hi can i ask you guys a mopar but non slant six question? i've got two slant six valiants, but i also have a 1954 new yorker that i was driving in to DC from virginia last weekend. after about 80 miles, just as i approached the beltway, my brake pedal started going soft and stopped braking. i heard a slight squeal when this happened. these are new brake parts all along but of course that doesn't mean they aren't defective. i am running dot 5 in the system and have bled them every year, including one month ago. i used the emergency brake the last 20 miles. a ton of fun with all the lane changers and cut off artists we have in abundance around here. brakes still soft as i rolled it into my mechanics yard.

so my mechanic takes a look bleeds them and pronounces them just fine. he said there was no shining on the drums to indicate hot brake syndrome. he said they braked great for him. plenty of fluid no evidence of leaks. braked fine for me on the two miles home.

but of course i am spooked and thought the wisdom of the forum might help. any ideas what could be going on with these old brakes? thanks

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cs hunley

DOT 5 is not necessarily a wise choice. It can make problems in systems not designed for it. How long since the hydraulics (master and wheel cylinders, hard and flex lines) were replaced?

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

all the parts are within the last year. i didn't choose 5, the mechanic did.

i was wondering if fluid was getting past the master cylinder piston because the fluid is too thin.

and how tough it would be to switch back to 4 since 4 and 5 are not compatible and create a big mess when mixed.

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cs hunley

Is it all original? Unless it is a show car I would look into a dual resevior master cylinder from somewhere. Even if it is a show car I would still probably replace it with a dual setup. I prefer safe and drivable to judge points anyday.

Switching from 1 spec of dot brake fluid to another requires draining the lines and flushing them out and then adding new fluid and bleeding. The standard choice for flushing the lines, master, etc is standard isopropyl (rubbing) alcohol. Use the strongest % that you can find. If you look 99% is available but not widely carried. I believe the extra % that isn''t alcohol is water which is not something you really want in your lines.

How did the brakes work after it sat awhile? Your story is tickling the back of my brain and sounds like something I heard from an old timer I used to work with, but I can't recall what it was. Maybe later in the day I recall it. Good Luck

that's a good idea. it's not a show car, it's a driver. my stuff will never win shows!! sounds like a good project to go dual, that would also mean splitting the brake lines fore and aft, but that is ok.

i may stick with the dot 5 if i follow this advice i found:

http://www.xs11.com/xs11-info/tech-tips ... versy.html

"if silicone is introduced into an older brake system, the silicone will latch unto the sludge generated by gradual component deterioration and create a gelatin like goop which will attract more crud and eventually plug up metering orifices or cause pistons to stick. If you have already changed to DOT 5, don't compound your initial mistake and change back. Silicone is very tenacious stuff and you will never get it all out of your system. Just change the fluid regularly. For those who race using silicone fluid, I recommend that you crack the bleed screws before each racing session to insure that there is no water in the calipers."

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cs hunley

I do not believe there is any merit to that babble about ooga-booga-silicone-sludge-monster-booga-booga. I'm not aware of any valid reason not to switch back to non-silicone brake fluid.

I think your mechanic made an error in putting in silicone fluid. Even the least expensive basic fluid available today is vastly, hugely better than the best fluid that was available when your '54 was new. I recommend not using silicone-based (DOT 5) fluid. Its lack of hygroscopicity, i.e., it does not absorb water. Sounds like a good thing, but in fact it's not. Moisture will get into the brake hydraulic system with normal usage and changes in ambient temperature and humidity. That's a given. Ordinary brake fluid is designed to absorb and assimilate a fair amount of moisture without causing substantial corrosion problems. With silicone fluid, the water will accumulate in slugs at the lowest points of the system...and stay there, where it will aggressively corrode whatever it's touching. Practically speaking, if there's more than a really small slug's worth of water in your system, it's faulty and/or neglected, but the fact remains, this slugging rather than absorption of water is just a change, not an improvement. It only takes a very small amount of concentrated water sitting in one place in a steel line to initiate dangerous rust-through. And remember, it doesn't matter if the brake fluid has a sky-high boiling point; if there's even a small slug of water in the system, it's still going to boil at 212°F, and turn into steam, making your brake pedal soft and squishy or worse. Furthermore, it is very difficult to get all the air out of silicone brake fluid that is introduced with just normal handling and pouring, so it is very difficult to get a good, firm pedal.

There is an enormous range of conventional non-silicone brake fluids on the market. You can get whatever properties you want (e.g., high boiling point) without having to go to a silicone-based fluid.

And as if that weren't enough, the cost and effort difference between regular and silicone fluid is such that you can flush the system with conventional fluid every few years for a long time before you equal the cost of just one silicone fluid changeover.

Shop carefully. All silicone fluid is "DOT 5". The highest spec category for non-silicone fluids is "DOT 5.1".

DOT 3 (original fill after '69, replaced the old J1703 fluid spec), DOT 4, and DOT 5.1 fluids are all intermixable.

DOT 5 (silicone fluid) cannot be mixed with DOT 3, 4, or 5.1.

We can get much higher performance brake fluid now than was available when our cars were new. I haven't looked around for brake fluid performance comparison tests — I imagine somebody's done them — but not long ago when I was shopping for brake juice, I was faced with at least four choices of Prestone DOT 3 fluid. I don't recall all the varietal names, but there was one that said "for Ford vehicles", one that said "for ABS brake systems", one that was just plain, and...at least one other. All DOT 3, 4, and 5.1 fluids are intermixable, so there's no danger of a situation like "ohmygawd, I put Ford fluid in my Dodge/I put non-Ford fluid in my Ford".

Each of these multiple types of Prestone DOT 3 fluid had different boiling points, though there were two boiling points listed on each bottle; one denoting the minimum required for the DOT 3 category, and the other indicating the characteristic of that particular fluid…read carefully; the labelling isn't very clear. It's even more confusing than that; some fluids list both a dry and a wet boiling point, and some DOT 3 fluids have a higher (better) boiling point than some DOT 4 fluids.

Really, it should not be necessary to spend money on exotic brake fluids. Use a good brand of DOT 3 or DOT 4. Shop carefully, use a reputable brand, and be choosy. I have tended to use Castrol LMA DOT 4 when I can find it. Flush the system every few years and you'll be in fine shape for a long time to come. Also See here for a comprehensive (and factually based) article about brake fluid types.

Dual master cylinder: absolutely yes! Could be tricky to figure out which one to use that will work and will fit the car; that's well outside the scope of this board, but I'm sure someone out there will have advice. Try for a new, not "remanufactured", master cylinder. New brake lines: www.cunifer.com . Disc brakes: even better; see here.

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

I've been running DOT5 in my Mopars (both show & drivers) and others makes for 20+ years in VA w/o problems, but I've always put it in after carefully rebuilding the entire brake system, so I never mixed types.

I would suspect a problem in the master cylinder 1st (perhaps attributable to changing fluids), because the problem apparently isn't always there, and as I think a '54 didn't use a split system, very very carefully check all the hoses. I've recently have gotten several brake hoses from Wagner (made in Italy and China) that failed in short order.

I'd also suggest you check the mechanical linkage, as I recently had a hydraulic clutch pedal crack half way through and feel quite spongy... I suppose a brake pedal could do the same.

Unreliable brakes are a scary thing, and the main reason I learned to do my own repairs was the rather sloppy work done on my brakes by many professionals - I treat my brakes like my life depends on them. Best of luck.

thanks for the information gents.

based on the information, since the problem arose only after two hours of driving and braking, i suspect Dan's thought that some water was in the system and boiled. particularly since the fault has not recurred in the 20 minute driving sessions that my DC mechanic and i have put on the car, while the system is cool.

when the luray VA mechanic put dot 5 in there i worried about exactly what Dan described, a bit of water settling to a low point in the system and corroding. DOT 3 or 4 is what i want to use.

as to the method to do this, can i just buy a large quantity of dot 3 or 4 and start bleeding the system copiously? or do i flush with another substance first? i've heard bad things about alcohol, even everclear. maybe it's not so bad if you flush with DOT 4 immediately after.

anyway, i am going to research going back to dot 4. i live on top of a hil with a busy street at the bottom that i dread coming to without brakes or only the hand brake to stop.

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cs hunley

Pick up a gallon of denatured alcohol from the paint aisle of the hardware store. Flush with that, then blow dry air through it if you can, then flush thru with cheap DOT-3, then fill with your preferred DOT-4.

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

thanks i will do this sometime in the next couple of weeks. and by the by, what size brake line kit would i need for my 73 valiant? i've got a leak on the driver front brake that may be a bad line or brake cylinder. i won't know till i get in there and the car is at a remote location (cape hatteras) and i need to take all the necessary tools and parts to go work on it.

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cs hunley