The Cleaning Begins

Now that the bulk of the strip down is done, the next step is to clean, paint and service the parts ready for use on the new chassis. To minimize this work make sure to only clean the required parts, by reading through the AK manual (spot the rogue parts later on). I should say that whilst this blog article appears after all the strip down of the subframes is completed, in actuality due to being stuck at various stages (fulcrum shafts, separating the rear diff components to name just a few), this cleaning progress was done alongside the stripping down process.

As both of the front a rear brakes came off first, this entry will cover their cleaning, as well the initial stripping down of the calipers.

First Clean

With the bulk of the parts removed, the scale of the cleaning task ahead was very uninviting. To make this more fun and less like manual labor, I broke out the pressure washer. This should give all the parts an initial clean and degrease. Whilst this did not remove all the grease and grim it did remove the majority of the surface dirt/grim.

Originally dirty parts.

To avoid spraying dirt/grease everywhere, I needed a contained place to pressure wash these parts. So the day after our recycling bin was emptied, I turned it on its side, placed each part in turn inside and gave them a good spray. To aid the pressure washer I connected it up to a bucket with very soapy water. Given the color and quantity of grit which came out the upturned bin, this process certainly did something. With the parts sprayed, I left them on the drive to dry. With the warm summer this year, this did not take long.

Comparison of rear brake caliper before and after a pressure wash.

Pressure washed parts drying on the driveway.

Removing the Rust

The next stage of cleaning is to remove as much of the rust as possible. I don’t want to say I will remove all the rust, as at some point I would like to start building up the chassis. The rustiest parts which need to be reused are certainly the brake calipers (shown below). Whilst I could use a wire brush and/or a Dremel to clean these parts, this seems like a lot of effort, and I don’t have a Dremel. Luckily there is an easy chemical based option, which requires no more effort than placing these parts in a bucket of a chosen chemical solution.

Front brake calipers – initial condition.

Rear brake calipers with the carrier – initial condition.

After watching numerous rust removal product review videos on YouTube and reading other cobra blogs, I choose to go with Deox-C from Bilt Hamber. Weighing up the options on their website I chose to go for the 4 kg bag, rather than smaller bottles or the pre-made solution. This should give me plenty of rust removing solution without needing to reorder any.

Using this solution was easy, I mixed a 25% ratio of the powder to hot water in a 20 liter bucket. I then placed the complete caliper assembly and carriers into this solution. The Deox-C should not attack any of the rubber parts on the calipers, so no need to fully disassemble them at this point. However, I won't be re-using these rubber components anyway, so the point is mute. When placing the calipers into this solution, I ensured that the cut end of the brake lines stayed above the water line. This should avoid water getting into the brakes. 

Then 24 hours after placing the parts in the Deox-C bath I removed and inspected the chemicals hard work. The initially less rusty parts came out with a dark surface coating which easily washed off. With these parts rinsed, the metal looked in brand new condition, ready for painting (right hand side of image below).

Caliper with no rust left on it. Notice the black surface coating on the left-hand side which has been washed off the right-hand side.

The more rusty parts certainly look a lot better, and the regions which still had surface rust had now turned a bright orange color. Scrubbing these areas further removed a lot of the now loose surface rust, but it did not remove everything. These then went straight back into the Deox-C bath for another 24 hours.

Rear Brake caliper immediately after coming out from Deox-C bath.

Front brake caliper – still rusty after 24 hours and scrubbing.

I repeated this process of leaving the parts in the Deox-C bath for 24 hours and then scrubbing the surface to remove the loose rust. After 4 days all the parts came out clean. I did not change or replace the Deox-C during this period, which further adds to how impressed I am with this cleaner/de-ruster.

De-rusted caliper.

When finished, the magic solution appeared very black and had a lot of grey sediment sitting at the bottom. Reading the literature that came with the product, it says it is safe to pour down the drain, which I carefully did. I then rinsed the bucket out and also poured this down the same drain.

In addition to the large parts, I also had to clean a lot of the smaller nuts, bolts, handbrake shoe springs, and assorted clips. The process for these was the same, although instead of the large bucket, these were placed in a small jar with Deox-C. For such small parts, a single 24 hours was generally sufficient to remove the rust before being taken out scrubbed and rinsed. 

To keep track of these small parts, I bought a small bits box from TK-Maxx. Once each part was clean and dry, it got placed in this box, along with a label explaining where it had come from. This should prove invaluable later when rebuilding. 

Box of clean small parts, with labels.

At later stages, I also cleaned the pendulum, differential tie bar, and both front and rear hubs, although not discussed above since they followed the same process. The rear aluminium hub carrier (IRS) was dealt with separately and will be tackled in a future blog entry.

Disassembling the Brakes Calipers

With the brake calipers cleaned and de-rusted the next step is to break them down further into their component parts e.g. caliper and piston. Hopefully, this will now be a slightly cleaner job… although I doubt it will actually be clean! For me, this started with ensuring that all the bleed nipples and brake hoses could be loosened. The bleed nipples are all 9 mm nuts, which came off with a little careful force. The brake hoses have two different size bolt heads (15 mm on the front and 14 mm on the rear), but oddly, the internal threads of both are the same.

My next plan was to remove the brake piston and the rubber components. After a little research online I found two approaches; one is to pump the brakes whilst on the car and the other is to blow the pistons out with a compressed air line placed over the open hose line port. Since neither of these methods would work for me, I needed to come up with a different solution. 

To replicate a compressed air line, I decided to use a bicycle pump. However, in order to get sufficient air/pressure into the caliper, I have epoxied a football pump needle into one of the removed brake hose lines. I can then attach the needle end of the line to the pump and use the hose connector to attach it to the caliper, as normal. I did originally try without the epoxy, with just using multiple cable ties, but this did not give a good enough seal.

Bicycle pump connected to brake line with an epoxied needle.

 With the DIY tool connected to a caliper, I then placed a piece of wood in between the piston and the opposing side of the caliper to avoid the piston hitting the caliper and damaging itself. Then with two strokes on the pump, each piston in-turn popped out. Such an effortless job! Even though I might not need this section of hose again, it is defiantly a keeper.

Piston removed from caliper using DIY tool.

With the pistons out, they can be inspected for scratches and damage. Luckily they all appear to be in good order, with no scratches or marks below where the rubber boot sits.

The key lesson which I learned here from Ian, was to only ever use brake cleaner on the internals of these calipers, never WD40, or my favorite go-to cleaning product: white spirit. Luckily, I had already ordered a large spray can of this from Amazon. The internals of the calipers are then cleaned with brake cleaner spray. I found it helpful to also spray cleaner through both the bleed nipple and the brake hose port. I was surprised by the amount of gunk that came out of these internal sections.

Front caliper with piston and seals removed.

The piston itself is a story of two parts. The external surfaces of the piston were cleaned by rubbing them with a rag and brake cleaner to remove small imperfections and dirt. 

Cleaned front brake piston.

The internal part of the piston, however, was a lot rustier/dirtier. With delicate fingers and some sand paper, it was a quick job to get these internal surfaces looking considerably better and ready for painting.

Sanded internal surfaces of the front piston. 

The painting and re-assembly of these components are still to be tackled and so will come later.