My 99 M3 has had a knock (maybe "piston slap") and the mechanic is
telling me I need the engine rebuilt. This car isn't my daily driver and
I was considering doing it myself. I've rebuilt other motors (domestic
and foreign) and was wondering how much more complicated this engine
would be and if there were any known difficult spots I may get hung up
on. It's the stock 3.2L M3 engine. Thanks,
What Floyd said. The only tricky part is holding the cams still and getting
the VANOS set up right. There is a special tool that makes this job pretty
easy, but I have no clue as to how you can get the tool.
Great feedback; thanks guys. When you say "getting the VANOS setup
right," is that part of the the holding the cams still issue? Ok so
cool, that sounds like something that is a "hit or miss" and it may be
trying on the patience, but once it's together I should be ok (?) I am
not in a hurry so I can always come back here and bug you guys too :)
Are there any good books I should get (aside from the obvious manuals)?
I would like to have as much text as possible and any websites so I can
do proper research and build up a plan first. Thanks a lot.
Yeah, I have that one. I'll score some other material online or otherwise.
In re to your other statement about my car not likely needing a rebuild,
I agree with you. It had / has a knock that would appear while
"cruising" - holding a steady spead/rpms. My mechanic replaced all 6 rod
bearings and the knock never went away. He has it now and said it's not
the valvetrain, but he thinks there's play somewhere between the piston
and the rod and that it may be slapping. The car has 60k miles and I've
taken it into the red maybe 10 times tops and _very_ briefly each time.
He says it may as well be rebuilt and it's crazy expensive. I just
wanted to sell the car, but didn't want to sell it with the knock. Maybe
should I see another mechanic. My guy seems good and he's cool, but it
won't hurt. I'm in San Diego if anyone can recommend a good bmw mechanic
here I'd appreciate it. I'd appreciate any other feedback as well.
Thanks for your help.
J Strickland wrote:
I'm in Murrieta, and my mechanic there seems to know his stuff. Try Steve at
Autobahn Automotive on Sandalwood Court. He's in the Yahoo Yellow Pages with
a ZIP Code of 92590. Tell him that I said hi.
My car met a sudden demise with the right side of a Buick LaSabre when an
old lady turned left in front of me to get to her bridge game in a
retirement community. I had 220,000 miles and there was no sign of any
impending heavy duty repairs such as those you are facing. I can't help but
think your motor is OK, and that you are likely to spend time and money, and
come away with the same noise. Not having heard your noise though, who am I
to say that everything is well?
I'm sure I kissed the red line a time or two in the 100,000 plus miles I
have put on my car in 5 years, but my motor purred like a kitten. It still
runs well, but is only a 2.5L engine, where you should have the 2.8L, so I'm
not sure that a swap would be the right move for you.
Yeah, I think I'm also in the "who am I to say" about my own car so
maybe I'll have it looked at again. I know about cars and motors to a
certain degree, but I don't know what's wrong with my car and that's the
key piece of info. As a matter of fact, my guy doesn't even know for
certain so he's just throwing out the rebuild as a catch-all most
likely. I'm going to take it for a 2nd look somewhere else. Maybe I'll
ping on your guy. Thanks, bye.
J Strickland wrote:
VANOS is a cam timing adjuster mechanism. The cams have to be held in the
right place, and the VANOS mechanism has to be attached and aligned. It
isn't a technically difficult job to do, but it has to be done just right,
and it can slip a bit and this might not be noticed until you determine that
the VANOS isn't working quite right.
If I understand it right, the cam and the VANOS mechanism can be off by a
tooth, and then you will notice it as a performance issue after the engine
is put together. The job of the VANOS is to alter the intake valve timing to
give low end torque -- I may be oversimplifying the description here. When
the VANOS is not set up right, then you may not get the low end kick that
you should. Basically, you should be aware of a feeling that reminds you of
the secondaries kicking in back in th eOld Days of the 4 bbl carburators.
VANOS is what causes this, if the VANOS is not right, the motor can run fine
but you don't have the 4bbl carb-opening-up-feeling that should be present.
Bottom line, if you take care to align the cams and be patient, you should
be OK with the rebuild.
Cool. I will be as careful and patient as needed. I guess though that
the tough part is, as you've pointed out, being aware of what's going on
enough so that you're sure you got it right before closing up the
engine. I'll read up on this. Thanks a lot,
J Strickland wrote:
It's one of those jobs that requires three arms, that's all. The trouble is,
you need to have all of those arms connected to you, having an arm from a
helper may only get in the way.
Since you have been warned, and if you take reasonable care, then you should
I have noticed that feeling on my '95 325i (single VANOS) but not with
my '97 Z3 2.8 (dual VANOS). I'm not sure if that is an artifact of the
earlier implementations or not, so the OP (with a dual VANOS M3) may or
may not get that sensation normally.
I'm not sure exactly what feeling you're talking about. My dad had a
tons of muscle cars (mostly mid year Chevys) when I was growing up and I
got to "borrow" a couple here and there and I'd get sucked into the seat
pretty good, but that's about it. I don't think I ever noticed
specifcially the secondary kicking in and changing the feeling. What is
With a 4-barrel carb (or, in the case of multiple carbs like the old
hemis with dual 4-barrel or Chevy triple 2-barrel) the throttle linkage
secondary barrels as you go deeper into the throttle.
I can't imagine how you could need a rebuild already, unless you visit the
Red Line often, and stay for a while. My car (M50 motor) had over 220000
California miles on it, and I was nowhere near thinking that a rebuild was
in the cards.
Having said that, the valve train is the most complicated, as we discussed
in another thread.
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