When first start engine makes a noise in the front of the engine

Tiny
ANONYMOUS
  • MEMBER
  • 2005 CADILLAC CTS
  • 120,000 MILES
Hello and thank you for taking my question. When I first start up my car after about 2 seconds, it makes a weird noise in the front of the engine like a machine gun going off. Rat-tat-tat-tat-tat, then stops. What is that?
Sunday, March 17th, 2013 AT 8:27 PM

3 Replies

Tiny
RANDICO
  • MECHANIC
  • 174 POSTS
Sound like a lifter noise, when the vehicle sit for a period of time oil drains out of the lifter and when you start it up it refills, Now this is normal if its about 2 seconds if it was 3 minutes or longer than you have a problem.
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Sunday, March 17th, 2013 AT 9:52 PM
Tiny
CADIEMAN
  • MECHANIC
  • 3,544 POSTS
Take it to the dealer and leave it overnight. Have them check it in the morning when first started. A noise like this will be under warranty still because it's in the engine. If they don't do anything about it make sure to talk to the factory representative. He can push to dealer to get the car repaired properly.
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Friday, April 26th, 2013 AT 11:23 PM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 108,005 POSTS
Hi,

The idea that it sounds like a machine gun is a concern. A collapsed lifter or low oil pressure can cause the lifters to make a tapping noise.

Here is what I suggest. First, open the hood and confirm the accessory drive belt is good. Stand back and allow a helper to start the engine while you try to identify an approximately location of the noise. Let me know what you find.

Also, you may want to consider confirming oil pressure when first started. Basically, all that is done is you remove the electric oil pressure switch and screw in a mechanical gauge. That way we could confirm the pressure isn't an issue. I attached a pic below showing the location of the sensor. See pic 1

One other concern is this. There have been technical service bulletins out related to valve noise on cold starts. The cause is a faulty o-ring where the oil pump pick up tube and block leak. Here is a portion of the bulletin. Please read through it and see if the symptoms are what you experience.

___________________________

Condition/Concern
A Customer may complain of a ticking noise or oil pressure fluctuation on cold start after sitting more than 6 hours or possible DTC's P05CF or P05CE.

The engine will usually start quiet, then make a ticking noise after a few seconds that lasts about 3 - 15 seconds and then go away for the rest of the day, or possibly set DTC's P05CF or P05CE and the oil pressure will continue to fluctuate.

Recommendation/Instructions
We have identified a possible concern with the oil pump pick-up tube to block seal being compressed. When this occurs there is the potential to draw in air when first started before the pump picks up oil to seal the gap,

Or to continue to pull some air causing oil pressure fluctuation.

If you encounter this concern, remove the oil pan and inspect the seal.

Note: THIS CONCERN IS MORE PREVALENT ON 50,000 MILE OR HIGHER ENGINES.

If this seal is compressed within the cutout of the pick-up tube, then replace the seal and reevaluate the concern.

(See Pictures Below)

Pic 2
This is an example of a new seal

pic 3
This is an example of a compressed (worn out) seal

_______________________________

Let me know if this helps or if you have other questions.

Take care,
Joe
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Friday, April 24th, 2020 AT 7:01 PM

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