Two Questions About My Recently Aquired '98 528i

[BimmerNoob2000]

Hi everyone, I got my first car on Thursday which is a 1998 528i (automatic). It's really great but there are two issues at the moment. One of the issues is the transmission oil needs to be changed, which has resulted in a check engine light and slight slipping. I plan on getting this done in the next week because I need to get car inspected. Once I get this changed, will the check engine light go off? There are no other known problems with the engine or transmission. My second question is, the alarm randomly goes off at inconvenient times. Sometimes this will happen when I unlock the car using the fob, other times it'll just go off randomly and disturb all my neighbors. The alarm is obviously faulty and I need to disconnect it to prevent this annoyance from reoccurring.

I do not have the owner's manual so I can't look in there to see which fuse to pull or what to disconnect so I am asking here to see if anyone can help with this. Also, I know this might sound dumb to wanna disable the alarm but there has never been a car theft or vandalism in the 14 years I've lived in this apartment. Plus I have a very good view of the parking lot from my window so I'd be able to see what is going on. I do not need an alarm, it's more of an annoyance than anything. Thanks for your help!!

[shogun]

No questions in E39 DIY. Moved to E39 forum

[1823alex]

For the alarm: Probably a bad hood sensor, you can test by opening your hood, finding the little button looking senor next to the driver cabin air filter & hold that down while simultaneously locking your car, keep holding it for about 1 minute I think then let go and see if it goes off.

If the little square with a wire is hanging from your car's headliner that'll definitely do it as well, it's an ultrasonic / tilt alarm sensor and is extremely sensitive. I once tripped my alarm by leaving the front windows down & walking past my car prior to unlocking it... You could test this one by hitting the lock button twice in like 2 - 5 seconds and that would deactivate the ultrasonic alarm.


As far as the trans fluid goes, most of the time I've heard if it's already slipping your clutch is already bad and it's easier to leave it as the old fluid has more grippy stuff to help the clutches engage - but wait for more opinions on this as I might be completely wrong. Google "Chris Fix Transmission Fluid" and you'll see a pretty good video about it.

[JaxPlanet]

The BMW tech I spoke to last week agrees with Alex. He said the old fluid contains suspended particles from wear that improve friction between the plates and the new fluid will not so it is likely that replacing the fluid will increase slippage.

[BimmerNoob2000]

The BMW tech I spoke to last week agrees with Alex. He said the old fluid contains suspended particles from wear that improve friction between the plates and the new fluid will not so it is likely that replacing the fluid will increase slippage.

But won't leaving the old transmission fluid worsen the condition of the transmission? Also, how can I turn the check engine light off so car will pass inspection? Thanks for your help!

[edjack]

No evidence exists that confirms the practice of leaving old fluid in. The CE light indicates something is wrong with emissions equipment, and has nothing to do with trans fluid.

Get the codes read. If you clear the codes, the monitors will reset, and you will need to drive the car in a specific fashion to make them ready. Otherwise, when the inspector checks for codes, he'll discover the monitors are not clear, and you will not pass.

Always report the miles on the car.

[computiNATEor]

The BMW tech I spoke to last week agrees with Alex. He said the old fluid contains suspended particles from wear that improve friction between the plates and the new fluid will not so it is likely that replacing the fluid will increase slippage.

This is patently untrue. The dissolved clutch material can not be used by the transmission to hold the clutches together. In proper, normal operation the clutches do not allow slip; the fluid forces the clutches together and they cannot (should not) slip. If they are slipping, the transmission is toast. If they're not, you may still have time. Clutch material suspended in the transmission fluid cannot cause the clutches to hold.

However. Transmission fluid is filled with detergents. These detergents can dissolve and dislodge pieces of gunk inside the transmission that were previously harmless if new transmission fluid is introduced after a long period of no transmission maintenance. These now-mobile particles can clog the valve body, which can cause the transmission to shift poorly, slip, or quit all together. That isn't to say that you shouldn't change old transmission fluid; you SHOULD. But you should also change that first batch of fresh ATF out far sooner than the next batch, for two reasons. First, you're only changing about 50% of the ATF in a transmission anyways, because of the fluid still in the torque converter and elsewhere. Second, the new ATF is going to have a far higher amount of deposits in it, because of the aforementioned detergent properties.

So how to prevent these maintenance headaches? Frequent, regularly scheduled transmission fluid changes. I personally suggest every 30k miles for any transmission.

On an old BMW transmission with no servicing history, I'd recommend doing a transmission fluid change ASAP (including filter), changing the fluid and filter again by the next oil change (~7500 miles or less), and then sticking to a 30k mile fluid change interval, and changing the filter every 60k.

From another forum:
"If you do in fact have clutch friction material suspended in the trans fluid, that material will/can not be used by the transmission in its operation. The material has already become separated from the friction disks in the clutch packs, and the only time that material will work is when it is still attached to the disk. The only damage the loose friction material can cause is to clog the internal filter screen. Removing this material by either filtering, or flushing it out, in of itself, will not cause a trans to fail. The real problem is why this material has become detached from the friction disks in the first place. In most cases, this material has become detached because the internal seals in the clutch packs are worn or torn, which reduces the amount of hydraulic pressure that is applied to the clutch pack when it is engaged. This loss of pressure will, over time, cause the clutch pack to slip when engaged. It is this slippage that causes the friction material to break away from the friction disks. Once this material has started to separate from the disks, the only fix is to overhaul the transmission, replacing the internal seals and worn friction disks."

[geargrinder]

What Nate said.

“You waited too long, and the transmission likes the old filthy fluid too much now so they can’t be separated without tramatic psychological consequences” is screaming bull crap and a sure sign the tech you’re talking to is mediocre at best but an untrustworthy idiot at worst.

“Particles of filth are now needed to cause friction blah blah”!?!? That’s even a new whacko idiot explanation for that wrongheaded concept. As Nate says succinctly if there’s any truth to it, it’s either 1. New fluid additives can dislodge larger clumps of stuff around causing some temporary issue (in which case almost always more flushing will sort it) or 2. Really really bad trannies can lose seals as the filth is washed away.

Half the time guys moan about a tranny fluid change related issue w the ZFs I think they have underfilled by not doing it via the right procedure - too hot or engine not running etc.

and in the exceedingly rare case where really and truly the tranny poops after a mere fluid change, well man, that box was gonna crap out any minute on you anyway.

[amancuso]

Your 98 528i has the 4 speed GM transmission. Just have the fluid and filter changed. I'll bet it's just low on fluid.

[Jason5driver]

Here are my threads replacing the ATF:

https://www.bimmerforums.com/forum/s...Don-t-Think-So!

LIFETIME FILL - ** ***! - Part II

[Mike WW]

If it's already slipping it's doubtful a fluid change would do any good. But at the price of a tranny and the cost of fluid, it's worth a try, just don't expect much. But the guy who says it needs grit in there to work is wrong. Just wrong.

On some cars the tranny, which is electronically controlled, does talk to the ECU and will trigger a CEL or just a background code under some conditions. I don't know if the GM 4 speed does that or not. At the end of the day you're probably looking at a new/rebuilt tranny. But again, Dexron fluid is cheap and worth a try.

E39 owners manuals are widely available online, search. Every year and submodel might not be, but many are.

[geargrinder]

^^^ yes to all that!