This happens after ive been sitting at a drive through or city driving with alot of stop and go and while running a/c. The temp gauge stays in the middle, but when i hit the gas, it makes a real loud "diesel" type intake sound.....Kinda like a loud whirl, and i have to give it alot of gas for it to get going, then the rpm's go up to about 3- 3 1/4 before they drop back down to normal. But when this happens the truck really doesnt have the power that it normally does....Then after aways of driving steadily, it goes back to normal. I changed the coolant and t-stat last weekend hoping it would solve this but no such luck. Anyone know what could be causing this or anything else i could check/change? Its weird because this only happens in the summer when its hot out.... Thanks

'01 f150 scab 4x2 5.4....

 

Yea , I know what you could do.

First - How many miles ? What mods do you have ?

 

Stock, 275k mi

 

My wife's expedition and my bronco had the fan clutch changed out a couple years ago. I replaced them with the heavy duty fan clutch model due to the extreme heat in louisiana during the summer. They both do the same thing when the fan clutch engages especially when the ac is running. The reason for this is the fan causes resistance on the engine and makes a loud sound like the engine is running really fast but not going anywhere. Simulate the problem, put it in park and pop the hood. If it is the fan clutch, it will be blowing a lot of air into the engine compartment, and moving the throttle up to about 2k rpm should make the noise stop in about 10-15 seconds.

 

Thanks but, I dont really understand the "Simulate the problem, put it in park and pop the hood. If it is the fan clutch, it will be blowing a lot of air into the engine compartment, and moving the throttle up to about 2k rpm should make the noise stop in about 10-15 seconds." part. Are you saying the fan clutch needs to be replaced?

 

Replace -

1. Forward O2's.
2. Injectors.
3. Coils.
4. Fuel Filter
5. Motorcraft Plugs

Clean -

1. Clean MAF Sensor.
2. Clean Throttle body and Elbow.

Parts can be found on Ebay - up to 75% off dealership prices- more in some cases.

Good Luck

 

Did the fuel filter and plugs already and sprayed down the maf today. Throttle body im going to clean tomorrow. Elbow meaning pcv elbow? Havent done the injectors, coils or O2 sensors, but would that affect the overheating problem?

 

Ok lets see if I can explain.
A fan clutch is a liquid filled clutch with a temperature sensing 'coil' on the front of it. As the engine temperature rises and the coolant temperature increases, the fan clutch locks in and increases air flow through the radiator. When it is not engaged, the fan still turns but not as fast. This keeps the load off the engine untill it is needed to keep the coolant temperature down. The fan clutch usually does not engage at highway speeds because you have air flowing across/through the radiator fins. Its designed to keep the vehicle from overheating while at idle and the air conditioning is running. Older vehicles did not have fan clutches and had a constant load on the engine as a result. Now when a fan clutch goes bad, the fan will spin quite easily while the engine is off. It also affects your idle temperature, and air conditioning cooling at idle as there is not sufficient air flow through both the condenser and radiator. Most new vehicles have gotten away from mechanical fans and gone to electric because it helps to save fuel. I'm not too sure if trucks have gone to electric yet but I know most cars have.
Here is how you can simulate the situation:
On a typical hot day, raise the hood of your truck, set the park brake and start it. Turn on the air conditioning (maximum) with the blower at the highest setting. As the truck starts to warm up to operating temperature you should hear changes in the amount of air being sucked into and blown out of the fan. If these noises are the same as what you have been hearing, then its just the fan clutch engaging (doing its job). My Expedition and Bronco both do this. Makes it sound like they are running in 4 wheel drive low until the fan clutch releases.
Hope that clears things up and that you don't have any real issues with your vehicle.

 

Hello Munoxide
Another possibility is a freon overcharge, if any has been added.
When you stop and the air acros the condenser slows , the head pressure of freon goes up. The more heat the more freon expands. The high pressure switch will cycle the compressor when limits allow.
If this is your cars condition, the noise is coming from the compresor and drive belt. It takes allot of torque to get things moving again in these conditions.

If you have added freon. get some gauge readings and make adjustments.

 

Didn't know you were over heating - Just said no power when hot ? I'll read it again, but I don't remember anything about "over-heating"..

Anyway, what I meant by "elbow" - Throttle body elbow - called the plenum. The ports get clogged in that elbow.

 

What do you mean when you say the rpms go up to about 3- 3 1/4?
Do you mean 3 thousand rpm?
In that case check the transmission fluid.

 

Thanks but, no freon added.....

 

Yes, 3k rpm, and i just changed tranny fluid. Thanks thou.

 

Well i didnt mention it but, the needle went almost all the way to the top while sitting in a drive thru with the a/c on......Its only doing what im describing while in a drive thru or stop and go traffic so thats why im thinking its overheating somehow, but the needle has only moved that one time. Ive check/done everything i can think of cooling-wise.....Next thing ill try is the fan clutch i guess.....Thanks for the help.

 

The only time it will make this noise is when i give it gas....and yesterday when i tried what you said about letting it idle and feeling for air blowing back into the motor, i felt alot of air being blown back towards the motor...I dont know weather i should be able to feel air blowing out of the front grill or not thou. Also the fan is really easy to turn while the truck is off....Thanks for the help