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  #1  
Old 11-10-2000, 06:50 PM
Nick Jamal
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I suppose this post is directed toward those brave souls that make it a point to check out each and every post (ahem, Larry...)
Been looking at a couple of Volvos recently, and just wondering why more manufacturers haven't engineered their engines with timing chains (vs. belts), as MB has for years and years. Even Volvos, with their reputation for longevity, deserved or otherwise, have belts - increasing the risk of catastrophe - I think (this from my inexperienced little brain...)
Why?
Have a great weekend, everyone.
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  #2  
Old 11-10-2000, 08:05 PM
djenkins2
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I can think of two reasonable ones. The first would have to be cost. The belt has to be cheaper than the chain in general. Second....the belt runs in a dry environment, and hence doesn't require any lubrication. The obvious drawback is the periodic changeouts of the belt,, typically 60K miles. Since most OHC belt driven transverse engines are not interference engines (I don't know of any these days....) the risk of bending valves when and if the belt snaps is nil. So probably a combination of cost and not having to include lubrication in the basic design.

And although most shops charge typically $150-250 or so to put in a new belt.....it really is pretty easy on a SOHC engine.
Some of the painful engines i.e. like the 89-94 Talon/laser/mitsu DOHC interference engines... actually have 6 separate belts on the cam drive side of the engine, i.e. timimg belt, oil pump belt, balance shaft belt, a/c belt, p/s belt and alternator belt. This is an exception..compared to say a SOHC engine, which can be changed in an hour or so.

But if I were the design guy,,,,I would go for the chain and make the beancounters include the cost. Less maintenance. I personally would pay for the difference as a customer.




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  #3  
Old 11-10-2000, 08:05 PM
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Join Date: Jan 2000
Location: Maryland. USA
Posts: 180
I own Volvos and Benz's. SO here's my two cents worth.

I used to own a 75 Volvo with the B20 engine. It used timings gears (no chain). The OEM gears were synthetic and prone to catastrophic failure, e.g. bent valves etc. They originally used synthetic gears to reduce noise. The after market/OEM steel replacement came along to resolve the failure issue.

I now own a Volvo with the B21 engine. It is the timing belt that you speak of. I have many shade tree mechaninc friends who own Volvos and the conclusion we've all come to is that the belts fail for two reasons. 1) failure to R&R every 50k miles or 2) failure to R&R if they get oil soaked (It is not uncommon for the B21 engine crankcase pressure to blow by the front and rear seals (this mainly happens because folks don't clen or R&R the crankcase ventilation)). R&R of the belt and/or the front seals is not a demanding task. I'm living proof of that and its a job that I don't particulary dread.

Benz chains on V-8s. They certainly learned their lesson on the 3.8 liter US motors (single row vice double row). Again the only thing I can fathom is noise reduction. Double row on everything but those. Chains vs belts? In this case I think chain makes more sense. TO R&R a belt every 50K would require a complete front end tear down to open the space. That's a lot of hours. At least with the chain, if you R&R oil$filter every 3k, inspect your topside every 15-30k, measure chain stretch using the degree difference method (difference between the CAM marks matched against the degrees difference at the balancer, and the listen for not so right noises right at start up (and head them), then it should last at least a 100k. I'm at 130k and 7 degrees. Benz doesn't make cam correction shims(?) for anything past 10 degrees, so I'm due to change mine soon.

The job I do dread is the one before me of R&R of the chain, tensioner, tops rails and/or bottom-side rails and gears for my 117 engine (80 450SEL). Why? Never done it before and I will have to acquire a new tool or two. And there is the added stress of doubt associated with "do I R&R all of the rails as a precaution, or just the phenalic rails? Do I use a chain with links that require peening or side lock? blah blah blah.

Well anyway. Those are my ramblings for the night. FOr our U.S. readers, take the time to thank a vet this weekend. They doing great work out there. I can say that from a position of personal knowledge.




------------------
S, J.R. Brown
1986 280GE LWB Anthracite
1980 450SEL Champange
1981 Volvo 240DL UPS Brown
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  #4  
Old 11-10-2000, 09:25 PM
Nick Jamal
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Incredible what you learn on this board... thank you both for your insight.
J.R., as a Volvo owner (even if it is UPS Brown!) and a man of mechanical means, it seems, do you know much about the '92 - '95 940 Turbo engines - any recommendations one way or the other? I'd welcome any comments on this please!
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  #5  
Old 11-11-2000, 09:09 AM
LarryBible
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Good thread!

Anyone who has read many of my "stubborn old man" posts knows that I like timing chains and overkill oil changing. These two go together well IF you are looking for very high engine life, rather than trading cars frequently.

In my experience, my overkill oil changes virtually prevent ANY timing chain stretch. By keeping the microscopic particulate matter out of the engine, timing chains benefit as much or more than any other internal engine component.

Before I bought my C240 when I was afoot a few months ago, I considered a Beetle/Jetta with a 1.9 diesel and a five speed. I considered this as a commuter car. Two things kept me from buying one; I don't like driving and working on a front wheel drive car, and they have timing belts. To make this car worse, it's a front wheel drive car with a timing belt, making it more difficult to change.

I believe timing belts are used to save bucks for mfg. I also believe that front wheel drive vehicles are built to save bucks for the mfg. This nice engine/trans/driveaxle unit comes down the assembly line and is plunked in with little labor. The unit itself is manuafactured cheaper than three seperate units would be as well. So, the manufacturers did a great job of convincing zillions of people that front wheel drive is superior.

Sorry to go off on the tangent, but it does add to my point. The mfg's are in business to make money and if they treat me fairly, I have no problem with that. Timing belts are a way to save money when producing the car, and generate more money into the service side of their business for their dealer network.

I realize that not all timing chain systems are trouble free, but many are.

In my life I've owned one car with a timing belt. My wife bought a Toyota 4Runner with a V6. It has a timing belt, and the recommendation is 90,000 mile replacement if engine is in severe duty. I saw a post by someone on another subject where they said that their wife driving a car constitutes severe duty. I consider that as good advice. My wife doesn't really submit a car to severe duty, but I don't want her stranded by the road, so I will proceed with a maintenance schedule as if it were severe duty.

So as you can see, I'll take front engine, rear wheel drive and a timing chain, over a combination that includes either one of these two.

Good luck,

------------------
Larry Bible
'01 C Class, Six Speed
'84 Euro 240D, manual, 533K miles
'88 300E 5 Speed
'81 300D Daughter's Car
Over 800,000 miles in
Mercedes automobiles
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  #6  
Old 11-11-2000, 10:14 AM
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Join Date: Jan 2000
Location: Maryland. USA
Posts: 180
Nick, I've been looking at replacing the ol' trusty swedish steed. Haven't finished my research on the 900 series. However, there are lots of 200 series on the road and lots of parts and after market stuff (IPD). Recommend you checkout Consumer Reports regarding reliability for those year models. I haven't yet.

Larry, Concur about the manufacturers' cost incentives to go belts and the oil changes.



------------------
S, J.R. Brown
1986 280GE LWB Anthracite
1980 450SEL Champange
1981 Volvo 240DL UPS Brown
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