What to use for brake fluid?

[jmooner3]

Guys - I'll be turning to brakes soon... Looks like my truck has had some new parts added...New hoses on the front and the pins visible through the backing plate are new...I didn't pull wheels to check pads. The master cyl is bone dry, I figured I'd add fluid and use the advice of some of you on the forum to bleed the system to see if what I have in place will stop the old girl. Can I just use Dot 3 brake fluid or is there some other coctail that should be used in these trucks?

[oldmopar]

Dot 3 is good for your setup, you could also use dot 4 which is compatible with dot 3. I personally prefer dot 5 silicone fluid but I replace every brake component including the steel lines. The dot 5 will cause problems if mixed with other fluids and the system at a minimum needs to be flushed with a brake cleaning product and all rubber parts should be replaced.

If you do not know the history of the truck you should pull all the drums and check the brake linings I have seen more then once the old adhesive break down and the shoes come loose.

[HanksB3B]

Is what I'm using. Not sure why I chose it (synthetic?), but everything is working well. New lines, MC and WC's all around. So far so good.

Hank

[oldmopar]

It does get confusing but what you are using is a synthetic Dot 3 style fluid The dot 5 I am speaking about is a purple color.

From Castrol.com

"Castrol GTLMA Brake Fluid's unique Low Moisture Activity (LMA) formulation provides maximum protection against vapor lock brake failure when compared to leading DOT 3 brake fluids. It is recommended for all anti–lock braking systems (ABS), hydraulic drum and disc braking systems, and hydraulic clutches requiring DOT 3 and DOT 4".

[desoto1939]

I have had the purple dot 5 synthethic brake fluid in my 1939 Desoto for over 23 years. I have not had any problems.

I flushed the entire system with denatured alchohol. Keep the same jar or container hooked up to the system. The fbrake fluid will sperate and if i remember correctly the old will be on top. Keep flushing until you only have the same color fluid in the jar. Use a clear plastic container so you can see the different fluid colors.

Keep extra dot 5 as a spare and make sure that if you ever take the car to a mechanic that you remind them that you use dot5 and also might put a sticky on the fire wall near the MC.

Rich Hartung

Desoto1939@aol.com

[grey beard]

Not all DOT 5 fluid is purple. I've used both purple and clear - Andy Burnbum sells the 5 in a clear quart can. Also, for those of you who decide to go this route, I strongly recommend a plastic sign or label near your firewall area in some visable place cautioning people to use only DOT 5. If the stuff ever gets mixed inadvertantly, it would be almost impossible to un-adultrate the mess unless you pulled every component apart and cleaned it with alcohol.

I use it in my Pilothouse and am very pleased. I also have a firewall-mounted remote reservoir for brake fluid. (Pegasus.com) It's opaque, like new cars - you can check the level with just a glance, AND it's a whole lot easier to fill then the original MC. JMHO

Good Luck

[jmooner3]

Thanks guys, sounds like if i run with the old plumbing I should stay DOT 3 if I refurb I should go to DOT5.

The hard lines seem easy enough to bend and rout, anyone have a good source for fittings, know the diameter of the lines, fittings needed, etc. Also there appears to be a 3 way proportioning valve in the rear, pretty rusted, but it looks like it might be welded in place? Is this part available?

[TodFitch]

Not sure that cleaning with alcohol is a good thing... I've heard from one reasonably reliable source that the swelling and damage seen on some conversions to DOT5 is because of alcohol damage to the rubber.

I did a full rebuild of my 1933's brakes using DOT5 about 12 years ago. Near as I can tell the hydraulic components are still perfect. Have to be careful about filling and bleeding as DOT5 is more likely to entrain small air bubbles. But if you spill some at least your paint is not ruined.

If it has DOT3 in it, I'd leave it DOT3 unless you are replacing/rebuilding all components including all hoses and all steel tubing. If you have a totally fresh rebuilt with all new or rebuilt components and are filling fresh from scratch, I'd go with DOT5.

What ever you do, don't do this (from the 1933 Plymouth owner's manual back in the day when most cars still had mechanical brakes and you couldn't find brake fluid just anywhere):

General

The master cylinder reservoir on the top of the master cylinder should never be less than half full of genuine Plymouth Hydraulic Brake Liquid, which is obtainable at any authorized Plymouth Service Station. This should be used to the exclusion of all other liquids, but if for some reason the genuine liquid is not available for an immediate requirement, a suitable substitute liquid may be made by thoroughly mixing equal parts of medicinal caster oil and No. 5 denatured alcohol free from acid (wood alcohol should never be used). This formula should only be used when the genuine Plymouth Hydraulic Brake Liquid is not available, and it is important that the improvised liquid be entirely drained from the system as soon as possible and replaced with Plymouth Hydraulic Brake Liquid. Plymouth Brake Liquid is make in very much the same manner, but certain chemicals are added by a very lengthy, as well as difficult, process which neutralizes acids found in the formula prescribed above.

[oldmopar]

Not all DOT 5 fluid is purple. I've used both purple and clear - Andy Burnbum sells the 5 in a clear quart can. Also, for those of you who decide to go this route, I strongly recommend a plastic sign or label near your firewall area in some visable place cautioning people to use only DOT 5. If the stuff ever gets mixed inadvertantly, it would be almost impossible to un-adultrate the mess unless you pulled every component apart and cleaned it with alcohol.

I use it in my Pilothouse and am very pleased. I also have a firewall-mounted remote reservoir for brake fluid. (Pegasus.com) It's opaque, like new cars - you can check the level with just a glance, AND it's a whole lot easier to fill then the original MC. JMHO

Good Luck

Are you sure the fluid is not purple I have used dot 5 silicone over the past 6-8 years in about a 1/2 dozen vehicles and purchased it from at least 3 different manufactures and all was a purple color. Which makes sense to protect the system from getting mixed. In any case I would not use any that was clear as it could cause problems.

[HanksB3B]

It does get confusing but what you are using is a synthetic Dot 3 style fluid The dot 5 I am speaking about is a purple color.

From Castrol.com

"Castrol GTLMA Brake Fluid's unique Low Moisture Activity (LMA) formulation provides maximum protection against vapor lock brake failure when compared to leading DOT 3 brake fluids. It is recommended for all anti–lock braking systems (ABS), hydraulic drum and disc braking systems, and hydraulic clutches requiring DOT 3 and DOT 4".

Oldmopar, so this is my understanding. I'm using Synthetic Dot 3 and not Synthetic Purple Dot 5. What is the difference between Dot 3 and Dot 5 synthetic. Do either of them dissolve paint? If there is a big advantage to going with Dot 5? Since they are both synthetic, would it be possible to simply add Dot 5 to the system and bleed till only purple was coming out?

Thanks,

Hank

[oldmopar]

The dot 5 is called silicone not synthetic. The Dot 5 silicone main advantage is that it does not absorb water as easily as the dot 3-4 variety and helps our infrequently used vehicles brake system parts last longer. It does not damage paint but that is just a side effect gain.

There is nothing wrong with the dot 3 -4 fluid but its tendency to absorb moisture can sometimes cause problems more so if you do not drive your truck often. But that can usually be solved by just stepping on the brakes a few times maybe once a week and flushing the system with new fluid every few years.

Here are a link that may help

http://en.wikipedia.org/wiki/DOT_5

[HanksB3B]

I do drive my truck often every day if I have the chance. What would be invovled to switch from GTLMA to Silicone. I might try to get some info from Castrol's web site. Remember all the commotion when synthethic oil arrived on the scene people said you couldn't switch? Just how incompatible is Dot 3 synthetic and Dot 5 silicone? Will try to find out mfg's specs on this. Castrol said they do not make a Dot 5 (correct me if you know differently) They also don't recommend switching from synthetic GTLMA to Silicone.

Thanks,

Hank

Edited March 1, 2010 by HanksB3B

[Young Ed]

Hank to be honest I've got a 51 ply that is horribly rusty and I don't care a whole lot about it. The previous owner told me it had silicone fluid in it. The front to rear line was shot when I got it and after fixing that I refilled the system with dot 3. That was like 3 summers ago and it still has brakes.

[HanksB3B]

I'm good with the GTLMA Dot 3 Dot 4 (wish they would make up their minds what to call it) Some time back I was having brake lock up problems after I totally rebuilt the MC and slave cylinders. There was some contamination involved where shoes got a splash of fluid. Mechanics had all kinds of recommendations. Short of having the Miller Brake Tool I was able to do the best I could without it after understanding the heel and toe adjustments. The grabbing was one of those problems that just seemed to go away by itself. Still would like to find one of those tools at an affordable price though.

Thanks for your help,

Hank

[oldmopar]

Hank like I said in a previous there is nothing wrong with the dot 3 it has been used for many years in many vehicles with no problems. Not really knowledgeable with Castrol's products but if they do not make a silicone of course they would not recommended it. Like so many things with our vehicles your choice of brake fluid is your choice and there are people on both side that would argue which is better. There is no perfect solution the dot 5 works for me so I use it However I do not like to tempt fate and would not as young ed did and switch without at least flushing.

I am a fanatic on brakes especially with single cylinder masters and my vehicles do not go on the road unless I completely check and usually replace all parts of the brake system. Yes we do have a independent hand brake system but again that is only a good back up if adjusted and in good working conition

[Young Ed]

Ed I normally wouldn't have tempted fate either but if you saw the current condition of this car you'd understand. Even the trans hump is rusty! The first time I drove it the seat fell through the floor.

[HanksB3B]

Hank like I said in a previous there is nothing wrong with the dot 3 it has been used for many years in many vehicles with no problems. Not really knowledgeable with Castrol's products but if they do not make a silicone of course they would not recommended it. Like so many things with our vehicles your choice of brake fluid is your choice and there are people on both side that would argue which is better. There is no perfect solution the dot 5 works for me so I use it However I do not like to tempt fate and would not as young ed did and switch without at least flushing.

I am a fanatic on brakes especially with single cylinder masters and my vehicles do not go on the road unless I completely check and usually replace all parts of the brake system. Yes we do have a independent hand brake system but again that is only a good back up if adjusted and in good working conition

Except for the backing plates, (which are powder coated and look better than new) my brake components and lines are all new. Somehow it is more important to be able to stop than go. It's not that they didn't recommend it but what they couldn't tell me how to go from Dot 3 to Dot 5 silicone or if it is even possible without disassembly or purging the entire system somehow I think it would just be a matter of pushing through till there was just purple coming out. But I don't know so I'm not suggesting that.

Hank

Edited March 1, 2010 by HanksB3B

[jmooner3]

Thanks for the discussion on brake fluid, ya'll have me thinking that simply adding the juice is not the smartest move...single cylinder system with surface rust showing on the lines would indicate a need for all new. From the sounds of the discussion dot 5 might be the way to go once all new.

Anyone have a good source for fittings, know the diameter of the lines, fittings needed, etc. (are these double flare fittings?) Also there appears to be a 3 way proportioning valve in the rear, pretty rusted and appears to be welded to the rear axle... Is this part available?

[Zeke1953]

Brake lines are all double flared. If I remember right, the diameter is 5/16" from mc to the front junction block then 1/4" for the other runs except 3/16" for the lines that connect the upper and lower cylinders in the rear wheels. Remove your old lines and use them for patterns. Decent bending and flaring tools are inexpensive and you will need to do a few practice flares before you get the hang of it. These trucks don't have proportioning valves; that thing on the top of the axle is the rear junction block and vent - should just unscrew. The vent needs to be clear or pressure can build up and push dif oil onto your rear brakes. If you replace the lines connecting the two cylinders in the rear wheels be sure that the new lines do not contact the brake drum when you reinstall it. I replaced the entire brake system in my truck. As others have said, this is one job that has to be done right. Glad to have another New Englander on board. Zeke (From Taxachusetts)

[Mustang6147]

DOT3 or 4 is more then enough for these vehicles. I use the synthetic. DOT 4 or 5 would be good if you road raced, and there were high heat situations.

I might also add, if you replace you brake lines, slide the fitting back, and put some anti seize on the tube, then slide the fitting over over it and up to the flair and screw it in. This will help you if you ever disconect the line, because the line always twists, when you unscrew it.

[oldmopar]

I would add to what Zeke1953 said that I use preformed lines from napa and a few couplings to put them together. The wheel and master cylinders can be purchased from napa, rockauto ,roberts and others as new or rebuild kits. I just get all new parts for the wheel cylinders and either replace or rebuild the master depending on its condition. You also will need to replace 3 brake hoses 2 front and one going to the rear axle vent. Once you go this far you also should clean repack and replace the wheel bearings and seals front and rear.

[HanksB3B]

Gary says that they are made by the original mfg. The master cylinder I think was $129 Napa wanted $179 the wheel cylinders are top quality $45 fronts (x2) 24.50 (x4) for UR,LR,UL,LL. I was pleased and they are working perfectly. The quote to rebuild my old ones was more than brand new. Can't beat that!

Hank

[jmooner3]

Thanks guys as I said looks like some of the parts have been swapped already, I need to get the wheels off and the drums off and see what I'm up against. All steel lines are old and rusted, but the front hoses have been replaced. Any tricks to getting the drums off or ways to set up the shoes without a miller tool?