> 2. unless you strip the motor, it's hard [and unusual] to remove a seal
> without damaging the seal running surface. if that gets scratched, any
> new seal is going to have a hard time sealing and won't last.
>> 2. unless you strip the motor, it's hard [and unusual] to remove a seal
>> without damaging the seal running surface. if that gets scratched, any
>> new seal is going to have a hard time sealing and won't last.
>
> If you can't get the seal out without scratching its bore, then you should
> definitely leave it alone.
not the bore, the shaft that the seal lip runs against.
> However, replacing the seals was standard
> practice at the independent Honda shop I worked at.
that's my point. "standard practice" why? has anyone done any testing?
or is "standard practice" slavishly following the other "standard
practice" of every other shop that inherited its ideas from detroit?
> It's fairly easy to get
> the old seals out without any problems using a small straight bladed screw
> driver. Indeed, I along with the other techs in the shop did it all the
> time and never had any problems.
how do you know? did you monitor vehicles after the work was done?
were comparisons done with vehicles where original seals were left in?
>
>> don't just slavishy follow bad habits born of mechanics
[quoted text clipped - 4 lines]
> nor do I consider my 10 years of professional experience to have been
> plagued by bad habits.
just doing something because it's "standard practice" and not analyzing
the problem is a bad habit.
> Moreover, a shop tech cannot control the type of oil
> someone puts in their engine at some point in the future.
that's true, but you can advise a client on what works best.
> Replacing the
> seals is therefore a good practice to ensure that the timing belt stays dry
> avoiding costly comebacks.
so really, "standard practice" is born of fear of comebacks, not
reliability analysis. and why not - the customer pays.
> In addition, in replacing the timing belt the
> gears are typically removed and cleaned which leaves the seals exposed. The
> cost of the seals and the small amount of labor is trivial compared to the
> cost of a prematurely failed timing belt due to oil contamination.
have you ever seen a timing belt contaminated by oil? i've seen engines
piss-wet with oil, but not a drop on the belt due to the pulley design.
bottom line eric, you're probably a sincere and conscientious guy that's
doing what he believes best based on what he was taught. but things we
get taught and which we then replicate, are not always best, simply
repetition of what we were taught.
another example is skimming heads when doing head gaskets. if the
head's not warped or pitted, it's inadvisable because it affects [albeit
to a small extent] the valve timing, compression ratio and surface
finish. it can also introduce grit to the motor thereby reducing life
significantly and leave the head scored making the gasket leak again.
but it's almost /always/ done. why?
1. it's quicker than cleaning the head instead.
2. fear of comebacks - "covering the bases".
3. it's "standard practice".
returning to seal replacement, the most vulnerable seal in the whole
motor, [apart from the distributor which for some reason always leaks
like crazy] is the output seal. but you can't get at that without
taking out the transmission. so it /never/ gets changed - not with the
timing belt anyway and hardly ever with a clutch. people only change
the other seals they can easily get at. and the customer pays. but
logically, if you're going to change seals, change them /all/.