318MoparGuy
MoparHokie
Might end up putting a new MC on my 73 Dart....manual brake all around...front discs and rear drums...thoughts? Thanks.. Greg
To use or not use DOT5 fluid?
- Thread starter 318MoparGuy
- Start date
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dusterdan
Sublime Member
Make sure you get all of the old fluid out of the system if you didn't use dot5 before...
dot 5 will mix with dot 3 and dot 5 is top notch
abodyjoe
Well-Known Member
I'd go dot5. I'd flush the system well though even though they say its not an issue these days.
sst3193
Well-Known Member
Used to run DOT5 in my drag racer, 'cause it sit so much. Got no clue of it causing problems, because I never had to touch it, in 8 years!
1970Duster
Well-Known Member
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Why haven't you touched it in 8 years?
ir3333
Well-Known Member
DOT 3,4 or 5 are all suitable.
your choice!
your choice!
I converted my 68 to DOT5 about 5-6 years ago. At the time I was converting the rear to LBP (fronts were already 73-76 discs) and thought it was a good time to do it. Added a Line-loc. adj prop valve, new rear wheel cylinders, and Mopar aluminum MC at the same time so a lot of parts were new. I average 1000 miles/year and so far there has not been a single problem so I would recommend it. I Made a DOT5 label with a label maker and put it on the MC as a reminder.
We also converted my buddy's 73 340 Sport a couple years ago but he hasn't driven it. The car was sitting for the last 20 years and both front hoses were actually blocked with rust in the steel tube area of the hoses. I told him the DOT 5 would help because it just sits there.
We also converted my buddy's 73 340 Sport a couple years ago but he hasn't driven it. The car was sitting for the last 20 years and both front hoses were actually blocked with rust in the steel tube area of the hoses. I told him the DOT 5 would help because it just sits there.
R4Sedan
Larry
I put it in the Valiant when I did my Brakes. Have you priced it?
318MoparGuy
MoparHokie
Hi Jim,
You mention DOT 3 will mix with DOT 5...is there a problem with DOT 4 compatibility? I am asking to gain knowledge and I don't know what DOT # PO used. To be safe I will flush out system...
Thanks , Greg
jos51700
Green Bearing thread connoisseur
You can get it cheaper at the Harley-Davidson dealer sometimes.
I run DOT5 in everything that isn't ABS (Although if I go RWABS on my Dart, I'll stay DOT5. It can't be worse than it is).
DOT5 is awesome!
I run DOT5 in everything that isn't ABS (Although if I go RWABS on my Dart, I'll stay DOT5. It can't be worse than it is).
DOT5 is awesome!
jos51700
Green Bearing thread connoisseur
They ALL mix.
pettybludart
Well-Known Member
I run DOT 5 in my race car.It also won,t remove paint if spilled.It also has over 500* rating.
71Scamper
Mopar runs thru my veins!
No, they do not all mix. DOT 5 is it's own animal. It's made of a synthetic material and cannot be mixed with DOT 3 or 4. If mixed you will loose the temperature resistance, its anti-corrosion properties, and it will turn a cloudy color.
If you wanna go with something a little better the DOT 3 without having to completely remove all the DOT 3 from the system, (and I mean all, not even a drop of it,) I would recommend going to DOT 4. You can mix with DOT 3 although you will want to get most if not all of the DOT 3 from the system. DOT 4 has a higher boiling point than DOT 3 does, hence removing as much of the DOT 3 as possible.
318MoparGuy
MoparHokie
Thanks KK for all the great info. Do auto parts stores carry the line loc brand in stock as I want to do an adj. PV also....what PV brand would be similar quality to line loc? I would like an aluminum MC in my car rather than have another one get rusty as time passes. Is there a particular year MC I need to get as I am looking for a 15/16 " bore too...and lastly can I use a power brake MC
on my 73 Dart and run it manually?
Thanks,
Greg
318MoparGuy
MoparHokie
No...what does it cost?
318MoparGuy
MoparHokie
Thanks to all for sharing their thoughts on this subject... All the best, Greg
805moparkid
Slant and AFX Guy
no doubt it would be best not to mix the 2 fluids but on my bottle of dot 5 it says it will mix with dot 3 with no side effects.
fstfish66
Well-Known Member
not good on a street car ?????? wow i didnt know that since i ran it for 28 years in the same car same rear wheel cylinders and lines,,, it is A perfect choice for a performance car,,,it doest attract water never rots your brake lines,,,as said if it gets on any painted items it wont take the paint off like dot 3 or 4 will,,,,its well worth the extra cost,,,
replace the master,,,blow out the lines and the wheel cylinders and make sure the calipers are clear of old dot 3 or 4,,,you will thank your self 10 years from now,,,,
replace the master,,,blow out the lines and the wheel cylinders and make sure the calipers are clear of old dot 3 or 4,,,you will thank your self 10 years from now,,,,
VSTwister
Well-Known Member
Well now, at first this was good news, as years ago I put a new MC and brake lines on my Scamp, and debated going DOT 3 or 5...I ended up going DOT 3 because I was seriously on a tight budget and I heard issues about DOT 5 being hard to bleed out bubbles and the pockets of water that get trapped. Seems that's still being debated.
Eventually I want to go to DOT 5. #1 reason? Won't eat paint. Although I have learned from experience that DOT 3 can't hurt paint that's 30-40 years old.
I was afraid I'd have to completely and thoroughly have the lines flushed...but if they mix and I can just pump out the DOT 3 as much as possible, then put in DOT 5 with some DOT 3 residue in there...that makes it easier.
Eventually I want to go to DOT 5. #1 reason? Won't eat paint. Although I have learned from experience that DOT 3 can't hurt paint that's 30-40 years old.
I was afraid I'd have to completely and thoroughly have the lines flushed...but if they mix and I can just pump out the DOT 3 as much as possible, then put in DOT 5 with some DOT 3 residue in there...that makes it easier.
fstfish66
Well-Known Member
read up on it silicon fluid will not mix with dot 3 or 4,,,you are talking about brakes,,,,never take the easyway out do it right,,it my be ur life u save,,,,too many people take short cuts,,
71beater
Well-Known Member
As many have said, DOT5 is NOT compatible with DOT3 or 4.
DOT5.1 is.
Why they chose to even use the 5 (for 5.1) designation is beyond me...
It's not silicone based, as DOT5 is...
DOT5, though having a high boiling point, is somewhat compressible, generally leading to a spongier brake feel.
DOT5.1 is.
Why they chose to even use the 5 (for 5.1) designation is beyond me...
It's not silicone based, as DOT5 is...
DOT5, though having a high boiling point, is somewhat compressible, generally leading to a spongier brake feel.
BillGrissom
Well-Known Member
The info about silicone fluid (DOT 5) being incompatible with glycol fluids (DOT 3, 4, 5.1) is unfounded. It is a long-spread rumor by most auto parts guys, but that doesn't make it true. I even read that warning on a bottle of DOT 5, as I recall. They do not react, and indeed do not even mix. I read a report where it was investigated by engineers and found untrue. The only problem with leaving some glycol in the system is that those are areas that can rust. I have always been changing hoses and wheel cylinders when changing to DOT 5 and cleaned all the tubes with alcohol then air first, so never even concerned me.
All brake fluids are synthetic, whether silicone or glycol. Always have been. Some marketing genius figured out they could sell more by adding "synthetic" on the name (I think Valvoline).
The military uses DOT 5. Indeed, mil surplus is the best source for less cost, if you buy a gallon. I just replaced the MC in my 65 Newport to change to a dual system one. I installed it w/ DOT 5 in 1992, and it looked new inside. No more rusty fluid or pitted wheel cylinders since I changed, and no more need to bleed the fluid regularly.
The main drawback of DOT 5 is that it is more compressible, so you get more pedal travel. If interested, here is a link to a detailed analysis by an anal engineer with a lot of time on his hands, a requisite for an owner of classic British cars: www.buckeyetriumphs.org/technical/Brakes/Fluid/Fluid.htm
I installed a 7/8" D MC in my Newport, compared with the 1"D factory one, and the pedal is quite stiff after I did the "back up and stop several times to set drum adjusters". I can skid the tires by pressing the pedal <25% of the way to the floor. I have never had any trouble with bubbles. Just pour it slowly down the side of a funnel, and if you drop the bottle let it sit for a few hours.
Don't get fooled by DOT 5.1. It is the first glycol fluid to meet the higher DOT 5 rating. The government makes them call it "5.1" to not confuse it with silicone. Think that works?
Finally, nobody mentioned the main problem with glycol fluids absorbing water. Sure, it rusts your brake parts and can pit cylinders and make them leak, which eventually makes your brakes fail. But, before that, absorbed water greatly decreases the boiling point, which can make your brakes totally fail, i.e. your pedal goes to the floor and no brakes. If worried about rust, note also that when glycol removes the paint around the MC, you get a lot of rust on the sheet-metal, which is typical on most old Darts. If still scared of DOT 5, or can't afford it, at least flush your glycol fluid every few years and quickly clean up any spills on the paint.
All brake fluids are synthetic, whether silicone or glycol. Always have been. Some marketing genius figured out they could sell more by adding "synthetic" on the name (I think Valvoline).
The military uses DOT 5. Indeed, mil surplus is the best source for less cost, if you buy a gallon. I just replaced the MC in my 65 Newport to change to a dual system one. I installed it w/ DOT 5 in 1992, and it looked new inside. No more rusty fluid or pitted wheel cylinders since I changed, and no more need to bleed the fluid regularly.
The main drawback of DOT 5 is that it is more compressible, so you get more pedal travel. If interested, here is a link to a detailed analysis by an anal engineer with a lot of time on his hands, a requisite for an owner of classic British cars: www.buckeyetriumphs.org/technical/Brakes/Fluid/Fluid.htm
I installed a 7/8" D MC in my Newport, compared with the 1"D factory one, and the pedal is quite stiff after I did the "back up and stop several times to set drum adjusters". I can skid the tires by pressing the pedal <25% of the way to the floor. I have never had any trouble with bubbles. Just pour it slowly down the side of a funnel, and if you drop the bottle let it sit for a few hours.
Don't get fooled by DOT 5.1. It is the first glycol fluid to meet the higher DOT 5 rating. The government makes them call it "5.1" to not confuse it with silicone. Think that works?
Finally, nobody mentioned the main problem with glycol fluids absorbing water. Sure, it rusts your brake parts and can pit cylinders and make them leak, which eventually makes your brakes fail. But, before that, absorbed water greatly decreases the boiling point, which can make your brakes totally fail, i.e. your pedal goes to the floor and no brakes. If worried about rust, note also that when glycol removes the paint around the MC, you get a lot of rust on the sheet-metal, which is typical on most old Darts. If still scared of DOT 5, or can't afford it, at least flush your glycol fluid every few years and quickly clean up any spills on the paint.
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