Latest consensus on using Silicone Brake Fluid
Thread Starter
Melting Slicks
Joined: Oct 2000
Posts: 2,144
Likes: 195
From: Englewood FL
Latest consensus on using Silicone Brake Fluid
There have been a number of posts on this over the years, but wonder how many are using it now?
I purchased my 1980 in 1999, converted over to Silicone and have used it to date. Every few years, I add some new brake fluid to bleed any moisture from the caliper pistons. Over the years I have replaced several brake calipers with chain store lip seal ones, none within the last 10 years. I am asking this question as sooner or later at least one of the calipers will leak.
The calipers from the Corvette Suppliers, now have a warning for both o ring and lip seal that using Silicone fluid voids the warranty.
I am wondering if o ring calipers are more prone to leaking with Silicone than the lip seal style? I would like to stay with Silicone if possible, as flushing it out will be a chore.
I purchased my 1980 in 1999, converted over to Silicone and have used it to date. Every few years, I add some new brake fluid to bleed any moisture from the caliper pistons. Over the years I have replaced several brake calipers with chain store lip seal ones, none within the last 10 years. I am asking this question as sooner or later at least one of the calipers will leak.
The calipers from the Corvette Suppliers, now have a warning for both o ring and lip seal that using Silicone fluid voids the warranty.
I am wondering if o ring calipers are more prone to leaking with Silicone than the lip seal style? I would like to stay with Silicone if possible, as flushing it out will be a chore.
Last edited by mark79,80; Apr 7, 2021 at 01:44 PM.
Melting Slicks
Joined: Dec 2009
Posts: 3,233
Likes: 657
From: Thunder Bay
I have spoken with one of the maor caliper rebuilders who advised that silicone fluid does in fact void their warranty. He also advises that the problem is good quality silicone fluid is no longer available. The stuff that we get nowadays will eat the rubber parts. I still have silicone fluid in my '79 that has been there for thirty years with no problem. I also have some old stock fluid. I will continue to use silicone until I have used up what I have on hand. When that day comes, I will have to convert to DOT 4 or 5.1. And before you ask, I don't know how you can tell if the fluid you have is good or not.
Melting Slicks
Joined: Nov 2006
Posts: 3,412
Likes: 1,823
From: Apple Valley, MN
Since you appear to have “cracked” the bleeders on the calipers periodically, flushing the system should be pretty simple. You might even be able to rent a pressure bleeder from a local parts store. If not, any competent shop should be able to do it without gouging you because it is a Corvette.
While you have had good experience with silicone fluid, since the suppliers won’t stand behind their warranty if you continue down that path, I’d simply convert to a glycol based product. There are several grades of DOT 4 ( Super DOT 4 and DOT 4 LV (see Pentosin’s website)) so just be sure if you select a DOT 4 product, check with the caliper supplier to be sure (in writing) they will honor their warranty with your fluid choice.
While you have had good experience with silicone fluid, since the suppliers won’t stand behind their warranty if you continue down that path, I’d simply convert to a glycol based product. There are several grades of DOT 4 ( Super DOT 4 and DOT 4 LV (see Pentosin’s website)) so just be sure if you select a DOT 4 product, check with the caliper supplier to be sure (in writing) they will honor their warranty with your fluid choice.
Race Director
Joined: Nov 2006
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From: Sunshine Coast, Queensland, Australia
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I to have been running Dot 5 for over 20 years. And I also have several bottles on the shelf that are at least 15 years old. (Sold my business years ago and kept a case). I've been running stainless sleaved lip seal calipers for over 20 years. I have had but one failure over the years. one seal just popped out of the bore. new kit. all fine. I'm not clear as to why they would manufacture brake fluid that isn't compatible with the rubber seals common in brakes.
Le Mans Master
Joined: Mar 2004
Posts: 7,499
Likes: 1,507
From: Little Rock AR
I have been using silicone fluid for at least 20 years in several vehicles. I have a gallon of NAPA DOT5 fluid bought at the time. I cant recall ever breaking the system open for anything.
Safety Car
Joined: Nov 2005
Posts: 3,961
Likes: 573
From: Lompoc, CA. Santa Barbara County
I switched to Silicone brake fluid back when my car was practically new, around 1980. It was a very popular mod at the time. Every time I do a canyon or mountain run, or autocross event, I would have to bleed again. That silicone compresses when hot. I use the DOT4 synthetic now. I also removed the factory calipers for Wildwood's and Hydroboost. None of that is necessary for normal street cruising though. I still have the stock stainless steel sleeved calipers if anyone is seriously interested. I think I got them from Ecklers when I used to go to the Cape all the time.
I do have a '88 Softale Custom Harley I bought new with silicone brake fluid factory filled. Seems to work fine there, but that is not a performance machine.
I do have a '88 Softale Custom Harley I bought new with silicone brake fluid factory filled. Seems to work fine there, but that is not a performance machine.
Last edited by Bee Jay; Apr 7, 2021 at 06:43 PM.
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1967 Pedal Car Champion
Joined: Mar 2020
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From: US-PNW
I've had silicone in my '67 for ~30 years with no issues whatsoever. When the brake rebuilders blame the fluid, I find that suspect -- I believe what could be an issue is that the rubber components have changed compositions and those new materials could be reacting with the silicone (which is hard to believe as silicone is pretty non-reactive).
My '72 just got new stainless calipers (been in storage for ~25 years and old DOT 3/4 was crystalized, gummy, and rusty) and I'm filling the system with silicone fluid. Of course the Lone Star box containing the calipers has the warning label about voiding the warranty with DOT 5... then I noticed that the info card inside the box states a 90-day warranty. Well, crap, they're not going out on much of a limb there! No matter what fluid you use, you're unlikely to have a warrantied failure in 3 months.
My '72 just got new stainless calipers (been in storage for ~25 years and old DOT 3/4 was crystalized, gummy, and rusty) and I'm filling the system with silicone fluid. Of course the Lone Star box containing the calipers has the warning label about voiding the warranty with DOT 5... then I noticed that the info card inside the box states a 90-day warranty. Well, crap, they're not going out on much of a limb there! No matter what fluid you use, you're unlikely to have a warrantied failure in 3 months.
Thread Starter
Melting Slicks
Joined: Oct 2000
Posts: 2,144
Likes: 195
From: Englewood FL
Someone asked if Silicone Brake Fluid can be used on Cardone brand calipers. This was the answer: Thank you for your question. The Cardone Industries 18-7019 brake caliper includes EPDM rubber seals which are compatible with DOT 5 silicone brake fluid.
Summit Racing Answer - 8/24/2020
Maybe the issue is with the rubber used in the o-ring calipers, which is different than in the lip seal style as indicated in the above response.
Summit Racing Answer - 8/24/2020Maybe the issue is with the rubber used in the o-ring calipers, which is different than in the lip seal style as indicated in the above response.
Last edited by mark79,80; Apr 8, 2021 at 08:59 AM.
Le Mans Master
Joined: Jun 2019
Posts: 5,484
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From: Loveland
What I read about silicone vs DOT3 or DOT4, is that it compresses more and can give a spongy pedal feel, but it doesn't rust. Maybe an issue with manual brakes, not so much with power brakes.
1967 Pedal Car Champion
Joined: Mar 2020
Posts: 9,137
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From: US-PNW
I think the pedal feel is firm and positive in my '67 w/ manual brakes and silicone fluid. The downside to silicone fluid is that it is highly susceptible to becoming air entrained if shaken. Pouring it into the master will generate quite a few bubbles but you just let it sit and release the air it picked up before bleeding the brakes. Perhaps this is the cause of the complaint; I searched but didn't find info on compressibility comparisons.
Le Mans Master
Joined: Jun 2019
Posts: 5,484
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From: Loveland
SILICONE BASED BRAKE FLUID:
The other option is Silicon based fluid. This type of fluid is non-hydroscopic, meaning it does not absorb any water. Often used in classic and vintage cars and military type vehicles because silicone based brake fluid will not corrode internal brake parts nor will it damage paint work. An added bonus when used in some show cars.This type of fluid is more compressible and can give the driver a feeling of a spongy pedal.
Silicone based brake fluid has not been developed for, or intended for, use in race applications.
Drifting
Joined: Aug 2019
Posts: 1,339
Likes: 225
The whole idea is for the brake fluid to absorb the moisture and keep it in suspension. Silicone fluid will not absorb it, and as a result the moisture will "puddle" in the calipers and master. I have used it in some of my cars, that are rarely driven with no problem. Silicone was hot years ago when there was only dot 3, so silicone had a dot 5 rating. It has remained on the market with this mystique. If you are already using it, stay with it. If not, save your money, and use a good dot 4. Do not use it with ABS systems, cause it will aerate. And if your brake caliper company says not to use it, then don't.
Safety Car
Joined: Nov 2008
Posts: 3,720
Likes: 554
From: Seattle Washington
Oh no. You mean when I switched to Silicone Brake Fluid in 1985 with VB&P SS Calipers and haven't had a problem since I voided my warranty...... Well I guess the Silicone Brake fluid out lasted VB&P..
1967 Pedal Car Champion
Joined: Mar 2020
Posts: 9,137
Likes: 4,248
From: US-PNW
SILICONE BASED BRAKE FLUID:
The other option is Silicon based fluid. This type of fluid is non-hydroscopic, meaning it does not absorb any water. Often used in classic and vintage cars and military type vehicles because silicone based brake fluid will not corrode internal brake parts nor will it damage paint work. An added bonus when used in some show cars.This type of fluid is more compressible and can give the driver a feeling of a spongy pedal.
Silicone based brake fluid has not been developed for, or intended for, use in race applications.
1967 Pedal Car Champion
Joined: Mar 2020
Posts: 9,137
Likes: 4,248
From: US-PNW
The whole idea is for the brake fluid to absorb the moisture and keep it in suspension. Silicone fluid will not absorb it, and as a result the moisture will "puddle" in the calipers and master. I have used it in some of my cars, that are rarely driven with no problem. Silicone was hot years ago when there was only dot 3, so silicone had a dot 5 rating. It has remained on the market with this mystique. If you are already using it, stay with it. If not, save your money, and use a good dot 4. Do not use it with ABS systems, cause it will aerate. And if your brake caliper company says not to use it, then don't.
Melting Slicks
Joined: Feb 2017
Posts: 3,232
Likes: 1,232
From: PHX AZ
In a nutshell don't use it.
LONESTAR voids the warrantee for a reason, Silicone soaks into EPDM (and other rubbers) lip seals and o-rings....causes them to swell and become non-functional.
My two cents...for a C-3 nothing but DOT4 should do.
You can mix dot 3 and dot 4....but dot 4 has a higher boiling point.
Unkahal
LONESTAR voids the warrantee for a reason, Silicone soaks into EPDM (and other rubbers) lip seals and o-rings....causes them to swell and become non-functional.
My two cents...for a C-3 nothing but DOT4 should do.
You can mix dot 3 and dot 4....but dot 4 has a higher boiling point.
Unkahal
Drifting
Joined: Aug 2019
Posts: 1,339
Likes: 225
I understand that moisture has the potential to enter the system through pores in the rubber hoses, seals, joints, and environmental exposure via the master cylinder, etc. Using a hygroscopic fluid (DOT 3, 4, 5.1), any moisture contacting the fluid is pulled into the fluid like a sponge, over and over. A hydrophobic fluid, like DOT 5, repels moisture, effectively sealing off pores, joints, etc and protecting the internal surfaces from moisture and corrosion. I am at a loss to understand how the moisture is puddling anywhere when the silicone fluid is sealing the system - unless you have a failure with major water ingress.
They have experience with returns, and they can tell which fluid was used. Like I've said., use it if you want. I've used it in the past, but brake fluid has improved, and if you use a good dot 4, and flush it every so often, you'll be fine.. But when it comes to warranties, and you spend a lot, why tempt the hand of fate?
Last edited by Mrvettenick; Apr 9, 2021 at 03:24 PM.