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Discussion Starter #1
Hello, I would like to buy overhaul kits for all 4 brake calipers for my 2006 F350 6.0 DRW. I had hot brakes on the front axle last year. I renewed the front calipers, now I have in front right again sticking pistons. The exchange calipers were from Raybestos and are badly made. I have an agricultural machinery workshop and have often overhauled brake calipers.
Only to get good parts for my SD is very difficult here in Germany. I am now looking for high quality overhaul kits. Thanks
 

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I usually stick w/ Motorcraft parts on the brakes. I am sure others have their favorites though.

Be sure to flush the brake fluid. Old fluid (especially if overheated) can contribute to caliper problems.
 

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Are you sure it isn't the slide pins that are sticking?
That's pretty common as well. Would be an easier fix. Replacement slide pin kits are available.

I agree on Motorcraft parts. I'd recommend contacting Autonation Ford White Bear Lake. They've been helpful, and could probably get the parts you need ar good prices. https://parts.autonationfordwhitebearlake.com/
 

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Discussion Starter #4
Brake Fluid ist brand new, calipers and slide pins are 18month old. Slide pins are ok. The pistons are very difficult to push back with large pliers. Under the protective rubber (sorry, don't know the word in english) you can see some rust. The pistons were unfortunately installed dry without lubricant, a professional does not do that. Calipers are overhauled from raybestos (Rockauto), but not well made. Therefore I would like to do now well myself with new pistons and new seals. I have done this many times with Mercedes-Benz Unimog calipers .
 

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Discussion Starter #5 (Edited)
The truck is not driven in winter/salt, it is a only summer driven camper vehicle. I am currently on a big trip around Ireland with it. I had to brake downhill with ~20mph shortly hard on a narrow pass road because of oncoming traffic. Arriving down the Pass Road I smelled the hot brake. Strange is also, it happened with the genuine caliper the previous owner also had same problems in front right side.
I had problems with hot calipers, 18 months ago the actual calipers were both fixed, I replaced them with those of raybestos.
 

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That does sound like a bad rebuild job on the calipers if the pistons are rusty. BTW, the rubber part around the piston is called a boot. I've rebuilt the front calipers on my truck. Used Motorcraft parts on them. It was kind of a pain to get the boots in place properly. I'm sure there's a special tool to do that, which I didn't have.
 

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Discussion Starter #7
Do you know how the tool looks like? For the calipers I've overhauled so far , you don't need any special tools.
 

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The service manual doesn't show a special tool, so there apparently isn't one. It calls for a boot retainer, but I don't recall that there was one on my truck, just a groove that the boot fit into (with difficulty) at the outer part of the bore.
 

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Discussion Starter #9
The camper weight is 6.5 metric tons. the brakes are not the best, I think about installing better ones. Does anyone know better brakes?
 

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Discussion Starter #10
I've tested how the piston "grows" when it gets warm. Dry installed, they probably get stuck.


 

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Not surprising. Phenolic or plastic has a much higher coefficient of thermal expansion than just about any metal. The pistons on my calipers are metal, so they expand at about the same rate as the caliper bodies themselves.
You might try to track down some metal pistons. That may solve your sticking problems, or at least lessen it drastically. I don't know if they're available anymore, but the loaded rear calipers I got from Ford a number of years ago also had metallic pistons.
 

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Discussion Starter #12
I have not found a supplier for steel pistons yet :|. Phenolic pistons are offered everywhere :frown2:
 

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I imagine SuperDuty Fords are like hen's teeth in wrecking yards in Europe, or I'd suggest harvesting some calipers off an older one with steel pistons.
 

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Discussion Starter #14
I'm afraid you're right. In Germany there are no SDs at all at scrap yards. The vehicles were never officially imported, so there are hardly any spare parts to get.
The calipers are from TRW. I don´t think the pistons were only used in these SD calipers. I would have to find out where they were still used. You can get the steel pistons for sure, but where?
 

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The '05+ piston sticking issue with the '05+ TRW calipers has been an ongoing issue that has bothered many. And I have no answer as that was after my time. Could it be phenolic pistons not processed well, maybe? It can also be the design of the grooves of the calipers. And it certainly can be an issue with rebuilt calipers, and if you hunt for some of my posts in the early part of this century I was recommending buying new calipers from the dealer while they were still available.

But when it comes to rebuilt calipers an issue that can reoccur with frequency is the loss of a good seal due to the corrosion that all rebuilt calipers suffer from.

Since the mid '90's vehicle manufacturers have gone away from steel pistons, they just transferred heat to the brake fluid too easily. And with the scheduled changeout of brake fluid not being performed on the service side (unlike Europe), phenolic was the choice.

There have been discussions on the forums that steel pistons have been available or used, but I've never had one in my hand. It's very easy to mistake the OE pistons for steel as they are provided with a stainless cap over the phenolic to protect the phenolic from abrasion. However, that does not protect them when people do not fully retract the pistons and drag them over the nubs of the pad steelbacks.

Here are a few examples.
 

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And here is an aftermarket example of a rebuilt caliper with an aftermarket piston on the left and an OE piston on the right. You can see the metal cap on the right being peeled off the phenolic.

If a steel piston was used, it would raise the potential of fluid boil exponentially compared to how these brakes were designed.

Also included is a view of the '99-04 Akebono caliper on the left and the '05+ TRW caliper on the right. Both per Ford requirements use a phenolic piston but capped, and these were both OE new calipers, not rebuilt.
 

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With any dragging brake issue, there are three things to look at. Slide pins, piston freedom, and pad freedom in the bracket. It can be very easy to overlook a hanging pad.


The other issue with rebuilt calipers is as I mentioned earlier, once pitting in the groove area, they will not seal as well and rust can migrate right through. This will rust jack the boot against the piston and if deep enough rust jack the O-Ring seal against the piston. And if that force is not enough to develop a high hysteresis, then the rust can also cause additional dragging.

If the brake fluid is used as a lubricant during the rebuilding process it just increases the development of rust as brake fluid is hygroscopic. And if the pitting allows for some brake fluid weeping, the rust grows faster.

The two ways of trying to combat this are by using silicone grease as the lubricant, or using glycerine as the lubricant and then using electronic RTV to seal between the boots and caliper. Electronic RVT as that does not give off acetic acid during cure and cause rust development.
 

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