Brake fluid, or grease, on caliper piston seals?

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SubLGT

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Is there any advantage to using grease on the piston seals? In my Subaru service manual, it states to use brake fluid on the seals when installing them. But the OE rebuild kit I bought includes grease for the piston seals.

What are the pros and cons?
 
Originally Posted By: SubLGT
Is there any advantage to using grease on the piston seals? In my Subaru service manual, it states to use brake fluid on the seals when installing them. But the OE rebuild kit I bought includes grease for the piston seals.

What are the pros and cons?


I would be concerned it would contaminate the fluid space in the caliper causing fluid boiling.
 
I've tried permatex brake grease and struggled to get it back together. I cleaned it off and used brake fluid and the seals went in very easily. Use brake fluid.
 
Silicone grease. An old tech taught me to use silicone grease on caliper pistons/square O-rings and also AC o-rings. I used the FoMoCo silicone grease (go figure) in the blue tube for this. In usually got a year or more of use from each tube of grease. Never had a recheck on any caliper/m-cyl/wheel cyl overhaul, and it was a lot less smelly/messy than using brake fluid as a lube.
 
I just used BF for yrs. But Syl-glyde makes the parts super slippery. I can clean and lube a caliper on the bench and put it back together with the same parts and have it work just fine. It is a silicon lube. It is way easier on the fingers. My breast cancer was caused by my environment. Ive breathed and worked in some pretty nasty places.Brake fluid and cleaner is pretty bad stuff. Silicon grease washes off easily.
 
unless you are contemplating on using DOT5 (silicone) fluid, otherwise: using silicone grease during the assembling of caliper piston seal is a big no-no, citing glycol brake fluid contamination issues.

Also: using brake fluid as lubricant while installing caliper piston seal is okay if and only if it(the caliper) gets put into surface right-away. Glycol based brake fluid is hydroscopic (water-affinity, or water-luving), so extended sitting around after assembly would do more harm than good.

I have long been using a brake assembly grease called PBS brake grease, made in Australia ...100% compatible with rubber parts and glycol based brake fluid.

Been using PBS for over 2+decades now, zero returns due to assembly errors or rubber seal swelling/failure due to lubricant issues.

I don't use any Syl-glide for I have never been able to confirm it's compatibility with glycol based brake fluid.

Q.
 
Looking at a tube of Syl-glide it does not say anything about using it internally.
It does say it is to be used on caliper slide pins, seal boots and shoe contact points.

On the seals themselves.
I have in the past used a little pack of grease that has come with a new set of seal (Girling used to always inclose this and instruct you to use it.

I never liked the idea of getting brake fluid anywhere other than where it needed to go.
 
Originally Posted By: Warstud
I would just use brake fluid. Is the grease clear?


The grease that came with the OE kit is a translucent pink.
 
Originally Posted By: SubLGT
Is there any advantage to using grease on the piston seals? In my Subaru service manual, it states to use brake fluid on the seals when installing them. But the OE rebuild kit I bought includes grease for the piston seals..


Interestingly, Subaru only includes piston seal grease for the front caliper rebuild kit. In the rear caliper kit, none is included. I wonder if this has anything to do with the owner reports of frozen pistons in the front calipers. Maybe the grease reduces this problem better than brake fluid?
 
I like to use Seiken PL-7S - it's a silicon lube for brake cup assembly. Best stuff ever, and made for the job.

1-5a.jpg
 
Originally Posted By: Merkava_4
McKay Brake Cylinder Assembly Lube is what you're supposed to use for brake seals.

50600.jpg

Where can I get the McKay lube? TIA
 
Originally Posted By: Merkava_4
McKay Brake Cylinder Assembly Lube is what you're supposed to use for brake seals.

50600.jpg

Where can I get some?
 
Originally Posted By: Dan55
I remember it being called brake assembly paste, it is used at the factory to prevent corrosion and extend shelf life. For you brake fluid is fine. More info http://www.ferrarichat.com/forum/technical-q/410361-brake-cylinder-paste-source.html


Brake assembly paste used to be pretty common in auto parts stores 20 years ago, as I recall. And uncommon nowadays, it seems.

Both ATE and Wurth sell them, as "Bremszylinder paste"

http://www.ate-info.de/en/products/datasheet/ate-bremszylinder-paste-180-ml/
 
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