Brake lines – part 2

In a previous post, I created the majority of the brake pipes, with the exception of the pipes around the brake servo. In this post, lets look at refurbishing a donor brake servo and master cylinder and creating a bracket for the end of the brake pipes.

Brake pipes taped to chassis.

Brake Servo

The AK 427 requires a Rover 25 (or Rover 200, MG ZR) brake servo and master cylinder. These are plentiful on eBay and go for around £25. After looking at the options I decided to purchase the item shown below, although it looked in better condition in the seller's photos. 

Donor brake servo – I swear it didn't look this bad in the seller's photos!

With a 13 mm socket, the two nuts which hold the servo on the master cylinder are removed. With these parts separated it is clear there is even more rust on the servo. It's like having flashbacks to the when I was cleaning/servicing the donor parts. 

Disassembled donor brake servo show signs of even more rust. 

As these two parts separate, be careful to keep track of a large O-ring, which seals the servo to the yellow collar on the master cylinder. With the nuts and O-rings stored away, both parts require a thorough sanding. After a morning of sanding the brake servo, it was starting to look a lot better and appears to have only been surface rust. 

Sanded down brake servo.

The rust was not limited to the servo and the brake cylinder also required a good sanding. 

Part sanded servo with masking tape.

Having finished the sanding, the prepped and keyed surfaces need a deep clean with plenty of white spirit. This included cleaning the white plastic reservoir on the servo to remove the old encrusted oil and some yellow writing. I had put this off until this point as I knew I would be making more mess with the sanding. To create a fresh protective base coat, I first gave these items a few coats of POR 15. 

Having left the POR15 dry, these parts were then given another light sanding, to create a keyed surface ready for a few thin coats of semi-gloss black topcoat. 

Parts awaiting a final top coat of gloss black paint. 

After leaving these parts to dry I was very happy with the final outcome. A marked improvement on the donor part which I started with. 

Freshly painted brake servo and master cylinder – looking much better. 

The final stage with this job is to resemble freshly painted parts. Before the actual assembly, it is worth checking the perishable parts on the servo, this includes two rubber boots which secure the reservoir to the servo and the previously mentioned O-ring. Both these parts can be found on Rimmer Bros and have the following part numbers. 

• Front reservoir seal: EJP1502
• Rear reservoir seal: EJP1503
• ring: EJP1504

Upon initial inspection, these seem to be in perfect order and so at least for now, I will re-use the current parts. This might all change when I come to test the brakes, but we will see. 

Image highlighting rubber boot on brake servo.

To reduce the wear on the internals a small amount of bearing grease was added to the end of the servo. This refreshes the grease that was originally on this part as it was pulled apart. 

Bearing grease added 

And with that, the final step is to bolt the parts back together using the original nuts. Looking at it now and remembering how it originally looked I'm actually very impressed with my self. 

Re-assembled brake servo and master cylinder.

Time for a Bracket

As I mentioned in the first brake line post, I wanted to hard mount the end of the brake lines to the chassis. This hard mount point will then have brake Flexi running up to the brake servo, but that’s a challenge for another post. With Stu's excellent blog post as inspiration, I decided to fabricate my own metal bracket to secure the brake lines to the diagonal front chassis rail.

Brake lines resting on chassis.

The initial plan was to create a bracket that would mount both the front and rear brake lines along with the clutch line to the chassis. I, therefore, purchased a couple of M10 union bulkhead fittings (from Merlin Motorsportl) for the brake lines and a 7/16UNF union with Right Hand Thread for the 1/4' clutch lines. With these parts, I started to design a template for the bracket using CAD (Cardboard Aided Design).

Initial CAD templates of pipe mounting bracket.

Whilst in this design stage I checked I had enough clearance for all the pipes to pass, and that I could fit a spanner around the bolts on the unions. Once I was happy with the design I transferred the pattern to a 1.2 mm thick piece of stainless steel and cut it out with an angle grinder. 

Bracket template transferred to metal.

Three holes were then drilled into the bracket with up to a 10 mm drill bit. These holes then have to be slightly further enlarged using a small rounded file. Then to make the part look presentable the sharp edges were filled down to create what we see below. 

Filled and drilled bracket.

The bracket was still a little 2D for it to be useful. However, after carefully placing it in a bench vice, and applying a little percussive persuasion it soon took on the desired 3D form. 

Bended bracket next to intended CAD model. 

The newly created bracket was then offered up against the chassis and secured temporally with a high tech sticking material or tape, if you like. I was careful to place the bracket and protruding unions in front of the chassis plaque to avoid the brake lines obscuring its view (an IVA fail I bet). Whilst I had carefully placed the bolt holes high enough from the bracket base so that I could get a spanner in and turn them, I soon realized another obvious flaw with this bracket. Due to the narrowness of the chassis and hence the bracket, it would be difficult to fasten the central clutch unions with the brake pipes attached to their unions. Bugger!! 

The mounting plate on the chassis

For now, the solution is to cut off the clutch mounting part of this bracket and pass that problem onto future Richard (I don’t think he will thank me for this, but oh well). Using the angle grinder and a file this is a quick job. 

Bracket in workbench read to be cut down.

Having made that bold decision, the brake lines can be cut to length, flared and ‘union-ed’ to the bracket. With that, the bracket now looks like this. 

Brake lines attached to the new bracket.

Once I have tested the brake line setup for leaks I will then securely mount this bracket to the chassis. For now, I will call this done and focus on the flexi lines which connect the freshly painted brake servo with these hardline pipes.

Fuel Tank

Shifting focus away from the brake lines, I decided to tackle the fuel tank next. I purchased this at the same time as my original kit order. Since its arrival, to save space in the garage the tank has been sitting in its correct location within the chassis, all be it with its tabs resting on the top of the chassis. Although the tank fits perfectly in this position, the manual states that these tabs should be on fastened to the bottom of the chassis rail (not the top). This creates a flat surface between the fuel tank and chassis rail for the boot floor to rest on. To achieve this fitment, we require some bolts holes to be drilled into the tanks mounting tabs and the chassis.

There does however appear to be two schools of thought around the best method to fasten the tank to the chassis:

• The factories (AK’s) suggestion is to drill holes in the fuel tank tabs, and then drill and tap a corresponding holes in the chassis which M8 bolts can be fastened to.
• Alternatively, some builders have proposed securing these fuel tank tabs with strips of metal held in place either side of the tab by M8 rivnuts.

The main motivation for the alternative method is the concern that the chassis rail is too thin to support an M8 bolt. However, I believe from memory that as part of the Gen 3 being nicknamed the ‘super-light’, it uses a thinner gauge steel for the chassis than the Gen 2 chassis (which I have). Therefore, at least for now, I will stick with AK’s method for securing the tank, although I may later add some extra metal straps to some of the fuel tank tabs.

Making holes in the tabs

The first step is to mark and drill holes in each of the 5 fuel tank tabs. These need to be drilled in the center of the tab and in chassis rail. I began by mocking up the location of the fuel tank in its correct location (from the top) within the chassis. To record this location, I placed masking tape around the edges of where the fuel tank tabs met the chassis.  As the chassis rail and fuel tank tabs are about the same width, I only need to determine the center point of the tabs. With a ruler and sharpie this is an easy job.

Fuel tank sitting in chassis with marked center of tabs marked.

To avoid the drill bit from walking, a center punch is used to create a small indent. Then before drilling and to avoid damage to the top side of the chassis I raised all the tabs with some wood offcuts. You will notice there is some ‘rust’ appearing around the tank weld locations. I’m not sure how to deal with this, but I will be coming back to this later.  

Fuel tank tab, with the center marked and punched.

Its then a case of slowly drilling through the tabs, firstly with a 2 mm drill bit and then increasing with larger drill bits up to an 8 mm diameter. This is the first time I drilled into stainless steel and its surprisingly a lot hard and slower than plain steel.

Initial pilot hole drilled

With all the holes drilled out to 8 mm diameter the tank can then be placed directly back top of the chassis rail.

Hole drilled out to 8mm.

The tank then needs to be supported, with the tabs touching the underside of the chassis. For this I broke out my new (second hand) engine hoist and the trolley jack. With the tank it is correct location and lined up with the tape, the location of the corresponding holes can be marked.

Support the tank as I mark the location of corresponding holes.

As before a center punch mark is made before a gradual increase in drill bits from 2 mm up to 6.8 mm. This odd size of the drill bit is required to ensure there is sufficient metal for the coarse M8 (1.25 mm pitch) tap to cut through in order form the desired thread.

Tapping the thread into the chassis.

Tapped hole.

With this process repeated on all five of the fuel tank tabs, the hard part of this job is done. The tank can then be raised back into its slot and fastened in place

Fuel tank mounted to chassis.

I should also point out during this job I noticed that there were more signs of paint bubbling on the rear bar of the chassis. A quick sand down to remove the paint and rust was then followed by a spray with primer and black paint. Despite a slight disparity in the gloss level along this back bar, the repainted areas look good. I’m not too worried about this paint mismatch, as this area of the chassis is covered by the body.

Flush fitting tank.

That’s the fuel tank fitted for now. As I said at the start, I may decide to go back and add some metal straps to some of the tabs for extra support, but we will see.