Differential Bushes

The differential has been sqeaking and nods up and down under load so it was time to get some new bushes.

Both sets of bushes are from – the main rear diff bush is the E30 188mm part – PFR5-300H from the heritage series.

The front two bushes are the same ones used on the front wishbones which is a Ford TCA bush; PFF19-102H also a heritage bush.

The heritage bushes are polyurethane same a the normal purple ones but in a darker OEM black colour.

Here’s a small video clip of the rear diff bush on video which shows the seperation:

Step 1 remove the differential, this was relatively straightforward. Unbolt and drop down with the jack.

Removed diff looking a little dirty, good time to give it a bit of a clean.

The rear bush – the middle part is separating from the outer part leading to excessive movement.

Removing the old ford bushes with the press

There’s some surface rust but overall not too bad.

Old ford bush next to the new poly bush.

Test fitting the diff hanger with the new poly bushes (some foreshadowing going on here)

Used the power saw to chop out the old OEM bush

Fitting the new powerflex bush, these always go in so easily compared to OE bushes.

This one has a big washer either side of the bush to keep everything in place. In addition to this is need two more small washers to space the bolt to the diff hanger (more foreshadowing, there 7 layers that need to line up here).

While everything was taken to bits it was a good opportunity to powdercoat the diff hanger with a fresh layer. Some of the original had flaked off and there was a little surface rust. Not much easy to clean up. Here’s the coated part baking next to the heat lamp to cure the powder.

Finished part cooling down, this is the ‘matt black’ finish which is still a bit glossy but has a bit of a rough texture.

Fitted back on the diff with the new poly bushes looking very shiny again.

So, the foreshadowing. This is after trying to fit the diff the first time. Couldn’t get the large bolts in on both sides. Ended up bending these hangers, so took the diff out, and both hangers. Bent the one that got messed up back into shape. Both got a new layer of powdercoat too. Re-fitting took a long time, it was easier getting the mounts back into the chassis than bushes into the mounts. However it took a lot of fiddling to get them seated in. This was with the rear bush held up with a screwdriver so it could move around a bit.

The new rear diff bush has a much tighter tolerance than the OEM one and required two washers either side of the bush. Took a load of fiddling to get all 7 layers (hanger, small washer, large washer, metal rod the bush sits on, large washer, small washer and finally the hanger on the other side).

Yes it did go dark while getting the diff back in. Here it is back in place.

The squeaking is gone, power transfers through the drivetrain smoothly. Overall bit of a pain but well worth it.



Engine and Gearbox mounting bushes

Recently the alternator hit the chassis when I changed direction, a good indication that the engine and gearbox mounts might need some attention. Unfortunately the alternator bearings were damaged due to this impact. I therefore ordered a new alternator (with the aim to rebuild the old one as a spare).

I then also changed the engine mounts & gearbox mounts. I used polyurethane from Duraflex (they sent the wrong bushes first time, but did swap them out after I sent them back for the right ones, did take a while before they responded to emails though so you’re aware if you choose to get some of these). The original engine mounts were supplied by Marlin so I didn’t have specific part references for them.

They are 35mm thick with M10 studs, the closest I could find were Land Rover Defender gearbox mounts. I ordered the ‘soft’ variant which is 70 shore. They had mounts for BMW gearboxes, went for the ’80 shore a’ ones which is the normal hardness option for the bush.

Land Rover gearbox mounts:–duraflex-urethane—-nrc9560-284-p.asp
BMW Gearbox mounts:–gearbox-mounting-257-p.asp

The engine is under much better control now, I get less oscillation / vibration into the front wings and feel better now when driving.

I also had two worn out cracking ball joint boots so I changed those too.


Gearbox Mounts

Old BMW bushes compared to the new poly bushes. The new bushes are a bit chunkier (same height)

Here’s the gearbox mount cross member – had to take this all the way out to get the new bushes in place, a little bit fiddly.

After some swearing the new bushes are in place with the cross member bolted back in.

As the new bushes are more chunky than the old one ones I had to use the deathwheel to grind down this spanner to fit between the chassis and the bush to hold the bolts when doing up the nuts inside the car.

Engine Mounts

Removed the bonnet and both side panels for this job:

Jacked up the engine after undoing the lock nuts until there was enough clearance to get the old bush out.

A comparison between the now deformed bushes and the new poly bushes. The studs are a bit longer on the new one so the engine needs to be lifted a little higher to get the new bush in (on the passenger / intake side)

On the driver/exhaust side the steering column linkage is in the way of lifing the engine high enough to get the bush out. It was much easier to take the 4 bolts out that hold the engine mount to the block and pivot it out the way.

Here with the new bush fitted and bolted down:

Alternator Change

Big ol hole where the old alternator was removed, added a small notch in the chassis here to allow more clearance in future.

I got the new alternator from in Denmark, mostly because I needed a glow plug control module for my daily and they were the only people in Europe that had stock at the time! The new one is very shiny!

New alternator in place, added a new v-belt while I was at it as the old one wasn’t brilliant anymore.   

Here’s the new alternator hiding away among intake and water pipes!

The really nice thing about the new alternator is that it charges straightaway after starting the engine. The old alternator needed you to rev up past 3000 rpm before it would start charging.

Ball Joints

These don’t last super long every few years I need to replace them, these were not damaged from dirt ingress yet so I was able to just change the boot (sourced from ebay ej-parts size 16/31/23). I did fit one new ball joint as I didn’t have enough time to wait for the boots to get it through the MOT this year so I was able to pick one up from Euro Car Part locally.

Yeahy rotten rubber (this is now an MOT failure, these might have squeaked through as they were not cracked all the way though, but it was time to change them):

One new ball joint fitted:

This ones pretty bad, but the ball part of the joint was still good.

New boot from ebay with the mounting hardware from the old boot

Reassembled, old ball joint with new boot:

Still to do are the differential bushes – the stock BMW M bush (from the Z3M) has a lot of movement, the centre mount hold is tearing out of the rubber. Additionally the ford TCA bushes used to mount the front of the diff to the chassis feel soft and are squeaking quite a lot. If you move the car by hand with a gear selected the diff does a nodding dog impression. I’ve got some poly bushes to install in the near future for that too.


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!


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!


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.


All the Brackets

Bracket Number 1:

The return pipe from the radiator to the header tank has always been attached with a zip tie holder, but only double sided taped on. Every time the tape fails the hose is a bit flappy.

To fix this issue long terms I’ve stick a rivet into the bracket that holds the AFM

This is not going anywhere now.

Bracket Number 2:

Brake Servo vacuum hose holder

This attached to one of the bolts holding the rocker cover.

Up to now the hose sat on the rocker cover which has rubbed the paint away. Now there is plenty of clearance.

Runs as it did before, only with a gap to the top of the engine.

Bracket 3

This is more of a closing panel than a bracket. There is a small hole pedal box into the engine bay behind the servo.

Can’t see it from up here with all the body work on, but should stop fumes getting into the cabin here.


New front wing stays

The front wing stays rusted and broke again, did a temporary fix a few months ago, but finally it’s time to make some new ones which will hopefully be more resiliant to the elements.

Started with two 1 meter 10mm diameter solid rods

A piece of bar to turn into the bracket that will hold the rod on to the front uprights with a U clamp (51mm u clamp)

Bracket cut shown with U clamp.

Test fitted to the uprights

Used a clamp to hold the round bar to the bracket to get a it roughly lined up.

Used a caliper to evenly space the round bar away from the alloy wheels

Held in by hand for a better view of the bracket and round bar

Tack welded the round bar to the bracket

My temporary workshop setup – don’t recommend using a workmate for welding due to the risk of burning wood and fire. Use a metal welding table, which I don’t have in my garage. Grabbed the round bar quite far away from the weld so it was fine. Also used a TIG so no splatter.

I’m still a total amature at welding but these are OK

The main thing is that is holds together well. The angle grinder hides the bad.

One of the most time consuming parts of the build was creating a jig so that all four final bends ended up very similar.

It may only look like two bends, but there are hours of measuing, eyeing up and carefully deciding where the bends need to go.

The rod lines up with the holes on the carbon wings.

Now here’s one of those things that happens all too often on a project – the rods ended up 10mm too high on the first go. This is jig MK2 with the height adjusted. It did mean having to straighten out the rod and rebend it to the right position.

Here’s a test fit of the front of the rod bent into place

The jig is holding the back up.

Left to right the mount positions are little way off on the back, so some creative bending and P clip positioning evens out the rod placement.

The back bent into shape, again two bends took many hours to get to the right position.

Here are the P clips that will mount the wings to the rod

First test fit of the driver side, got some really nice new A4 grade cup washers, bolts and nuts from Westfield Fastners to finish it off.

Test fit on the passenger side. The wing was too close to the tyre so this one needed a bit more fine tuning to get it right.


A view from underneath with the wheel off.

There is enough gap between the tyre and the carbon, looks quite close from this angle. If there are problems it is easy to tweak the bends to create more clearance.

Before and after, the before is version 3 of the mounts which also failed eventually.

Ahh shiny parts!


Upper wishbone refresh and wishbone mounting rod

I changed the upper bushes today. They were rally design ones, which I’ve now replaced with Powerflex. I thought the bushes had worn as things didn’t look straight anymore. Turns out it was actually the rod which was bent and the bushes are OK. I’m going to use two of them on the diff mount (still original rubber mounts) and keep the other two as spares:

It’s pretty clear this is not so good, both sides were bent:

As I don’t have replacement materials to hand as a temporary measure I’ve straightend out the rods. Here are some sizes for reference:

Installation of new bushes:



There are powerflex product number PFF19-10 – also available in the black series which is a higher shore hardness: PFF19-102BLK


3 point reel seat belt conversion

ziptie test, safety 3rd!

Hole cut for threaded belt insert

Test fit of new piece

Use the lathe to clean up these spacers

Reel mount

Reel mout welded in

Upper mount welded in and test with spacer

Reel mounted

Otherside done too

Works quite nicely, could do with a guide for the belt on the seat

And finally plugged into place!


Rear rust clear up

Doing some clean up work, the Sportster has been on the road for a while now so it was time to check for rust and clear anything up

Little bit inside the shock tower area, most was on the metal upright towards the back of the car.

More from inside the shock tower

This part is covered by the tub down to where the E30 A arms mount.

Under and below the tub area in the rear

The good news is that it was all surface, no structural issue. The worst part was the end of square bar under the back runs along the tank.

Cleaned everything up with a wire brush on the angle grinder, treated with loctite rust remedy and painted with chassis and rollbar paint. Also to go on later some underseal with waxoil.