On to the Brakes...

Discussions related to braking systems.
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JPGoebel
Posts: 14
Joined: Wed May 29, 2019 1:33 pm

On to the Brakes...

Post by JPGoebel » Sat Jun 15, 2019 3:51 pm

Hello All,

A thousand thanks again for your help in replacing the head gaskets on my 1955 Patrician. It was successful, and the engine runs as strong as ever!

Now that I've taken it on a few drives, I've noticed a new problem. After a lot of stop-and-go driving (for at least 30 minutes) the brakes seem to disappear. And it doesn't feel like the normal fade from overheated brakes, the petal travel increases three fold and barely stops the car. The next day, I hop in and drive to work with the brakes working just as they ought to.

I can't figure what would cause this. I checked the vacuum lines, and they seem tight (though the hoses are worn). Is there something I'm overlooking, or is the unit worn out?

Many thanks in advance,

JPG

Howard56
Posts: 1117
Joined: Mon Dec 24, 2012 11:35 am

Re: On to the Brakes...

Post by Howard56 » Sat Jun 15, 2019 4:34 pm

Pedal travel increasing three fold is disturbing. Am assuming since it is a Patrician you have power brakes and the normal travel on those units from application until the brakes lock up is typically less than an inch -- sometimes much less. Assuming you have shoes in good condition and a decent wheel adjustment, good hydraulic hoses and nothing dragging so fluid is not heating up and causing a problem it only leaves the master as the potential problem.

The Bendix Treadlevac or BTV for short is a unique unit. It has no piston as such but rather uses a ram moving into a chamber filled with fluid to displace an amount of fluid to the wheels. It relies on a single large seal and a rubber valve to contain and trap all the fluid so it can be forced to the wheels as you apply the brakes. Anything that prevents this valve from seating such as old or contaminated fluid with blobs of congealed whatever in the fluid that can float and get under the rubber valve and affect it's seal and you have no brakes. At the very least do a fluid change.

I would suggest you have the brake system and particularly the BTV gone thru by a competent person who is familiar with its operation. Wheel cylinders and shoes could be part of the problem but from the symptom I am thinking more the BTV. There are kits available and you can go thru the BTV yourself but if you are not familiar with the unit it is easy to miss a potential trouble spot. Be sure and read up on the operation and procedure in the 55-6 shop manual if you want to do it yourself. Old rubber and dirty fluid can do a real job on them and if seals are leaking and allowing fluid to be drawn into the power side that is another potential problem.

If you don't want to do the work yourself you can get an exchange unit from Kanter or Max Merritt or Kanter does rebuilds. Another excellent rebuild is by Ross at Speedwell Garage in Parkton, MD. The BTV is unique enough that I would not trust it to just anywhere. There are some less than inspiring stories at packardinfo with units done by mass market rebuilders.

You might also think about replacing hoses and lines since there is a good chance they are 65 year old originals. Steel lines rust from the inside and hoses crack and could blow under pressure or if the inner liner separates could prevent fluid from returning from a wheel cylinder and cause problems.

If you have manual brakes then kits are available and that master is no different in operation from modern units and again, old rubber can cause all kinds of problems.

Dave Czirr
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Location: New Jersey

Re: On to the Brakes...

Post by Dave Czirr » Sun Jun 16, 2019 5:05 am

I would certainly check all those things Howard has suggested, and absolutely replace all the steel lines if they haven't been replaced already. But I've driven enough miles in 55/56 Packards to say your symptoms sound to me like just classic brake fade, Caribbeans and Patricians are particularly likely to experience it.

JPGoebel
Posts: 14
Joined: Wed May 29, 2019 1:33 pm

Re: On to the Brakes...

Post by JPGoebel » Sun Jun 16, 2019 4:48 pm

Excellent! Many thanks, though I feel a bit foolish not having checked this first - the brake fluid was nearly empty (rather tricky to get at it, I notice). I'll check it every day this week to see how quickly it disappears.

This of course is a good transition to your advice since there is evidently a leak. I shall have a closer look!

Howard56
Posts: 1117
Joined: Mon Dec 24, 2012 11:35 am

Re: On to the Brakes...

Post by Howard56 » Mon Jun 17, 2019 7:14 am

I would absolutely put going thru the brakes at the top of the priority list to the point of not even driving the car until the issue is resolved. To be that low on fluid is serious. Fluid doesn't evaporate quickly so to me it indicates that either the car sat for a long time and was put into service without checking the brakes at which case the BTV reliability is seriously compromised or it could be a leak that could suddenly open completely. Leaks in old lines, hoses or cylinders are not uncommon but there is generally some indication of moisture around the leak. If you see nothing obvious on the outside then it could be a bad seal in the BTV and fluid is getting sucked into the power section. That situation doesn't usually improve on its own.

BTVs were used on many brands of cars in the 50s but rightly or wrongly, they have developed a bad reputation. Properly maintained and they seem to be reliable but reports of stopping a car at one light and rolling thru the next are too frequent and the failure is sudden and completely without warning. One common thread seems to be reports of the failures are mostly on cars (Packards at least) that have sat for long periods and then getting them started and put back into service. Other than maybe changing oil and fresh gas my recollection is no mention being made of a thorough check out or a lot of work being done elsewhere. As I mentioned a few days ago the stopping power of a BTV resides in two pieces of rubber. A leak in an old seal around the ram or some kind of debris floating in old fluid that lodges and prevents the compensator valve from tightly closing and you have no fluid confinement and no brakes. Unfortunately if the fluid has been low and rubber was exposed and dried out, just adding new fluid is not likely to correct a problem.

JPGoebel
Posts: 14
Joined: Wed May 29, 2019 1:33 pm

Re: On to the Brakes...

Post by JPGoebel » Mon Jun 17, 2019 10:29 am

That shall not be lost on me - I do fit rather neatly into the picture you've painted regarding putting a car that sat for decades into service again. I'll rebuild the whole system directly so as to be certain of it's reliability. As far as I know, it hasn't been addressed for decades.

Thanks again!

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