Loud Flapping Noise Coming from Dash Area

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June 25, 2020, 05:08:55 pm

I am wondering if anyone else has experienced a relative loud flapping noise that seems to come from the dash area maybe behind the radio. Only does it when hot, and when accelerating. Even in Park it does it though not as bad. Don’t hear it outside with hood open, or even inside when removing doghouse. When gets really hot and going up steep hills gets super loud and turns into something like loud slapping. Note that the engine runs perfectly. The engine has been triple checked but the mechanics never hear it because they don’t drive it long enough. I swear it’s coming from up in the dash area.
Is the top dash cover something that can be removed without too much difficulty?

Re: Crazy dash noise

Reply #1 – June 25, 2020, 05:23:37 pm

Hi Jack. Well something hitting the engine fan perhaps?
Maybe look for a small vacuum leak in the hoses that operate your heating/airconditioning system. When going up hill, the engine is using a lot of gasoline, and air to go with it. At full throttle, the intake manifold doesn't have much vacuum in it. The A/C, heat default with no vacuum is defrost, and the internal flap that directs air from floor, to vent, or defrost will flap back and forth. Not really a fault inside the heater, just a lack of sufficient vacuum to operate properly. It might also do this in Park. Rodents chewing on hoses cause a lot of this type of problem. Of course something could have come loose, the vent damper could be broken, or loose. When this is happening, is air coming out of your vent consistently, or changing to other outlets?
I know that other people have put in vacuum canisters with a check valve to keep the A/C flaps stable. One of my old cars with a turbo had a separate electric vacuum pump and cannister to provide vacuum to the brakes and vent system. Engine vacuum turns to pressure when the turbo is pumping air into the engine. RonB

Re: Crazy dash noise

Reply #2 – June 25, 2020, 07:28:26 pm

This is much good information and I probably need to find a better mechanic in South Orange County Ca.
We are in the Tetons now. No other Lazy Daze insight.
I am thinking when I get better cell service I can see some videos on checking the things you mentioned.
I’ve noticed this is worse at higher altitudes so it ma be related to a vacuum leak or such

Re: Crazy dash noise

Reply #3 – June 25, 2020, 07:42:48 pm

There is a cover in the middle top of the dash - pry it off and you will see the vacuum actuators for the ventilation system. If they are causing the noise, you will see it by their action.

Steve

Re: Crazy dash noise

Reply #4 – June 25, 2020, 07:43:19 pm

Ron is on to the problem, it sounds like it's vacuum related. I would suspect the check valve in the vacuum supply line to the HVAC is defective or there is a leak in a vacuum line. The heating air, ventilation, and conditioning system (HVAC) controls operate off vacuum supplied from the engine's intake manifold.
Vacuum powers motors that open and close flaps under the dash that direct air through the heating and cooling coils before blowing it into the cab.

Long upgrades will bring the vacuum down to near zero and keep it there until cresting the hill. During this time of low engine vacuum, vacuum to operate the HVAC system is stored in a canister, isolated from the intake manifold by a one-way check valve.
If the check valve is defective, the system's vacuum will vary as the engine's vacuum varies. A leak in the system will do similar things. If so, it should flap when the vacuum is oscillating from high to low as the throttle is opened and closed.
The noise you hear may be a leaking vacuum line or motor.

I would start by finding the vacuum line, under the hood, that supplies the HVAC and start from there, making sure it is intact.
If you are sure the noise is coming from inside the dash, the dash will need to be partially disassembled, a job that you may want to farm out.

Larry

Re: Crazy dash noise

Reply #5 – June 25, 2020, 08:10:52 pm

Quote from: Steve - June 25, 2020, 07:42:48 pm

There is a cover in the middle top of the dash - pry it off and you will see the vacuum actuators for the ventilation system. If they are causing the noise, you will see it by their action.

Steve

wow. I see the cover. Thought it was an air bag. Will pop it off and look

Re: Crazy dash noise

Reply #6 – June 25, 2020, 08:12:25 pm

Quote from: Larry W - June 25, 2020, 07:43:19 pm

Ron is on to the problem, it sounds like it's vacuum related. I would suspect the check valve in the vacuum supply line to the HVAC is defective or there is a leak in a vacuum line. The heating air, ventilation, and conditioning system (HVAC) controls operate off vacuum supplied from the engine's intake manifold.
Vacuum powers motors that open and close flaps under the dash that direct air through the heating and cooling coils before blowing it into the cab.

Long upgrades will bring the vacuum down to near zero and keep it there until cresting the hill. During this time of low engine vacuum, vacuum to operate the HVAC system is stored in a canister, isolated from the intake manifold by a one-way check valve.
If the check valve is defective, the system's vacuum will vary as the engine's vacuum varies. A leak in the system will do similar things. If so, it should flap when the vacuum is oscillating from high to low as the throttle is opened and closed.
The noise you hear may be a leaking vacuum line or motor.

I would start by finding the vacuum line, under the hood, that supplies the HVAC and start from there, making sure it is intact.
If you are sure the noise is coming from inside the dash, the dash will need to be partially disassembled, a job that you may want to farm out.

Larry

I will mess with this myself at first but probably end up paying someone. At least now I know what to start looking at.

Re: Crazy dash noise

Reply #7 – June 25, 2020, 08:25:02 pm

Interesting that through the years, we have had as many complaints about HVAC problems as engine problems, most of them were vacuum related.

Larry

Re: Crazy dash noise

Reply #8 – June 25, 2020, 09:18:53 pm

I like listening to Car Talk. According to them, a flapping noise in the dash area is usually a flapping gate for the HVAC system, just as Ron and Larry said. And that is the extent of my knowledge on the subject.

Ken F in WY

Re: Crazy dash noise

Reply #9 – June 26, 2020, 12:07:57 am

I’m convinced it’s what you guys are suggesting. The Ford fleet service manager told me it was probably the fuel filter and would cost $1,200. I declined.
The mechanic at Elite service in South Orange County changed 2 “bad” coils. Didn’t fix of course and was pricy.
When I get home from Yellowstone I will look for you tube videos, maybe diagrams, etc., and make a stab at fixing myself. If I’m lucky I’ll have to buy some new tools. Thanks

Re: Loud Flapping Noise Coming from Dash Area

Reply #10 – June 26, 2020, 07:28:03 pm

I have a 2005 RB. Sometimes the noise around my dash is all the crap in the cup holders, etc. I know this after panicking from the noise and dumping everything off!