I am about to buy a 1991 BMW 535i (in Canada) that has 345000 km and a
leak in the air intake manifold as well as an engine oil leak. Price
300 dollars. Car still runs. I plan on repairing the intake manifold
and sealing the engine oil leak. Then I will work on strapping on a
hydrogen booster. Can anyone assist me with the air intake manifold?
How do I replace it and what does it cost?
Sounds like the rubber boot connecting the airbox to the air flow meter,
shaped like an "L". It runs about $28. There's another straight rubber boot
between the air flow meter and the throttle body, about $25. Don't forget
the myriad rubber hoses that are cracking. Easy and cheap, but
time-consuming to replace. Check this site:
Bill in Omaha
I'll second the suggestion that the big rubber intake boot is cracked
and likely has a vacuum leak on the bottom. You can check for it by
squeezing the thing with the engine idling. If the idle changes
(either up or down) as you do so, that's the problem. It's a half-
hour job for a fumblethumbs like me.
There is also a very common and very cheap and easy-to-fix oil leak on
the M30. Check the oil pressure switch at the back of the head.
Costs about $8 (even AutoZone stocks 'em) and 5 minutes to replace.
Next most likely (and next cheapest/easiest) is a leaky valve cover
I have *never* seen a reason to replace one, so there ought to be
about a bazillion of 'em around, used, very cheap. But I'll bet you
the rent that's not the problem.
(Been there; done that)
Thanks Krieger. I sincerely appreciate the insight. Thanks to you, I
can get this fixed more quickly and cheaply. I may not even need my
brother-in-law mechanic to look at it. What does the oil-pressure
switch look like?
Yes! Thank you Bill in Omaha. With your help, I think I am going to
just about steal this thing off of the seller's hands tonight for only
300 Canadian. I will try these simple fixes first. I hope these work
and I don't have to get at the head gasket. Is it common for head
gaskets to blow on these cars, I mean, the car is 345000 kilometres
and 16 years old.
M30 head gaskets are pretty tough and most would say the M30 is
bullet-proof... if the basic maintenance has been done. I like mine for the
timing chain and seemingly over-engineered design. No belt to break, just
change the oil regularly, air and oil filters, plugs every other year, and
valve clearances every other year or so.
Do a compression check on the engine and that will tell a lot. Cylinders
should be within 5% (?) of each other. Mine are and it has 173,000 miles.
Air leaks are the main thing, but the M30B35 has a newer ECU and should be a
little more tolerant than my M30B34. Don't look at the miles, look at the
condition of the engine/body. Cheers!
Bill in Omaha
I did it! I bought the BMW for 300 bucks Canadian. What a steal! I
drove it home about 20 miles and it now sits in my garage awaiting my
tools. The engine sounds really rough and it obviously wouldn't start
in the winter, but only when idling. As soon as you drive away, it is
almost as smooth as my brand new Odyssey or Altima. I figure the
problem is with the air intake. On idling, it also misfires
occasionally, so I think the compression of the cylinders is not in
I bought the BMW for 300 bucks Canadian. What a steal! I
Vacuum problems or air leaks usually present themselves as stalling or
constant poor running at closed throttle with fine running at open
Occasional misfiring at idle is more likely spark plugs and things
like that in my experience.
$300 might be a steal but I figure you're either going to learn a lot
about this car or end up spending a lot of money. Usually if there's
one thing the owner doesn't want to fix then there's half a dozen more
they haven't told you about.
Ahhh...a pessimist. You gotta take a gamble sometimes. Thanks for
the insight on the air leaks and misfiring. I am surely going to
learn a heck of a lot about this car...I hope the oil leak isn't too
much of a problem...
Can you determine where the leak is originating from? MAybe spray some
engine cleaner, soak about 30 minutes, pressure wash off. Run engine to
operating temp to dry off. I used a car wash for $2 and did mine before
finding the front crank seal was leaking. Quick and easy. I know of several
locations and possible quick fixes. Please let us know where it is.
Bill in Omaha
Looks ok. You might consider a transmission fluid and filter change, too.
You'll only be able to change half of the fluid due to half being in the
torque converter, but it will make a difference. Considering the price of a
new trans plus labor, you decide. I did my '98 528i in about an hour. You're
lucky in that you have a fluid dip stick, the 528i did not. It shouldn't
need special fluid either.
Bill in Omaha
I noticed that there is a timing belt missing. It connects from the
main rotating mass which houses all of the belts to the rotating mass
at the bottom right front of the engine. I am guessing that this runs
the a/c unit because there are hoses with deteriorated foam casings on
this side of the engine, and the a/c controls inside the cockpit are
not functional. If I simply put this belt on and let 'er rip, what
The A/C belt (to the compressor). It may have been removed to prevent
parasitic drag from a component that a) isn't needed at the time or locale,
b) needs recharging to be useful and owner couldn't afford it, or c) belt
just came off (unlikely). At best the A/C will work, at worst it will not.
Maybe the charge leaked out due to cold or bad seal. Judging from the snow
in the pic, you don't need the A/C anyway. I've had my A/C belt off since
last August in Omaha.
Bill in Omaha
There have been cases (mostly in the SW) where the compressor
froze and the belt broke, which caused the engine to overheat,
because the brilliant designers of US-made autos only use one
belt for everything - a/c and water pump.
Thank heavens for German engineers.
I can see where the intake manifold is leaking. Right at the 6
connections where it meets up with the engine block the seals have
stripped away. Looks and feels like cardboard now, but I'm sure they
were originally a yellow coloured rubber of some sort. I haven't done
any work on the car yet except unplugged the ICV while the engine was
running to determine if the ICV was contributing to the rough idle (I
mean the car is shaking, man), but this had no effect, so I will have
to replace all of the hoses and the spark plugs, but first I will
reseal the air intake manifold. Any idea on how to change the spark
plugs without taking apart the engine?
The spark plugs are on the passenger side of the engine. You are looking at
the injectors. You'll need to remove the intake manifold to replace the
gasket. I believe there is a support bracket and 12 nuts. While you're at
it, get the injectors cleaned. They'll be easier to remove when the intake
is off the engine. The six spark plugs take about 30 minutes to change.
Check here: www.realoem.com It gives a full part breakout of each section
of the car with part numbers.
Bill in Omaha
Hi Bill. Believe me, I have memorized the diagrams on that site.
Thank you. Do I just pull the suppressors off the plugs and then
unscrew the plugs out? Lucky for me the ignition wiring is all brand
new! Thats a couple hundred bucks right there, and if the rotor is
also new, then damn doobie scoobie, I paid only 300 which is less than
the cost of just these components alone! With regards to the
injectors, do they just screw out as well? I plan on using Simple
Green for cleaning everything in the engine. Stuff is awesome, I used
to use it to clean injection molds back in the day. Advantage: You
can drink the stuff if you were thirsty and it would supply vitamins
to your body, and yet it would clean the bejesus out of anything
(except glass, but they have one variety of Simple Green for glass now)
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