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Brake fluid in brand new system: is it synthetic?
#1
Hey all
A local Mechanic says he put Dot 3 in my brand new brake system but when I researched and finally asked the shop owner, he said he thinks he put synthetic in...
I’ve seen threads on how to identify synthetic from non
Please see my photo and let me know what you think
Thanks for any and all feedback!!![Image: 599-B1064-908-E-4-DC9-89-E5-1-ED06495-CDF7.jpg]
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#2
All brake fluids, except one made for Citroen combined hydraulics system, are synthetic. The confusion comes about because of people confusing silicone (DOT 5) brake fluid with synthetic brake fluid. Basically all DOT 3, 4, and 5.1 brake fluids are synthetic and are glycol-ether based, whether they are labeled synthetic or not, and can be mixed. DOT 5 is silicone based and cannot be mixed with DOT 3, 4, or 5.1 glycol-ether based brake fluids. You need to find out what is in yours. If the shop owner doesn't know what they use, I would find another shop.

So, are you trying to find out if you have silicone based or glycol based brake fluid?
https://youtu.be/THyz-VRvtOg



“If you can't explain it simply, you don't understand it well enough.”
--Albert Einstein
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#3
Hi don
Thanks for that clarification And they dint seem to know!
Yes I’m going to learn and do these things myself as I have another mechanic that is very busy but does know this stuff well.
I assume that since it’s coagulated at the top and is purple, that it is Silcone based Dot 5 and not 3 as they stated
The vid is very good and I’ll try another test and not shake the cup this time
I really hate think I’ll have to flush the system or worse!!
Thank you for the insight!!
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#4
(10-05-2019, 12:55 PM)Rmach1 Wrote: Hi don
Thanks for that clarification And they dint seem to know!
Yes I’m going to learn and do these things myself as I have another mechanic that is very busy but does know this stuff well.
I assume that since it’s coagulated at the top and is purple, that it is Silcone  based Dot 5 and not 3 as they stated
The vid is very good and I’ll try another test and not shake the cup this time
I really hate think I’ll have to flush the system or worse!!
Thank you for the insight!!
Ok finally got to the bottom of this. The shop used a freelancer who specializes in classic cars and he confirmed he used Dot 5 silicone based fluid. He uses this because some cars sit most of the time and it’s a precautionary step. So mystery solved. I did suggest that they put a label or something in the car dated and describing fluids used if not standard products... so it’s purple, it coagulates and has been verified
thanks again Don for the insight!
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#5
You're welcome, glad you got it solved. I can understand and agree with using DOT 5 in seldom used vehicles and classic cars, it's not hygroscopic and it's paint friendly. The only thing I don't like about it is that it can cause a soft or spongy brake pedal because it can absorb air, making it difficult to get the brakes bled. I believe that using a vacuum pump, with too much vacuum, at the wheel cylinders and calipers can cause it to aerate.

Hopefully they completely flushed the entire system, glycol-ester and silicone fluids are not compatible and can cause the fluid to gel, as well as damaging seals.



“If you can't explain it simply, you don't understand it well enough.”
--Albert Einstein
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#6
(10-05-2019, 03:25 PM)Don C Wrote: You're welcome, glad you got it solved. I can understand and agree with using DOT 5 in seldom used vehicles and classic cars, it's not hygroscopic and it's paint friendly. The only thing I don't like about it is that it can cause a soft or spongy brake pedal because it can absorb air, making it difficult to get the brakes bled. I believe that using a vacuum pump, with too much vacuum, at the wheel cylinders and calipers can cause it to aerate.

Hopefully they completely flushed the entire system, glycol-ester and silicone fluids are not compatible and can cause the fluid to gel, as well as damaging seals.
Yes for the readers benefit, the entire system was new so we shouldn’t have any cross contamination issues here.
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#7
From the LEED Brakes website:
Silicone Brake Fluid Caution:
While silicone brake fluid has its many advantages it also has a few weaknesses with today’s brake systems. In order to use silicone brake fluid your entire brake system must be composed of all peroxide cured EPDM seals. Silicone brake fluid will distort and break down standard rubber seals causing your system to leak and fail. Silicone usually will break down standard seals in a very short amount of time. If you are not sure if your seals are peroxide cured EPDM seals check with the component manufacturer before using silicone fluid.
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#8
(10-06-2019, 08:29 AM)Bill73Ragtop Wrote: From the LEED Brakes website: 
Silicone Brake Fluid Caution:
While silicone brake fluid has its many advantages it also has a few weaknesses with today’s brake systems. In order to use silicone brake fluid your entire brake system must be composed of all peroxide cured EPDM seals. Silicone brake fluid will distort and break down standard rubber seals causing your system to leak and fail. Silicone usually will break down standard seals in a very short amount of time. If you are not sure if your seals are peroxide cured EPDM seals check with the component manufacturer before using silicone fluid.

Great note Bill.  Puts it in black and white.  I would rather stay with dot 3 than take any chances of brake failure or having someone else accidently put in the wrong type if I was having the car service by an shop.

Kilgon


"The only dumb question is the one not asked"
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#9
Ok so next question is if someone didn’t know it had dot 5 and bled the front brakes like the shop said they did because a hose had a leak, and topped it off with dot 3...
What should be done now?

I assume it’ll be evident if we purge the system and we’d see dot 3 floating around. Can we go back to dot 3 now?
This is worrisome because it’s all brand new lines, calipers, hoses and booster
Please advise
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#10
(10-06-2019, 11:15 AM)Rmach1 Wrote: Ok so next question is if someone didn’t know it had dot 5 and bled the front brakes like the shop said they did because a hose had a leak, and topped it off with dot 3...
What should be done now?

I assume it’ll be evident if we purge the system and we’d see dot 3 floating around. Can we go back to dot 3 now?
This is worrisome because it’s all brand new lines, calipers, hoses and booster
Please advise

You would need to flush the lines and wheel cylinders with dot 5 and refill.  I like many other do my own maintenance so I know what I'm using.  If I was using a shop to service my car I would put a bold label in plan sight that had the type of fluid to use. 

The difference in the dot's 3, 4, and 5.1 are the boiling points.  You can  use a higher number in a lower number system but not the reverse.  So if you had dot 3 in your brakes and someone added dot 4 it would not create a problem.  But if you brakes system called for a dot 4 or 5.1 and you added dot 3 it could cause brake failure due to the boiling point.  You need to use at least what the manufacturer calls for. See below

[Image: dot-fluid-boiling-points.png]


[Image: brake-fluid-compatibility-chart.png]

Kilgon


"The only dumb question is the one not asked"
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