Knocking noise after cold start

[Josef161]

Hello i have a 2005 ford explorer xls. I noticed a knocking/ticking noise when i start the vehicle. The noise only appears if the engine is cold and it seems to be coming from the bottom of the engine or transmission. I researched it and only found out that it should be a rod knock or bad rocker arm (but those should cause noise on the top of the engine or?). I dont think that it is the flexplate bc i have no issues with starting the engine.

 

[Rick]

Rocker arm noise would be from the top of the engine, rod knock from within the block.

A good way to listen for valvetrain noise is to use a long screwdriver as a stethoscope. Put the blade on the valve cover, and the plastic handle to your ear. If there is valvetrain noise you will definitely hear it. You can compare one side to the other, to isolate.

 

[Number4]

If it’s a rod knock, you should have glittery oil.

 

[Josef161]

Ok i just did that and i couldn't point it down to the valve train.

And I don't have glitter/metal shavings in the engine oil. But there was a lot of metal shavings in the transmission oil when i changed it (had to replace the solenoid pack too ever since then it runs good except a whinny noise that's probably coming from the transmission fluid pump).

 

[imp]

If it’s a rod knock, you should have glittery oil.

What is "glittery" oil?

 

[Number4]

What is "glittery" oil?

Metal shavings. Or flakes.

 

[Josef161]

Ohh they are metal flakes (my first language is German, sorry for that).

 

[Josef161]

Figured out that it is almost for sure a bad cat. The OBD2 reader says that the cat is "incorrect" and the noise is coming from that area. I guess that my problem is "solved" for now. Thank you all

 

[Number4]

I’ve done my timing, albeit 100k miles ago. But my rattling is different now and it’s not the cat conv heat shield. I suspect it’s the cat(s) for a couple reasons.
1. When reversing and coming to a stop, there’s a bad gas smell.
2. MPG’s have gone down
3. Happens randomly but mostly under hard acceleration.

No codes, fuel trims are fine.