4m40 mystery noise

chuvsta · Post by **chuvsta** » Wed Jul 29, 2020 12:07 pm

Hey all,

I am new to the Canada forum so thank you for allowing me to be apart of this awesome resource. I just recently made the switch from a '93 L300 to a '94 L400. I have been hearing what almost sounds like a metallic slapping a noise coming from what seams like around my alternator, it is very pronounced at start up when cold and then after a few minutes it almost completely goes away. My first thought was timing chain rattle or maybe tubo, I did the old mechanics trick of putting a screwdriver to the timing cover in a few spots and putting my ear against it and from I could tell the sound wasn't coming from there. Haven't had time to take a look at the turbo. The previous owner replaced the alternator a few months back and didn't notice the sound until a few weeks ago before I purchased the van. Any insight is greatly appreciated. I have attached a video of the sound at startup and then after a few minutes.

https://youtu.be/t_5sBiLSe80

https://youtu.be/uxDbGgwLfp8

poochike · Post by **poochike** » Wed Jul 29, 2020 1:03 pm

Alternator could be loose. The mounting bolt is tough to get at and is often under torqued. Good place to start. While you're down there check for play on the turbo spool.

chuvsta · Post by **chuvsta** » Wed Jul 29, 2020 1:44 pm

poochike wrote: ↑Wed Jul 29, 2020 1:03 pm Alternator could be loose. The mounting bolt is tough to get at and is often under torqued. Good place to start. While you're down there check for play on the turbo spool.

Sounds good, I'll crawl under some time this week and take a look! Thanks.