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DOT 5


lepic56
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Go to solution Solved by Adam H P15 D30,

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I owned a 1951 Dodge Crusader,  with stock brake system..

Should I switch to DOT 5 brake oil, or stick with DOT3 spec oil,, 

with DOT5, you have to flush the brake system,,  But do you have to replaced all rubber composants??

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Are you having wheel cylinders seizing up with corrosion from not being driven enough?

Is the car stored in a unheated and possibly somewhat damp building?

If you answer yes to the above DOT 5 is a good fluid to use.

Yes you have to replace all rubber..hoses and cylinder cups and residual valve.

Silicone fluid will leak on any pitted cylinder. So new or sleeved cylinders should be installed.

If you drive the car a lot, live in relatively dry country and flush the DOT3 fluid every 2 years...and the braking system has never been much of a problrm stick with DOT3...preferably higher temp DOT4.

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1 hour ago, kencombs said:

Here's a good read: 

 

https://techtalk.mpbrakes.com/brake-fluid/can-i-use-dot

 

After reading that, I concluded that the answer is no.  But, your car, your money, your decision.

I can not make the link to work!!

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I have used DOT 5 inmy 39 Desoto for over 30+ years. Knock on wood no major issues.

 

Yes you will need to flush the entire system with denatured alcohol. replace all rubber hoses and rubber cups and rebuild your mater cylinder.

 

Rich Hartungj

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3 hours ago, lepic56 said:

I can not make the link to work!!

Well, I tried it and it won't go direct to the tech article  But, delete everything after .com and go to there home page Now select 'tech talk', then search the site for dot 5.  It is there.  Promise.

 

Bottom line for me, a lot of extra work and cost, unless you are planning on all new stuff anyway, with a small risk of rust anyway, and very little return.

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  • Solution
18 hours ago, lepic56 said:

I owned a 1951 Dodge Crusader,  with stock brake system..

Should I switch to DOT 5 brake oil, or stick with DOT3 spec oil,, 

with DOT5, you have to flush the brake system,,  But do you have to replaced all rubber composants??

No, stay with Dot 3 

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  • 1 year later...

Dot-5 has a high boiling point making it good for high-heat conditions, but it is glycol based, making it suitable in vehicles with ABS and compatible with Dot-3 and Dot-4 (though it's best to stick with one type and follow the manufacturers recommendations.) 

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If you car is a daily driver Dot 3 will work fine. If it is an occasional weekend driver switch to Dot 5 and you brake jobs will last a lot longer. When Dot 3 brakes sit they tend to have corrision issues, like rust and leaks in the wheel cylinders. Remember if you switch to Dot 5 you really need to switch out everything with rubber and flush steel lines. 

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1 hour ago, Bob Ritter said:

Dot-5 has a high boiling point making it good for high-heat conditions, but it is glycol based, making it suitable in vehicles with ABS and compatible with Dot-3 and Dot-4 (though it's best to stick with one type and follow the manufacturers recommendations.) 

DOT-5 is silicone based brake fluid, DOT-5.1 is glycol ether based brake fluid...Dot-5 is not compatible

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  • 2 months later...

DOT 5 is silicone, DOT 5.1 is glycol - very important, but my mechanic did not know....

The color is to identify the spec: DOT 5 is purple.

You can feel it with Yout fingers: silicone is "fatty" and slipping, alcoholes are not.

Military (stored vehicles, Coast Guard hydraulics etc.) uses silicone as no periodical changing is ever needed. Silicone doesn´t absorb humidity.

 

 

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  • 1 month later...

I've read that even though Dot 5 will not absorb moisture, the moisture still gets into the system (because of the vent hole in the master cylinder lid and any that the maintainer lets in by removing the lid to top off the fluid) and this moisture will settle to the bottom (lowest points) of the system.  Seems like that has potential to still cause problems.  I suppose if the lowest point is a cylinder (wheel or master), then those cylinders will still corrode.  If the lowest point is a brake line, then that line will eventually corrode, unless it's the nickel-copper variety.

 

I've also heard that if the vehicle is stored in a place where it can get cold enough, then any moisture that has collected in the system can freeze, and if there is enough of it, then it can block the line where it sits.

 

Does any of this sound correct?  Maybe these things are possible, but are they very realistic possibilities?

 

I've toyed with idea of changing from Dot 3 to Dot 5 in my '49 Power Wagon, and now would be the time to do it, as I'm doing significant brake work on it.

 

Thanks.

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