Caliper refurbish

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[url=https://imoc.co.uk/app.php/kb/viewarticle?a=97&sid=f5a04049f3cf8a362b711c6f95e30cdd]Knowledge Base - Caliper refurbish[/url]

\\Refurbishing Front Brake Calipers Off A Rev 1 Turbo\
by Brian Johnson\


I had to refurbish the front brake calipers of my 1990 rev 1 Turbo after the passenger side caliper was found to be sticking. (Sorry no pictures as I was in a hurry to complete the job). I have gone into quite a bit of detail to help, and to cover things, which would have been easy to explain had I bothered to get photographs.

Checking The Caliper is Binding

It’s worth checking first that the caliper is actually binding. The MR2 MKII’s are prone to this, but a sure-fire way of knowing is if the caliper and the wheel are hot, in fact they’re likely to be very hot depending on how far you have been driving.

Other tell tale signs are during slow driving depress the clutch pedal and freewheel, the car may slow quicker than normal or feel as though the handbrake is on.

Also under braking the car may ‘pull’ towards the side which is sticking.

You will need:

* Brake cylinder seal kit which is £43.75 including VAT from Mr T.
* Bottle of brake fluid at £5.99 inc. VAT from Mr T (1.2 litre) - will do about 1 x flush of the reservoir which should be enough.
* Assorted sockets and spanners
* Plenty of clean rag
* Wire brush
* Chrome cleaner or polish

\Removing the Caliper\

1. Jack up the car and remove the road wheel. Make sure handbrake is on and remaining wheels are chocked if necessary.
2. You will need a tie wrap and the finger from a rubber glove…!! More details below…… (I use the very thin surgical type disposable rubber gloves for any work as they avoid spending hours scrubbing hands. They’re about £5 for a box of 50 pairs).
3. Have plenty of newspaper (or suitable receptacle) below the car and the caliper to catch any brake fluid, which \WILL\ leak when you loosen the hose. Using a spanner, loosen and remove the banjo bolt which secures the brake hose to the back of the caliper.
4. Once the hose is removed and the bolt from the hose use the rubber glove finger to put over the end of the hose, securing with the tie wrap. This will prevent brake fluid from continually leaking over your drive and draining the whole system. Try and do this quickly, as it’s a messy job with brake fluid leaking all over the place.
5. Find a \CLEAN\ piece of rag and wind it into the brake hose hole on the caliper.

Once this is done I strongly suggest you clean up all spilt fluid from the caliper and surrounding area, and get clean pieces of rag. Brake fluid is horrible stuff and will damage your paintwork. It is therefore essential to clean up and use clean rag to prevent it getting onto everything and everywhere.
6. Halfway up the brake hose, there is a bracket on the side of the suspension leg through which the hose is passed. On the underside of the bracket is a spring clip, which can be removed with a small amount of leverage from a screwdriver. Once removed the hose can be moved freely. One side of the bracket will need to be very careful bent up or down to create a large enough gap to remove the hose completely. NOTE that you should open up the bracket only enough to get the thin solid section of hose end through the bracket gap. I would not advise opening up the bracket so far as to try and get the wider rubber section of hose through the gap.
7. Once the hose is free carefully put the hose end up high near the suspension top to minimise the amount of fluid trying to leak out. A tie wrap here may help stop the hose falling down.
8. Remove the caliper from the car by removing the 2 x securing bolts behind the disk, one top and one bottom.

This should take about 20-30 minutes

With the caliper in the workshop/garage/kitchen it can now be refurbished.
\
Caliper Dismantle and Clean Up\


1. With the caliper removed, the brake pads can be pushed out. Do not lose the 2 x spring clips which are slotted in behind the pads. There are also 2 x pressed metal plates on the rear of each pad. Make a note of which way round they go before taking them off or before they fall off during pad removal.
2. Once removed the pads will benefit from a clean up with a wire brush to remove all the brake dust deposits.
3. There are 2 x parts to the caliper, the main body with 2 x pistons in it, and a sliding section which allows the caliper to ‘float’ on the disk. The floating piece is easily pulled straight from the main body. Just make sure you pull it away squarely. It moves on the 2 greased pins, which are protected by rubber bellows.
4. Once this piece is removed, the 2 x rubber bellows can be removed using a thin edge to prise them off and binned. (New ones in the kit)
5. There are 2 x spring clips on each end of this piece on which the brake pads ‘slide’ these can be removed and cleaned up if required.
6. Give the piece a clean up with a wire brush and set to one side.
7. It’s a good idea at this point to take the rag out of the brake hose connection hole and try to drain as much excess fluid out of the caliper as possible; a good shake will help. Replace the rag in the hole.
8. The two sliding pins can be unbolted from the caliper body and cleaned ready to replace later. When removing these, use an open ended spanner on nut on the pin, as its easier than trying to remove the bolt on the outside of the caliper.
9. Next remove the pistons from the caliper body. Sounds simple but isn’t.
10. There is a rubber gator around the top of each piston, this can be ripped off (new ones in the kit) or just moved out of the way to get access to the recess around the top of each piston. I used a large flat bladed screwdriver inserted into the recess to lever the piston up and out of the caliper. You will need to employ some cunning here depending on how seized it is. I put the caliper securely into a workmate bench and used a block of wood to get leverage against the piston.
11. Work the piston as far around the edge as possible to ‘work’ it out, and don’t just concentrate on one location.
12. Once the piston is out, set it to one side noting which side of the caliper it came from. (Ideally you want to put all the parts back in the same locations). Use a spare small piece of rag to put into the caliper hole to prevent dirt going in and excess fluid coming out.
13. Repeat steps 18 to 20 for the other piston.
14. You should now have both pistons out. Next remove the rubber gators (or what’s left of them) by using a small flat blade screwdriver to remove the circular spring clips which hold the rubbers in a recess in the caliper body.
15. Remove the main piston rubber seal, which is located further inside the caliper.

Now take a tea break and survey the damage. The pistons will both have rust like markings around them, which causes them to stick. This is easily removed with chrome cleaner or similar polish combined with elbow grease!

Do not use anything else to remove this build up, as you do not want to scratch or damage the surface of the pistons.

Remove the rag from the 2 x piston apertures and have a good look for any damage such as scratches. The inside of the caliper wont need more than a good wipe round, but get a small screwdriver and rag in the recesses for the seals and make sure there is no dirt left in them. Replace the bits of rag.

You will probably find that the outer edge of the piston bore (above the recess for the piston gator) will be rusty. This will probably need more of a clean up, and I found a penknife used to carefully scrape away the surface rust prior to a polish was sufficient.

It’s a good idea to wire brush the caliper body at this point, but make sure all the bits or rag are in place preventing dirt entering the caliper.

Depending on how hard it is to remove the pistons, this process may take anything from about 1-2 hours.

If you are one of those boy racer types, this is the point to apply bright red caliper paint, prior to re assembly.

\Caliper Rebuild\

1. Before starting the rebuild, it’s a good idea to have some fresh rag you don’t want any dirt getting into the caliper.
2. Remove the rag from inside the caliper body and insert the 2 x new rubber seals into the caliper body.
3. Wipe a small amount of fresh brake fluid around each of the seals once in place.
4. Wipe some brake fluid around the bottom half of each piston and carefully push into the caliper body. Only push the pistons in about halfway at this stage.
5. Next install the rubber gators which fit around the top of each piston. A small flat bladed screwdriver will help to seat the seal in the recess in the caliper, be careful not to puncture or damage the new gators. Once seated, the part of the gator around the piston can be seated in the recess around the top of each piston in a similar way.
6. Next insert each of the spring clips into the caliper recesses to hold the gators in place. Again take care not to puncture the gator with the end of the spring clip.
7. Once everything is back in place the pistons can each be pushed fully home into the caliper. These should move gently and freely into the caliper body.
8. Install the sliding pins back onto the caliper body and apply grease.
9. Retrieve the other caliper piece previously cleaned up and set to one side. Install the 2 x new gators, which are a push fit but might require some gentle persuasion!
10. Make sure that the 2 x spring clips are fitted back onto the two ends of this piece. Remember these are the ones on which the brake pads run. I didn’t apply any grease here but a VERY small amount might help.
11. Push the piece back onto the caliper sliding pins. Once in place hook the rubber gators over the end of the pins to secure them in place.
12. You can now replace the brake pads into the caliper. Don’t forget to fit the 2 x spring clips, which locate in holes at each end of each brake pad. These are a bit fiddly to do.
13. Once all pads and clips in place the caliper is ready to fit back on the car.

This bit should take about 30 minutes
\
Fitting Caliper and Bleeding brakes\


1. Place the caliper on the car and fit the 2 x fixing bolts top and bottom.
2. Remove the rag from the brake hose hole on the caliper, get some newspaper or a receptacle below the car to catch any excess fluid lost while re fitting the brake line.
3. Drop the brake line down through the bracket on the suspension leg, straighten the bracket and re-fit the clip to secure the hose in place.
4. Get ready with plenty of rag, the banjo bolt and the new washers before removing the ‘rubber glove finger’ off the end of the brake hose.
5. Fit 1 new copper washer to the banjo bolt (washers come with the kit), and pass through the hose end, fit the second copper wash and then screw the banjo bolt into the caliper body. Secure with a spanner but do not over tighten which may cause damage.

This bit should take about 20 minutes

As everything is now back on the car, I would recommend an old sponge and some soapy water over the caliper and surrounding area to remove any excess brake fluid which will have leaked when re-fitting the brake hose.

Once dry you can check for any sign of brake fluid leaks around the hose connection.

The only thing left is to bleed the brakes; you can refer to the technical notes on the website for further details.