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Brake fluid question

Printed From: Unofficial Allis
Category: Other Topics
Forum Name: Shops, Barns, Varmints, and Trucks
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URL: https://www.allischalmers.com/forum/forum_posts.asp?TID=182145
Printed Date: 24 Aug 2025 at 3:47am
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Topic: Brake fluid question
Posted By: bobkyllo
Subject: Brake fluid question
Date Posted: 30 Jul 2021 at 2:49am
This question goes to two different groups. Group one is auto shop owners/mechanics group two is just the general group here.

Watching YouTube and a channel was suggesting that mechanics buy this certain brake fluid tester because it'll make the shop so much money.

So my question is do you guys that are mechanics do many brake fluid flushes. How about you weekend warriors do you concern your self with your brake fluid aside from the fact that there is enough.



Replies:
Posted By: Thad in AR.
Date Posted: 30 Jul 2021 at 5:48am
I live in Humid Arkansas. I change the fluid in my motorcycle every year.
My trucks not so much even though I feel a person should flush those once a year as well.
I just recently replaced a wheel cylinder on my work truck. I know for a fact it was 4 years old.
It looked like it had sat in a swamp for 30 years


Posted By: plummerscarin
Date Posted: 30 Jul 2021 at 6:28am
Seems every couple years I have to replace a brake line so it gets changed whether I want to or not. But yes, fluid should be changed once in a while


Posted By: Lars(wi)
Date Posted: 30 Jul 2021 at 6:32am
In my younger days, I replaced a brake line or two, on a couple of old beaters. That is one of the items I now take to a mechanic for repair, I don’t fool around with brakes. What they do as far as the brake fluid is up to them. I routinely check the the brake fluid on all my vehicles, and top off if needed.

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I tried to follow the science, but it was not there. I then followed the money, and that’s where I found the science.


Posted By: Ed (Ont)
Date Posted: 30 Jul 2021 at 10:13am
Just suck the old stuff out of master and put some fresh stuff in every few years. Better than not doing anything. 


Posted By: dee_veloper
Date Posted: 30 Jul 2021 at 12:27pm
Originally posted by Ed (Ont) Ed (Ont) wrote:

Just suck the old stuff out of master and put some fresh stuff in every few years. Better than not doing anything. 


That's what a lot of shops do and they charge for a complete flush


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Don't confuse my personality with my attitude.
My personality is who I am. My attitude depends on who you are.


Posted By: DaveKamp
Date Posted: 30 Jul 2021 at 4:00pm
I second Thad-  My motorcycles get the calipers pulled off, bleeders screws broken loose, and all the old fluid pumped out from top to bottom, forced out by new fluid.

Reason:  DOT4 brake fluid is hygroscopic:  It absorbs moisture from the air, and that moisture includes contaminants that, once mixed with the coctail of master cylinder, calipers, and hoses, turns into a brownish-black gak that plugs up everything, especially the return hole on the master cylinder.

My GL is due for a new set of brake lines.  Next time I do it, I'll be replacing the pads, resurfacing the disks, replacing the flexible lines with braided stainless, adding a crossover tube to the front calipers, and replacing the front brake MC with one from a larger road bike... and replacing the REAR MC with one that doesn't have a second segment to control the front caliper.  Reason?  The GL1200 is set up for 'integrated braking', which is where you step on the brake pedal, and applies the rear and ONE of the fronts, while the front MC controls only ONE caliper, which means when I grab the front brake, I only get HALF the available braking power.

But yes, a full flush, but many auto shops will 'advertise' and charge you for such a service, without actually doing anything.  DIY, man!


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Ten Amendments, Ten Commandments, and one Golden Rule solve most every problem. Citrus hand-cleaner with Pumice does the rest.


Posted By: HD6GTOM
Date Posted: 30 Jul 2021 at 4:03pm
Had my motor home done in June. On top of a new master cylinder they did a complete flush and checked the brakes. She's ready to head to someplace cooler. Brake fluid looked like runny brown baby poo. Probably been in there since 1996.


Posted By: JTOOL
Date Posted: 30 Jul 2021 at 7:58pm
@bobkyllo; In all of my years as a mechanic, I don't recall myself or anyone flushing the brake system as preventative maintenance. My gut tells me that flushing (in a mechanic shop) is kind of a scam but on the other hand maybe some of the problems I/we did deal with could have been prevented if PM had been done. In my personal/weekend warrior life, I've only had to deal with hard part wear/failures.


Posted By: fixer1958
Date Posted: 31 Jul 2021 at 7:39am
Been doing brake flushes for 20+ years. Part of the scheduled maintenance if anyone has ever bothered to pay attention to that. It does make a difference in brake reliability/longevity/performance and all that other happy chit.

All brake fluid is hygroscopic. Depends on the equipment you are using to do it. What type of vehicle it is etc. Use synthetic brake fluid if you really want to get assnine about it. Doesn't absorb moisture as much. Good for long term storage vehicles. You should go with new parts though. Restores etc. 

Flushes or not it's not going to reduce some of the brake failures that happen. Rusty brake lines, collapsed hoses etc. Most of that is manufacturer issues. They know they have a problem and still keep churning them out.

Just what I see and I see a lot.







Posted By: DMiller
Date Posted: 31 Jul 2021 at 9:14am
Each brake job I perform on my own machines, bleed until get New Fluid from bleeders, start at furthest wheel then back to the closest as last bled out.  Not an issue with aged fluid at that point,  All flushed of contaminants and corrosion compounds.


Posted By: DaveKamp
Date Posted: 01 Aug 2021 at 9:45pm
Originally posted by fixer1958 fixer1958 wrote:

All brake fluid is hygroscopic.


DOT 3,4, and 5.1 are glycol-based, and thus, hygroscopic.

DOT 5 is silicone based, non-hygroscopic.


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Ten Amendments, Ten Commandments, and one Golden Rule solve most every problem. Citrus hand-cleaner with Pumice does the rest.


Posted By: bobkyllo
Date Posted: 03 Aug 2021 at 10:37pm
Thank you everyone for your thoughts. It seems as if we are divided a bit on this subject. As I'm torn also. I want to do best for my customers but I'm unsure how to sell the service as some might find it hokus pokus.


Posted By: fixer1958
Date Posted: 04 Aug 2021 at 6:45am
Find a BG rep. Stuff is pretty good. They furnish the equipment.


Posted By: Stan IL&TN
Date Posted: 04 Aug 2021 at 8:25pm
My 1994 is my daily driver. Been flushed 3 times in the 27 years. One master cylinder. Front brake hoses. Rear wheel brake cylinders replaced.

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1957 WD45 dad's first AC

1968 one-seventy

1956 F40 Ferguson


Posted By: shameless dude
Date Posted: 04 Aug 2021 at 9:30pm
i don't ever recall changing the brake fluid in the older cars/trucks, pre-1990. but i've sucked out the old stuff from about all of the vehicles made after 1990 several times. i too just take a turkey baster and suck out as much as i can, and refill with a new bottle of fluid. sure makes the steering turn easier for a long time. when the steering gets harder, i suck out another pump and refill. i'm sure the older stuff will work it's way back up to the tank then i can suck that older stuff out. my '15 burb needs it done now. have done the '98 pickup several times thru the years.  



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