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Old 12-03-2012, 06:22 AM
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DHoang DHoang is offline
Gearhead
Location: Austin, Texas
 
Join Date: Dec 2008
Posts: 982
Mein Auto: '98 528i, '82 323i
Quote:
Originally Posted by vavet5308 View Post
e Let's say you need to replace the valve cover gasket ($50). Well, while you're at it you could also
rebuild the VANOS ($140 for the seals and washers)
replace the spark plugs ($10 each online, $25 from the dealer)
ignition coils ($60 each)
replace the secondary air valve ($100) and vacuum line($20)
oxygen sensors ($100 x4).
It's true, all this work does require some of the same preparation to gain access to where you're going, but you've just turned a $50 valve cover gasket job into a $1000 job replacing a lot of components that will eventually need to replaced, but are fine for the time being. it's unlikely any of these parts will fail catastrophically and leave you stranded so unless you're doing a lot of long-haul driving, my advice is to wait until they need to be replaced. This advice does NOT apply to the cooling system.
i'm on the opposing side here...b/c if you're already in there, you may as well change anything you can gain access to. Just take the costly hit once, reset your parts baseline, and you be proactive in maintaining your car's relative health, not let the car dictate your time and cost.

And even though those parts listed may not leave you stranded, but by the time you figure out that they need to be replaced, the failed parts cold cause problems for other parts down stream. Take oxy sensors. if failed, you could have been running too lean or too rich w/o knowing. Both cases, you subject your costly catalytic converters to a period of damage.
vanos seal....if you wait until they are a goner, by then, the solenoid would have rubbed itself raw against the sidewalls, and so instead of just replacing a $50 beisan seal, you could be looking at a complete vanos unit due to a scored or out of round cyl wall.
2nd air valve. if the valve is left until it's 100% failed, it could take out the pump.
spark plugs...can't imagine why anyone would reuse old spark plugs after a gasket change. They're so cheap, and besides, for 100% combustion seal, you cannot reuse old plugs b/c the washer is a crush washer, a one time use.
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