Brake Caliper Slide Pin Cleaning and Lubrication

I agree that it's strange people have all these signs of rear brakes getting so much hotter than the fronts. That shouldn't happen unless the rears are failing to release. Prius brakes shouldn't often get very hot at all except due to rare emergencies, to "aggressive" driving habits, or to failing to use "B" mode when appropriate.

Frequently, I too check all four disk temperatures (if only subjectively with a finger) after parking. So far, none ever feel significantly above ambient.

 

Maybe because Toyota does not always have the best maintenance plan in their manuals.
For example: Transaxle ATF change intervals. (Not required according to Toyota. And dealers and some owners blindly follow that.)
And on this subject: Routine cleaning and lubing the brake slider pins BEFORE you have a problem.

 

In the Repair Manual there's a very generic description for the pin grease:

Lithium soap base glycol grease

That said, I believe there's a specific Toyota grease you can get.



I did a front and rear brake inspection about 16 months back. I thought I'd put the rear brakes back together ok, inner pad's pin aligned with piston cross, but over the course of the next few months things went south. After about 4 months I opened it up again, and found the the inner pad's pin was riding up onto the piston spoke, causing uneven contact, scored disc, a mess.

Could have been that, or a body shop that had redone the entire rear suspension, maybe a year further back.

Anyway, what I take away is that alignment of that pin, and careful seating of the pads prior to applying the parking brake, to ensure that pin stays aligned, doesn't slip and ride up onto a piston spoke, is essential to avoid uneven brake seating, and drag.

After replacing the rear pads and shims, and following the above steps during assembly, to keep the pin aligned, It appears to be all good. The discs have "cleared up", brakes not running hot.

 

just from reading here, it seems 2010's have the most problems. i could be wrong, but i wonder if they made any changes after the first iteration. they have been used outside the u.s. for a long time though.

 

There were changes and these TSBs were to address some those before the changes.
http://priuschat.com/attachments/t-sb-0136-11-pdf.32233/
http://priuschat.com/attachments/t-sb-0102-11-pdf.31926/

...and for those that want it...

 

correct.



Breaks inspection: my observations and surprises. | PriusChat

 

...and it's not lifetime either.

 

Just did this lube job and used Sil-Glyde but will be redoing it with better lube since OP's follow up on post #72 shows stuck rear slide at 15k miles post service.

So far in my google research, I see plenty of caliper pins getting stuck at even low mileage intervals like 50k miles. I've not come across anyone indicating a grease last beyond this range. Love to hear if there are longer lasting options.

Having seen other caliper pin designs. I think I know the reason for this one getting stuck so easily.

I think most if not all disk brakes on cars these days are floating calipers which means they kind of "float" around the rotor and slides on the pin

- When the caliper piston presses against the rotor on the inside side, there is a natural force to twist the caliper. The caliper body on the outside of the rotor wants to use the piston as the pivoting point and rotate away from the axle center. If this is allowed to happen, you will get angled brake pad wear and lower braking force due to less friction surface contact. So how do you keep the caliper from twisting?

- On other brakes I've serviced, caliper design often include a spring on the outside to pull it tight against the mounting bracket. This spring tension naturally counters the twisting force upon braking. The caliper is kind of tensioned down on both the inner and outer side of the rotor to prevent twisting motion. Here is a pic for reference



With the caliper anchored well on both sides of the rotor. The tolerance on the pin can be huge. In fact, don't even really need to lube it.

Actually, I learned about the desire for the caliper to twist when I reinstalled tensioning spring incorrectly. Without the tension and lots of play on the sliding pin, caliper twisted, pads wore at an angle and reduced friction contact surface.

- The Prius's caliper design, there is no outer spring so the slide-pin's gap with the sliding tube has to be really small to prevent the twisting motion. But the twisting force is there nonetheless and the pin will grind against the hole opening it inserts into. When you inspect the pins clearly, you can see wear marks right where it wants to twist against the hole opening on the bracket it slides into. I'm also guessing the black color we see on the old pin lube isn't dust. Rather, it is metallic mud similar to what you find on magnetic oil or atf drain bolts.

So this is the reason I think why all the grease including factory ones only last maybe 50k miles in the best case. Just a thought. Love to hear what others think.

 

Just wondering, belatedly: does that grease have any of the descriptive words, lithium, soap base or glycol?

 

FWIW, SilGlyde looks very similar in appearance to the OEM grease, and is recommended. I'll have a look at ours down the road, suspect it'll be ok.

 

FYI, looked over my records. 2011 Prius 69k miles. Dealer relubed the front brakes at 25k and they were pretty much stuck when I relubed them today so didn't quite make 45k miles (although service paper work didn't explicitly said they relubed the pins, could have just relubed the pad ears.

Rears were free at 69k miles and color is orange. Google finds Toyota Disk Brake Grease (08887-80609) in Prius service bulletin

http://priuschat.com/attachments/t-sb-0136-11-front-brake-caliper-rattle-pdf.32705/

This doc says Lithium soap based glycol grease (Toyota Rubber Grease 08887-01206) is incorrect

http://s48.radikal.ru/i122/1107/18/dfa141839537.jpg

08887-80609 (Toyota Disk Brake Grease or high temp silicon grease) is white colored

Came another grease for the guides slide 08887-80609.

08887-80206 is pink and here is the datasheet

http://priuschat.com/attachments/img_20141130_110432-jpg.72809/
http://dolphinmsds.taiamerica.com/MSDSImage/907500/907769.pdf

Anyhow, white color 80609 appears to be the correct grease while my factory lube that lasted 69k miles in the rear is orange and unknown part number.

BTW, given the harsh condition faced by this design, a friend suggested Moly Lube (they add this to the engine oil (slick50) and include molecular bonds to the metal to enhance lubrication). I had a sticky shifting 5 speed manual transmission after rebuild once and the VW specialist put in a tube of Moly Lube. That tranny shifted like butter for the next 150k miles (when I sold it) I'll probably give it a try and monitor it. Flash point is 220C which is same as most brake caliper lube

LIQUI MOLY - Motor Oils, Additives, Car Care - Products - LM 47 Long-Life Grease + MoS2
https://agscompany.com/images/stories/MSDS/English/Sil-Glyde-Grease_English.pdf
Permatex® Ultra Disc Brake Caliper Lube – Permatex
05351 -- Brake Caliper Synthetic Grease, 2.5 Wt Oz

 

LIQUI MOLY - Motor Oils, Additives, Car Care - Products - LM 47 Long-Life Grease + MoS2


LM 47 Long-Life Grease + MoS2
High quality special grease. The MoS2 content provides the selected base grease with outstanding lubricity and high performance properties that normal grease simply does not have. During operation, a permanently adhering, ultra-thin molybdenum disulfide film forms on the sliding points. The film retains its lubricating action for a long time even after the grease supply completely fails. Extremely long lubricity, transportable in central lubrication systems. Designation acc DIN 51502 KPF2K-30. Service temperature: – 30 °C to + 130 °C.

Intended use
For installation, maintenance and repair of vehicles, tools, construction, agricultural and printing machines. For highly stressed bearings and joints, splined shafts, threads and guides. For constant-velocity drive joints.

 

Not sure about anything with terms moly and paste. Silglyde (and similar) are silicon grease, recommended for pins. Moly paste is commonly used on pad backs.

 

My impression is SilGlyde is a bit thicker than just about any other grease I've seen. Contacted the good folks at artsautomotive.com to see what they use and will report back. I'm guessing they see sticky pins all the time on this car.

 

My understanding of the lithium soap based glycol "rubber grease" (the pink stuff) is that it is only specified for the parts that contact rubber (that is, the slide pins with their boots, and the piston with its boot and square-cut seal), and it's specified there because Toyota knows what their rubber formula is and what won't make it swell and stick. If you buy a Toyota rubber kit to do your own rebuild, the grease packet that comes in it is still the pink rubber grease, and if you buy a Toyota-rebuilt caliper, that's still the grease that's in it (at least as of last summer, when I did), so I don't have any indication that they've changed the spec.

For other locations on the brakes, such as pad ears and shims, where contact with rubber isn't part of the requirement, they specify other greases. You get a small packet of their gray shim grease when you buy a shim kit.

-Chap

 

there's a person in another thread, who's rear brakes were completely shot at 17,000 miles. i wish he had seen this thread, he's selling the car because of it.

 

the answer is yes. compare the part number with your service manual.

i saw that (confusing) document before, but according to toyota it's correct for the rest of the free world. do you trust russians?

 

While I was putting on the summer tires today (hope we don't get any more snow , I lubed the pins on all 4 wheels. Since I had bought the brake tool, my pistons didn't spin and I didn't need to use it (go figure). I disconnected the
12V battery and waited overnight for the pressure to bleed off, so maybe that is why it didn't move. Well I'll have the tool when the pads need replacing

 

Check your rears aren't binding, having disassembled and reassembled them. Chock the front, raise the whole rear and with parking brake off, check if the rears turn with minor resistance at most. There's a pin on the rear pad backs that should lock in between the piston face spokes. When you reassemble it can be aligned correctly, but if you apply the parking brake before pressing the brake pedal repeatedly, getting them well seated: the pin can ride up on a piston spoke, which skews the pads, causes uneven wear, brake drag, rusting up and scored brake rotors, war and pestilence. Just kidding, that last bit.