BMW 760i Repairs page 3
Liquid cooled alternator rebuild
Oil change - rear differential
Brake fluid flush
front axle overhaul (new upper/lower control arms, tie rod ends, brake rotors and pads)
Throttle bodies
High pressure fuel pumps
Intake manifold
New hood insulation
Front alignment
Sun roof seal
IVM module (inspect/repair)
Fuel tank breather valve
1. Alternator repair
This Alternator is from my 740i. The 760i alternator is identical just with some slightly beefier parts inside (760i is a 180A alternator vs. this one which is 150A). This is a liquid cooled alternator.
Most would simply buy a replacement alternator but it is possible to repair these yourself...
Here's what it looks like inside. There are 6 diodes (3 x positive and 3 x negative) and the black plastic case is the regulator.
The rectifier assy unscrews from the main body of the alternator. I applied fresh heatsink compound on the mating surfaces.
My alternator was dead - the Battery light illuminated on the dash and the battery voltage was at ~10V and did not increase when the car was running. After opening I determined one of the diodes was shorted. Although I could have simply pressed in a new diode, I elected to replace the complete diode assy and regulator. The kit below was purchased on Ebay for $79 and includes replacement bearings as well. It's made in China, not oem Bosch which I'm sure would cost a lot more.
The messiest part of this job was re-sealing the plastic cover (I used black RTV). Otherwise it is a straightforward job and has been working perfectly ever since.
2. Rear differential fluid change
No pictures for this straightforward job. I removed and replaced ~ 1.7liters of 75W90 gear oil. Access is excellent... a very simple job.
3. Brake fluid flush
No pictures of this job either, just a note here to record that I did it.
4. Front Axle overhaul
I replaced the front control arms, tie rod ends, rotors and pads.
I went with Lemforder (oem) control arms, TRW tie rod ends (also oem), ATE rotors (which are massive) and Wagner MX918 brake pads.
I always shop for deals... I purchased one of these tie rods from AMAZON (last one) and the 2nd came from Ebay, $52 for the pair which is a pretty good deal.
New rotors.
As you can see below, one of the lower control arm bushings was completely shot.
A lazy mechanic knocked holes in the air ducts that vent the font brakes to simplify control arm replacement. I taped over them after installing the new arms.
The lower arms appear to have been swapped out once already but the tie rods and upper arms appear original.
I removed the calipers, rebuilt them and applied a light coat of high temperature enamel. The Pistons were in excellent shape... everything cleaned up real nice.
I installed Wagner brake pads...
All back together... new upper and lower control arms, tie rods, rotors and pads.
I'll do an alignment myself (toe in) when the car is back together.
After changing the brakes, fluid, and engine oil I tried to reset the maintenance intervals (press and hold the top left button in the cluster). All went well except the Front and Rear brake interval... it acted like it reset but the indicator still shows '!' and the red brake lining warning came on!
Checking for errors, this one (5F26) kept coming back as soon as I tried to reset.
When I changed the front and rear brake rotors and pads I did not change the brake wear indicators... they were not worn through so I assumed they were still good (WRONG!).
When I checked their resistance they were about 500 ohms each! New indicators are 0 ohms and jump to 500 ohms when they start to wear and then to an open when the pads reach their wear limit. The car expects the wear indicators to be replaced when the brakes are serviced and so set an error because the wear indicators were not 0 ohms! After changing the wear indicators, then clearing the error, I was able to reset the brake maintenance indicator and the brake lining warning went away!
5. Throttle body testing
I picked up a throttle body connector and pigtail from the junkyard.
The throttle bodies in this car are not really serviceable other than to clean them up and verify they are working correctly.
As a sort of fail safe mechanism, this throttle body has 2 x position sensors (potentiometers) that are wired opposite to one another... with 5 Volts applied across these, one will output a voltage that increases with opening and the other a voltage that will decrease. The sum of the 2 voltages is always 5V. In this way the ECU is able to verify the throttle bodies are working correctly and will shut down the engine if this condition is not met. I used a variable lab power supply to actuate the motor in each throttle body, verified smooth operation and monitored the voltages on an oscilloscope to confirm they sum to 5V and that each voltage was clean during movement of the flap.
6. High Pressure Fuel Pumps (HPFP)
These are a common failure on this car... the diaphragms tear/wear out and leak fuel into the breather hose.
To replace the diaphragms (which I purchased from Germany) you will need to fabricate a 5 sided tool to remove these bolts. I used an old hex bit which I ground to shape using a dremmel.
Here's what lies under the top cover...
Note the orientation of the domed (spring) washer.
Lift out this plastic spring seat.
To remove the metal sleeve (which is stuck to the diaphragm) I used a 16mm deep socket with a couple layers of plastic tape.. A little bit of bending pressure locks the socket to the ring and you can then gently pull until it pops out.
And here are the diaphragms... note there are 2 (on top of each other).
After removing the diaphragms you can see some residue from them stuck to the pump which must be gently cleaned away.
And now ready for the new diaphragms.
New diaphragms I purchased were pre-cut and ready to install (2 per pump). I paid about $130 for these!
Diaphragms came with new (brown) O-rings.
7. Intake manifold repaint
I gave the intake manifold a custom paint job...
First I sprayed it silver then masked off and went over with black. I think it looks better!
8. Hood insulation
The original hood insulation was burned from what appears to have been a small engine fire!
I checked every E65 I saw at the junk yard for several months but none that looked that great, and then this one showed up... which looks almost brand new! Unfortunately it has a couple of small tears but for only $6 I'm OK with it... it looks much better than the one I took off.
9. Front alignment
Since I replaced the front control arms and steering end joints, a front end alignment is needed. The only adjustment is the 'Toe in', which is easy to do myself.
I use 2 x 6ft levels and a couple of tape measures all purchased from Harbor Freight for a very good price (always use their 20% coupon).
Each level is elevated off the floor until there is just enough room for the tape measure to pass under the car without obstruction. Each level is centered on the front wheel and pushed up against it.
The car needs a very slight 'toe in'.
Here are the final measurements...
77" behind the front wheels and 76 7/8" in front of the front wheels (1/8" of toe in on an effective wheel dia of 6ft).
This method is very accurate but I find it difficult to ensure the steering wheel is always centered, but it is easy to take an equal amount of adjustment out of one side and add it to the other to center things up afterward if necessary (after test drive).
In case you doubt the accuracy of this method... I had my 540i professionally aligned and quickly trashed a set of front tires. I checked it myself using this method and found the toe in to be miles off (almost 3/4")! After adjusting it to about 3/16" toe in, the new tires are wearing much more evenly.
10. Sunroof seal
There was some wind noise from the sunroof so I needed to replace the seal.
Below is the replacement seal
First slide the front seats forward as far as they will go and tilt the seat backs forward as well. You can then climb in the rear door and stand up in the sunroof opening.
The old seal peels away but leaves a lot of glue on the car. A little heat form a heat gun helps the old seal peel off the car. Unfortunately it leaves a lot of glue behind on the car.
I found the best way to remove the glue was to roll it back with some firm pressure from a thumb. It took about 45 mins to peel it all off the car.
After the glue was removed (next to the pencil below) the surface was cleaned with goof off and then Alcohol. The blue masking tape was to mark the mid point of the opening but this was not necessary as there is a small dimple in the body at this location... the starting point for applying the new seal.
The new seal is adhesive backed with a peel away strip. I used the roll of blue tap to guide the top edge of the new seal and keep it flush with the body (any flat surface you can slide across the car body without scratching the surface will work). Gently work your way around the opening. The new seal does not stretch easily so just roll it out being careful in the corners to make sure it hugs the surface. Once in place it ran a plastic bag with finger pressure across the surface of the new seal to ensure it is firmly attached to the car body.
Once the new seal was in place, where the ends meet, I placed a small dab of black silicone glue. Once that set the only thing left to do was reset the sunroof (press and hold the tilt button until it moves through its adjustment range).
11. IVM module (inspect/repair)
This module is a common failure in BMW's causing intermittent engine problems. This was preventative maintenance for me.
The IVM module is in the E-box under the passenger side cabin air filter... it is the one with the green connectors. It has a bunch of relays and fuses on it... distributes switched power to other modules. To play it safe I disconnected the battery before removing it.
It has connectors on both ends.
The cover is held on with 3 x tabs each side and when removed reveals the bottom side of the circuit board.
The 2 x solder connections that often give problems are bottom right in pic below.
Fortunately, mine were OK (below) although you can see possible stress cracks just starting to form on the lower joint below. To be safe and prevent future issues, both of these connections were re-soldered (to get a good joint it is best to heat up the area with a heat gun first).
Below is the same connection on a module I removed from the 2002 745i (same part#). You can clearly see the broken solder joint!
12. Fuel tank breather valve
I had this error (below).
My car has 2 x fuel tank breather valves that are located side-by-side in front of the PS reservoir. They feed Gas fumes from the gas tank and high pressure fuel pumps into the intake manifold adjacent to each throttle body (part of the emission control system). These valves are normally closed and will open when energized. Gas vapors enter at the hose connection on the side and exit the nipple below (arrow on part in pic below).
I checked the resistance across each valve and found one was 24 Ohms (perfect) and the other between 60 Ohms and open (definitely bad). You normally replace these with a plastic pipe attached (you buy them this way) but I elected to try and replace just the valve with a good used part from a salvage yard
Below is my defective part... the plastic tube that was attached to the lower nipple has been cut off and will be mated up to the new valve.
It wasn't until I got home that I realized the replacement valve is not quite the same as my original part... the nipple diameter is a little larger and the connector orientation is rotated 90 deg. Otherwise they appear identical. To accommodate the replacement valve I removed the shell on the mating connector and flipped it 180deg and to accommodate the different nipple size I fitted the original thinner plastic pipe from the intake manifold inside a short piece of thicker pipe that came with and mates to the replacement valve (its very snug fit and I super glued them together).
The replacement valve is on the right in pic below. Note both valves now oriented differently.
In the pic below you can see the short piece of thicker plastic pipe connected to the bottom of the new valve and the original (thinner) pipe fitting tightly inside the end of this (super glued together). It worked out perfectly and saved a few $$!
