Update: Camshaft Holder Seal Replacement (Oil in Spark Plug Tubes)

Discussion in 'General Motoring' started by Elle, Oct 21, 2005.

  1. Elle

    Elle Guest

    A few weeks ago I reported that my 91 Civic LX (manual transmission, 170k
    miles) was slowly accumulating oil in the spark plug tubes. Regular posters
    Eric and Tegger proposed that the cause was aging of the O-rings that are
    installed between the camshaft holders (also known as "camshaft bearing
    caps") and cylinder block, and around the spark plug tubes. They advised on
    how to replace them. From the archives, these O-rings do have a record of
    failing after mega miles. Not all Honda designs have them, but mine does.
    Today I replaced them. Here's the update and sequence of steps I took, for
    the archives. Thanks to Eric and Tegger for giving their time a few weeks
    ago to discuss this here.

    I bought new O-rings from www.slhonda.com . Three of them appear to be
    ordinary O-rings. If someone can confirm that the OEM ones are not made from
    some special, say heat resistant rubber, then I would be tempted to save
    several dollars and buy ordinary O-rings at my local True Value Hardware
    store. The fourth seal is a custom design. One can see all the O-rings at
    www.slhonda's parts drawings, under "Cylinder Head."

    I referred often to two sections in my Chilton's manual, as well as some
    notes I copied from this newsgroup. The two Chilton's sections are "Rocker
    Arms/Shafts Removal & Installation" and "Valve Lash."

    Disconnect negative battery lead.

    Block the car's back wheels. Put the front driver's side on a jackstand and
    remove the corresponding wheel, for access to the crankshaft pulley bolt.
    Put the car in neutral, to facilitate turning the crankshaft.

    Partially remove air intake housing so that the one piping connection to the
    valve cover is freed.

    Remove the valve cover.

    Set crankshaft so #1 Cylinder is at TDC of its compression stroke. Use the
    timing mark and a long screwdriver or other thin rod in #1 spark plug hole
    to feel for the piston at TDC. I also watched #1 cylinder's intake valve
    springs operate over a few revolutions of the crankshaft to identify when
    intake, and subsequently compression, were taking place.

    Loosen the lock nuts on all valves. Chilton's says to do this "two turns at
    a time, in a criss-cross pattern" to prevent damage, because the springs of
    the assembly are still loaded, and tolerances are close. Ultimately back off
    the valve lash adjusting screws at least until they become difficult to
    turn. Eric said to back them off until flush with the rocker arm, but I didn
    't like the resistance I was feeling, and so just made a large gap. (Before
    messing with the valve lash adjusting screws, I took some quick measurements
    of the lash ( = air gap between rocker arm and valve stem). They've never
    been messed with before, so I wanted to have a feel for how my gage would
    read, etc.)

    Loosen the 16 camshaft holder bolts in the opposite order that one is
    supposed to tighten them. (See a Chilton's manual or www.autozone.com 's
    free repair guides.) Loosen them like a half turn at a time, so the camshaft
    isn't distorted by the force of the assembly's springs. (This may have been
    overkill on my part, but I wasn't sure, so. )

    Then came the toughest part of this job: Freeing up the rocker arm/shaft
    assembly. It doesn't just lift off. The old oil and perhaps the seals I was
    trying to replace were baked into place after 14 years and 170k miles,
    gluing the thing down. I tapped and pried a bit. Use a rubber mallet,
    because the metal used under the valve cover is very soft. Tap, don't bang,
    because the camshaft lobes are mated against some of the lobes on the rocker
    arms, and tolerance are close. Tap in a lengthwise direction and pry only
    upwards. Tabs are on the outer corners of the two end camshaft holders that
    might help you to pry. A 12-inch crowbar ultimately freed one end. Then I
    found some more places to pry and it came off pretty easily.

    Removing the top half of the timing belt cover (two small bolts) might give
    you a bit more space to pry and so free the rocker arm/shaft assembly.

    Once the assembly was freed up, it wasn't too hard to maneuver it out, with
    all the bolts still in place like Eric and Tegger said earlier, and walk it
    over to a bench. Just don't turn the assembly sideways or upside down; then
    the bolts will fall out, and the assembly may come apart, whence I suspect
    life as you know it will end for a few days.

    I never actually set the valve lash before. Doing 16 of these is tiresome
    but got easier with each one. I double-checked (maybe triple-checked) that I
    had a feel that seemed right with the feeler gage. I aimed for the center of
    the specification but am sure I could be off by the 0.001 inch tolerance
    (but not more than that) allowed. (E.g. the intake valves are supposed to
    have a gap of 0.007 inch to 0.009 inch. I used the 0.008 inch feeler gage
    but tried to go a little tight.)

    The archives have some chatter about having to detension the timing belt to
    remove the camshaft holders. On the other hand, the Chilton manual's steps
    for removing the rocker arm/shaft assembly said nothing about this. Chilton
    manuals are not perfect, so I still prepared to at least loosen the
    tensioner adjusting bolt and so detension the timing belt. Getting the
    rubber blanking plug off to access this bolt was not looking easy.
    Fortunately and ultimately, I found doing so wasn't necessary. I did jiggle
    the crankshaft a little (five degrees?) clockwise when I was trying to free
    up the rocker arm assembly, thinking the timing belt was holding the
    camshaft lobes fixed and so making it harder to free up the rocker arm
    assembly. I thought turning the crankshaft a little clockwise would tend to
    detension the timing belt. I don't know if that was really necessary.

    Altogether this took about seven hours. I went very slowly and took breaks
    whenever I felt tired or a bit annoyed (really, only when trying to free up
    the rocker arm assembly), because doing so keeps me alert and less likely to
    say things I don't want to hear the neighbor's kids repeating.

    I took one short test drive and am now going to let 'er rip on a grocery
    run. My biggest concern is that I didn't set the valve lash well.

    My experience level and assessment of the difficulty of this job: In the
    past, I have replaced the timing belt and also checked (but did not adjust)
    the valve lash. I have had the valve cover off many times before, usually to
    replace its gasket. I'd call the "camshaft holder spark plug tube seal
    replacement" an advanced beginner or intermediate-level job.
    Elle, Oct 21, 2005
  2. Elle

    TeGGeR® Guest


    Way to go!

    A lot of stuff like this is time-consuming and fiddly, but not beyond the
    home mechanic. My rear suspension was like that (probably the scariest
    thing I've ever personally done).

    I do mine once per year, and have done so since the car came out of
    warranty 11-1/2 years ago.

    I use the max gauge as a "no-go" and the min gauge as a "go". It should
    slide in with zero resistance to the minimum, and not go in at all with the
    maximum. This way I know I'm at least within tolerance.

    The very most important thing is to be absolutely certain you've got the
    cams on their heels. If you messed up, you'll know right away, as there
    will be an alarmingly loud ticking noise that wasn't there before.

    The clearances normally don't change much. Most are unchanged from year ot
    year, and I get the occasional one that's changed (usually closed up) by a
    thou or so.

    If you did it as per the above, you're fine.

    And if you can go that far, then you can easily do a timing belt.
    TeGGeR®, Oct 21, 2005
  3. Elle

    Elle Guest

    Re setting valve lash (after removing the rocker arm/shaft assembly to
    replace O-rings yada)
    I was wondering if there was a good methodology or two out there for setting
    valve lash. Good tip.

    The first time I checked the valve lash was at year 13 (about 155k miles) of
    my 91 Civic's life. It appeared in spec, so I made no adjustments.

    I know the manual says to check it much more often (15k miles/1 year per my
    91 Civic's owners' manual). But for the record...
    That's the kind of experience on this subject I needed to read. Thanks.

    My Civic so far sounds good and runs well.

    More importantly, being able to do something like this: That's wealth. Love

    Interestingly, it would not have been all that possible without interactive
    community fora like this. Such fora are incredibly valuable educational
    tools. I pay my internet service provider happily each month. Of course,
    these fora rely on well-meaning people who, just as interestingly, do come
    out in reasonable abundance to help others. Next time I'm cussing out
    society, I will have to remember all these folks who take their passion for
    their hobby or profession and share it with others online by, effectively,
    //Teaching.// True teaching.
    (Yes, did the timing belt, including the upper camshaft seal, last year.
    Having that experience definitely helped yesterday's job go more quickly.)
    Elle, Oct 21, 2005
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