Thump and sometimes SCRAPING noise 1-4sec after engine start

[BLandau]

After starting the engine, I will hear a thump from the floor board area. Twice I have heard a SCRAPING noise for about 2seconds. All of the noises usually occur between 1-4 seconds after startup. I am not sure if the two are related. I am very concerned about the grinding noise. I have also had one instance of the truck starting properly, but during my acceleration onto the main road, I heard a scraping noise from the engine compartment. When I would let off the throttle, the noise would stop. After about 20sec of drive time on the main road, the noise went away. The scraping while driving has only occurred once.



Her are the facts:



1. I hear the thump nearly every time I start the truck. (HVAC damper?)

2. I hear the scraping/grinding noise after the truck has sat for an extended period (8+ hours)

3. Both noises appear to be resonating from the center floor board area towards the engine.

4. 6. 7 engine with Auto Trans

5. 22,000miles on vehicle

 

[mcurtice1]

I have the same experience with my truck. Evertime I start it up I get the scraping sounds. I think it started when I had the recall done last year.

 

[TAbbott]

My bet is that it's the A/C clutch engaging. The scraping sound could mean that it's slipping a little when it locks in.

 

[mattymac]

My bet is that it's the A/C clutch engaging. The scraping sound could mean that it's slipping a little when it locks in.

X's 2 ^^^^

 

[BLandau]

Yes, but the sound does not seem to be quite that far forward. I have check the past few days and not heard a thing.



Do you think it could be the engine or transmission starved for oil upon startup??

 

[grasmo]

Mine makes a weird noise at random... . swear it sounds like a bicycle went under my truck... ... and occasionally it sounds like a backfire/thump. I have actually gotten out on 2-3 occasions to look under my truck and see if I have backed over a bicycle.

 

[TAbbott]

Pretty easy to rule out if it's the a/c or not. Start the engine with the a/c and defroster off. If no sound in a few seconds, turn on the a/c and see what happens... .

 

[EArp]

x3 on the A/C clutch. Mine was making the exact same sound as you're describing. Seems like it only does it if I haven't driven the truck in a couple days. From what i've researched, if it is the A/C clutch it's a relatively normal thing for our trucks and is nothing to worry about in spite of how terrible it sounds.

 

[snidley1]

Yeah mine too!!!

 

[Trashdawg]

X5 does w/AC on, and thump from vent doors closing.

 

[Garry Verheyden]

I think it's just the egr vave opening up to let the engine warm up quicker on start up. I bet the scraping sound is the cable moving on the egr valve on exhaust manifold.

 

[grasmo]

Very probable Garry Verheyden!

 

[BLandau]

I think it's just the egr vave opening up to let the engine warm up quicker on start up. I bet the scraping sound is the cable moving on the egr valve on exhaust manifold.

I am checking every day, but the noise has not happened lately.



As I recall, the noise sounded rotational or cyclic. Again this happend for a couple of seconds before stopping. Do you still think it might be the EGR valve?

 

[Garry Verheyden]

I think likely. It could be that the egr isn't open until you are running less boost. It could be that when you slow down near the intersection, the boost decreases as you let off the throttle, then the egr valve opens back up. Just guessing though!

 

[jmorse]

The variable turbo closing for engine warm up makes a thump on my C&C. As for the scraping noise, I,ve never heard that on my truck.



Jim

 

[EStarns]

The pump for the ABS makes a noise like you are describing. Occasionally it will happen just after a startup. It's not a problem but it is an odd noise. My 6. 7 has done it a couple of times. Had a old Jeep that did it a lot so got used to it.

Dave

2007 6. 7 quad cab longbed Inferno Red Insight guages