/
In summary, there are a few key components on the F150 that can result in your auxiliary fans to engage and thus emit a loud noise, even when the engine is shut off. If you are not mechanically savvy or unable to diagnose and resolve the issue yourself, it’s safer to have your F-150 inspected by a qualified Ford Technician who can troubleshoot the exact cause of the noise and perform the necessary repairs.