Dirty E30 (Pt.2)


Parts are in!!

Redline  MTL 75W80 GL-4 for the transmission, Redline 75W140 GL-5 for the noisy differential, Febi oil pan gasket, magnetic oil pan plug, oil filter housing o-ring, Mann oil filter, new light bulbs all round, and a new set of Bosch copper spark plugs. Let’s see if I can squash this noisy drivetrain issue.

I went with a higher viscosity oil for the differential than what the factory says. Stock it calls for 75W80, but there’s stories of E30 owners fixing their noisy diff by moving up to a 75W140. Hopefully this’ll do the trick. I proceeded to drain the transmission fluid. It didn’t look bad, but was definitely old. Still had some color to it, at least. The magnetic drain plug had an acceptable amount of metal on it. Pumped in the new Redline 75W80 and plugged it up. I then moved on to the differential. Popped the fill and drain plug and decent-colored fluid poured out. Not much metal on the plug (good sign). Pumped in the new 75W140 and plugged that one off as well. I completely forgot to take pictures of the trans and differential change. I got wrapped up in the moment.

Next, spark plugs.

BMW E30 German Autohaus spark plugs engine Chattanooga Tennessee 325i
M20 ready for its new spark plugs!

I popped the hood and started removing each plug wire one-by-one. Grabbed the appropriate-sized spark plug socket and ratchet and started turning. Man, those suckers were tight! They also had a worrisome amount of resistance. At no point could I have removed them by hand. Oh well, a liberal dose of anti-seize on the new ones should help alleviate that. After removing the first plug I was in shock of the condition. Very well might be the worst condition plugs I’ve seen!


BMW E30 spark plug insulator German Autohaus Chattanooga Tennessee 325i
Spark plug with cracked and broken insulator.
1989 BMW E30 325i spark plug German Autohaus Chattanooga Tennessee European Repair
Every plug looked the same. At least they’re consistent!

I don’t know what the heck was going on there, but it reeks of pre-ignition. Lot’s of deposits and cracked/broken insulators. Maybe the owner was running 87 octane coupled with a once-clogged fuel filter? Who knows. Something to keep an eye on, though. I unboxed the new Bosch copper plugs, checked the gap at .025″, spread some anti-sieze on the new plugs, and popped them in. The plug wires looked fine, so i’m not worrying with replacing those… for now.

Next was the oil filter housing. Man, I love the room in the engine bay these things have!

1989 BMW E30 325i Chattanooga Tennessee German Autohaus
Oil filter housing removed.

I cleaned the passenger side of the engine block with a considerable amount of brake parts cleaner, but it was still dirty. Clean enough to replace the housing o-ring, though. I unscrewed the filter, removed the two oil cooler tubes, and then unscrewed the housings retaining bolt. Placing the dirty housing aside, the o-ring looked OK, but was obviously leaking. Once this is fixed, no more oil leaks! (Engine oil, at least).


BMW 325i E30 German Autohaus Chattanooga Tennessee
Oil filter housing midway through cleaning.
Cleaned housing mating surface








After easy 45 minutes to an hour of cleaning I finally got everything satisfactory and ready to bolt back up.


BMW 325i E30 oil filter housing OEM gasket Chattanooga Tennessee German Autohaus
Cleaned oil filter housing with new OEM gasket.
Mann oil filter on 1989 BMW 325i E30 Chattanooga Tennessee German Autohaus European
Installed housing with new gasket and Mann oil filter.







Now that everything is nice and tight, onto the oil change!

As I started loosening the drain plug, thoughts of metal bits flowing out of it started running through my head. I typically have a hopeful outlook, but there has to be an Achilles heel with this car somewhere.

1989 BMW 325i E30 oil drain German Autohaus Chattanooga Tennessee European
Flushing out the oil fan with some fresh spare oil.

After the majority of the black coffee finished coming out of the drain I proceeded to pour in some fresh Mobil1 to help flush out the remaining used oil and any crud that might have have settled in the bottom. This also makes for a good opportunity to send off a virgin oil sample for the Mobil1 0W40 Euro Formula.

Mobil1 Blackstone Labs oil sample German Autohaus Chattanooga Tennessee European
Preparing an analysis sample of Mobil1 0W40 Euro Formula.

I’ve been running an oil analysis program for German Autohaus for quite some time now. Any chance I get to send off a fresh sample of the latest concoctions, I do so. I also want to know first-hand how our customers engines are holding up. Any time a customer comes back to us for an oil change, I take a sample and send it off. The analysis results show everything from coolant in the oil, main/rod bearing wear, fuel dilution, aluminum from detonation, acid level, to the mount of anti-wear additive remaining. So far we’ve had excellent results from the Motul oil line, specifically the 8100 X-cess 5W40. We’ve had customer vehicles push out to 20,000 miles on the stuff and the reports still come back OK. We don’t recommend going past 14K, but it’s good to know.

Anyway, back to the good stuff!



While observing the old oil getting flushed out by the Mobil one, I happened to spot something a little out of place… a helicoil in the drain plug hole! Noooooo!!!!! (As you can see it in the previous picture). Well, nothing I can do about that now. If it works, it works. I  then proceeded to remove the new magnetic drain plug from its packaging to prepare for installation. Here’s a picture of the old and new one…

BMW 325i E30 oil pan drain plug German Autohaus Chattanooga Tennessee European German
(Left) Original drain plug. (Right) New magnetic drain plug.
Magnetic drain plug German Autohaus Chattanooga Tennessee BMW E30 325i European
New magnetic drain plug installed.

After tightening her down and wiping off the old oil, now to move on to adding the new oil. I decided to go with Motul 8100 X-clean 5W40 for the first oil fill. The X-clean line is one of Motuls diesel engine oil. It’s loaded with detergents, so that’ll help clean out the engine a bit without being too aggressive, which could potentially knock loose large chunks of  debris and cause damage. After 4,000 miles or so I plan on switching to Motuls 8100 X-cess 5W40.

Motul 5W40 X-clean German Autohaus Chattanooga Tennessee BMW 325i E30
Motul 8100 X-clean 5W40

After filling her up with fresh Motul I started the engine to let it get it up to temperature so I can check for leaks and get the oil level where it should be. No engine oil leaks! Hurray! I wanted to continue the forward movement of progress, but 11PM came too soon. Time to drive her home and see if the new fluids helped with the drivetrain noise. Unfortunately, no change. The differential still had its race-car whine and the transmission still had its ever-so-slight geary noises. One thing I did notice is that there’s a very odd drivetrain ‘clunk’ that happens when transitioning on/off throttle while cruising in high gear. Worn diff mount? Worn diff? Driveshaft U-joints? Intermediate shaft bearing? Guibo? Worn rear subframe mounts? Who knows. All for another day.



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