Do we know about BMW Diesels?

Straight six, same displacement as the gasser; stick.  History, issues, "class" type problems? 

Once upon a time I bought a Fiat 128 brandy new, nothing but trouble!  Friends said:  "Well, everyone knows....."   clearly not everyone.  I've learned to look before jumping.

Anything to watch out for?  Car has 120k miles but 47k on a rebuilt engine.  Rut-Roh.

Dan

My friend who's a BMW service writer warned me off of the X5 diesel. Said they were a maintenance nightmare.  Not sure about the others.

My only experience with them was an X5 that took an Act of God to get to run the emissions monitors.

Which BMW diesel are you referring to?  The later version or the old one from the 80's that was made by VW?

The one from the 80s was not made by VW. It was actually made by Steyr in Austria. It's essentially an m20 with the injection pump from a Cummins straight six. 

I own a couple. They're goofy, parts are hard to find, and the only modifications available are adapted from other cars. Tons of fun though, plenty of torque. At least between 2000 and 3500 rpm. I could probably get more power out of it, but I don't want to go crazy without an egt gauge.

Drove a friend's 5 series automatic a couple years ago. In ECO mode on the highway, it sips fuel, but won't pass a school bus. Put in Sport mode, and it takes off like a rocket. 

In reply to Cactus :

Interesting.  I've read for years it was VW sourced.  But if you own them I'll accept that info as often-repeated internet lore. 

Funny you should ask...my X5 xDrive35d is sitting at the dealership right now.  We're investigating whether the two latest Service Engine Soon codes relate to known issues that prompted BMW to extend the emissions warranty to 120k or 10 years.  I think one code is the expected failure of the other NOx sensor that hasn't been replaced under warranty yet.  The first was replaced with around 100k miles and they are a maintenance item and around $300 each (there are two).  The other code indicates a temp/level sensor in one of the two Diesel Exhaust Fluid (DEF) tanks, either the "active tank" (which has heaters, sensors and associated DEF transfer pump) or the "passive" tank.  The active tank is replaced as a whole under the same extended emissions warranty.  The passive tank is on the owner's dime.  There is a reasonable method/kit to repair the active tank with cheaper VW parts if out of warranty but the passive tank is somewhere around $2200 from BMW (a company up north will repair yours for ~$600 if you send it to them.  Repair involves plastic "welding" which may present a challenge to some on this forum, not me).

Last month I replaced the electronic "throttle valve" ($220) due to oil migration into the integral printed circuit board caused by the valve being in the turbo pressured inlet to the intake manifold and a presumed weak seal around the throttle plate shaft.  The oil killed the potentiometer eventually, which causes the "ECU" to not properly cause a regeneration of the Diesel Particulate Filter (DPF) and can lead to an early death of that expensive part.  While changing the throttle valve I could see a boat load of oily junk in the inlet tract caused by the EGR valve/system that indicates the need to remove the whole intake manifold and swirl flap arrangement for cleaning to stave off further problems.  Might as well do the walnut shell blasting of the intake valves while in there...

There are other known emissions issues and other known fixes for when these issues crop up (notice how I said "when" and not "if"?).

Do you want a diesel BMW?  If you enjoy a challenge and unraveling mechanical puzzles I say go for it.  Some people go to the extreme of deleting the emissions systems, either in part or in whole, and unleash significant amounts of horsepower and even more torque (downside being questionable legality in some states and possible diesel exhaust smell).  Most that go this route say it transforms this platform.

I question my sanity about this sometimes, but I do like my diesel X5.  I've been able to keep up with its problems by doing the diagnostics and repairs myself.  I learn quite a lot along the way.  It gets phenomenal mileage for a vehicle that weighs this much and is an absolute joy on an interstate.  It can haul a bunch of cargo.  It's just a drag when in the middle of all this enjoyment that little SES light on the dashboard lights up.

Ian, it's a 1986 variety.

In reply to Ian F :

Crank drops right in an m20. Same stroke as a 2.7L, and it's forged to boot. Manifolds will swap over with a little adapting. I've seen somebody use the diesel exhaust manifold to put a turbo on an m20.

914Driver said:

Ian, it's a 1986 variety.

Well, that’s different then.  Never mind 

In reply to Cactus :

Now that you mention it, I do remember guys from the E30 forums talking about doing that.

I've blocked a lot of my E30 experience from my memory.

So what sort of questions do you have about the engine? There's a timing belt, 60k/6 year service interval. Timing the injection pump is a dark art, you can use drill bits to lock that pulley in place and also the crank pulley. I forget which sizes fit perfectly, mye28.com knows. I'll have to figure that out this winter since mine is due. The valves need lash adjustment. You can put a manual boost controller on, turn it up to 15psi, but anymore and the blow off valve on the bottom of the intake pops. Nasty whoosh noise coupled with an oil pressure light, spooks the unprepared. Turbo is out of its efficiency range above 15psi anyway. You can turn up power with a screw (full load fuel) and off boost fuel as well, both will add smoke. Turn it too high and you will melt your pistons. I highly recommend a hungrydiesel fuel pin, makes it much more responsive and fun.

Mine is manual swapped. Unless you get the proper euro dual mass flywheel, it rattles at idle with an m20 single mass flywheel. The only real issue I have had was the in tank pump dying and an O ring on the injector pump sprung a fuel leak. Would recommend.

My biggest concern is why was the engine rebuilt.  With 120k miles and a rebuild 47k ago, can I expect a rebuild in 40k miles? 

Another question: l driving through Nowhere Iowa and something craps out can it be repaired by local talent and parts availability?

Ian F said:

In reply to Cactus :

Interesting.  I've read for years it was VW sourced.  But if you own them I'll accept that info as often-repeated internet lore. 

The Internet may have the BMW confused with the VWAG 6-cylinder 2.4l that was put in Volvo 240s for a while.

In reply to 914Driver :

Tough call. They're very reliable, I've seen them go for hundreds of thousands of miles with neglectful ownership (most of the bmw diesels I've seen are in very rough cars) but any competent diesel shop should know how to work on the injection pump.

Why it was rebuilt?  I'm really not sure. That's pretty low mileage for such an old car. Seals on the IP were probably leaking from age, if it sat, the fuel tank might have been full of gunk, the cylinder heads are known to crack between the valves. I'm not sure that last bit actually hurts the engine all that much. I bet at least one cylinder on my head is cracked right now. I'm prepared to buy a new head. New castings are available from AMC (the Spanish company) 

Edit: no affiliation with ECS, just first to come up on Google. https://www.ecstuning.com/b-amc-parts/m21-cylinder-head-with-valves/908175~amc/

Pics of cracks: http://www.mye28.com/viewtopic.php?t=103856

The owner does not know why it was rebuilt, wasn't on his watch.  It may have sat for a bit in off seasons, so fuel's a real possibility.

Aww hell, I was expecting a 524td, not a vixen.  Buy that mofo right now.

In reply to Knurled. :

Ca ca... Yes - the "internet confusion" is "me".  

Otherwise, I agree - if a Vixen suites your needs, I'd buy it now. Worry about the engine later.

The only positive is it fits in my garage, even a Toyota Dolphin can't do that.

914Driver said:

The owner does not know why it was rebuilt, wasn't on his watch.  It may have sat for a bit in off seasons, so fuel's a real possibility.

Talk about burying the lede. 

Oh my god!

talk about burying the lead!

Que?  I only speak English and bad English.  What's "burying the lede"?  or lead?

It basically means failing to reveal the most important part of a story at the outset. As for the spelling, it depends on how much time you spend hanging with journalists. It's pronounced "leed" in both cases.

Thanks Kieth, the vehicle type wasn't relevant to the question; wasn't burying it on purpose.

Does the vehicle effect/affect the answers?

Dan