Maintenance questions

Hello,
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.
Tia,
Will
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complete drain and refill w/bmw coolant" versus a "complete flush every 4 years?"
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 my coolant....
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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 the system.

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 flush.
Hope this makes sense.
Tia, Will
bfd wrote:

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weng94 wrote:

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).
--
-Fred W

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My BMW mechanic likes Mercedes coolant.
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http://www.valvoline-technology.com
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Jeff Strickland wrote:

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...
--
-Fred W

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Confused by you saying you're "planning" on replacing your O2 sensor. Is it actually faulty? If not there will be no benefit in replacing them?
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zerouali wrote:

...except that it is standard procedure to replace them prophylactically at ~100k mile intervals.
--
-Fred W

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Fred W wrote:

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 -:)
Frank
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Raybender wrote:

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 AFAIR.
--
-Fred W

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weng94 wrote:

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.
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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 of it.

Yeah, like they say.....take care of your car and it will take care of you :-)
Will
admin wrote:

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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.
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I'm not sure, but I think you don't need to replace any O2 Sensor until your car tells you too. The O2 Sensor does its job until it doesn't do its job, then it tells you that it isn't doing its job.

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Jeff Strickland wrote:

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.
--
-Fred W

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