Topic: caliper piston seal (help)

[75cb550 (kyle)]

i put a new honda seal in the 550's front caliper bore a few months back. the bike has sat since then but now im trying to get her road ready...
however, the seal is leaking. i pulled the piston back out and i cant see anything wrong with the seal or bore. any one run into this or have any ideas.
thanks....

[Duke McDukiedook]

Did you possibly get a little overzealous in your cleaning/scraping of the seal groove?

[OldSchool_IsCool]

Or underzealous in cleaning the seal groove and left some crud behind?

[Johnie]

Did you lube that seal and piston before you put the piston back in?

[JS550]

The first time I did it, I sheered the seal when I reinstalled the piston. Not enough lube.

[Johnie]

You narrowed it down to 3 things: bad seal, piston with pits, seal groove bad or dirty. I would do it again with another seal if you determine the piston is not overly grooved. Once it starts leaking you have to change something. I do not think cleaning and putting the same seal back in would be the answer. Unless you feel there is a ton of dirt on the seal? Did you use OEM or aftermarket seal?

[JS550]

You might tear or mess up the seal taking it out anyway. I would just plan on a new seal. Again.

[75cb550 (kyle)]

thats what i was thinking. and yes it was a honda seal.... ill need to pull it out and give it a good look. i cleaned out the groove with a pick i think. i tried not to scrape anything too hard but that could be it. what did you guys use to lube the seal. im pretty sure i lubed it but i cant remember what i used. that could be the whole problem.

[Johnie]

To clean that groove I did not use a pick, but instead used a Dremel with a brass brush on it. The lube I used was high temp silicone for brake applications.

[75cb550 (kyle)]

k. i actually think i have another seal for it. i will give that a try.
thanks...

[Duke McDukiedook]

I used Brake Assembly lube, McKay brand if I remember right.

http://www.airosol.com/50600.html

[TwoTired]

I used Brake Assembly lube, McKay brand if I remember right.

http://www.airosol.com/50600.html

That is what I use, as well.  I do NOT want any silicone inside mixed with the brake fluid.

The silicone lube is for a water shed on exposed-to-atmosphere portions of the caliper.

There is a caliper rebuild walk though in the brake FAQ.

[Johnie]

Wish I knew about the silicone earlier. Oh well, I will report back if I have caliper problems. What I used was NAPA Sil-Glyde. Says "non-melting, non-freezing, non-gumming and weatherproof. For brake pads, calipers, rubber boots, etc. Eliminates caliper sticking." This was all on the tube from NAPA. I will use the McKay in the future. I figured out why I used the silicone grease. My Honda shop manual says, "use silicone sealing grease (temperature 67-392F). Do not use molybdenum grease known as brake grease". I am not saying the Honda manual is correct now days since it was written in the late 60's, but that is where I got the information. I also note that in the FAQ area this is what I found: "Clean all the exposed surfaces of the piston and caliper with the cleaning solvent. Using the High Temperature silicone grease, coat the back of the brake pad puck, the piston face, and the caliper socket for the puck. Don't get silicone grease on the fiction surfaces of the brake pads! " If this is incorrect information we should correct it there.

[TwoTired]

Wish I knew about the silicone earlier. Oh well, I will report back if I have caliper problems. What I used was NAPA Sil-Glyde. Says "non-melting, non-freezing, non-gumming and weatherproof.

And they are Fcuking liars, too, IMO.  It only contains silicone, is NOT pure silicone.  And, is in no way proper for use on the SOHC4 caliper seal.  I did an oven test on it years ago, it smoked off and left a brown tar residue at around 300F, if I recall correctly.  There have been several prior threads on this stuff.

For brake pads, calipers, rubber boots, etc. Eliminates caliper sticking." This was all on the tube from NAPA.

This stuff ruined my brake pads as it creeped/ran onto the pads and caliper surface, losing most of the braking action.  What little silicone was there permanently ruined my brand new pads.

I will use the McKay in the future. I figured out why I used the silicone grease. My Honda shop manual says, "use silicone sealing grease (temperature 67-392F).

Yes.  Search the forums for DOW Corning Hi temp Grease.  This stuff is unworldly.  I couldn't get this stuff to show any change in characteristics up to the limit of my 500F oven.

Do not use molybdenum grease known as brake grease".

No, that stuff still lubes at hi temp, but oozes, creeps, and runs, needing some kind of lip seal for containment.

I am not saying the Honda manual is correct now days since it was written in the late 60's, but that is where I got the information.

The manual is still correct, I believe.

I also note that in the FAQ area this is what I found: "Clean all the exposed surfaces of the piston and caliper with the cleaning solvent. Using the High Temperature silicone grease, coat the back of the brake pad puck, the piston face, and the caliper socket for the puck. Don't get silicone grease on the fiction surfaces of the brake pads! " If this is incorrect information we should correct it there.

I wrote that in the FAQ.  I'm sorry you misread it.
The seal itself gets Brake parts assembly lube.
The exposed surfaces are those exposed to the atmosphere/rain/contaminants.  The caliper design has no way to keep water from getting getting behind the brake puck, the non-brake fluid side of the piston, the caliper cylinder wall and side of piston.  A coating of silicone grease on those areas repels water in this area preventing corrosion.

How would you recommend the prose be changed for proper reading?

[Johnie]

TT...tell me if I have this correct as I do admit I am trying to grasp it. The Dow is used on the caliper wall from the seal ridge out including the edges of the pads and the area under each pad. Dow is also used on the piston & puck area once it has been started into the seal. The McKay brake assembly lube is what I should use on the seal only. Do I put McKay lube on the caliper wall on the opposite side of the seal which is in contact with the DOT 3?
Lastly, can I just clean my new seal and reapply the McKay with no problem or do I need a new seal now? The bike has not been driven since the seal was installed 2 weeks ago. I have ordered the Dow but am still trying to find the McKay assembly lube or something which will work...any other product you recommend?

[TwoTired]

TT...tell me if I have this correct as I do admit I am trying to grasp it. The Dow is used on the caliper wall from the seal ridge out including the edges of the pads and the area under each pad. Dow is also used on the piston & puck area once it has been started into the seal. The McKay brake assembly lube is what I should use on the seal only.

By George, I think he's got it!   

Do I put McKay lube on the caliper wall on the opposite side of the seal which is in contact with the DOT 3?

If you are going to store it on the shelf for ten years, probably.  But, in service the interior walls are wetted by the the DOT3.  The proper assembly fluid kind of dissolves in DOT3.

Lastly, can I just clean my new seal and reapply the McKay with no problem or do I need a new seal now?

Silicon can only be flushed, as it dissolves in nothing.  The rubber is porous, so there is still silicon in it.  I don't know for sure reusing it will cause a problem.  But, I wouldn't reuse a seal contaminated in that way, if I could avoid it.

I have ordered the Dow but am still trying to find the McKay assembly lube or something which will work...any other product you recommend?

Sorry, I know the proper fluid is hard to find these days.  But, I know of no proper substitute in this application.  If pressed, I would just use DOT3 sparingly on the seal.  However, that portion of the seal that faces the atmosphere, or more importantly the metal it whets, will be prone to corrosion, as DOT3 absorbs water.  And of course, the atmosphere has oxygen in it to promote corrosion.

Honda got much better at designing calipers to withstand weathering without the special greases and fluids.  But, it wasn't until after this design.  Still, this one works well if maintained correctly.

Cheers,

[Johnie]

Excellent...I got the Dow from eBay. Does anyone have a source for the McKay assembly lube? If not, I will just use the DOT 3 on the seal surface per TT's message. The local auto parts store has some made by Raybestos, but I am not sure what it contains yet.

[OldSchool_IsCool]

I found Dow Corning Hi Vac Grease 150 gram tube on Amazon.com for $49.02. Is that about what you paid?  Any better deals out there?

[TwoTired]

Both these work for the caliper seal.  And master cyl rebuilding, too.

[Johnie]

I found Dow Corning Hi Vac Grease 150 gram tube on Amazon.com for $49.02. Is that about what you paid?  Any better deals out there?

My Dow cost was $24 for an unopened 5 oz. tube including shipping.

[OldSchool_IsCool]

5oz = 142g so you got the best deal so far!

[Johnie]

None of my parts stores here in WI have the Raybestos assembly fluid, but I think this is it on Amazon. No picture but I think this is it for $15.

http://www.amazon.com/Raybestos-BAF12-Brake-Asembly-Fluid/dp/B001ANJ2GE

[75cb550 (kyle)]

ill be checking autozone/napa tonight... im glad i asked.... i never would have thought about it....

[TwoTired]

Yes, BAF-12 is the what the Raybestos bottle has on it.

[Johnie]

ill be checking autozone/napa tonight... im glad i asked.... i never would have thought about it....

My Autozone, NAPA and United Parts do not carry Raybestos. The Amazon bottle has the TT approval so I will get it tonight.

TT - thanks once again for all your time on this topic. I luv you man!!! 

[spill]

I'm considering applying CRC synthetic brake caliper grease to the caliper piston outer wall and piston seal before assembling. It reads 600 degrees as the max of the temp range. Any experience with this black MOLY, PTFE, and graphite goo?

[TwoTired]

You have to be careful of the "specsmanship" of the product.  The writer's job is to make the product appealing to the widest amount of purchasers, often hiding important characteristics.

For example, if the product stops lubricating at 600 degrees, they can put that on the label.
But, that same product can phase change from a gel to a liquid at 300 degrees.  It still lubricates. It won't stay in place unless held captive by seals.  They didn't lie to you.  They just didn't tell you the whole story.

Does the product combine with water?  Can it be washed away by water?  Some petroleum based products can.  "Synthetic" can still mean it behaves as an oil or grease and be derived from a petroleum product.  This product's specs:
 "Water Washout       <5%"
...looks pretty good.  But, if the film thickness loses 5% each time it gets watered, when will you know it is time to be renewed in order to maintain protection?  The Dow Corning pure silicone grease will never, ever combine with water.

Where used on the SOHC4 caliper is behind and right next to the friction surface.  It needs to be a water repellent to keep water away from the metal surfaces where water can ingress.  This design has no seals and relies on the silicone grease (such and the Dow corning product) to do all the water repellent, and stay in place when hot, so as not to contaminate the friction pads and disc.

Another property of greases is its "creepage" characteristic.  Some of the grease may always stay in gel form, but some percentage of it can liquify and run or creep away from the gel binder in the grease base.  This won't help your friction pads stop the bike.

Have I tested the product to which you prefer?  No. 

The specs that worry me.
"Base Type       Polyalphaolephin & Pentaerythritol Esters w/ fumed silica"
Silica is the thickener.  At what point do the lubes separate from the silica?

"Working Temp       -40 to 600°F intermittent"
Intermittent?  So how long will it take for 600 degrees (or less) to phase change the product?

"Drop Point       >600°F"
The drop point is where the ENTIRE mass of grease becomes liquid.
Unfortunately, it can still be partially liquid at a lower temperature, unless they add a phase change spec.

"Oil Separation       <10%"
Note it is non zero.  So, I wold assume there can be some creepage/weepage/running onto your brake pads in the SOHC4 design.


Personally, I'll stick to the proven Dow corning product for this application in SOHC4 calipers.  It is also what Honda specified, btw.

Cheers,

[spill]

Thanks Lloyd. 

So, I hate to waste the CRC synthetic grease.  Two of the reasons I bought the bike in the first place was to, one, restore an unused vehicle; and two, to reduce my consumption of petroleum. Do you know how much petroleum it takes to manufacture a new vehicle (that's a question for another thread)?

O.K., I admit, I bought it because I love to ride and I love the asthetics of the 70s CBs.

Where (on the bike) can I use this black goo?  How would it perform in less, stressful, for lack of a better adjective, situations?  How about the rear axle [not that I already didn't apply it during assembly today . . . *crossing fingers* . . .]?

[TwoTired]

Some materials are special purpose, limited application usage.

I still have two tubes of Syl-glide I bought (ruined the brake pads), before I got the proper Dow Corning stuff.
Syl-glide cost me a set of brake pads and doing the job twice.

[OldSchool_IsCool]

At the risk of a set of pads and doing the job again,  Is this stuff worth a look?

http://www.permatex.com/products/Automotive/lubricants/specialty_lubricants/Permatex_Ceramic_Extreme_Brake_Parts_Lubricant.htm

Sayz there is no drop point.

[TwoTired]

At the risk of a set of pads and doing the job again,  Is this stuff worth a look?

http://www.permatex.com/products/Automotive/lubricants/specialty_lubricants/Permatex_Ceramic_Extreme_Brake_Parts_Lubricant.htm

Sayz there is no drop point.

Says there is no drop point per ASTM d2265 test.  Which specifies a limit of 625 degrees F.  Remember the drop point is where the entire test sample phase changes from gel to liquid. There is an orifice at the bottom of test vessel where they watch for the first drip.
I hate it when MFGs hide information, in this case the limit of the test.  It make the product sound better without any quantification.

Anyway, the product does look promising.  The only thing missing is a spec about creepage/weepage/running.  At whatever temperature.  Syl glyde does that at room temp, as do many other greases that are used primarily for lubrication.

The SOHC4 caliper doesn't need lubrication qualities where it is used.  It is used as an atmospheric and elements barrier on the exposed metal surfaces.  It has to stay put, and not allow any part of it to wander at any temperature that the caliper experiences in operation or storage.

Cheers,

[OldSchool_IsCool]

Buttered the caliper, piston and pad back with Permatex Extreme.  It has the consistency of thick tooth paste.  Will report back by next tune up if it has stayed put.  Sooner if it doesn't stay where it
s supposed to.

[TwoTired]

Try not to follow other vehicles too closely.


 

[OldSchool_IsCool]

Try not to follow other vehicles too closely.


 

Lloyd,

I highly value your opinion.  I will be the first in line if you ever write a book on the care and feeding of the middle fours.  If you think this product really isn't worth a shot or if you think my application technique is unsafe, do my dependents a favor and let me know.

[TwoTired]

I did a test in an ordinary gas fired oven in my kitchen.
 Put a small sample in an oven with a thermometer.  Set it to 250 F, and observed it through the little window while the temp rises.  After temp stabilization, I bumped it up 50 F increments, until I eventually got to the 500F limit of my oven.

I know the Dow Corning silicone was unaffected by heat to the limits of my oven (just like their product data sheet indicates).  It remained a gel glob on a little aluminum foil fashioned into a cup.  (Syl-Glide did not.  It partially puddled at 300F and vaporized at about 350F)

I did the oven test AFTER I ruined a set of brake pads with the auto parts store counterman's recommendation that Syl-Glide was the right choice for this (SOHC4 Caliper) application.
To this day I am convinced that he was willing to say anything that created a sales slip.

Having that experience, I would not test a new product and my safety on my bike without an off bike test to see if it meets the boasts of the salesman/marketeers.
If I WERE to test it on the bike. I would find a safe place to do 5-10 full braking stops in a row from high speed, to heat up disk and caliper, then examine the caliper and pad for lube leakage/weepage/creapage.

It's your call, though.

[OldSchool_IsCool]

Thanks Lloyd, your approach makes much more sense then my head long jump into a live test.