DOT 3 to DOT 5 Brake Fluid ?
Thread Starter
Instructor
Joined: Mar 2008
Posts: 193
Likes: 17
From: Greer SC
DOT 3 to DOT 5 Brake Fluid ?
I`m changing a 1980 L82 to O-ring calipers,Is now the time to change to DOT 5? Or should I just use Dot 3 ,flushing brake fluid every couple years is no big deal.
Burning Brakes
Joined: Aug 2005
Posts: 801
Likes: 1
Dot 5 is cheaper than a re paint.It dosent deteriorate seals as bad as dot 3,4.The only bad thing is that it dosent like mixing with dot 3,4.It turns into a gel like substance.Looks like replacing the rubber lines and flushing out the hard lines would help.Also changing seals in mastercylinder and flushing it out with denatured alcohol would be a good idea.
Drifting
Joined: Aug 2009
Posts: 1,635
Likes: 8
From: Enid Oklahoma
I would not mess with it....DOT 5.1 is a non silicone sybthetic that is anti hygromic(won't pull in water) lasts almost indefinatley and mixes well with DOT 3 or 4. I have always used Valvoline. It used to be called synthetic ABS brake fluid. But I am NOT a fan of siliconized fluid at all, it is too hard to get all the other out, in reality it all needs flushed with alcohol and I have not seen any benefit over the synthetic.
Burning Brakes
Joined: Aug 2005
Posts: 801
Likes: 1
Each his own.I went with it because the po put it in.He replaced all the lines and components.So incompatiblity wouldn't be a problem.The stuff has been around for quite sometime.I had never used it before now.I went ahead an kept it as I was replacing other components and it was already in there.I put wilwood d8 calibers on it with a wilwood aluminum mastercylinder.That and the hydroboost unit give a pedal as hard as a rock.As far as pedal feel gose.
Melting Slicks
Joined: Mar 2005
Posts: 2,838
Likes: 10
From: Austin TX
I run Dot 4 in all my rigs. Higher boiling point than Dot 3 and Dot 4 is much more resistant to moisture absorption. And the two are compatible so there's no need to completely evacuate the system of one for the other.
As far as ruining paint jobs, I'll just say millions of cars and trucks, which run Dot 3 & 4, are free of paint damage from brake fluid. Simply be careful when pouring and keep the lid on the master when working the pedal.
FWIW
As far as ruining paint jobs, I'll just say millions of cars and trucks, which run Dot 3 & 4, are free of paint damage from brake fluid. Simply be careful when pouring and keep the lid on the master when working the pedal.
FWIW
Melting Slicks
Joined: Aug 2008
Posts: 2,200
Likes: 3
From: Lehigh county Pennsylvania
I've used DOT 5 for more than 20 years when I changed to the stainless sleeved calipers. I replaced the flex hoses to the teflon lined braided type. I blew out the hard lines and master cylinder with compressed air.
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Le Mans Master
Joined: Apr 2007
Posts: 7,353
Likes: 72
From: Graceland in a Not Correctly Restored Stingray
There remain a number of reasons not to use silicone based brake fluids, despite testimonials on its behalf from those who have been lucky enough not to run into them. Dot 4 Valvoline should be all you need for most street applications.
Safety Car
Joined: Nov 2004
Posts: 4,359
Likes: 57
From: Mundelein Illinois
As you will read above, you will never get everyone to agree. I've used DOT 5 for years and my decision was based on moisture in the system and not wrecking the paint if something ever leaked. I have a 12K paint job invested in my car. The cost is more than DOT 3 or 4 but we all have many dollars into these cars, so I believe cost is not a big deal.
I have taken apart brakes that were 15 or 20 years old and with DOT 5 everything inside looked brand new.
DOT5 can not be used with ABS but for these cars it great!
I have taken apart brakes that were 15 or 20 years old and with DOT 5 everything inside looked brand new.
DOT5 can not be used with ABS but for these cars it great!
Le Mans Master
Joined: May 1999
Posts: 6,692
Likes: 29
From: Texas
I would not mess with it....DOT 5.1 is a non silicone sybthetic that is anti hygromic(won't pull in water) lasts almost indefinatley and mixes well with DOT 3 or 4. I have always used Valvoline. It used to be called synthetic ABS brake fluid. But I am NOT a fan of siliconized fluid at all, it is too hard to get all the other out, in reality it all needs flushed with alcohol and I have not seen any benefit over the synthetic.
Melting Slicks
Joined: Apr 2005
Posts: 2,777
Likes: 105
I installed SS Sleeved calipers in my 67 in 1982 and used DOT5 fluid. To this day, (30 years later) I have never had to touch them again and they are still working flawlessly! IMO DOT5 is the way to go for the long run! 
Melting Slicks
Joined: Jan 2012
Posts: 3,041
Likes: 505
From: myrtle beach sc
Army
I have used dot 5 in my 68 vette for about 35 years now, when I changed to stainless steel sleeved brakes with Chevy's cup seals. No problems. I would not trust an "O" ring to seal the pistons. They were designed to float. I have 109,000 miles on the car.
Team Owner
Joined: Jul 2004
Posts: 40,422
Likes: 792
From: Redondo Beach, California
My 68 has DOT 5 silicon brake fluid. I now have a stone hard pedal.
OK. I cheated, I didn't do it myself. When I installed the silicon brake fluid (from Stainless Steel Brake Corporation), I did have a little bit of a soft pedal. So I had Guldstrand Motorsports in Burbank,California bleed the brake system and prep it for silicon. 100% braking was the result. Switching to silicon was a less problem decision since the brake system on my 68 was 100% new, and dry.
OK. I cheated, I didn't do it myself. When I installed the silicon brake fluid (from Stainless Steel Brake Corporation), I did have a little bit of a soft pedal. So I had Guldstrand Motorsports in Burbank,California bleed the brake system and prep it for silicon. 100% braking was the result. Switching to silicon was a less problem decision since the brake system on my 68 was 100% new, and dry.
Safety Car
Joined: May 2004
Posts: 4,365
Likes: 1,589
From: los altos hills california
I tried switching to dot 5 after experiencing corrosion and having to replace all my calipers. Drove my kid to college, went over the grapevine and my brakes immediately went soft. It was frankly dangerous. This was some 20 years ago, maybe the stuff is better these days. But as I later came to understand, Dot 5 absorbs more air. Not a problem if you don't change altitude, but otherwise beware and be very careful about bleeding all the air out.
Burning Brakes
Joined: Oct 2003
Posts: 1,090
Likes: 74
From: New Carlisle IN
Dot 5 has no place in a performance car. It frankly sucks when you get the braking system hot. Doesn't work worth a darn. A properly maintained system with DOT 4 works much better. Keep the water out of the system and bleed the brakes every year and you will have 0 problems. I've been using th Valvoline synthetic DOT 3/4 fluid in my 73, 76, camaro, dad's 90 ZR-1, sisters 40th, and brothers 04 Z06 with no issues. Dad had a issue after he bought my sister's vette when he was at Sebring. Whatever the previous owner had in the car caused the brakes to fail. Dad bleed the system and put fresh Valvoline in the car and hasn't had a problem since.
As far as ruining paint, if you are that worried, put a rag under the reservoir when filling. Also keep a bottle of water handy. The fluid doesn't eat paint instantly and you have time to wash it off before it does.
As far as ruining paint, if you are that worried, put a rag under the reservoir when filling. Also keep a bottle of water handy. The fluid doesn't eat paint instantly and you have time to wash it off before it does.
Melting Slicks
Joined: Apr 2005
Posts: 2,777
Likes: 105
Le Mans Master
Joined: Sep 2004
Posts: 5,116
Likes: 5
From: Livonia MI
Maybe good idea doing a little more research, than opinions on DOT5 before putting it in. There's good reason manfucturers stay with glycol based fluids, as it's water and sediment absorbing features, are actually a good thing. True, you need to bleed things through sometimes, but silicon fluid tends to leave all the crap laying in the systems low spots, potentially causing more problems.
Melting Slicks
Joined: Apr 2005
Posts: 2,777
Likes: 105
Maybe good idea doing a little more research, than opinions on DOT5 before putting it in. There's good reason manfucturers stay with glycol based fluids, as it's water and sediment absorbing features, are actually a good thing. True, you need to bleed things through sometimes, but silicon fluid tends to leave all the crap laying in the systems low spots, potentially causing more problems.
Drifting
Joined: Aug 2005
Posts: 1,372
Likes: 4
From: Springfield VA
I remember working on many hondas that had steering problems and told after the owner was putting in reg steering fluid not the special Honda fluid.