Run the equator: 2009

Thursday, December 17, 2009

Replacement of the BMW E30 rear subframe bushings

The rear axle carrier – also called cross-member or sub-frame – is attached to the chassis with a pair of sturdy bushings made of metal and rubber. Over time the rubber in these bushings weakens. Some bushings break, others merely sag. The overall effect is that the whole rear of the car feels a bit loose, as if it were moving sideways on its own when you turn. Shifting may result in a loud “clunk” when the clutch is pressed; momentum pushes the chassis forward while the final drive is suddenly decoupled; since the bushings are weak the subframe will jolt and bang against the chassis.

My car showed three different symptoms of mechanical failure in the drive train:

  • A loud clunk when I shifted while accelerating, especially from first to second gear, louder when moving uphill – presumably caused by front-to-back play in the bushings. Let’s call this “the big clunk”. This one felt like the car was coming apart.
  • A sudden bang when driving over certain small bumps or cracks in the road – probably caused by up-down bushing play that makes the subframe hit the supporting plate or the chassis
  • A weak dangling sound when pressing the clutch, as if something were swinging side to side and banging against metal. Not sure what this sound is caused by. I can hear it even if the “big clunk” doesn’t occur. Let’s call this the “little clunk”.

Click on each picture to see a larger version and access the image notes. Click here for the whole set (contains some additional photos not included in this article).

Sagging subframe
A good indication of the condition of the bushings is the gap between the cross-member and the support plate. If the bushing bottom touches the support plate, the bushing is worn out. The rubber that holds the bushing’s central hollow rod anchored to the outer sleeve weakens, making the subframe sag.


Normally I raise the rear and place the jack stands under the crossmember. Since you will be lowering the crossmember, the jack stands have to go somewhere else - the jacking point is right in front of the subframe support plate. The standard jack stands fit there, but the body rests on them in a rather precarious position. Maybe this support point is meant to work with a special BMW stand or a lift, neither of which can be found in my tiny garage.

The exhaust pipe is merely an inch or so under the subframe. Release the support brackets that hold the muffler and lower the exhaust to make place for the subframe. I am not sure this step helped at all.

To create more space below the subframe, unhook the differential from its support bracket and lower the final drive (which is attached to the subframe with bolts). You should support it with a jack or blocks of wood. I forgot to support it for some time but luckily no damage occurred.

I thought that by lowering the trailing arm I would gain some additional space for the subframe, so I unscrewed and removed the shock absorber bolt. In retrospect this turned out to be unnecessary. I did not do the same on the right side and the subframe dropped just fine. Support the trailing arm if you chose to go through with this step.

Give a good tug with a large wrench or breaker bar to the 22mm nut on the subframe bolt to loosen it. I had to use my large torque wrench for this; the nut wouldn’t budge with the regular ratcheting wrench. Support the subframe with a floor jack. Remove the 6mm Allen bolts that hold the support plate to the chassis. They come out easy, together with the reinforcement piece.

Remove the subframe nut and the support plate.

Worn out bushing
The rubber insides of the bushing look quite worn. Start banging on the bolt with a mallet or a hammer until it slides up the shaft. This part wasn't easy; it took a lot of hitting, sweating and cursing. There wasn't much space between the bottom of the car and the garage floor so I couldn't take a wide swing at it. It finally budged a tiny bit, then a little more until finally I was able to push it out with a screwdriver and the tap of a mallet. Some write-ups tell you to cover the top of the bolt inside the car with a towel so it doesn't fly against the ceiling when you hit it. This bolt never flew anywhere - it moved bit by bit with every blow.

Subframe lowered
Release the jack and lower the subframe. It didn't go down too far; I had to push and pull and fight for every inch.

There wasn’t enough space to squeeze the bushing tool between the subframe and the chassis, so I decided to unhook the stabilizer bar from the trailing arm to gain some additional room. In retrospect, just like with the shock, I am not convinced this step was necessary.

The tool

Subframe bushing tool parts
I bought the subframe bushing tool on eBay for $150. It seems to be part of a multi-model bushing tool kit code-named BMW2336, made by a manufacturing company called Sir Tools and sold by resellers like Zdmak and Technictool, for about $300. This kit is no longer for sale; it has been superseded by tool set BMW3026. The tool I bought is limited to the parts that are needed for the E30.

Since the parts did not come with instructions I emailed both Sir Tools and Zdmak asking for a courtesy copy (it was quite obvious how it worked, but nonetheless). Sir Tools answered a week later and actually sent me a copy by email.

Instruction sheet
These are the tool directions as found on the internet. The removal steps are accurate but the installation instructions go against common sense. In order for the tool to push the bushing in the subframe when the bolt is tightened, the top piece (#R) must sit on top of the collar (#J) which sits on top of the subframe. The instructions say something else. They must have been written by someone who has never seen the underside of a car.

I could have tried to build a similar tool myself, but I just felt like spending the money this time (unexpected bonus at work helped too). Building a tool requires some pipe fittings and caps, a few nuts, a long threaded bolt and a bit of drilling. The sizes of pipe fittings must be carefully chosen to ensure they match the subframe cavity. You can find examples of home-made tools here and here.


Place sleeve (B) over bottom plate (A) and ring (C) on top. Slide bolt through plate. Grease the threads well.

Tool in place for removal
View from the top
The ring pushes against the bottom of the subframe “cup” that holds the bushing. The bolt is threaded through the bushing and screwed onto the cap, which sits on top of the bushing. The vertical notches in the “cap” must line up with the dimples in the subframe, otherwise the cap won't slide down when the bolt is tightened.

The ring is designed so that the metal collar at the bottom of the bushing can slide through it in the sleeve, while its two opposing protrusions push against the subframe.

The tool must be perfectly centered - if it's not, it may slip on one side and the ring bites through the subframe exterior coating - which is what happened to me. I re-centered the tool and it stayed in position this time.

The actual removal of the bushing only took a couple of minutes.

The inner metal cylinder of the old bushing is higher up in the sleeve than the new Lemforder bushing. This is because the rubber around it has weakened. This is probably the original 21-year-old bushing.


Tool set up for installation
View from the top
Set up the tool for installation. The top cap piece sits on the collar which rests on the subframe. The top of the bushing will pass through the collar and go into the cap. The slits at the bottom of the cap engage the tracks that jut out of the collar, so the cap doesn't move when the bolt is tightened. The threaded bolt must go through the chassis hole where the knurled bolt was; otherwise the bushing can't rise in the subframe cup.

The rubber is lubed with a very thin solution of water and dish soap. It evaporates almost instantaneously. The vertical groove in the bushing must be aligned with the dimples in the sleeve of the subframe.

Remove the tool. Raise the subframe. Don't forget to put the washer back on top of the bushing before raising the subframe.

To make the knurled bolt drop all the way down and lodge itself in the chassis I had to push and pull on the subframe to align the bushing with the hole in the chassis, I raised the sagging differential a bit, and then hammered away on the bolt head from inside the car. The hammering was needed because the last inch or so would not go down freely and when the nut was tightened the bolt would just turn on its axis. I couldn't find out if the nut was supposed to be a single-use self-locking nut, so I used some red Loctite and 120 foot-pound of torque. I found the number somewhere on the BFC forum; it may not be accurate, but the Bentley does not say anything about the subframe, so there...

Notice the healthy gap between the support plate and the bushing. It will become smaller when the car is back on the ground.

Installing the right-side bushing
Now do the same thing on the passenger’s side. The subframe dropped much easier and lower than on the driver’s side without removing the shock absorber bolt. Actually, everything went easier on the passenger’s side: I didn’t have that much trouble removing the bolt (it moved after a few hits with the hammer) or putting it back in.


Tool: $150+shipping.
Parts: $45.50 for Lemfoerder bushings on

Time & effort

Around 8 hours – I started at 9:30 AM; the car had its wheels back on the ground shortly before 6PM. This includes jacking up, a short trip to the auto parts store and lunch. Most of the time was spent ratcheting, banging on stuck bolts and in procedures that weren’t strictly necessary. The actual removal and installation of the bushings was a matter of minutes. I can’t imagine how long this procedure would have taken without the special tool. It’s one of the most complex procedures I have completed, albeit less complex than the front suspension upgrade. It was very demanding physically: that evening my hands and forearms were so sore and swollen I could barely turn a door knob. Lifting the glass of beer to my mouth was painful. I hurt until the following Tuesday.


I drove for a few days on steep Seattle streets full of potholes before posting this. I can confidently say that clunk #1, “the big clunk,” is gone. Going over bumps and cracks feels more solid now as well – I don’t get the impression anymore that the rear of the car would fall apart, but this may be just wishful thinking – I have sport suspension, the ride is a bit rough anyway. Clunk #3 is still there, though. Now with the subframe bushings out of the way I can only ascribe it to the differential dangling in the center support bearing. Or something. The quality of ride has definitely improved, but not dramatically.


Do it. If you get “the big clunk” changing the bushings will result in a clear improvement to your shifting. If you decide to do it the barbaric way – removing the subframe entirely, cutting through the bushing with a saw, burning the rubber, taking the cross-member to a mechanical shop to have the bushings pressed in, doing whatever you need to do - it could take much longer, depending on your experience and whether you're working alone or with a helper. Things have been done that way many times and you will find a few write-ups online to guide you. To each his own.

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Saturday, September 26, 2009

When your fuel pump goes...

I knew it had to happen to me sooner or later, and it did: as I left the grocery store heading home, my 21-year-old BMW did not start. A nice lady asked me if I needed help to jump the car, and I had to decline her offer; it wasn’t the battery, it had to be something else. Good thing the store was only a few blocks away from home. I had the car towed the next day, pushed it into my garage and started debugging.

There’s a straightforward step-by-step procedure you can follow to find the cause of a non-start. After eliminating the obvious suspects – a dead battery and the absence of spark – the most obvious component that needs to be tested is the fuel pump. In later E30 models (starting with production month 9/87) there is only a single fuel pump, located in the fuel tank, accessible through a hatch under the passenger’s side rear seat. It’s easy to check if the pump is working: remove the rear seat, remove the pump cover, crank up the car (or have a helper turn the key instead) and listen. The pump should make… well, pumping sounds, just as you imagine a fuel pump would sound. If you can’t hear anything it could mean that:

  1. Either the pump is broken and you need a new one, or
  2. You have no voltage at the pump – because either the wires are interrupted (pray that they aren’t because fixing wiring in a car is a terrible job) or your fuel pump relay is bad

To check for voltage remove the power connector from the pump, stick the probes of a voltmeter in the connector and crank the car – if the relay works the probe should show battery voltage, about 12V. Operating the ignition while holding the probe in the connector and reading the voltmeter display can be a pretty cumbersome task - another set of hands greatly helps. If you’re working alone you can simplify your life if you bypass the relay: remove it from its socket and link the connector’s pins 30 and 87 together with a wire (preferably a fuse holder with a 15amp fuse); this will bypass the ignition and supply constant battery power to the fuel pump (that’s also a good way to make sure the wiring is fine).

If there’s voltage at the fuel pump but the pump is silent it’s time for a new pump. There are a few models for sale that can fit the E30. The OEM pump for the ’88 E30 is a VDO. The good thing about it is that it comes with the complete assembly: fuel pump, mounting frame, filter and O-ring; you just swap the old one out and re-connect the hose. The average price online for this OEM part is about $200. The cheapest I could find it for was $176.35 at Unexpectedly, my usual supplier sells the VDO pump for an ungodly $362.95.

The TRE 340 in a box
The alternative is a pump from an aftermarket supplier like TRE or Walbro. The TRE 340 had good reviews (if you can ever take seriously anything you read on internet forums) and it’s for sale on eBay. The noticeable price difference ($78.98, shipping included) tipped the balance in its favor. However, generic aftermarket pumps come with a catch – they require some wiring work, and they may need modifications to the fuel pump assembly to fit.

This is the whole procedure, step by step. Click on each picture to see a larger version and access the image notes. Click here for the whole set.

The Bentley recommends disconnecting the battery (as it does for almost every procedure); I didn’t. Anyway, be careful when you work around fuel lines. Don’t smoke.

Remove the rear seat and then unscrew the four bolts that hold the black oval access cover on the passenger’s side. There’s a similar round cover on the driver’s side – that’s just a fuel gauge sending unit; leave it alone.

Remove the electrical connectors: the connector with 2 pins is the power supply. The other is the fuel gauge sender connector.

Loosen the hose clamp and remove the hose. Either end will do. The one on the fuel-line side was easier to remove. Fuel may be discharged – in my case there wasn’t any fuel in the line since the pump was broken.

Remove the four 8mm mounting screws on top of the fuel gauge sending unit.

Pull the sending unit out of the tank. Wait until all the liquid drips back in the tank. There is a lot of gas in the can, and it all drips out through a tiny hole at the bottom.

Rotate the fuel pump assembly counter-clockwise to loosen it.

Remove fuel pump assembly out of the tank. Make a note of the position of the assembly when it comes out. You will have to put it in the same way.

Look at the assembly and notice the alignment of the fuel filter relative to the frame. You will need to install the new filter in the same position.

Remove the filter by pulling on it, and then remove the pump from the frame. The connector wires are soldered to the assembly. You will have to melt the solder or cut the wires.

There’s an obvious size difference between the old pump and the new. Fit the sleeves that came in the package around the new pump - it will increase its diameter and make it fit snugly in the frame. The sleeves are optional.

The short feeding tube at the bottom of the TRE pump and the similar tube on the OEM pump have different diameters and are positioned differently. To make the new pump fit we have to tinker a bit with the assembly frame.

Carefully carve in the bottom support of the frame until the feeding tube of the new pump can fit through. Be mindful not to damage the frame too much. Either way, it’s not going to look pretty, but who cares – it goes in the tank!

Solder the connector wires that came in the package to the terminal pins on the frame. I wasn’t very good at that job. I hadn’t soldered anything since shop class in school. So far I’ve used butt connectors for all the electrical work on this car.

Use the short fuel hose (came with the package) to connect the pump’s outlet and the metal tube which is part of the assembly.

Pressing gently against the pump’s bottom tube install the filter maintaining the same orientation that the original filter had. I also strapped the pump to the frame with a zip-tie although it wasn’t strictly necessary; the pump was snug enough in place.

Insert the whole assembly with the new O-ring back in the tank. I couldn’t find an O-ring of the same size in any automotive shop and the local BMW dealer didn’t have one in stock so I decided to re-use the old O-ring. Let posterity judge me…

Reconnect and install the other pieces in the order they were disassembled.

Work time: about three hours.

After I completed the procedure, the car started immediately, as expected. I have not noticed any unpleasant noise when the pump is in operation. Now I can only hope that this new pump will last as long as the original one did...

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Sunday, July 5, 2009

Rear brake pads and rotors

Fresh from Germany
The rear brake pads and rotors on my BMW were still the ones that came with the car when I bought it in 2005. They were worn out to the point the sensor was touching the rotor and although they may have had some life left in them I decided to replace them now rather than wait longer. The rotors were likely worn out beyond the minimal thickness suitable for re-surfacing (it turned to be true when I measured them) so I bought pads, wear sensor, rotors and rotor mounting internal-hex screws. It’s a simple procedure. This write-up is loosely based on the procedure described in the Bentley manual. Click on pictures to see notes indicating the location of various components.

Jack up the car and remove the wheels. Release the hand brake.

On the right wheel, disconnect the brake pad wearing sensor and release the connecting wire from the clip that secures it to the guide bolt cap.

Remove the plastic caps that cover the caliper guide bolts.

The next step was to remove the guide bolts themselves, and here’s where I noticed that I lacked the tool for it. The guide bolts have an internal hex head and my largest Allen key was still too small to fit in the opening. So here I am taking another trip back to Schuck’s in my wife’s car. This sort of emergency trip seems to happen every time I attempt a new maintenance procedure… I bought a full set of metric hex keys.

Remove the caliper guide bolts.

Remove the anti-rattle spring by pressing on it and pulling, and pull the caliper out with the brake pads. It should come out without effort.

Continue with the removal of the rotors. Start by unscrewing the brake pad carrier bolts.

Do not let the brake pad carrier assembly hang on the brake line. I suspended them with zip ties to the frame. S-hooks would do as well.

Remove the mounting screw from the front of the rotor and pull the rotor from the hub. If the rotor is stuck to the hub use a soft mallet to free it.

That’s when I noticed that the left-side shock absorber had a build-up of grease at the bottom. There is no motor oil in that area and the only place this could have come from was the shock itself. I traced the leak to the top part of the shock. To get to the source I pulled down the plastic boot that covers the piston (it was a bitch to put it back on the top cupped waster) and there it was: a puddle of clear oil on the cylinder cap. I’m pretty sure the shock is not supposed to leak. I must call BavAuto…

Install the rotors on the hubs. I used new mounting screws; the old ones were rusty. Clean the rotors with brake cleaner before installing the new pads.

Compress the piston back into the caliper to provide space for the new, thicker brake pads. I used a C-clamp. If the brake fluid reservoir is full to the brim, pushing in the piston may make the brake fluid leak through the screw cap of the reservoir.

Install the pads in the calipers and put the whole thing back on. Don’t forget the new pad wear sensor on the right wheel.

Cost breakdown

All parts purchased from Pelican Parts.

  • ATE brake pad set - $37.25
  • Brake pad wear sensor - $4.75
  • Balo rear brake disks (rotors) - 2 x 33.75 = $67.50
  • Brake Disc and Drum holddown bolt, 11mm Head - 2 x $2.00 = $4.00
  • About 5 hours of work, including two trips to Schuck's

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