Date: Thu, 13 May 2004 14:36:18 GMT From: -Bob- <uctraingNOSPAMnospamanet.com> Subject: Re: Timing Belts (was Re: Cost of repair Audi BMW Saab...(crossposting))
On Thu, 13 May 2004 14:22:37 GMT, "eBob.com" <eBob.comnospamllybogus.com> wrote: >That's interesting. Since all of the brands of cars which I have owned have >had them, I just assumed ... > >Anyway, how 'bout educating me on two things. Just exactly what do timing >belts do? (Yes, I am pretty dumb in this area.) And what do the BMWs w/o >timing belts have which perform that function? > >Thanks, Bob Timing belts or chains connect the crankshaft to the camshaft(s). As the crankshaft turns, the cams are rotated to open and close the valves. In the old days they always used chains. Chains tend to be a little noisier - not much, just a little. In an attempt to eliminate the sound, very slight additional vibration, and to cut production costs, many manufacturers started using timing belts. Because it's a high stress application, timing belts typically go 60K miles although some now go 100K miles. Chains last well over 100K miles in most engines. The failure of a timing belt can range from "you stop and call a tow truck" to "you just destroyed your valves, pistons, and are looking at $3-6K in repair costs". That depends on engine design and is related to a whole bunch of other issues. That is, it's not that engineers can't design engines that fail gracefully when the belt goes, it's that it forces other compromises to use that type of design. Replacement of a timing belt ranges from $250 to $600 with most engines.
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