M151A2 Brakes locking

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Re: M151A2 Brakes locking

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Re: M151A2 Brakes locking

Postby halftracknut » July 27th, 2018, 7:10 pm

Don't pump the master cyl. like a madman or you just might stick the cup at the back of the cyl...and that is just more work...
slowest mutt east of the missippi..
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Re: M151A2 Brakes locking

Postby Eddie Holland » July 27th, 2018, 11:03 pm

hmmm so it sounds like you recommend removing all wheel cylinders and draining the system. That is what I planned to do and a so called mechanic said no dont do them all at once you will never get the air bleed back out... he said do one at a time .. right rear left rear front right left front. But i didnt see how in the world i would have the fluid completely out by doing this and I was afraid of getting 2 types mixed. I bought 3 big bottles of DOT3 today....big difference in price and it was on sale at auotzone for $5 each.
Last edited by Eddie Holland on July 28th, 2018, 7:59 am, edited 1 time in total.
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Re: M151A2 Brakes locking

Postby Eddie Holland » July 27th, 2018, 11:21 pm

check out this article from Military Vehicle Magazine. Especially the last 4 lines.

TEST REPORT: Silicone Brake Fluid
by David Doyle



Almost everyone in this hobby has an opinion about silicone brake fluid, why the US military uses it, and how to convert a system to it. Unfortunately, there seems to be as much misinformation as there is factual information in circulation about this subject. In May 1966, the US Army Coating and Chemical Laboratory began aggressively looking for a brake fluid that was less sensitive to water than the three fluids in use at that time. The three fluids in use were “Hydraulic Fluid, Polar Type, Automotive Brake, All Weather,” “Preservative Fluid, Automotive Brake System and Components,” and “Brake Fluid, Automotive.”

As their names indicate, each of these had a specific purpose. The first, obviously was used for arctic regions where temperatures were expected in the -30ºC to -55ºC. The second listed was used as a preservative in not only the brake systems of vehicles in long term storage, but also in the packaging of wheel and master cylinders. The last one listed is the “normal” or standard brake fluid.

SILICONE FLUID INTRODUCED
In 1967, various makers of silicone hydraulic fluids became interested in the brake fluid market. Because of the perceived ability to replace three fluids with one, as well as perhaps to address the matter of water sensitivity, the Army Coating and Chemical Laboratory encouraged this development work. Union Carbide, General Electric (GE), and Dow Corning all submitted fluids for evaluation. GE and Union Carbide each submitted two fluids, one each slightly water tolerant (because of the belief that water will somehow enter the brake system), and one each completely intolerant of water. The Dow Corning entry was a water-intolerant fluid.

EXTENSIVE TESTING
Three years of testing by Chemical and Coatings Laboratory found deficiencies with respect to poor lubrication properties and rubber incompatibility. These were mostly overcome by incorporating additives into the various fluids.

When the lab work was done, the Laboratory conducted field tests. Three test locations were selected with widely different weather conditions: Arctic Test Center, Fort Greeley, Alaska, the Yuma Proving Ground, Arizona, and the Tropic Test Center, in the Panama Canal Zone. The results of a one-year test were detailed in Mobility Equipment Research and Development Center Report 2132. The test vehicles for this program at each location were two M151 series vehicles and two M715 1¼-ton trucks. For the testing new wheel and master cylinders were supplied, filled with the various silicone fluids, and new rubber hoses were supplied. The balance of the brake systems were flushed with alcohol prior to the installation of these new components. This trial is quite likely where the trend for alcohol flushing during conversion began.

After one year of service, half of the cylinders in Yuma and Panama were torn down for inspection. Samples of the brake fluid were sent back to the CCL for testing. All the cylinders in the Alaska test were examined. Testing of the Union Carbide and Dow Corning fluids in Alaska were discontinued early because of concerns about crystallization of these fluids under arctic conditions. The GE fluid did not have this problem and both Dow and Union Carbide were able to later correct the deficiencies in their fluids. The cylinders were torn down and inspected for corrosion, pitting and scoring.

The results of these tests demonstrated that the fluids were equal to their predecessors, and in the case of equipment operating in tropic conditions, were superior to the conventional fluids because of less water-induced corrosion in the brake system. The biggest benefit to the military was the anticipated 10 million-dollar annual savings by reducing the number of brake fluids in the supply system from three to one. After extensive testing, the Army published TB 43-0002-87 Brake Fluid, Silicone (BFS) Conversion Procedures for Tank-Automotive Equipment in February 1982.

Whether you are in a tropic area or not, you may choose to convert your vehicle from a conventional brake fluid to a silicone brake fluid. If you convert, remember, do not use air to expel the old fluid from the system. The vaporized brake fluid is extremely flammable.

Silicone brake fluid is completely compatible with elastomer materials used in conventional brake systems. Although it does not mix with conventional-type brake fluids, it is completely compatible with glycol brake fluids as a 2-phase mixture. In other words, an accidental mixing of the two fluids will not cause mutual precipitation or leaching of additives in this type of environment. Thus, the procedure developed for brake fluid conversion is detailed in TB 43-0002-87, February 1982. Essentially, it amounts to opening the bleeders, and with a pressure bleeder begin forcing DOT 5 through the system until all the DOT3 has been expelled and DOT5 starts coming out.
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Re: M151A2 Brakes locking

Postby rickf » July 28th, 2018, 8:01 am

Eddie, That is fine when you are in a military motor pool and the brake fluid is supplied in 55 gallon drums and has no price tag attached to it. You can flush to your hearts desire until the fluid runs purple. I can assure you from past experience with both conversions and also as the owner of a 4x4 shop that if you do not open the wheel cylinders you will not get the old fluid out of the bottom of those cylinders. I can also assure you from past experience as can others on here that when you mix DOT 3 and DOT 5 in any quantity besides trace leftover in lines that you will get gunk. You have to remember that the military did not care about cost, they would hook up a bleeder and let it flow a couple of gallons through the system. And chances were that they were also going to be tearing the brake system down for overhaul before the leftover had a chance to gel anyway. I don't think the average collector plans on tearing down his brakes more than once.
1964 M151A1
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1967 M416
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12/1952 M100- Departed
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Re: M151A2 Brakes locking

Postby Eddie Holland » July 28th, 2018, 10:32 am

I think at this point my system is gonna end up with all wheel cylinders being removed and inspected and flush anyway.. I decided to take a look at the front right...while taking the front right drum off something fell out, looked like a rivet head. I thought oh great. Wasnt hard to figure out what it was when I got the drum off. The top little stud head that the springs attach to on the backing plate... So now that backing plate needs replaced. I do have an old complete front end I could pull one off of but may just see had much they cost and get one. I hate to leave that complete front end all torn apart. Also trying to decide should I replace the bearings and seals while i got the hub off. I have a bunch of new old stock bearings but not the seals..
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Re: M151A2 Brakes locking

Postby Eddie Holland » July 28th, 2018, 4:30 pm

more fun the left front I had cleaned up and reinstalled was leaking so stuck a new one on it. Its bad when you are able to bleed the left front with the right front off. Why? No fluid coming thru the right front at all :/ Stopped up!
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Re: M151A2 Brakes locking

Postby rickf » July 28th, 2018, 5:27 pm

Fairly common problem with old rubber lines, the inner part of the line brakes loose and collapse blocking the line off. That is why the left one was locking. It is best top replace all of the rubber lines.
1964 M151A1
1984 M1008
1967 M416
04/1952 M100
12/1952 M100- Departed
AN/TSQ-114A Trailblazer- Gone
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Re: M151A2 Brakes locking

Postby Eddie Holland » July 28th, 2018, 7:03 pm

Ok luckily I happen to have some. Thanks for all the help
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Re: M151A2 Brakes locking

Postby Eddie Holland » July 31st, 2018, 9:50 pm

While I wait for 2 new front hose to come in I decided to cut thru the old hose on the jeep. It was so stopped up you couldnt even tell it was a hose. I cut another place further back and the brake fluid started running. I tried to remove the old hose but no luck. I think Im gonna get a 6 point flare wrench and give it a try. Im also gonna replace the rear hoses and wheel cylinders
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Re: M151A2 Brakes locking

Postby Fil Bonica » August 1st, 2018, 9:58 am

If you are introducing Dot 5 in to the system and there is moisture wont it rise to the surface and ultimately flush out the bleeder?
Additionally ,the longevity of silicone brake fluid far exceeds that of Dot 3
Had to perform emergency repair on a A2 with silicone fluid in it after 11 years.
It was clear and showed no signs of contamination.
The idea of flushing every few years does nothing for my good humor!
The military used it for a good reason and longevity is one of them.
Just another perspective.
Been using a military pressure bleeder for years.
Ince set up it is a breeze to bleed a jeep.
The one I have has the 151 adaptor cap the merely screws in to the master cylinder.
Jusy some thoughts.

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Re: M151A2 Brakes locking

Postby rickf » August 1st, 2018, 10:22 am

Water will sink in the silicone brake fluid and therefore any damage done with DOT 5 in the system will usually be rusted bottoms of wheel cylinders. The moisture will not flush out through the bleeders, it will just lay on the bottom. With DOT 3 the moisture is absorbed into the fluid so when it is flushed out all of the moisture goes with it. The military went with DOT 5 so they could consolidate the three fluids they were using. They had one for arctic conditions, one for normal conditions and one for jungle conditions. The military is all about consolidation of supplies and logistics. That is why they went to all diesel and also why they went to only 15W-40 motor oil. Only one fuel to deal with for the entire military machine and only one motor oil for that entire machine and only one brake fluid for the entire machine. Logistics plays as much of a part in the decision to use certain things as operating efficiency.
1964 M151A1
1984 M1008
1967 M416
04/1952 M100
12/1952 M100- Departed
AN/TSQ-114A Trailblazer- Gone
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Re: M151A2 Brakes locking

Postby m75 » August 1st, 2018, 10:41 am

Eddie, if you need a backing plate, PM me and I'll send you one.
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1961 M151 -Sold
1974 M151A2, Working It!
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Re: M151A2 Brakes locking

Postby Fil Bonica » August 1st, 2018, 12:55 pm

I would feel better with a brake system containing silicone rather than Dot3.
Unless the system was flooded with water I would think that silicone would ultimately displace any moisture.
The longer Dot 3 is in place it could cause even more damage.
The economics of that damage would be far greater.
Just another perspective.

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Re: M151A2 Brakes locking

Postby Eddie Holland » August 1st, 2018, 9:31 pm

When I saw the price of DOT5 verses DOT3 the decision was easy. Thanks Jim I took a backing plate off another front end I had. I already have it installed. I thought I had front brake lines but they were rears. waiting on fronts to arrive. In the mean time I had sprayed all the brake line fitting with PB Blast and bought a 3/8" flare wrench. Will probably replace the rear wheel cylinders and rear hoses tomorrow.
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Re: M151A2 Brakes locking

Postby m3a1 » August 2nd, 2018, 2:14 pm

Dot 5 can be had at O'Reilly's, Walmart, and all the other local auto parts suppliers for a very fair price. Not too far above the price for DOT 3. However, if you buy the "mil spec" DOT 5 from the parts suppliers it's gonna be be a real kick in the old peas and carrots, simply because of the packaging.

Ask me how I know. :roll: Live and learn, eh?

Cheers,
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