Front Caliper piston removal question

[79X19]

I am in the midst of rebuilding the front calipers on my '81 X. I need to remove the pistons in order to replace the seals and I am at an impasse due to the banjo bolts. I have seen numerous YouTube videos on the subject some recommending compressed air and others the grease gun method to put pressure on the pistons to force them out. In either case I have to seal off the area where the banjo bolt secures the hose to the caliper. I cant seam to find a standard bolt to screw into this area of the caliper so I can force the pistons out by grease gun (that is the method I will use). I have an entire bin of old metric fasteners taken from my parts X but not one of them fits! If anyone has a solution that I'm not thinking of please let me know. Or if you know where I can get a bolt to fit this purpose Id appreciate a recommendation. Thanks!

I checked through the forum and didn't find a thread on the rebuilding of the front calipers.

 

[dragonsgate]

I use air. My air chuck has a rubber tip that seals enough against the opening of the banjo nut to pop the piston out. Be sure to close the bleeder and put piece of wood between the piston and the caliper flanges. I then shoot it the rest of the way out into a padding of rags. Watch your fingers. If you do not use something to stop the piston it can shoot across the room at enough speed to do some damage.

 

[Dr.Jeff]

I use air. My air chuck has a rubber tip that seals enough against the opening of the banjo nut to pop the piston out.

What he said.

 

[EricH]

Go with compressed air.... Much easier and much less messy than grease, and you don't need anywhere near a perfect seal to get enough pressure to drive the piston out. If you don't have an air compressor (a dinky little three gallon $75 one, the kind you'd keep around for inflating tires, is plenty for this job) you can take the calipers to any local mechanic who does have one and they'll be able to do it, probably won't even charge you.

 

[Dr.Jeff]

If you don't have an air compressor

Could possibly take it to a gas station with one of those air stations you put a quarter in.

This is something like the air nozzle you would use with a rubber tip, pressed into the hole where the banjo bolt goes:

If you already used grease be sure to thoroughly clean every trace of it out from everywhere in the caliper, otherwise it will contaminate the fluid.

 

[Rupunzell]

Using pressurized grease from a grease gun will contaminate the brake caliper and possibly the entire brake system with petro based particles that will slowly destroy the seals in the brake system. EPDM & SNBR seals are NOT petro compatible. Compressed air works and the pressures needed should not be very high, about 20-40 psi MAX!!! More will explode the piston out of the caliper with more force than suspected.

The caliper internal threads are 3/8-24 SAE, this is a very common tube fitting thread size. Make a compressed air adapter using a fitting of this size or apply a rubber nozzle blower to remove the piston. In all cases of pressurized air piston removal. Put a pad of cotton towel or similar between the piston and caliper body where the brake pads once lived to prevent damage to the piston, caliper body or possible bodily injury, Use a pressure regulator to limit the air pressure applied to the brake caliper piston.

DO NOT APPLY TYPICALLY 100psi air lime pressure directly to the caliper. the resulting force is NOT small with the risk of exploding damage is pretty high.



Bernice

 

[MikeHynes]

Sorry 79X19, this is a bit after the fact, but the easiest way to remove a stuck piston is to use the brake system pressure. Don't begin by removing the calipers all the way off the car. You simply remove the calipers from their holders (don't "open" the system, leave the flexible hose connected), and hang them from the strut with a bit of bailing wire. Then place a piece of wood in the caliper where the pads/rotor were so that the pistons can't come all of the way out. Then pump the brake pedal. Just make sure that none of the pistons can come all of the way out and even the stuck piston one will come out far enough to allow you to get them out with modest air pressure through the banjo bolt hole as described above.

 

[79X19]

Once again the Xweb community delivers timely and very good advice. I haven't yet applied grease to the calipers so i'm good there. I have all the tools outlined in the recommended actions above so it should not be difficult to follow the directions and execute this rebuild successfully. I have already removed the brake system for complete overhaul including the pedal box, associated tubing and reservoirs so using the system to remove the pistons is not possible. Thanks for all you're help. Its just like anything else with a rebuild when you think its just a few things you have to do to get her back on the road it turns out to be best action if you just do it all!! The deeper I dig the more I find.

 

[79X19]

I have success to report and more questions. So I followed the instructions and was able to push the pistons out of the calipers. One came out relatively easily however it was not budging at 20-40 PSI.
I steadily increased the air pressure until i noticed it began to move, this was at 70-80 PSI. I was able to mitigate the potential for an explosive situation by allowing air to bleed back from the rubber tipped nozzle by letting off hand pressure and allowing air to escape. I was the safety valve so to speak. This way I controlled the movement of the piston and protected against the piston from getting away from me. I had the wood and rags placed as instructed and they were key to safely removing the piston as well. The second caliper (pictured here) was like my third child very stubborn and difficult to move. So I had to increase the air pressure to almost the max my small compressor could produce. The piston would not move until I hit 120-125 PSI. It moved very slowly and I was keen to keep bleeding off air to control its movement. Again the wood block and rags were key to safely removing the piston. One recommendation is to remove any painted surfaces nearby that you care about when completing this work. When using the rubber tipped nozzle air blow back occurs and it sprays a fine mist of residual brake fluid into the air. It is also wise to wear a respirator due to this fact as well. Please take a look at the pics and the following questions apply:

1. Whats the best process/chemical to rid the calipers of the baked on grease and road dirt?
2. How much scoring of the piston surface is considered allowable before they need to be replaced?
3. Is there a tool or brush attachment for a drill or Dremel that can be used to safely clean the internals of the caliper?
4. What sort of lubricant is recommended when reassembling the caliper? I have seen videos showing a lubricant being applied to the piston and seal when inserting the piston back into the caliper. Also the same is true when installing the dust seal. What is this lubricant?

 

[79X19]

After cleaning of the pistons its clear that Ill need new ones as the one on the righ has pitting along the surface where the seal will be impacted. The one on the left has much smaller surface pitting but its only a matter of time before it too gets worse. So I've decided to replace the pistons as well.

 

[Andy]

I have given the caliper bodies a good long soak in my parts cleaner (kerosene) and some brakekleen for stubborn spots.
After that a trip through the bead blast cabinet typically makes them look pretty good. I use old bleeder and banjo bolts to keep the bead out of the internal area. Duct tape over the piston hole too.

There is no need to hone the bore unless it is really grungy, the piston rides on the square rubber o-ring not the metal. It is critical to get the groove that ring sits in clean. I use dental picks and machinist scribes to dig any deposits out of the ring.

Use brake fluid as lubrication for re-assembly.
Fronts are easy, rears are a bit more difficult due to the e-brake mechanism.

 

[mikemo90]

I am in the midst of rebuilding the front calipers on my '81 X. I need to remove the pistons in order to replace the seals and I am at an impasse due to the banjo bolts. I have seen numerous YouTube videos on the subject some recommending compressed air and others the grease gun method to put pressure on the pistons to force them out. In either case I have to seal off the area where the banjo bolt secures the hose to the caliper. I cant seam to find a standard bolt to screw into this area of the caliper so I can force the pistons out by grease gun (that is the method I will use). I have an entire bin of old metric fasteners taken from my parts X but not one of them fits! If anyone has a solution that I'm not thinking of please let me know. Or if you know where I can get a bolt to fit this purpose Id appreciate a recommendation. Thanks!

I checked through the forum and didn't find a thread on the rebuilding of the front calipers.

you wont find a bolt with those dimensions being a brake component and considered "safety" hardware. best bet is compressed air, but make sure you use a piece of wood between the outer ears and the piston.. not your thumb as I have seen some do. unless you have a plethora of cuss words and a lot of bandages. fast and simple. besides grease and brake fluid are not the best of friends and cleaning the caliper of all the grease is more work and any residue is detrimental to the new seals
mikemo

 

[Dan Sarandrea (Phila)]

I have success to report and more questions. So I followed the instructions and was able to push the pistons out of the calipers. One came out relatively easily however it was not budging at 20-40 PSI.
I steadily increased the air pressure until i noticed it began to move, this was at 70-80 PSI. I was able to mitigate the potential for an explosive situation by allowing air to bleed back from the rubber tipped nozzle by letting off hand pressure and allowing air to escape. I was the safety valve so to speak. This way I controlled the movement of the piston and protected against the piston from getting away from me. I had the wood and rags placed as instructed and they were key to safely removing the piston as well. The second caliper (pictured here) was like my third child very stubborn and difficult to move. So I had to increase the air pressure to almost the max my small compressor could produce. The piston would not move until I hit 120-125 PSI. It moved very slowly and I was keen to keep bleeding off air to control its movement. Again the wood block and rags were key to safely removing the piston. One recommendation is to remove any painted surfaces nearby that you care about when completing this work. When using the rubber tipped nozzle air blow back occurs and it sprays a fine mist of residual brake fluid into the air. It is also wise to wear a respirator due to this fact as well. Please take a look at the pics and the following questions apply:

1. Whats the best process/chemical to rid the calipers of the baked on grease and road dirt?
2. How much scoring of the piston surface is considered allowable before they need to be replaced?
3. Is there a tool or brush attachment for a drill or Dremel that can be used to safely clean the internals of the caliper?
4. What sort of lubricant is recommended when reassembling the caliper? I have seen videos showing a lubricant being applied to the piston and seal when inserting the piston back into the caliper. Also the same is true when installing the dust seal. What is this lubricant?

Cleaning brake parts that will carry or seal brake fluid is best done with denatured alcohol, which can be purchased at big box hardware stores. Isopropyl alcohol is also a good choice, BUT most of the isopropyl alcohol you see in retail small containers is a 70% solution with the rest being water, not something you want to introduce into a brake system. If you can get 100% pure isopropyl alcohol, OK to use that, too.

Assembly lubricant for parts that will carry or seal brake fluid should be new brake fluid only. Do not use drained fluid, and do not use fluid from a previously open container. Almost all brake fluid is hygroscopic, meaning that it absorbs water from the air, and water in brake fluid = water vapor (a gas) in the brake lines when things heat up = compressed gas = loss of braking power = NOT GOOD.

 

[79X19]

I cleaned up the housings with non petroleum based cleaner safe for seals then cleaned it further with new brake fluid to remove any residual cleaner. I then hit it with compressed air to assure that no dust and particles remained. No grease was used during the piston removal (Used Compressed air), I used new brake fluid as lube and they went together perfectly. Cant wait to try them out in the spring.

 

[Rupunzell]

Internally threaded hole on the front caliper is 3/8" x 24 threads per inch. SAE standard, Stock oem fitting is a banjo bolt with two copper washers to seal the joint. 3/8" x24 tpi is also a US standard tube fitting thread size for AN-3 and 3/16" tube fittings.

Bernice

 

[Dr.Jeff]

nternally threaded hole on the front caliper is 3/8" x 24 threads per inch. SAE standard, Stock oem fitting is a banjo bolt with two copper washers to seal the joint. 3/8" x24 tpi is also a US standard tube fitting thread size for AN-3 and 3/16" tube fittings.

Bernice, I always get a kick out of oddities like this; the calipers are mounted with a common US thread size, as are the banjo fittings, but the tube nuts (other end of hose) are a rare uncommon metric size.

 

[Rupunzell]

US regulations made this so at the time when the exxe was designed and produced. These regulations resulted in 3/16" OD brake tubes made of steel. 1/4" OD clutch tubes, 45 degree SAE spec double internal flares in the brake pressure differential switch found on the 74' and others.

Modern cars no longer have many of these mixed oddities, except it appears the 3/16" OD brake tube standard continues to live on.

The M10x1.25 long style tube nuts used for the brake system is common in Italian cars, French cars of this era. Some years ago when re-doing some of the brake tubing in the 74' ordered up a bag of 100 of these from the UK. They were about $30 USD to the door.

The M12x1.25 tube nut on the end of the clutch master is another matter, this one is Unobtanium unless source from Fiat. When this needed to be replaced, made one on the lathe out of 316 stainless steel hex bar.


Bernice

Bernice, I always get a kick out of oddities like this; the calipers are mounted with a common US thread size, as are the banjo fittings, but the tube nuts (other end of hose) are a rare uncommon metric size.

 

[aarpcard]

The M12x1.25 tube nut on the end of the clutch master is another matter, this one is Unobtanium unless source from Fiat. When this needed to be replaced, made one on the lathe out of 316 stainless steel hex bar.

That's getting added to the list of things to pull if I ever run across a junked X.

 

[Dr.Jeff]

Actually the M10 (1.25) long nuts are still available from two suppliers. One of those suppliers said he also has the M12 (1.25) ones. I verified the M10 nuts are correct, but I did not follow up on the M12 nuts so I cannot say for certain:
https://xwebforums.com/forum/index.php?threads/brake-line-nut-replacements.33258/