Oil type and timing chain rattle on start-up
 

Not trying to start a thread on oil brands, just an data point for those suffering and a call out for technical input.

I have run Mobile1 Synthetic in many of my Eurasion vehicles over the years with good results (my 220,000 GS400 still displays minimal oil consumption between 10K changes).

I am too swamped for a DIY at the moment, so I had my local shop change my oil recently. They filled my 2002 S (81,000) with Motul synthetic 5W-40 instead of M1 synthetic 0W-40 I've used at home.

When I picked up the car, there was zero rattle on start-up. Engine was cold, so I assumed someone had recently moved the car outside and that the tensioners were still full of oil. The next morning when I started the engine The lack of noise got my attention. There was a barely audible difference in mechanical noise for the first .10th of a second, but not really what could be considered a rattle. The car is no longer "embarrassing" to cold start up in front of people.:o

Can any one explain why heavier weight oil would pressurize the tensioners faster than lighter weight oil...especially on sub freezing mornings?

I'm baffled by this.

higher cold weight means less drain-down and ensures that a light film of oil remains on the chains/pads for start-up. i only run 5w40 and, with the oil piston update, no longer have start-up rattle.

Higher base weight oils typically demonstrate higher film strength than their lower base weight analogs. This increase in film strength results in slower drain down over time and that gives better parts coating at start up. What you are seeing is the most commonly observed result.

Hey King,
What is this oil piston update you speak of?

I've tried everything from 0- 40 to 20-50 oil in my car and the startup rattle does not go away. I've also replaced the lower two tensioners with no change. one of these days I may replace the upper tensioner but for the moment I just live with the start up rattle.

part # 26 in the attached link:

Oil Pump

note that it is a 997 part number. it is beveled where the original was square. my understanding (worth what you pay for it on the internet) is that the original was binding, and the role of the piston is to increase oil pressure at start-up. a 5-minute job at your next oil change.

it's an interesting exercise to go through the parts catalog and look for superseded part numbers and 997 part numbers - aos for example ...

Thanks! I've got some rattle, maybe this will help.

I did this two oil changes ago and it was very easy to do and only a few $$$.

Is this readily accessible from the bottom of the engine?

Did that, no change in the start up rattle, but definitely something you should do.

It is, I don't think I had to remove any panels or anything to get to it, I think it was right in front of the sump cover.

I think it was parts 5, 25, and 26 that I replaced from this diagram.

http://www.********************************************.com/porsche-parts/hardparts.php?dir=986-97-04&section=104-00

It was easily accessible from the bottom. And now maybe I am remembering that I did need to remove the rearmost plastic underbody tray... It has been a while :)

Tightening torque for the bolt (part 4 in the diagram) is 25NM/18FT/LB.

Thanks! Appreciate the info.

You might ask Jake if he will part with a couple of his master link chains so you can cut yours out and replace them with new without the inconvenience of removing and completely disassembling the engine. It may be stretched (read that worn) chains contributing as much or more to the rattle than weak tensioners.

Wow I would like to know how this is accomplished with the engine in the car!

Oil does impact tensioner rattle.. This is in part to the way oils will retain pressure in their tensors, as well as how well the boundary layer protection is able to buffer the sound of the chains.

Oils high in Moly love tensioners. The best oil to quieten tensioners has always been redline. Our latest generation of DT40 is the best its ever been for this, as well.

I tried Redline and as the french say, no diffrance.

Wow. Thanks for tHe tip, but I have to say Im not that ambitious. Many many of 986 and 996 motors rattle on startup but apparently there is no correlation between start up rattle and engine failure. Its one of the quirks of the brand, like when I had Alfa Romeos, the synchros were horrible, but you learned how to double clutch and they drove wonderfully.

Then you have a tensioner issue, or chain issue, or both. The IMS tensioner is the worst for this, and as it rattles it hammers on the IMS bearing, and it's tensioner paddle and wear pad. I think this contributes at least some to IMSB failure.

Its not a normal occurrence; just because most do it, doesn't make it mechanically acceptable. The tensioners for 5 chain engines have been revised 7 times, 3 chain have been revised 3 times.

If its rattling at start up, things are wearing. Period.

A huge amount of preventative packages we are doing these days end up getting chains, as most are stretched and send the tensioners out of range.

Thanks, Jake. I always knew this was coming, but never knew the exact timing. When I asked about this in December/January, last year, the timing was not known, and you had a good inventory of the first gen DT40. When did the update take place? Is there a way to know if the new formula is in the bottle by looking at a specific code or something? Thanks again.

DT40 has been a continual development since it's conception as "JD Raby's Snake Oil".

The product changed last year, as you are referring to. The new batch is fully developed and is just awaiting blending, and bottling. This newer version improves MPG, helps with tensioner quietness and has proven to pick up a few more ponies in the top end.