3 Taps/Knocks as engine warms up

[JasonA]

I'm sure I've seen this posted before, either here or on the other board, but I can't find it.

When my car warms up, there are 3 distinct tapping noises that occur in succession. Tap, tap, tap. It sounds like it's coming from the engine, but it's hard to track down. It sounds like a little man inside the car somewhere with a little miner's hammer...knock, knock, knock. When it does occur (probably half of the mornings), it occurs at the exact same place on the temperature gauge (about the 10:30 position). It doesn't matter which road I drive out of the neighborhood; it doesn't matter what the ambient temperature is outside. It's just three quick taps and that's it. It'll never do it again until the next day (or the following day).

The only reason I post this is because I just KNOW I've seen a fix posted before for it...I just can't find it. Anyone remember such an issue?

[Ranger]

Very strange. I don't recall anything anything like that. Can't even guess at what it could be.

[MAC]

Does this thread help describe the problem?

94 STS rattle/knock

[JasonA]

Thanks Mac. No...I remember seeing it specifically in the DeVille section of the Cadillacowners forums. I'll have to keep digging through there. I know it was mentioned repeated times in there...and I think it's specific to the G-body cars (98-04 Seville, 00-05 DeVille).

[Texas Jim]

Jason,

Fairly long thread... no one seems to really know what it is. This is in the 2006 or newer DTS forum

http://www.cadillacforums.com/forums/cadil...king-sound.html

[Logan]

Here are a few bulletins..

Popping Noise in the Footwell Area - keywords fit frame front intermittent jounce loud poor rebound suspension #PI00112B - (03/21/2005)

The following diagnosis might be helpful if the vehicle exhibits the symptom(s) described in the PI.

Condition/Concern:

The #2 lower body cradle mount may be moving within the cradle mounting hole on either side of the car. This may exhibit a pop noise in the footwell area during hard acceleration, braking or turning maneuvers. This noise may also occur while driving on rough roads.

Recommendation/Instructions:

Remove the lower portion of the #2 cradle mount (The second mount from the front of the car under the longitudinal body rail which is closest to the stabilizer bar) and apply epoxy material around the perimeter of the mount and reinstall it. Make sure the mount is clean and free of rubber flashing in the area in which the adhesive will be applied. The mount must be reinstalled prior to the epoxy "Setting Up" (Usually around 15 minutes). Perform this operation on both the left and right side mounts and allow the vehicle to sit for 2 hours after reinstallation.

Please follow this diagnosis process thoroughly and complete each step. If the condition exhibited is resolved without completing every step, the remaining steps do not need to be performed.

Models:

(2000-2004 Cadillac DeVille) and (2000-2004 Cadillac Seville) and (2000-2004 Buick LeSabre) and (2000-2004 Buick Park Avenue) and (2000-2004 Pontiac Bonneville) and (2001-2003 Oldsmobile Aurora)

.............................

Loud Pop from A-Pillar Area When Going Over Bumps - kw front noise pop strut suspension #PIC3070 - (07/27/2004)

The following diagnosis might be helpful if the vehicle exhibits the symptom described in the PI.

Condition/Concern:

Loud pop from A-pillar area when going over bumps.

Recommendation/Instructions:

Noise may be caused by a slip/stick condition between strut and upper mount bushing, right below the threaded portion of the strut piston. To diagnose this noise, with the suspension loaded, remove the upper strut attachment nut and bevelled washer at the top of the strut tower. Spray lubricant into bushing sleeve between the strut piston and steel bushing in the upper mount. Reassemble and road test to check for improvement.

To permanently correct noise, following published service procedures, remove strut from vehicle and remove the strut bushing plate. Clean any penetrating oil residue with a solvent such as brake parts cleaner P/N 12378392 (In Canada, 88901247). Wrap upper strut piston at bushing surface with mylar tape, P/N 22602686 to eliminate possible movement. ONLY WRAP WITH TAPE UNTIL STRUT PISTON TO PLATE BUSHING CLEARANCE IS EFFECTIVELY MINIMIZED. Lubricate base of bushing in upper strut mount with Silicone based brake lubricant, P/N 89021537 (In Canada, 89021538). Reassemble per service information.

.........................................................

Squeak/Squawk Noise from Front of Vehicle When Traveling over Road Bumps/Swells (Replace Front Spring Seat and Upper Insulator) #02-03-08-004 - (04/09/2002)

Models: 2000 2001 Buick LeSabre, Park Avenue

1998 2001 Cadillac Seville

2000 2001 Cadillac DeVille

2001 Oldsmobile Aurora

2000 2001 Pontiac Bonneville

Condition

Some customers may comment on a squeak, squawk or creak noise from the left or right front of the vehicle heard in the passenger compartment as the vehicle travels over bumps or swells in the road.

Cause

This condition may be due to a front suspension strut spring wearing through the spring upper insulator and making contact with the spring seat.

Correction

Verify the vehicle condition and perform the front suspension and/or strut noise diagnostic procedure. Refer to the Suspension General Diagnosis sub-section of the appropriate Service Manual.

Important: Carefully inspect all of the strut assembly components for damage.

If the condition is due to the spring making contact with the spring seat, replace the existing front spring seat and the front spring upper insulator. Refer to the appropriate Service Manual for the Strut, Strut Component and/or Spring Replacement procedures.

................................................................................

Could be the exhaust system is expanding as it heats up.

Maybe damaged Air Pump.

[Ion]

I'm sure I've seen this posted before, either here or on the other board, but I can't find it.

When my car warms up, there are 3 distinct tapping noises that occur in succession. Tap, tap, tap. It sounds like it's coming from the engine, but it's hard to track down. It sounds like a little man inside the car somewhere with a little miner's hammer...knock, knock, knock. When it does occur (probably half of the mornings), it occurs at the exact same place on the temperature gauge (about the 10:30 position). It doesn't matter which road I drive out of the neighborhood; it doesn't matter what the ambient temperature is outside. It's just three quick taps and that's it. It'll never do it again until the next day (or the following day).

The only reason I post this is because I just KNOW I've seen a fix posted before for it...I just can't find it. Anyone remember such an issue?

While trying to troubleshoot my '94 Eldo's issues, I heard the same sounds. It was coming from the throttle body "butterfly" valve opening and closing against it's frame. Check your error codes and see what, if anything, it reveals. I'll bet it related to either your TPS or MAP sensors.

[Dadillac]

I'm sure I've seen this posted before, either here or on the other board, but I can't find it.

When my car warms up, there are 3 distinct tapping noises that occur in succession. Tap, tap, tap. It sounds like it's coming from the engine, but it's hard to track down. It sounds like a little man inside the car somewhere with a little miner's hammer...knock, knock, knock. When it does occur (probably half of the mornings), it occurs at the exact same place on the temperature gauge (about the 10:30 position). It doesn't matter which road I drive out of the neighborhood; it doesn't matter what the ambient temperature is outside. It's just three quick taps and that's it. It'll never do it again until the next day (or the following day).

The only reason I post this is because I just KNOW I've seen a fix posted before for it...I just can't find it. Anyone remember such an issue?

I have the exact same noise from my car. It happens at exactly the same temperature every day, just as yours does. I am almost certain that it is the emissions canister under the drivers side of the car, just in front of the rear tire. One morning, look under there and you will see a black box with wiring harnesses connected to it. Start your car and when it gets close to the temp, go near the black box. you will hear a distinct tapping sound. That is the only thing that I have been able to figure it can be.

Don

[JasonA]

I have the exact same noise from my car. It happens at exactly the same temperature every day, just as yours does. I am almost certain that it is the emissions canister under the drivers side of the car, just in front of the rear tire. One morning, look under there and you will see a black box with wiring harnesses connected to it. Start your car and when it gets close to the temp, go near the black box. you will hear a distinct tapping sound. That is the only thing that I have been able to figure it can be.

Don

Don, my hunch deep down was that it's from an emission control device, only because the ONLY way I can predict it is from the coolant temperature. It's not bump-related at all. Thanks for the tip on the emissions canister. When you listen for the tapping down at the box, are you only hearing 2 or 3 or 4 tapping noises, then silence? It's so weird, but it's so distinguishable from the other various noises the car makes from the engine running to an open window, etc.

[Dadillac]

When I first started hearing the noise, like you, I heard a tap tap tap. I initially thought I was hearing it from over my left shoulder. Then i figured it was coming from the engine bay by the firewall. When I listen to the emissions canister, I hear what sounds like a rubber bladder moving. I hear four distinct noises. It just seemd very strange that it happened when the temp hit its special mark. I discovered this when I was replacing my rear brake line. I had the car on jackstands, with the engine running. I was working the brakes, as well as the e-brake cable. I went under the car to check for leaks, when I was surprised by the noise. I quickly got out from under the car to check the temp gauge, and guess where it was. I am not sure that the canister is supposed to make the noise or not, nut at least I know where it is coming from.

Don

[JasonA]

I originally said that mine wasn't ambient temperature-related, but I think it is, to some degree. That is, I think I remember hearing it when I first got the car last winter/spring. But it didn't do it all summer. Now that it's cooled off again, I'm hearing it again in the morning. Don, does yours do it year-round, or only during the colder months?

[Dadillac]

Year round for my car.

Don

[GreenMachine]

guess cadillac did their job of making a near silent powertrain that you guys are picking up on this