I'm planning on replacing spark plugs, O2 sensor, and the coolant soon.
Is it true there are two sensors to replace on an 2002 325i? I wasn't
sure on this one.
Also, can a 2 year complete drain and refill w/ bmw coolant be a
substitute vs. doing a complete flush every 4 years?
Any other details that I should know about will be greatly appreciated.
Re coolant change, can you explain the difference between a "2 year
complete drain and refill w/bmw coolant" versus a "complete flush every 4
For older BMWs, e.g., pre-99, BMW recommend a complete drain (opening both
the radiator AND block plugs) and replacing it with BMW "blue" coolant
(Valvoline Zerex G-48).
I found Saab coolant is also Valvoline Zerex G-48. At $12/gal retail, its
about 1/2 of BMW "blue" stuff. Guess what I'm using the next time I change
What I meant was can I just do a drain and refill every 2 years instead
of flushing the system with a chemical cleaner. (That is opening both
the radiator and block plugs). This may not empty to entire coolant in
entire system. In which the entire coolant is drained out completely.
What I wanted to know was instead of doing this, can I just drain and
refill with new coolant, without using the so called chemical cleaner?
Someone told me doing a drain & refill more often will not need the
Hope this makes sense.
When people talk about a "flush" they are not talking about using any
any chemical cleaner. Regular proper maintenance (even done every 4
years)will prevent the need for any such chemicals. That is unless you
consider Hydrogen Dioxide a chemical. ;-)
Just drain the existing coolant and flush the system ouit with good ol'
H2O until is runs clear. It helps if you remove the thermostat from the
housing first to allow the coolant to flow through the entire system.
It's probably a good idea to replace the t-stat every 4 years anyway.
Drain again, replace the stat and refill with the previously recommended
blue coolant (either BMW or SAAB brand).
Assuming the Mercedes coolant is the golden yellow (not greenish yellow)
stuff, that is Glysantin G 05 which is very close in content to G 48
specified by BMW. G 05 is available at many mass-market auto parts
stores in the US under the Zerex brand at a very reasonable price.
I would not hesitate to use that (G 05) in a BMW, especially if you are
faced with using the dreaded green stuff as an alternative...
This is true, however, since his car is OBDII, why not wait until the computer
says to replace them. There are several fault codes for each sensor - bad
heater, lazy sensor etc. I'm at 125K on my car and all 4 sensors are still going
strong - at least according to the DME. Unfortunately, I cannot say the same for
the heater blower final stage unit - it just croaked -:)
Yeah, even on my OBD1 cars I have waited until I get some sort of
symptoms before replacing them. But I have not been so lucky. My E34
needed (2) at 112k miles and the E36 (only one) at about the same, 115k
There may be 4 O2 sensors - at about $125 each.. so replacing them when
not needed is a rather expensive thing to do. The number you have is
dependent on if you have a split (dual) exhaust - or the combined one
with a single catalytic converter. The parts book isn't clear on this -
and would have to use a VIN# to really check (or eyeball..) You can
look up your car and it's parts at http://www.realoem.com
Unless you're seeing a check-engine-light (or service-engine-soon) and
are over 100k miles, I'd leave them alone. They typically will last
longer than 100k miles. The O2 sensors that are behind the catalytic
converters rarely ever need replacement - they are almost along for the
ride. They are used to monitor how well the cat-converters are working
The plugs on your 2002 are also 100k mile items.
Yes - and that will probably be overkill (the frequency)
It's good to see you're maintaining the vehicle.. it will make a fine
used car for someone someday.
Thank you! and especially to all of you for the comments.
The O2 sensors are not defective, I was almost about to replace them
just for preventive care. Since I can leave them alone, I may
reconsider. This car is for keeps and am looking to get the most out
used car for someone someday.
Yeah, like they say.....take care of your car and it will take care of
Besides changing coolant every 2 years (using BMW or Saab "blue" stuff), you
may also want to consider changing your transmission and differential fluid
every 30,000 miles, flush brake fluid every 2 years, and depending on the
type of engine oil used, change every 3,000 to 5,000 if dino oil; 7500 to
15,000 miles if synthetic. Of course, engine oil depends on type of usage,
i.e., stop and go city traffic versus long freeway miles.
Well, that's not entirely true...
Since the ECU depends entirely upon the O2 sensor (just the forward one
on OBD2 cars) for information on the exhaust gas content, when it begins
to "go bad" the mixture will not be optimized and either performance or
fuel economy will suffer (slightly). Eventually, the sensor feedback
drifts outside the allowable range programmed into the ECU and it will
then throw a "check engine" code.
Motorsforum.com is a website by car enthusiasts for car enthusiasts. It is not affiliated with any of the car or spare part manufacturers or car dealers discussed here.
All logos and trade names are the property of their respective owners.