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BMW Tech Letters

Jun 10, 2003

Stuck on a Water Pump
I am stuck and wondering if you can help. I have a 1991 BMW 318is and I'm trying to remove the old water pump to install a new one. I have already removed the fan clutch and the pulley also have removed the four bolts on the old pump. Now, after all that, the pump won't come off. It won't even budge. I need help.
Dorothy Parker
via the Internet

The M42 water pump is sealed with an O-ring seal, not a gasket. This means it tends to stick to the water housing. BMW has provided an easy way to remove it, though. At approximately one o'clock and five o'clock around the outside edge of the pump, you'll note two threaded bolt holes that are not used to actually secure the pump. Take two of the M6 bolts that you just removed, and slowly thread them into the threaded holes. This will prise the pump away from the water housing.

I'm not sure if other cars experience tramlining like some BMWs do but, upon adding larger tires to my 1998 328is, I have experienced steering that rivals my grandfather's 1946 International H tractor in a field of mud pulling a crap spreader! Other Bimmerheads have recommended changing control arm bushings as well as upper strut bearings from a 1995 M3. This will induce a positive 3 degrees of castor. On the other hand, the dealer suggested I allow him to play with the alignment until he gets it right. Has anyone there come across this before? Any suggestions other than keeping the original 15-in. tires?
Larry Kutcher
Gansevoort, New York

Tramlining generally has a great deal more to do with the road than with the car. But BMW engineers are paid a great deal of money to determine optimum suspension geometry for use with a given tire size in BMW steering and suspension systems, and your letter illustrates nicely the problems one can encounter when second guessing them. While you don't mention the size of the wheels and tires you have fit, I suspect they are 8x17-in. wheels and 235/40-17 tires, or 7.5x17-in." wheels and 225/45-17 tires. This is an acceptable upgrade for the E36, and is actually found on factory sport package cars and the M3. But these cars also have added negative camber and positive caster--exactly the changes invoked by the M3 control arm bushings, upper strut mounts, and suspension geometry. Part of this is also achieved by the M3's shorter coil springs. Your original shocks are also a bit underdone for 17in. tires.

I would say let the dealer align the car and see if that corrects things to your satisfaction, but you would be better off with the bushings and mounts.

OBD-II Performance
I have a 1997 M3 with a Conforti cold air intake, and a UUC twin silencer cat-back exhaust. Could I get 300 hp at the crankshaft by adding Schrick cams and a manifold from Turner Motorsport, a Conforti Shark Injector, and Supersprint headers? Will OBD-II allow these mods? What's the deal with OBD-II cars anyway? What makes them so unfriendly to aftermarket performance parts?
D.M. Williams
via the Internet

We spoke with Doug Mahar at Turner Motorsport. He replied, "Yes, the kit we offer is made specifically for OBD-II M3s. Typically, with these mods, we see between 285 to 300 hp. Differences depend on dyno manufacturer, differences in cars, and atmospheric conditions. Unfortunately, you will need to change the CAI as well. The kit we offer uses a larger diameter HFM and that requires a larger diameter intake tube, heat shield and filter.

"OBD-II cars do not have a Motronic unit like the 1995 and earlier BMWs, so when you make a change to the engine, you can't perform a simple chip swap. The Siemens unit in your M3 requires a flash memory upgrade, and this is quite complex compared to a simple eprom swap. Therefore there are not a lot of variations offered yet. The custom software we offer with the cam/intake kit is the first variation on our OBD-II software to come out since the release of the Shark Injector."

The brunt of the OBD-II mandate from the federal government deals with anti-tampering--they don't want us messing with cars anymore. However, as long as you don't increase vehicle emissions or run without a catalytic converter, you are unlikely to run afoul of the law. Mahar is correct--OBD-II cars are not amenable to a simple plug-in-and-play chip swap, hence tools like the Shark Injector. It is also easy to "set check engine lights" on OBD-II cars, because the system may think there is an emissions problem when in fact there is not. Get used to it, D.M. Someday the government will be able to click on "Find D.M. Williams Now," activate your implanted GPS chip, and see a little blinking dot wherever you are on the planet.

Steering Difficulty
Just what is good steering? I find that my 2000 BMW 323i is difficult for me to steer. It does not know straight ahead. The restoring force on a hard corner is high, but decreases and becomes vague when you approach center. It is tiring on long trips since steering commands are generated from sight, not from steering wheel feel. My best long-distance car is a Volkswagen Eurovan that I routinely drive on 600=mile day trips. Does this explain why you see so few BMWs on the interstate. How about a article on this subject.
Tom Barr
Huntsville, Alabama
P.S. The BMW is hands down fun to drive to the office.

Well, initially we have to recognize that what a given person likes and dislikes in an automobile is, to a large extent, entirely subjective. That said, unless there is some mechanical problem or tire issue plaguing your Bimmer, I would say that the overwhelming majority of BMW drivers would disagree with your assessment. BMW steering is very precise and the cars respond at once to input. This means you have to have a steady hand on the wheel. I suspect you may be gripping the wheel too tightly.

I'll never forget being strapped into the right seat of a Ferrari Challenge car while the late Michele Alboreto negotiated Las Vegas Motor Speedway at 150 mph with his fingertips. He said, "You donna need a death grip onna da wheel to drivea fast, Michele..." Alboreto was critiquing my style, and he was right. I tried the fingertip method and it showed me the error of my ways. I'm not suggesting you drive everywhere with your fingertips, but you should try it now and then. You may find the problem is not in the car's steering, but in the driver's steering.

On the other hand, it may be that you simply prefer a more muted steering experience.

Idle Trouble
I have a BMW 525i, production date 11/92. The car shakes at idle--the rpm is at 500 as opposed to other 525is, which are around 750. I used a Bentley manual and replaced the throttle positioning sensor, the car idled at 1100 rpm then later dropped to 750 rpm as I drove. The next time I turned on the car the idle went back to 500 rpm, the only difference being that I heard a clicking noise from underneath the intake manifold. Should I replace the idle control valve? Also, why is that when I do the check code diagnosis I get a 1216 code (check the potentiometer or wiring)? Isn't it true that if the wire was bad the TRANS PROGRAM message would display on the dash as it did when I initially disconnected the cable just to explore the behavior of the car when replacing the throttle sensor.
Fred. N.
via the Internet

Almost all BMW idle problems are the result of idle control valve (ICV) malfunctions. If the ICV is readily accessible, always start there regardless of the trouble tree in the Bentley manuals. On your car, the ICV is under the intake manifold--right where you're hearing that clicking noise. This is most likely your problem. Bear in mind it is often possible to resuscitate a failed ICV by cleaning it out with carburetor cleaner or something similar, but this is often a stop-gap measure at best and, because the unit is so hard to reach on the M50 engine family, you're better off just replacing it.

There is not necessarily a correlation between a 1216 code and the TRANS PROGRAM message.

E39 Motor Swap
First, I'd like to say your magazine is the shit! But you do need more E39 coverage. Second, I would like to know the basic components needed to do an engine swap on my 1997 528i. I had a swap done in my E36, so I am aware of some of the expected problems, such as tearing the rear-end out from under the car because of too much torque and super-sticky tires. So far I have sourced a Euro-spec 300-hp 3.2L M3 motor, which should fit with the 2.8 mounts without much fuss. Of course, a supercharger and/or NOS will be in order to bring up horsepower without too much added weight. The automatic transmission and differential may be tossed out for a five-speed manual, otherwise the automatic will be built and a limited-slip differential installed. What other parts do I need for this swap, and can you point me in the right direction to a reputable shop that can perform this work in the San Diego area?
Richie Ramnarain
via the Internet

We're the "shit" eh? I guess I have to update my hip dictionary! But thanks, I guess.
1. The E36 3 Series will sometimes tear the differential mounts (actually rear suspension mounts) out of body regardless of engine power. The failure is very rare, though, and Turner Motorsport ( has a set of reinforcements for the body. Correct installation is very involved, highly specialized and very expensive.

2. Almost every BMW letter we receive that mentions NOS also mentions the words, "blown motor." Be careful. And we know of no supercharger kits available for the European-specification S52 or S54 engines.

3. An automatic transmission in this car would be pure folly, and competent domestic BMW transmission rebuilders are harder to find than Osama and Saddam, wearing matching bras and panties, dancing in a water fountain. BMW factory rebuilds are the way to go. But in your case, you'll want a five-speed ZF S5D 310Z or 320Z from an E36 M3 or a late 328i. The driveshaft will probably have to be custom fabricated using an M3 unit as a starting point.

4. You'll need to find a donor car for the pedal assembly, or else buy the parts from BMW.

5. For the differential, you'll want an E36 M3 unit, either the 3.15 from the 1995 cars or the 3.23 from the later cars.

6. Contact Carl Nelson at La Jolla Independent (858/488-1555), and be ready with a fresh VISA card. Silly me. From that donor European-specification M3, you will also need the radiator with integral engine oil cooler and associated plumbing and hardware (much fabrication may be required here), along with the engine harness and ECU.

E36 M3 Brake pedal play
Good magazine--I have all issues going back the the late '80s. Some are lost in time and not even you have the back issues. Anyway, I've never used you as a resource, but here it goes:

I just replaced my front and rear calipers on my M3. While they were off, the makeshift caps on my brake lines leaked some of the fluid out. I reassembled everything, flushed the system, and now I get about 2 to 3 in. of play before the brakes grab. I went to the dealer and had it connect its ABS+T module to cycle the valves and pressure bled the system. No improvement. Any thoughts?

I checked the Web and this seems to be a somewhat common problem without a solution posted.
via the Internet

Well, if we divorce ourselves from trying to determine the ultimate reason and focus on what can can cause this problem, essentially we are left with two possibilities: 1) There is still air in the system; or 2) The brake master cylinder is faulty. It could be both, too.

I doubt the problem is air in the hydraulic lines because dealers usually do a good job of brake fluid changes. You don't mention how many miles are on this car, its model year or its brake fluid change history, but brake master cylinder failure is not uncommon on cars that have not had annual brake fluid changes. I would replace the brake master cylinder.

Build What?
Love the magazine, ever think of going bi-monthly? I can't wait a full 30 days for the next one! Project Greyhound is either in the same financial situation as me or Dan Erwin is preoccupied with other projects (also like me). Hurry up already! Where can I follow your detailed progress?

Here's what I have:
* 1977 BMW 320i four-speed, runs good, very rusty, no title
* 1985 BMW 528e five-speed, engine fire, not too bad--wires, hoses and sensors, slightly rusty, clean title
* 1985 BMW 735i automatic, runs great, no rust, clean title, needs paint and minor work (my baby, not part of this Frankenstein project)
* 1987 BMW 735i electronic automatic, runs good, slightly rusty, EH transmission only works in drive (computer?)

And here's what I'm wondering:
Besides the '85 735i, should I make a '85/77 520i/four-speed (using the 528e body and 320i drivetrain), a '87/'85 735i/six-speed (using the '87 735i body/motor and the 528e gearbox/driveshaft, fix the firebomb 528e, fix the EH automatic in the 735i, or scrap them all (except usable parts for the '85 735i)?

After you make your choice, a list of which parts would be needed from each vehicle would have to follow. I wouldn't want to build a whole car and be an inch short or a sensor away from finishing.

Now the fun part, with these projects which would be the most straight-foward swaps of drivetrains requiring the least amount of mods. By the way, I am a backyard mechanic who thinks I should work in the Spartanburg plant next to the production workers (only a dream).

Also, Project M3 either makes way too much money, or Pablo doesn't eat. Thanks for the articles.
Joel Burger
via the Internet

Bi-monthly, eh? Joel, we need to water our plants once in a while, okay? And Dan Erwin's "Project Greyhound" involves a great deal of rust, which, as any restoration tech can tell you, involves a great deal of time. In this case, Erwin is making all the replacement panels rather than buying factory parts, which takes even more time.

Now, on to your problem--and it is a problem, Joel. You don't get out much, do you? First, a 320i, especially a 1977 model with the big vented front brakes and the 2.0-liter engine, can be a fun, durable and efficient Bimmer. Problem is, they rust with the morning dew. On a crisp cool morning, that crinkling sound you hear is E21 3 Series BMWs rusting all around the world. But with a few parts (Bosch ID48X distributor, Bosch Blue Coil, 2002tii exhaust manifold, Bilstein shocks and a set of larger sway bars combined with decent tires), the 320i is a very cool car that also gets 33 mpg, even with a four-speed gearbox. I'd leave the drivetrain like it is, but whether you want to do a rustoration on this car is up to you.

The Getrag 260 gearbox in the 528e has a baby six-bolt pattern on the integral bellhousing, so forget about using this gearbox behind an M30 big six.

The ZF 4HP22EH automatic transmission in the 1987 735i is history--it's not the computer.

Here's my recommendation:
Blitz the 320i as best you can, make it run as good as it can, and sell it. Use the money to buy used parts to make the 528e run, and blitz the body on this car, too. Sell it for more money. Use the money from the 528e to buy a Getrag 260 with a big six-bolt pattern (the better ones are found in the 1986-on 535i, 635CSi and 735i, and are identified by cooling fins on the bottom of the cases), and a 1987 735i manual gearbox driveshaft. Buy the driveshaft already rebuilt from one of the domestic rebuilders such as Portand Driveline, and make a deal where you can send them the automatic driveshaft as a core--they need them more often anyway. These invariably need new universal joints and center bearing assemblies. The center bearing is no problem to change, but the universal joints are ridiculously hard to change.

You will also need pedal linkages, clutch hydraulics, shifter parts inside and out, a manual gearbox 735i center console, flywheel, clutch parts, guibo, gearbox mounts and gearbox support. Some of this will have to be purchased new, possibly from BMW. Other stuff you can find used. I'd recommend buying the clutch parts, including the clutch master and slave cylinders, along with the hydraulic line, new from an aftermarket supplier.

Finding an E23 five-speed parts car is a tall order, but that would certainly simplify things. Bear in mind you can also install the bulletproof Getrag 262 four-speed from the pre-1980 633CSi or 733 CSi.

You're right about project M3--for the cost, Pablo could have himself a formidable Porsche 911 Turbo that would suck the headlights out of just about any M3 that isn't sitting in a secret building in Germany with an S62 V8 nestled between its aluminum fenders.

BMW Project
I have quite a few questions that maybe you can or can't answer. Any input would be helpful. I'm 14 and am looking into a 1986 to 1989 E30 3 Series BMW for a project car to start and to have when I first start to drive. First and foremost, do you know of any Web sites that I might be able to go to to get a use one for a cheap price? Second, I want to have enough power to beat an M5--Like twin charged power. Do you have any recomendations of companies that might have turbo- and supercharged or twin turbo kits available for such a motor? Third, and maybe the most in reach, would be the addition of a six-speed manual gearbox. Has such a thing ever been done? And last, where can I find a good aerodynamics package that will keep me on the ground at these sub-sonic speeds that I intend to hit?

I'm asking you these because my dad owns a 2001 Audi S4 Avant with an MTM chip, APR Bi pipe, UUC Velocimax 1 exhaust, RS4 suspension and front bumper, 18-in. BBS CHs and eurolights. Whenever we come out of the gas station he floors it and with my head indented firmly into the seat, it always brings a smile to my face. I want that kind of power.

Keep up the good work and keep the pedal to the floor.
Patrick Cushenberry
via the Internet

Thanks for writing Patrick--surefire proof that our "indoctrination of the young" program is proceeding as planned. I was one of the first. When other boys were reading comic books, I was pouring over VW & Porsche (our predecessor) and european car magazines.

I'm going to give you a hard lesson in reality on two fronts. First, speed costs money, lots of money. While cheap performance is possible, the term is relative. There is no car you can buy for a couple grand that will beat your dad's S4, except maybe only in acceleration, and there is much more to driving than acceleration as you will soon learn. Your dad's S4 cost him a great deal of money, and what you want to build will also cost a great deal of money.

This brings me to my second lesson in reality: You need to embrace the concept of design limitations. There are no supercharger or twin turbo systems available for the BMW M20 engine, nor, if there were, would the car be likely to touch an E39 M5. Now, you could install an S38 engine from an E34 M5 in an E30 and give an E39 M5 a run for its money, but you will have spent at least a full-year's college tuition in the process--back to harsh reality lesson number one. Similiar things apply to the six-speed. Could it be done? Sure, but why would you want to? Six-cog gearboxes have a great deal more to do with marketing and one-upsmanship than they do actual performance benefits. Most cars with sixth-gear intergallactic overdrive, including the E46 M3 in my opinion, do not have sufficient differential gearing to take advantage of the fact.

My best advice to you is to concentrate on learning to drive first, and I don't mean parallel parking and three-point turns (although these are important, too). I think you should get that E30, but I think you should keep it virtually stock in the beginning, and focus on bringing it up to snuff mechanically and cosmetically. Your dad is obviously a hotshoe. Tell him you want to attend BMW Car Club of America chapter driving schools in your area ( At these events, you will learn car control and smoothness at speed. Without that smoothness, speed and skill will never come. With it, they will come naturally.

The best car to learn in? One with moderate to low power, skinny tires, and lots of body roll. A 325e or 325i with a stock suspension and decent 195/65-14 tires will be perfect. Just make sure the brakes are in good shape (new rotors and pads, fresh DOT 4 brake fluid), the suspension bushings, ball joints, and steering links are on-spec, and all the safety requirements set by the driving school organizers are met.

I know this does not comport with your present plans, but if you follow this advice you will become a much better driver than 99% of your peers with flashier cars, some of whom will wind up being a dark wet spot on the pavement.

BMW 325i vs. 328i
What is the difference between a BMW 325i and 328i? I knowthey are different models but are their engines differerent?
from Ohio

Initially, recognize that the BMW 325i was and is built in three body styles--the E30 from 1987 to 1991 (1992 for the convertible), the E36 from 1992 to 1995, and the E46 from 1999 to the present time (2003). The 328i was also built in two body styles--the E36 from 1996 to 1999, and the E46 from 1999 to 2000. With the 328i, you would also be talking about a four-door car, but a 325i could be a two-door or a four-door if it is an E30 or E36. An E46 325i is a four-door car. This confusion results from BMW's virtually inexplicable changes to its naming conventions.

Now, that aside, the answer is yes, the engines are different:
1. The E30 325i has an M20 2.5-liter sohc engine, with 8.8:1 compression, 168 bhp at 5800 rpm, and 164 lb-ft torque at 4300 rpm.

2. The E36 325i (1993-on with VANOS) has an M50 2.5-liter dohc engine with 10.5:1 compression, 189 bhp at 5900 rpm, and 181 lb-ft torque at 4200 rpm.

3. The E36 328i has an M52 2.8-liter dohc engine with 10.2:1 compression, 190 bhp at 5300 rpm, and 206 lb-ft torque at 3950 rpm.

4. The E46 325i has an M54 2.5-liter dohc engine with 10.5:1 compression, 184 bhp at 6000 rpm, and 175 lb-ft torque at 3500 rpm.

5. The E46 328i has an M54 2.8-liter dohc engine with 10.2:1 compression, 193 bhp at 5500 rpm, and 206 lb-ft torque at 3500 rpm.

There are myriad other differences between these models as well, including gearboxes, differential ratios, suspension designs and interior appointments. For a nauseatingly thorough education, I recommend you procure the following light-reading materials:

* european car, March 2003; "BMW Best Buys 1992-1999 3 Series"
* "BMW 3 Series Enthusiast's Companion", by Jeremy Walton, Robert Bentley, Publishers
* "BMW Buyer's Guide," by Fred Larimer, MBI Publishing Company

Another 1997 M3 question
Can I use an adjustable fuel pressure regulator to push more fuel into my OBD-II M3? Does this make the ECU upgrades (Dinan, Conforti, AA) unnecessary? Also, I would love to see a comparison of the most popular ECU upgrades done on the OBD-IIs with minor mods (cold air, cat back).
via the Internet

The answer is yes, but there is no benefit to doing so unless your engine needs more fuel pressure due to the addition of other modifications. Performance ECU software revises the ignition timing and optimizes the system for high-octane gasoline. It remaps fuel delivery at high rpm, eliminates the top speed limiter and raises the redline. More fuel pressure isn't going to help you unless you need it.

Examples of mods that might require more fuel pressure include performance camshafts, head porting, exhaust headers and forced induction.

On some BMW engines, most notably the M30 sohc six-cylinder, age and wear can make them want a scooch more fuel pressure--like maybe 0.5 psi. This can correct a stumbly idle and flat spots in the acceleration curve in the M30.

Also, some stock fuel pressure regulators like to hang out on the low end of their operating specifications. So, if you have an adjustable regulator and you can dial in the pressure exactly at spec, so much the better. I especially like the adjustable regulators with the integral VDO fuel pressure gauge, such as the ones sold by BMP Design ( But the overwhelming majority of cars out there with adjustable fuel pressure regulators need to have them set at the stock specification.

1989 325i Question
I have a 1989 325i, and I was wondering if I can swap the differential with a M3 diferential, and if so, what year M3 diff could I use. Also, what is a good chip for my car.
via the Internet

Sure thing, Luis, the E30 M3 4.10 limited-slip differential is a direct replacement for your original 3.73 unit. However, if your 1989 325i has an automatic transmission, it already has a 4.10 differential; the 3.73 was used with the five-speed overdrive manual gearbox. Toward this end, you may get a better deal on a 4.10 diff from a 325i automatic than an M3, and it is the same part. However, the 325i automatic differential may or may not be a limited-slip unit. You can determine whether it is in three ways:

1. If you turn one output flange or the input flange, both output flanges will turn in the same direction on a limited-slip differential.

2. A BMW limited-slip differential will have a white "S" painted on the top (not visible with the diff installed).

3. A BMW limited-slip differential has an "S" on the ratio tag, which is attached via one of the cover bolts on the right side.

For the chip, I've always preferred Mr. Conforti's work, but most of the popular plug-in BMW chips are the same.



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