100K Service - Question

IIRC, O2 sensors & spark plugs are recommended at 100,000 miles. So if you have recently had an oil service or inspection, you might wait 'til the next one to do them. The other services are scheduled according to your dash readout (roughly every 15,000 miles - check your manual).

Your car doesn't have a timing belt, it has a chain which shouldn't require replacement. Perhaps the dealer meant the serpentine belt ("fan" belt) which should probably be changed by now.

Tom

In addition to the Oxygen sensors that should be replaced, the transmission fluid and rear diff. fluids should be replaced. The fuel filter and spark plugs should also be replaced. These items are known as "long life" or "lifetime" fluids or components, but whenever BMW says that they mean that they should be done every

100,000 miles. As stated previously, any other repairs or maintenance items should be covered or noted in a scheduled maintenace inspection.

"as3" wrote

There is absolutely no reason to replace the O2 sensors, since the engine warning light will come on when they fail.

FloydR

There is a good reason to replaced it, it will fail slowly, before the light will turn on, will mess your computer input data, and increase your gas consumption. At $3.00 a gallon, it will save you a lot of money and be good to the enviroment too.

But they do tend to fail soon after the 100k mile mark. If you want to avoid the problem you can replace them prophylacticly.

Given that the *ACTUAL* mileage that they fail at is usually less than

100K, you'd be replacing a good one with a new one. My '91 525i: 60086 miles(about 300 miles after my 60K I2). I expect the one in my '01 330xi with 76K miles to go anytime.

FloydR

I've has the opposite experience. '87 325iC never went (sold at 115k miles). '94 540i went at 112k miles. '95 325i went at 108k miles. '97 Z3 2.8 hasn't gone yet @ 22k miles.

I would say that your failure @ 60k was very premature. Not just from myy experiences, but from conventional wisdom as well. O2 sensors can be made to go bad if they are contaminated, especially with silicone such as found in common RTV sealant. Any chance that stuff got used on your engine somehow?

"Malt_Hound" wrote

Nope, no silicone. Possible cause might be a too-rich exhaust because two coils went bad around then (1st generation coil-packs sucked.) But subsequent ones haven't lasted much longer, either.

The O2 sensor (different kind) went out on my Toyota T100 V6 at 95K, and the one in my mother's (LOL - drives fast but not much) '99 Camry V6 went out just a couple of months ago at 45K. So our experiences cancel.... Aren't anecdotal stories wonderful?

FloydR

Your family is tough on O2 sensors. Maybe it's where you buy your gas? I know it's anecdotal, but I have heard many cases of them lasting over well over 100k. Yours is the first I have heard of them being so short lived. Makes me wonder...

There is a difference in the Oxygen sensors on a 91 525i and this vehicle. The oxygen sensor in the 91 525i is known to go out early. They are sensitive to impacts. On several that I have replaced due to check engine lights being on, there are fresh scratches on the exhaust in that area behind the transmission. Most times the owners don't remember running over anything, but this small of impact will damage the internals of the O2 sensors. On newer BMWs the O2 sensors are up on the exhaust manifolds and are made beter, so it is rare to see them fail until over 100,000 miles.

Replacing the transmission fluid on an auto trans after 100K miles usually will kill them if it hasn't been done more regularly. As weird as that may sound. Something about the new fluid working loose all gunk that has collected over time. Personally I would change the fluid every 25k on any auto transmission if you want them to last for a long time.

You would, would you? Even if the manufacturer fills it with semi-proprietary (supposedly lifetime) fluid that costs over $100 for a

5 liter bottle and you would need at least 2, possibly three of these bottles plus the labor charges and other parts to do it?

So the total added expense would be approximately $500 per event, times three additional changes over 100k miles because of a rumor you have heard.

Something to think about... how many folks do you suppose pipe-up after they change the transmission fluid and nothing bad happens?

for the record,,, what he said is known to be true in some bmw trannys.

5hp30 in my 540 for example. there are a lot of write ups on this, If the tranny has never been serviced, they suggest changing the filter and whatever fluid comes out ONLY after 100k ( if anything), or you will very possibly have major problems.

Lifetime is 100k, the first owner, and warranty are gone by then, the car is disposable to bmw after that.