One problem related to engine knocking noise has been reported for the 2004 Volkswagen Passat. The most recently reported issues are listed below. Please also check out the statistics and reliability analysis of the 2004 Volkswagen Passat based on all problems reported for the 2004 Passat.
I purchased a used 2004 vw Passat with 34k miles in September 2007. The car was running file and has been kept current with oil changes. On April 3, 2009, my fiance was driving us home from work and a loud knocking noise started and a message displayed saying stop! oil pressure low. This has never happened before. We were still far from home so we pulled over and took a look under the hood. The oil was low for some reason, although it was recently changed, so we purchased a quart to get us home. We continued to drive home and starting losing power as this knocking noise continued. We did make it home. The car was towed from our home to a vw dealer the next day. We were told that the crank shaft was damaged due to oil sludge build-up in the engine. Basically, the engine was shot and I needed a new one, which would cost about $4k with about $2k in labor. The car only has 55k miles on it - how could this happen? we then went online and conducted a search. We found that this is a well-known problem with 1. 8 t engines between 2003-2005. I was mortified. I was never given any information from vw about this issue, although the car was purchased used. The dealer told us that vw extended the powertrain warranty for to 8 yrs due to this issue but we must provide oil change receipts. We had none, because not only did we not have ones from the previous owner, but my fiance changes my oil and although he used the required synthetic oil, the dealer told us that there are "approved brands" that must be used. We were never given this info because the owner manual only says use 5w40 or if not available, use 5w30 oil. So, we are left with nothing. It can cost anywhere between $4-8k to fix. The cost to get a new or used engine plus labor is ridiculous. I'm driving my old Honda that has 231k miles while my vw sits at the shop waiting to be fixed. I fear the bill. I planned to purchase a new vw in a couple years, but now I will never buy a vw again and will make sure my story is heard!!.