I did it, Put DOT 5 silicone fluid in my new brakes Options

[worn]

The car is pretty much a lot of new. Rebuilt engine and transmission, a lot of reddish steel replaced by grey galvaneal. New rotors, calipers, shocks, master cylinder, new windscreen. New silver paint. So, this was the perfect opportunity. As background, my TR6 has run silicone hydraulics, brake and clutch for almost twenty years. That is simply the accepted way of doing things in the LBC world. The TR6 was a sales and sometimes race competitor with the 914, so why not? I have enough toy cars that annual brake bleeding is a PITA, yet since I am the person rebuilding cylinders the idea that rust doesn’t sleep comes to mind.

So I put in DOT 5 silicone in the completely new system. Pedal went straight to the floor. Belly pan off to find that a grommet had come loose and all the fluid leaked out.

My normal 914 practice is to bleed the breaks and drive a bit and then bleed them again. That produced a very firm pedal and spraying gravel. Yeah, I still haven’t taken the car out on the freeway in traffic, but now I am not afraid to try. So far, so good. That will leave only four toys for annual testing moisture content and bleeding through new fluid. Time after time.

I will keep you posted.

[Jack Standz]

(IMG:style_emoticons/default/agree.gif)

We are with you. The bigger your fleet or the number of other projects you have makes flushing normal brake fluid more of a pain. DOT5 brake fluid lets you flush and bleed much less often, unless you're doing it wrong.

I've run DOT5 in one of our other mid-engined cars for years (can't remember how many). When the entire suspension front and back, as well as all brake components, including master cylinder, Iines, calipers were replaced on the '74 914 a few years ago, we used DOT5.

Higher Boiling point, doesn't attract water (and resulting corrosion), doesn't destroy paint if you get any drips and doesn't require as frequent flushing/ bleeding, etc. Good stuff and don't believe the naysayers about a spongy pedal. It works really good.

[Root_Werks]

I'll be watching this thread for updates. Yes, a lot of cars makes bleeding brakes a PITA. I'll admit, I don't bleed annually. Usually every 2-3 years. I know lazy I am.

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[mlindner]

Hi Worn, just checking if your going to the Chicago tomorrow.

[mgphoto]

I used a Dot 5 silicone in my 914 about 20 years back, took more than a year to soften up the seals between the rear caliper halves that began to leak.
Back to using the ATE stuff.

[mepstein]

If you read up on dot 4 vs dot 5, I doubt most people will use dot 5. Other than the fact that it doesn't attack painted surfaces, there's no upside to using it. Since it doesn't attract water, moisture can pool in a localized site and cause corrosion. It can cause seals to swell and leak. Very little upside and lots of possible downsides. I've never heard of anyone really familiar with Porsche brakes reccomend dot 5 over dot 4.

[Ninja]

Heads up guys...

Dot 5.1 is available. It's normal, mixes with Dot3/4 and is NOT compatible with Dot5.

I've had one vehicle in 40+ years of wrenching that had been changed to Dot 5.

It was a completely restored 1970 Chevelle big block 4 speed, # matching, 100K plus car.

In the last 10 years, the owner put less than 100 miles on it.

He had owned it for 10 years before I worked on it. The brake hydraulics had been fully restored before he bought it, and the previous owner had put Dot 5 in it.

Andy had driven it approximately 500 miles before I met him. He is my landlord.

It needed the front calipers rebuilt and new wheel cylinders due to leakage with 500 miles and ten years on the system...

Andy didn't want to completely rebuild the hydraulics again (master/prop valve/hoses) and we put Dot 5 back in it.

I still have the extra bottle on Dot 5 and I am looking at it now.

It says "for occasional driving and special vehicles" directly on the bottle. It also says "not for use in vehicles with ABS".

I use Dot 4 in every car I service and will use Dot 5.1 in track cars.

The only benefit I see for Dot 5 is the wicked color, fluorescent purple...

I truly believe Andy's Chevelle would NOT have needed brake hydraulic work had Dot 3/4 been utilized.

Most of the appliance cars I service have not had the original Dot 3 brake fluid flushed at the 10-year point, they have 100K+ mileage on them, and don't need hydraulic work at that point...

Andy recently sold the Chevelle and I'm chucking the Dot 5 in the trash today!

I back dated the AC to R12 and fully restored the factory under dash stuff which hadn't been restored during the "restoration". (IMG:style_emoticons/default/headbang.gif) (IMG:style_emoticons/default/headbang.gif)
They had changed over to R134 and it didn't work worth a shit.

Picture of it
https://granburyautoac.com/vintage-classic-...-block-4-speed/[u]

[worn]

If you read up on dot 4 vs dot 5, I doubt most people will use dot 5. Other than the fact that it doesn't attack painted surfaces, there's no upside to using it. Since it doesn't attract water, moisture can pool in a localized site and cause corrosion. It can cause seals to swell and leak. Very little upside and lots of possible downsides. I've never heard of anyone really familiar with Porsche brakes reccomend dot 5 over dot 4.

But quite a lot of people with older cars than ours swear by it. They just don’t post on Porsche sites. I have one car that hasn’t had a leak or corrosion problem in 15 years at both brakes and clutch with the original fluid. But that isn’t evidence nor is it reason to decide. I cannot imagine even thinking about using silicone with ABS: the potential for harmonics would be enough to keep me from trying. As a chemist I can imagine and have witnessed water in the gas phase entering something hygroscopic like the DOT4 glycols and slowly accumulating over time. I bought a meter. That transfer of water from the air ain’t gonna happen with silicone, so the only way for water to pool in that fluid is to have it added as a liquid, or already be in the system. In that case dilution into the glycol would certainly dilute the water, but that doesn’t seem like a benefit.
I will keep you posted. As I said, a seal already failed, but that is because I hate those grommets and didn’t get one in right. What were they thinking?

BTW, DOT5 doesn’t play well with paint. It doesn’t eat what is already on the car, but it will create fish eyes like crazy if it contaminates a surface being painted. Mixed bag.

[worn]

Heads up guys...

I truly believe Andy's Chevelle would NOT have needed brake hydraulic work had Dot 3/4 been utilized.

That is pretty much what I expected to hear based upon bringing it up in the past. Which is why I am trying it and telling all y’all about it. If I get leaking cylinders and calipers you will be the second to know. When my other cars with DOT4 start leaking I won’t say a thing. Of course if you are tracking your car none of my experience is of any value and please don’t even think about changing brake anything because of something I write. Please be very cautious regardless.