Hello Chaps -

So... the good ole Timing Chain Guides - the bane of existence to the M62TU engine.....

I have been around these engines for a few years now and have owned a few cars with this engine - both good and bad engines. Hopefully, it gives me a little bit of credibility on this issue.

The Timing Chain Guides on the M62TU engine and even the M62 (Non-VANOS) engine WILL FAIL at some point. It's inevitable. Past 100K is usually where owners have to start thinking about that repair job.

While replacing the Lower Timing Chain Tensioner is a prudent move, it only prolongs the life of the chain guides - if you are lucky to catch it before they start to deteriorate. It will however NOT prevent the eventual failure.

There are other corresponding things that contribute to this like the type of oil you use in the car and of course general maintenance.

The Tensioners come with a preload spring in them (This was revised at a later date) which is designed to pre-prime the tensioner at start up. This basically pushes the timing chains "off" the guides and once the car starts, the tensioner then operates using fluid pressure from the oil circulating in the engine.

As some posters have already pointed out - there are two types of start up rattles. The most commonly identified one are the chains literally slapping against the guides due to a failed or poor tensioner. This can be alleviated by replacing the tensioner. At the end of the day, replacing a $62 dollar part as insurance for your engine is worth it.

The second rattle is the VANOS rattle. This usually signals the start of the failure of your VANOS seals. Eventually, this rattle will turn into a constant rattling / dull clunking sound from the engine once warmed up. These days, you can get the Besian VANOS kit to replace your seals or replace the VANOS units at about $500 a piece + labor. The VANOS rattle will not kill your M62TU - it is just quite annoying to pull up to a light and sound like a diesel. Maybe just add a "D" to the car's model tag on the back and tell people it's a diesel

The issue with the timing guides is they are plastic - hard plastic, but plastic nonetheless. These will eventually failure through a number of reasons as mentioned in Bobzdar's post. However, it's not just heat cycles - it's plastic - it doesn't last forever. The chains are also metal and they DO rest against the guides (that's why they are called guides) and eventually the actually wear a groove into the guides which will eventually cause them to get slack and start slapping against the guides and then - BOOM! Eventual failure.

However, as importantly pointed out by Bob - they do tell you before they go. You will hear them rattle or start slapping around prior to catastrophic failure. I have never heard of any case where they JUST failed out of the blue. So, keep an ear out for that dreadful noise and if it does happen - stop driving the car and get it fixed.

I am happy to tell you that the M62TU engines themselves are quite sturdy and robust engines. If you intend to keep your car for a while it is worth the effort and cost to fix the guides and enjoy another 100K or more miles of driving pleasure. A dealer once reported a case where a lady brought in a 740i M-Sport with 198K miles when the guides failed. They fixed the guides for the owner and during the job, they took a peek at the short block and noticed barely any scarring on the cylinder walls - AT 198K MILES!

As far as your VANOS, I think they belief in the past was to use thicker oil or engine snake or voodoo oils to alleviate this - wrong! The issue with VANOS was a lack of oil around the seals and units at start up and during running. As we know, thick oil does not flow as well as thinner oil. THe better solution was to use lighter weight oil - and synthetic. Owners have had great success with oils like Mobil 1 Synthetic 0W/40 or 5W/40 or 30 oils. They leave a coating on the moving parts at shut down and flow tons faster at start up to help protect your moving bits and the VANOS units.

Eventually those seals do fail though and if you can't stand the noise, then you can acquire the Besian kits for a fix.

Cheers,

Michael

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