03 ext sounds like a knock

Ghost

Original poster
Member
Jun 1, 2012
932
Alright it's been a while since I have had time to post this but here we go. When my heater is on in the truck I get this sound in the engine what sounds like a knock it only does it once after every stop light 0 to 45mph±. Is it possible that the k&n metal air intake tube and the 9" LARGE AEM prodry filter has anything to do with it ? Only has hmm about 58k miles. It also bogs like a mofo sometimes which I'm assuming is the large airfilter (I cut out the OEM air cleaner cover and use that to cover the filter because its a cone filter and way way too loud.
 

RayVoy

Member
Nov 20, 2011
939
So, just to clarify, are you saying if the heater is not "on" there is no knocking?


And, if that is what you are saying, just what do you mean by my heater is on? Are you talking about the blower, or the temp controls on the dash?

And, do you have a manual temp control, or the auto unit?
 

Ghost

Original poster
Member
Jun 1, 2012
932
RayVoy said:
So, just to clarify, are you saying if the heater is not "on" there is no knocking?


And, if that is what you are saying, just what do you mean by my heater is on? Are you talking about the blower, or the temp controls on the dash?

And, do you have a manual temp control, or the auto unit?

Thermostat set to heat (red) left knob at 5 (Max) doesn't matter if it's set at the floor or front or windshield. Manual temp for the heater settings. Engine Temp doesn't move much when driving. If I push the blower motor button it produces cold air so I don't use that when using the heater, hope that helps ?
No knocking sounds when heater or air is off. I never use AC cause if I press the blower button it makes ice cold air.
Cleaned the throttlebody over the weekend and it was clean but scrubbed it anyways.
 

The_Roadie

Lifetime VIP Donor
Member
Nov 19, 2011
9,957
Portland, OR
If you have the rotary knob for the blower speed control, what is this "button" you're pushing?

I'm also confused about how you can "bog" if you have a large air filter? Are you blocking any of the intake airflow to the filter?

Did you put on the aftermarket filter thinking it would only affect airflow? :confused:
 

Ghost

Original poster
Member
Jun 1, 2012
932
the roadie said:
If you have the rotary knob for the blower speed control, what is this "button" you're pushing?

I'm also confused about how you can "bog" if you have a large air filter? Are you blocking any of the intake airflow to the filter?

Did you put on the aftermarket filter thinking it would only affect airflow? :confused:

I use a aem prodry cone filter with a metal k&n intake tube. The k&n metal wall that surrounds the airfilter is not used I use the OEM top plastic cover I had to hone it out. The button for the air is below the speed control knob
 

The_Roadie

Lifetime VIP Donor
Member
Nov 19, 2011
9,957
Portland, OR
See why we're confused? If it's the little button with the snowflake symbol, that's the AC compressor control, not the "blower motor button".

In any event, that's not your noise. I think you're right. Just remove the metal tube for a short test ride.
 

Ghost

Original poster
Member
Jun 1, 2012
932
the roadie said:
See why we're confused? If it's the little button with the snowflake symbol, that's the AC compressor control, not the "blower motor button".

In any event, that's not your noise. I think you're right. Just remove the metal tube for a short test ride.

There's 3 buttons on mine, circulation button which causes the forced cold air(not sure why I said blower) , the AC button and lastly the rear defrost button.
 

Ghost

Original poster
Member
Jun 1, 2012
932

chief0299

Member
Jul 1, 2013
67
The button on the left is the re-circulate button. It recirculates the air in the cabin versus pulling fresh air from outside the vehicle. The next button to the right is for A/C and the next is rear window defroster. Are you hearing the knocking only while the fan speed control is on 5? Do you hear it when you choose any of the other numbers? If so, does it slow down a little bit with each lower number?
 

Ghost

Original poster
Member
Jun 1, 2012
932
chief0299 said:
The button on the left is the re-circulate button. It recirculates the air in the cabin versus pulling fresh air from outside the vehicle. The next button to the right is for A/C and the next is rear window defroster. Are you hearing the knocking only while the fan speed control is on 5? Do you hear it when you choose any of the other numbers? If so, does it slow down a little bit with each lower number?

Ye I know what they do. I mainly run the air @ 5 never use 4,3,2,1 but tmrw when I drive to L.A I'll try a lower setting and see what happens. The re-circulation button turns the air to ice cold...not sure if that's normal ? This is a brand new switch and brand new blisterpack from delco. yes all #'d buttons work per speed.
 

tbyoda

Member
Apr 19, 2013
187
Ghost said:
The re-circulation button turns the air to ice cold...not sure if that's normal ?
The re-circulation should make the air colder if the AC is on because of less heat load from the cabin and warmer if the hear is on. IDK Could the switch wiring to the re-circulation and AC be swapped some how or could the AC be always on but the switch is not show it?
 

Ghost

Original poster
Member
Jun 1, 2012
932
Rs8892 said:
The re-circulation should make the air colder if the AC is on because of less heat load from the cabin and warmer if the hear is on. IDK Could the switch wiring to the re-circulation and AC be swapped some how or could the AC be always on but the switch is not show it?

Don't see how that could happen.
It's just something I have noticed when pressing the circulation button when using front vents only. Anyways I'm more concerned with the knock sound my engine makes than trivial air lol. I'll report back tmrw
 

Ghost

Original poster
Member
Jun 1, 2012
932
OK it only does it when I'm using the 5 setting with the ac on or with just cool air or just the heater.
 

chief0299

Member
Jul 1, 2013
67
I know you keep saying that it sounds like the engine is knocking, but I can't come up with any scenario where your heat controls make that happen. If your A/C compressor had a bad bearing or internal parts, it might knock though. However since it only happens when the fan is on the 5 setting, it isn't the problem. It sounds like you have a blend door actuator problem based on the fact that you get COLD outside air when you turn off re-circ. I'm willing to bet that the knocking you are hearing is one of the doors being rattled by the high pressure air being forced on it by the fan at the #5 speed.

The below thread goes into details about the doors.
http://gmtnation.com/f23/hvac-actuators-dash-removal-2193/

I would read through that and check all your doors and actuators. Also be sure to search the forum for blend door actuators and see what other options there are.

There's lots of good diagnostic info you can glean from the search option.

Good luck, and be sure to let us know what you find.
 

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