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Welcome

It took 2.5 years to build the car and pass SVA (now IVA) and a lot longer to get to where it is now! To see the Sportster out on the road have a look at one of the videos here.

During 2008 we rebuilt the BMW engine from 2.5 to a 2.8 creating an M20B28 stroker engine. It uses the crankshaft from the later BMW M52B28 and the conrods from the M20B20. Not much more work is needed other than a clean up, slotting those bits together and a crank spacer. To read about the engine build click here (very picture heavy!)

In March 2009 it was painted, a full set of images is here.

Wires

Reverse a switch – upated brake fuild level warning circuit

On a 1988 car the brake level sensor works the opposite way around to a 2011. On the 1988 when the brake level gets low the switch connects the circuit and turns the light on. On the 2011 it is the other way around, a reed switch is close so there is power through the circuit until the fluid gets low and opens the circuit.

This presents a problem when you use a 2011 level sensor on a 1988 circuit. Fortunately there is a solution in the form of a relay. It needs to be a normally close type. Or one with open and closed contacts, but connect to the NC terminal. Normally closed means if no power is applied to the relay it is close.

The normally close part of the relay replaces the old level switch. This means when power is applied to the relay the circuit is open and the light is off. When power is cut the circuit closes and turns the light on.

Power is taken from ignition runs through the relay and the new level sensor. This means the relay is power as long as ignition is on and the brake fluid is full. 

The advantage of the new brake sensor circuit is that it will pick up low fluid but also any brakes in the wiring to the sensor.

Shiny new brake level sensor

New relay, normally closed. Pin 30 and 87a take the place of the old sensor, Pin 30 and 86 take power from ignition and are connected to the new sensor.

Used a ratcheting crimper to – highly recommend getting one of these as it makes crimping terminals really easy.

Couple more terminals, these go into the car’s E30 1988 circuit.

This handy relay holder/fuse holder combo makes it easy to change should the relay ever fail, or if the fuse blows.

Using a power probe to test the relay, it simulates the new level sensor circuit, with power applied the brake warning light is off, this would be the normal state when the car is on.

Power disconnected from the relay the warning light turns on – if the fuse blows, the brake level is low or a wiring breaks it will show the warning light.

All the wires added to the fuse and relay holder.

Zipped tied up into place under the dash where it’s easy to get to and service if needed.

     

Chassis

Brake Fluid Reservoir / Expansion Tank

Recently tried to flush the brake fluid with a pressure bleeder. It uses a chain to hold a top on the fluid reservoir/expansion tank. That doens’t work at all well, didn’t hold well, brake fluid went everywhere.

On the other cars I look after there’s a screw on cap type that works really well with the pressure bleeder.

The reservoir that’s been on the car since building it was from Marlin, I don’t know what car it’s from but I can’t find an adapter for the pressure bleeder. So the next best thing was to change the tank for an OE BMW one that works with the bleeder.

The new part is from a 1972 BMW E21 BMW Part 34321112399 – ATE Part 03.3508-5851.3. It doesn’t come with a level sensor, for that I used a newer part from an E9X BMW part 34336774451. I had to modify the expansion take slightly to allow clearance for the sensor. It is about 0.5cm longer than there is room in the expansion tank, just meant chopping a small amount of the wall between the front/rear fluid chambers. There is a sensor specifically for the E21 tank 34321153157 but I wasn’t able to get one.

Removed this one, set it aside so the system remained closed while creating the mount for the new one.

Cut out an aluminium plate and added some riv nuts in the top to bolt the the tank to. Made sure the tank is level fron to back.

The rear bottom is the same mount as the old one, drilled a hole for the front riv nut. 

Transferred the clutch and two pipes over from the old tank to the new one. Added some clips to be sure they’ll stay there under pressure.

Added a new plug on the end of the level sensor wire, this one is off ebay from an E46. Could figure out the part numbers for the plus so that was the easiest way to get one.  

Clearance check for battery.

Battery back in, lots of clearance for the bonnet.

View through the louvers

Fluid change should be relatively clean and easy next time!

Engine Work

Fuel Injector Rebuild

In 2005 when we build the car we had the fuel injectors out, added new o-rings and gave them run in an ultrasonic cleaner.

They are now 33 years old and are overdue for a refresh. Found this company here in the UK who supply rebuild kits: https://mrinjectoruk.co.uk/ I send them an email before ordering and they advise BMW kit 10 was suitable for the 0 280 150 715 injectors. Arrived next day.

Rocker cover off for access, took the wiring harness off, loosed the 4 bolts holding the fuel rail on and pulled the injectors up and out. Had to remove the clips from the top of the injectors which hold them to fuel rail and I was able to get them out one at a time.

Condition as removed, pretty dirty. The o-rings are still in reasonable shape as they have been changed before.

The filters on the the other hand were dark and old looking. Getting the filters out took some careful manoeuvring with a screw driver and a pick.

While the cap, o-rings, spacer and filters were out dropped them into the ultrasonic cleaner

After all 6 injectors it was starting to look a bit disgusting

Shiny new parts!

Pushed in a the new filter and added a new o-ring:

Installed the new spacer, o-ring and cap on the other end.

 

Repeat 6 times for a full set!

   

Installation is reverse of removal, put all the injectors into the fuel rail first and add the retaining clips. Then carefully line up with the intake manifold and push into position. Reattach the fuel rail with the 4 bolts and reassemble the rocker cover and crank vent tube.

 

Took it for a good drive today, seems to run smoother and idle better, so I’d call the a success!

Engine Work

Oil Filter Housing Plug Replacement

The M20 engine leaks oil, this is one of the places it started leaking from recently. The housing which the oil filter connects to and the oil cooler pipes has a plug. This plug has an o-ring which has gone solid and started leaking. BMW Part number 11429059338 – comes with a new plug and o-ring.

Some shouting and swearing to get the retainer clip out – nothing to grab on to so screw driver in the divet on the left.

Quite a bit of oil comes out here when it’s unplugged.

This is the content under the plug, shown with new plug and o-ring.

 

Cleaned up the old parts to go back in.

 

Getting this thing back in was not the easiest job. Ended up using a clamp to force it into place and put the retaining clip in. Used screw driver in the cap to move it to the correct angle and location before removing the clamp.

This job took a suprisingly long time to do as it was quite fiddly.

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Vacuum Leak Testing Smoke Machine

I watched this video from martinbuilt showing a DIY build, after seeing a pro grade unit being demoed used by the Car Wizard in his essential shop tools video. The cheapest commercial smoke machine I could find is about £180, so a DIY one is much more suitable for the few times I’m likely to need this like I did today.

This ones diy with a bit of design flare to it, only because of the fancy oil container I found on amazon.

I built this last year but this is the first time I’ve been able to use it to test a problem on a car.

Chopped the top off (it’s not very air tight unfortunately, but good enough).

Mock up using some foam a lid with two electrical connection and two tyre valves.

Cut out an aluminium blank to use for the new top.

Foam design revisions 2, move some things around and put in the original fill lid to make it easy to put the white mineral oil in.

Cut all the required holes into the blank.

Mounted all the hardware and added a wick and some resistance wire. These will generate the smoke, as the resistance wire heats at lot and the white mineral oil smokes when it’s heated.

Tested the resistance wire, pulls 5 amps at 12 volts.

Assembled, the lid is not a 100% seal but that does avoid an over pressure situation.

First smoke during testing!

Had a good chance to test this, we’ve got an E36 Compact with an M52B28 engine swap done many years ago. The engine has been idling high randomly, normal RPM with the MAF off. This suggested a vacuum leak, but the question was – where is the vacuum leak. Did try changing out the idle valve as we’d picked up spare on ebay but that didn’t help.

So we used this setup to test and find the leak. First pulled the airbox so there’s more room.

Hooked the plus and minus up to the car battery, ran a tyre inflator into the smoke machine. From there put a latex glove over the maf and poked a brass pipe into it. Theres a rubber pipe from there into the smoke machine.

As there was quite a bit of smoke coming out of the tin I added a load of tape to reduce that.

Started to see some smoke waft out from under the intake manifold. 

Took the pipe off the alternator for a better view.

It was clear then that the smoke was coming from the crank case pressure regulator valve. Time to order a new set of hoses and the regulator valve.

Some testing on video:

Engine Work

Coolant Expansion Tank

Purchased a new coolant expansion / header tank to replace the original 1988 part from the donor car. For the first time since building the car you can see the coolant level! Should have replaced this years ago, but it’s not the cheapest part to get new. The nice thing is you can still get new original ones. They were use on the E30 and on the Z3.

Added a new blank cap to replace the level sensor cap with a fresh o-ring as well.

Needed little bit of modification for the lower mount – a hole drill into it.

The old one is almost solid, the lower hose connection was coming to bits too, the metal insert on its way out the end.

Looks a lot nicer with the new tank.

You can really see the opacity difference.

Nice clear fill level:

Engine bay looks much cleaner now.

Chassis

Heater Fan Fix

For a number of years now the heater has caused problems with the fans moving out on the shaft and scraping against the side of the outer casing. The tick tick scraping noise can be heard even with the exhaust on the louder setting.

It’s finally time to fix it properly.

Step 1, spend a few hours swearing at hard to get to bolts to get the outer casing off and the wiring disconnected.

Here’s the culprit – right next to where it’s supposed to be stuck to.

It moves out here and scrapes on the case.

Decided to use a few different methods, first drill a 2.4mm hole down the end of the shaft.

Tap the hole using set of M3 taps.

Test fit (this is a super long bolt, use a much shorter one)

Added a number of washers

This will stop the fan from moving off the end of the shaft.

Then to add a bit more security roughed up the motor shaft and the inside of the fan, then used some epoxy to keep the fan on, and the washer on and the bolt in place.

Reassembled the whole lot:

Put a fresh connector on for the earth (had to cut that to get fan off the car, with the scuttle panel in place it’s hard to get to some of the wiring).

Re-arranged the wires, new connector for the earth and zip tied everything back up.

Heater snapped back together, bolts put in and the 6 metal clips back on. Used tape to seal the front panel and connected up the window de-misters.

Re-installed the headunit

And now it’s back to looking like nothing happened.

On the plus side I can use the heater again without it being super irritating!

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Rear Brake Pressure Regulator

Someone pointed out the stock BMW rear brake pressure regulator was incorrectly mounted on the car. Not sure if this made much difference as it has always worked. However decided to fix this and add some adjustability if needed in future in the form of a Wilwood Brake Proportioning Valve.  The wilwood valve part number 260-12627 has M10 threads so the existing pipe fittings could be used.

Marked up the position for the first mounting hole.

First hole drilled, inserted a rivnut here.

Test fit, checking alignment for the top hole.

Both holes drilled and rivnuts inserted.

Final fit of the Wilwood valve.

The inlet and outlets are in roughly the same place as the old valve which will make moving the hardline easier.

Removed the P clip holding the pipe and added two new bends bringing the pipe up to the new valve.

View from above – it’s easy to get to and make adjustments.

The input pipe from the master cylinder is a braided flexi pipe which made installation easy. Lining the threads up too some effort as the tolerances are really close.

Close up view from above.

The final step was bleeding all four corners, replaced the fluid throughout as it had gone quite dark, photo shows the old colour. New fluid is much clearer.

Not done any testing/setup yet as it was raining all day.

Chassis

Radiator Return Pipe

Since the car was built the return radiator hose as been a long flexi pipe, this was never a good solution. At some points the pipe rubs which eventually would have cause a leak.

To solve this the flexi pipe has been replaced with a 90 degree aluminium bend and very short run of flexi pipe on either side.

Aluminium bend installed in the car

 

New pipe from below (missing the hose clamps in this photo!)

Filled and bled the coolant system, checked for leaks.

No functional difference, but safer long term.

Engine Work

Varex Exhaust Video

Had a chance to record some new footage of the exhaust. XForce Varex VMK51-250 variable volume exhaust – it’s pretty much straight through when it is open. Here’s a few runs with the back boxes set to closed and open for comparison. The engine is a BMW M20B25 with a crank from an M52B28 making it an M20B28. It has a dbilas 282°/272° camshaft. It’s running the original 80’s motronic from Bosch with a chip map design for the stroker conversion. It does pop a bit when the exhaust is warm and you change down. Would benefit from a more modern ECU and tuning (someday!)