Gethen

Pardon my ignorance, but which is more superior - timing belt or chain? Chain seems like a more durable option to me, less maintenance spending. So why MB uses timing belts?

patrick

Which MB has a timing belt???????

Gethen

Doesn't term "poly-V belt drive" imply use of timing belt? Specifically talking about 2003 E320

patrick

No.

suginami

The Poly V belt drive is the belt that runs your alternator, a/c compressor, and water pump.

A timing chain (or belt) connects your crankshaft to your camshaft(s), which opens and closes your valves.

Mercedes has never used timing belts. They always use a chain.

sosh

Timing chains are far longer lasting than belts and are much more durable. Only advantage of a belt is that they are quieter and easier to replace which is good as for the fact they generally last only 50000 miles. Most Japanese cars and some European cars use belts. I know of no German cars that do. Volvo did and may still use belts. Many poeople who have belted cars ignore the change, usually with catestrophic results

mleskovar

Chains are more durable and I believe just as easy/hard to replace. In the past belts were more quiet but I don't think that's true anymore...I don't hear MB chain noise in their modern engines...do you?

suginami

I sincerely believe it depends on the car whether or not a chain or a belt is easy or hard to replace.

You guys are right. The benefits of a belt over a chain is that they were quieter and much cheaper.

The problem is that belts wear out quickly and need to be replaced every 60,000 miles and chains, in some cars, will last the life of the car.

Nektopoli

My old 450 SLC had dual row timing chains on both banks, it threw both chains on the same side, the engine wouldn't rev over 5000 RPM but I was still able to drive it to the shop, the only damage other then the two chains(and tensioner) was the spark plugs and wires. The old 3.8L V8s had a single row timing chain which I believe MB will still convert to dual row free of charge to this day.

My Toyota MR2 has a timing belt, but it's a Non-interfrence motor, if the belt snaps the pistons don't come in contact with the vavles.

NP

Gethen

Thanks for explaining this stuff! Here is another one:

If poly-V belt breaks, multiple pieces stop working. Add multiple bends in the belt to the picture. Why not use multiple belts instead and so replace total system failure with partial failures?

sosh

Thats the way it used to be done. With the Serpintine poly belt it runs quieter, there is less slippage and the belt lasts much longer. In addition the belt is self adjusting, with the individual belts there was always a maint proceedure to re adjust the tension. I have had Poly belts last 50 to 60 thousand miles and have never had a failure. They should be replaced when they show some cracking or fraying at the edges.

patrick

How many MB's you know of have their poly-V-belt broken?

If something is (very) reliable, why change it or make it much more difficult than it should be?

Darkmann

Sosh is absolutely correct. I believe there's a safety issue here also. With individual belts, the only one that would not cause a serious problem if broken while driving is the A/C belt. All the others may cause problems. EG: water pump belt breaks ->overheating, probably b4 you know it. PWR Steering belt -> may loose vehicle control, etc, etc.

If the Poly V belt breaks, everything will gradually slow down safely.

mittalv

Someone mentioned above that NO German cars use belts for timing. Audi/VW use belts for timing and not chains. Porsche also uses belts on some models. Same hold true for BMWs. MBz seems to be the only manufacturer who has consistently used chains for timing.

I have found that the belts on my Volvo and Audi last 100K miles easily. Even then, they have had no cracks but I have replaced them to be safe. There are cases where the tensioner freezes prematurely causing the belt to snap.

However, I do prefer the chain in my S430 over a belt.

sosh

What I said was I did not know of any German cars with belts. I had forgotten that years ago my wife had an Audi that lunched the timing belt and the engine at 25000 miles. Ended up in court and she prevailed getting back the full purchase price of the car plus damages for breach of warranty. Would never consider owning one of those ever again.Re the BMW if any have had belts it must be the small 4 cyl 3 series. I have owned 5 Bimmers and all have had chains. I would really think twice before I bought any expensive performance or luxury vehicle that had a timing belt. Guess its OK for the small displacement economy cars.

Darkmann

Belts have come a long way though. Nissan recommends a 60K interval between belts for my 89 300ZX turbo. On my 95 Pathfinder, the interval went up to 105K. That's very impressive. However, in all their new cars (eve the new Z), Nissan switched to chains!!! Belts are very expensive to maintain and get more so for the high end luxury cars. The chains are a bit noisy, but companies like Nissan have managed to quietten them down substantialy. Don't chains require some service at some point?

mleskovar

Chains do not require maintenance because they are constantly lubricated with oil. They can stretch over time but not enough to cause problems. Yes, they can break as well. Somtimes pieces of links break and flop around causing a loud rattle. In the past MB (and others) had trouble with chain tensioners wearing and causing noise.

sosh

Chains require no service or adjusting. They are to be changed out at engine overhaul. As far as the increased duration of the belts in some Nissans good luck. One trip where the engine gets too warm not even overheat will cause the belt to become brittle and will drastially reduce its service life, by about half. Nissa dealers do lots of belt changes and in their service departments consider this a real profitable item. The new Z has a timing chain for a reason, figure it out!!

David N.

You are correct. The last bimmers to have timing belts were the old 4 cylinder e30's. e36's and e46's have chains (including 4 cylinder models). I don't believe any 5 or 7 series use belts either.