Problem with lubricating slide pins - air in boot

[The Critic]

I recently began using Motorcraft Silicone Paste for brake caliper slide pins and am running into a problem. I believe it’s very similar to the 3M silicone paste product.

The stuff is quite thick. On cars with brake caliper slide pins that remain on the bracket and have boots attached to them, I am having problems with the boots binding up.

Here is the situation that arises: I would put a moderate amount on the slide pins and reinsert the pin into the bracket. The boot stays with the bracket and is not taken off with the pin.

When I try to “exercise” the pin and boot together after lubing, the boot becomes full of air and the pin binds up and cannot slide.

Someone suggested that I “burp” the air out. So, I tried lifting up a corner of the boot with a pick and let all of the air out. When I do this the boot then sticks to the pin like a skin.

So, what’s the issue here? Grease too thick and sticky? Or technique.

I don’t remember having this issue before but then again, I did not start dealing with this style of calipers until recently.

Thanks.

 

[Trav]

Too much grease.

 

[JamesBond]

When you slide the pin back and forth with the caliper out during a brake job, you are moving the slide the distance that it usually takes several years to move as the pads wear down. During normal operation the distance the pads, slides and calipers move is very small.

I look at caliper slide grease as something durable that prevents rust should the boot wear out or leak. It provides a little bit of lubrication to keep things moving but that's about it.

Just make sure the boots are not ballooned up or appear to have a vacuum inside them when you put the caliper back on and they should be fine.

 

[The Critic]

Thanks guys.

 

[doitmyself]

So, following Bond, JamesBond's advice, they are to be burped at the position they will be in during the install. Not fully compressed or fully expanded.

On my recent Caravan brake job, for the first time, I also had to burp the piston boot in order for it to retract/fold up correctly.

 

[The Critic]

Thanks guys, I cleaned and relubed the slide pins on all four corners of this car tonight using the Motorcraft XG-3A.

The idea to twist the pins while inserting and to also burp the boots by lifting up a corner, worked great.

The old grease was 4 years and 62k mile old, but still seemed ok. However, on the test drive after the service, I noticed that the first 1/4 stroke of the brake pedal was more responsive and linear.

 

[mechtech2]

Get as much lube in there as you can.

Having to burp it is kinda rare, but after installation is the best time.

 

[Merkava_4]

Why aren't you using Permatex Ultra brake caliper slide grease?

That stuff is fantastic - I don't know why anyone wouldn't wanna to use it.

 

[SIXSPEED]

I've been using CRC synthetic brake grease to lube the guide pins on my Honda vehicles. Ford recommends use of Motorcraft Silicone Dielectric grease for my Mustang's calipers.

 

[The Critic]

Originally Posted By: Merkava_4
Why aren't you using Permatex Ultra brake caliper slide grease?

That stuff is fantastic - I don't know why anyone wouldn't wanna to use it.


The Motorcraft silicone paste does a better job with slide pins than a synthetic grease. No complaints of drying out and major automakers recommend it.

 

[SIXSPEED]

Originally Posted By: The Critic
Originally Posted By: Merkava_4
Why aren't you using Permatex Ultra brake caliper slide grease?

That stuff is fantastic - I don't know why anyone wouldn't wanna to use it.


The Motorcraft silicone paste does a better job with slide pins than a synthetic grease. No complaints of drying out and major automakers recommend it.

I'll probably use the Silicone grease next time since I have a tube. I read that CRC grease may not be compatible with some rubber boots ... but have not confirmed. I'll see how well the CRC grease held up next time I replace the brake pads.

 

[mechtech2]

SylGlide or the Ford silicone grease is best.
The Permatex or CRC dries out, and I've seen rubber swelling.

 

[Merkava_4]

Originally Posted By: The Critic

The Motorcraft silicone paste does a better job with slide pins than a synthetic grease. No complaints of drying out and major automakers recommend it.


You said in your first post that the Motorcraft grease is "quite thick." I took that as meaning too
thick. That's why I mentioned the Permatex green grease because it's such a light viscosity.

 

[The Critic]

Originally Posted By: Merkava_4
Originally Posted By: The Critic

The Motorcraft silicone paste does a better job with slide pins than a synthetic grease. No complaints of drying out and major automakers recommend it.


You said in your first post that the Motorcraft grease is "quite thick." I took that as meaning too
thick. That's why I mentioned the Permatex green grease because it's such a light viscosity.


I cleared this up in the earlier post - the issue turned out to be user error. I simply needed to burp the pin several times in order for air to not remain trapped.

 

[JHZR2]

I had to do this with my 3m silicone brake paste.

Question is, assuming it is burped, is there such a thing as too much? I'd think you would want as much as possible to ensure some is still there in case of high temperatures and water ingress.

 

[Trav]

Sure you can have too much in there. You need just enough to lube the pin and leave a coating on the bore not bung it full then try to squeeze it out from around the pin.
Many people do this mistakingly thinking they are somehow waterproofing the pin in case the boot doesn't do it job.

The lube gets real thick when cold and can cause cold stiction it there is too much in the bore. The rubber boots are what keep dirt and water out, if they don't you have boot or boot retention issues.

 

[JHZR2]

Great...