When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
So my sister just bought a 99 E350 with the V10. 150k miles. When she bought it it was making a knocking noise. The previous owner said it had been making the noise for awhile. The van seemed to run just fine. She just drove 1,000+ miles out to me and now I'm borrowing the van to transport some stuff around town and I'm a little worried. It's a pretty loud knock. I haven't had time to poke around the engine with a screwdriver to my ear and probably won't have time to do that for another week so I figured I'd post.
The knocking seems like it's dependent on throttle position / load. Nothing at idle. Nothing at low throttle positions (0-15%). It starts at about 15% throttle and gets worse (louder and higher frequency) up to 40% throttle. If you go past 40% throttle it disappears completely. That's the weird part to me. Give it more gas and it goes away. I could be way off on the throttle positions but you get the idea. If you want to cruise on a level road at 70mph the engine will be knocking. As soon as you go up a hill at 70 the extra throttle makes the noise disappear. It's not RPM dependent because the noise goes away instantly when you give it more gas. Any ideas?