Brake Fluid Question

Status
Not open for further replies.

mikester

Comic Book Super Hero
Mar 10, 2010
2,904
3,639
113
Small town NY
What are you guys using for brake fluid ? Ive got a full container of silicone DOT 5 fluid out on my shelf. Is it compatible with the systems in G bodies ? Or should I use something else ?
 

melloelky

Comic Book Super Hero
Oct 22, 2017
4,136
9,486
113
mass
I thought about that when i put my car together because it doesn't eat the paint but after some reading i decided against it.long story sort it's not a very good performing fluid,you'll find the petal getting softer on you as it heats up.fyi you can't mix it with dot 3or4.if you go with the 5. You gotta flush or replace some components as they don't get along.i see it the Harleys but they're not doing any thing special in the brake department.
 
Last edited:
  • Agree
Reactions: 1 user

vanrah

G-Body Guru
Apr 16, 2013
879
1,189
93
Near Afton, Wisconsin
Greetings NailHead & all; When I switched to the WilWood GM III calipers & went threw the entire system I wanted to replace the master cylinder. Well the 9C1 master is not the same as other G cars. Even though the calipers are! So after a few returns & mine not available from GM we discovered that I have an Eldorado, Rivera- Tornado master cylinder from 1980. No new ones available from GM so I went to Bumper to Bumper & got a rebuilt. Well it was ugly & mine looked new yet. So I dissembled both & to my amazement mine was in like new condition after 24 years (2003). So lesson #79 use 5 dot silicone fluid. I had put 5 dot in back in 1980 when I took off the Full metallic (9C1) brakes & had changed once around 1991? The only less than perfect parts were the rear wheel cylinders. The rubbers were soft & playable, the bore was perfect in my old cylinder. I put it back on the car with fresh 5 dot. And the new rebuilt unit is in the box as spare parts. The only down side of 5 dot that I've encountered is the pedal is maybe (?) not as hard as the new 3-4 dot synthetic? But I can lock down all four. If your have trouble finding the cylinder that Mr Turna is recommending, & I'll bet that it is the exact same one (?) I sell ya my Bumper to Bumper spare. Good luck, Ole' Bob.

Ps; A repeat form another question. I'll chime in later with more info if you like.
 

mikester

Comic Book Super Hero
Mar 10, 2010
2,904
3,639
113
Small town NY
Well, now it gets more interesting. All the local auto parts only stock synthetic brake fluids. None have DOT 5, some have DOT 3 and also DOT 3+4. All synthetic. I asked and was told once you put synthetic in you can never change or add non synthetic. I was also told you cant drain silicone DOT 5 and replace it with DOT 3. What a pain in the *ss. I think we used silicone in my 81 but drained the system when I pulled the rear to sent it back to Moser. That was a few years ago and I cant remember what I used for sure.
 

Flyers9928

G-Body Guru
Jul 30, 2014
597
1,515
93
South Central Pa
DOT 5 is not meant for a vehicle that is driven regularly . It is designed for cars that are sitting for long periods of time like a museum car or static display. It does not have the ability to absorb moisture. All the different DOT numbers are not compatible with each other.
 
  • Informative
  • Agree
Reactions: 1 users

Longroof79

Rocket Powered Basset Hound
G-Body of the Month
Oct 14, 2008
12,156
9,762
113
Gainesville, Fl
I actually use silicone brake fluid in my Porsche, simply for the reasons stated....it doesn't absorb moisture...it won't eat into your paint...and it has a higher boiling point. ...and the fact that the car is rarely driven, it won't degrade like the conventional hygroscopic stuff.
Mich, I would go with the conventional Dot 4.
I also think you can't just flush out either/ or and switch over. I think it would have to be a freshly gone over brake system.

I used it in my old Porsche 914 and was disappointed that I couldn't get a firm pedal. I rebuilt all four calipers, new 911master cylinder, etc. As much as I bled the system over and over, I just couldn't get a firm pedal.

Silicone fluid is not recommended for race cars or any track use, and can't be mixed with conventional brake fluid.

I wasn't aware that you couldn't mix synthetic brake fluid with non-synthetic.
 
  • Like
Reactions: 1 user

mikester

Comic Book Super Hero
Mar 10, 2010
2,904
3,639
113
Small town NY
I actually use silicone brake fluid in my Porsche, simply for the reasons stated....it doesn't absorb moisture...it won't eat into your paint...and it has a higher boiling point. ...and the fact that the car is rarely driven, it won't degrade like the conventional hygroscopic stuff.
Mich, I would go with the conventional Dot 4.
I also think you can't just flush out either/ or and switch over. I think it would have to be a freshly gone over brake system.

I used it in my old Porsche 914 and was disappointed that I couldn't get a firm pedal. I rebuilt all four calipers, new 911master cylinder, etc. As much as I bled the system over and over, I just couldn't get a firm pedal.

Silicone fluid is not recommended for race cars or any track use, and can't be mixed with conventional brake fluid.

I wasn't aware that you couldn't mix synthetic brake fluid with non-synthetic.



I think this is going to cost me some time and a decent amount of money. I dont even remember why my friend talked me into using the DOT 5. Now Im assuming I'll have to replace the master, calipers, wheel cylinders, and the proportioning valve on the 81.
Any ideas of what I can use on the SS lines ? What about the rubber lines ? Replace them too ?
THIS is exactly why Ive grown tired of working on this crap. Time and money and me crawling around under the car AGAIN ! This sh*t will never get finished.
 

Longroof79

Rocket Powered Basset Hound
G-Body of the Month
Oct 14, 2008
12,156
9,762
113
Gainesville, Fl
I think this is going to cost me some time and a decent amount of money. I dont even remember why my friend talked me into using the DOT 5. Now Im assuming I'll have to replace the master, calipers, wheel cylinders, and the proportioning valve on the 81.
Any ideas of what I can use on the SS lines ? What about the rubber lines ? Replace them too ?
THIS is exactly why Ive grown tired of working on this crap. Time and money and me crawling around under the car AGAIN ! This sh*t will never get finished.
Mich,
I wouldn't replace any of the lines or hoses, only if they really needed to be replaced. I think it's mostly the hydraulics would need to be rejuvenated. I would just flush out all the lines and probably even the combination valve.
 

vanrah

G-Body Guru
Apr 16, 2013
879
1,189
93
Near Afton, Wisconsin
Mikester let me say that in 1980 when my car was about 6 months old we flushed the dot 3 out with DOT 5.... We did use nearly 2 quarts. And I didn't touch the brakes again until 1991 or 92. Replaced the pads & shoes, flushed the system with just under 1 quart of 5 dot. Then in 2003 I opened the whole system replaced the rear wheel cylinders as they had just a bit of pitting. Everything else was perfect including the master cylinder that I completely disassembled. It was like brand new inside. I've auto-X's around 9 or 10 times, drag raced nearly 30 passes since 1999 & had it on the road course once for 5 laps. My brakes work perfectly, you do what you want, but it's BS that 5 dot doesn't preform! And when you've had the same car for 39 years next week you find out what works & what doesn't. Oh I should add that's over 100,000 miles. And yes it's due for a re flush as it's been 15 years on the same fluid, 5 DOT! Just don't use it on a modern car with anti lock brakes as it too thick for the anti lock valving. My $.03 cents< Ole' Bob.
 
  • Like
Reactions: 1 user

mikester

Comic Book Super Hero
Mar 10, 2010
2,904
3,639
113
Small town NY
Mich,
I wouldn't replace any of the lines or hoses, only if they really needed to be replaced. I think it's mostly the hydraulics would need to be rejuvenated. I would just flush out all the lines and probably even the combination valve.

Jack, everything Ive seen so far says you cant really flush it out. I find that hard to believe. Im asking for info on a few other forums also. One thread had people saying denatured alcohol will flush it out. This is something I want to do right since the 81 has a little HP. Hate to lose a car if the brakes fail.
 
Status
Not open for further replies.

GBodyForum is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to amazon.com. Amazon, the Amazon logo, AmazonSupply, and the AmazonSupply logo are trademarks of Amazon.com, Inc. or its affiliates.

Please support GBodyForum Sponsors

Classic Truck Consoles Dixie Restoration Depot UMI Performance

Contact [email protected] for info on becoming a sponsor