: 1969 DeVille - Slammed Brakes - Now brake trouble!



69Chateau
05-03-11, 11:19 PM
Trouble!

Going through my post-winter storage car tests, I locked up the brakes at a stop sign to see what would happen. Didn't notice any change in the brake characteristics after the test so assumed all was well. YEAH!

Parked the car for about 10 days and I rolled it out of the garage today for a drive. IMMEDIATELY I noticed a spongy brake pedal (long travel) and it went almost all the way to the floor before any real braking action occurred. There was still a little bit of brake there however. If I continued pushing the brake another 1/4" - 1/2" it would brake harder but felt like the pedal was up against something. This is bizarre and doesn't make me comfortable at all!

I mentioned locking up the brakes, because it's the first time
I ever locked them up like that since I bought the car. May have nothing to do with my new issue, may have EVERYTHING to do with it. My family rides in this car! I gotta have a rock solid dependable braking system otherwise not anymore!

cadillac kevin
05-03-11, 11:29 PM
I'd say you blew a brake line (something came loose and you lost alot of fluid).

sven914
05-03-11, 11:36 PM
Check the rear pistons. The linings will blow out and cause a slow leak and spongy pedal. If they are leaking, you should see fluid on the back, where the line connects, but you should still take the wheel and drum off to be sure.

cadillac_al
05-04-11, 12:36 AM
You should see some fluid leaking somewhere, sounds like a blown line to me too. If not check inside the firewall around brake rod, the master cylinder could have let go too. Locking up the brakes on these old cars will definitely test your break lines. I blew a couple last winter avoiding an accident. If I wouldn't have had to slam the brakes on they may have lasted a few more months; until the car got retired.

69Chateau
05-04-11, 12:47 PM
I have mixed emotions about having discovered/created this scenario. On one hand, blowing a seal or connection was inevitable had I actually needed to slam the brakes during normal operation. But I'm bummed that I created more work by TESTING it!

CADforce69
05-04-11, 06:29 PM
If you had not "tested" your brakes they would have failed some weeks or months after, and maybe in worse circumstances. Now you know that your brakes need to be checked. As soon as I started my 69 SDVīs trip home (300 miles) the brakes telltale light turned on although the car still braked fairly well. The first parts I ordered were brake cylinders, hoses, pads and shoes (master cylinder seemed to be ok). When they were changed light was off. Iīts highly recommendable to change these elements when you buy an 42 year old car unless you check they are new.

69Chateau
05-06-11, 12:39 AM
Ok... Here's what I did with the limited time I had tonight to play around. Started at the master cylinder. Opened it up and the fluid was about 1/4" from the BOTTOM of each reservoir. Fluid was moderately clear on the front reservoir and a dark, milky green/brown in the rear reservoir. The reservoir seal rubber cups were completely extended into the reservoir and the seal edges were caked with old crud all the way around. I threw on some rubber gloves and put the seal cups back, took a Terry cloth and cleaned up the top seal edge of the master cylinder and the rubber seal. Filled the MC reservoirs up to about a 1/2" from the top. And reinstalled the top on the master cylinder.

Garage Test:

1). started the car
2). Pumped the brakes a couple times them held pressure on the pedal
3). Pedal held firm and didn't seem to fade
4). Repeated steps 2 - 3 several times
5). Shut off the car and reopened MC. No noticeable decrease in fluid level. Reinstalled MC top.
6). Visual check around MC and around each wheel beneath car. Nothing wet.
7). Repeated steps 2 - 7 again and nothing noticeable.

Road Test:

1). Drove down the block. Brakes were there. Travel of pedal still seems long but it would stop the car quickly and there was "good bite" still left in the pedal.
2). Repeated various braking scenarios, 40 mph down to 20 mph, 40 down to 0 and even a couple low speed lockups.
3). Got home, parked and opened the MC. Fluid murky but no negligible loss in fluid.

The only scenario I didn't like was the slow braking coast to a stop sign/light. At about 5 mph I'd apply a little more pedal pressure to test for "bite" and I'd hit the backwall or floor. It would bite, but that just seems like WAY TOO MUCH pedal travel.

Reading the Shop Manual (pg. 5-26), pedal travel should not exceed 1 7/8"!!! I can take the pedal nearly to the floor. Many inches more travel that the shop manual states! Evidentally the brakes are supposed to be touchy, responsive and take very little travel to operate. (true??) The shop manual does state that long pedal travel, the system "most likely has air in the lines and should be bled".

I'm going try and bleed brakes this weekend and see what happens. If it was a low fluid/air in the lines scenario, I'd be tickled! Sorry for the book!

cadillac_al
05-06-11, 07:49 AM
Does the brake pedal firm up if you pump it a few times while you are stopping? If the pedal gets nice and firm after a couple pumps it may have air in it. If it doesn't seem to pump up the master cylinder may be going out.

69Chateau
05-06-11, 11:20 AM
Does the brake pedal firm up if you pump it a few times while you are stopping? If the pedal gets nice and firm after a couple pumps it may have air in it. If it doesn't seem to pump up the master cylinder may be going out.

I believe it did firm up if I pumped it while stopping....

CADforce69
05-06-11, 11:58 AM
You could take the opportunity to change cylinders and brake hoses (If they show wear signs). Itīs advisable and after you do it, you will have to bleed the brake circuit.

69Chateau
05-06-11, 03:13 PM
CADForce69,

I agree with the theory of replacing calipers, cylinders and lines and start with a relatively clean slate. But I think I'm going to just bleed them first and see what happens. I might achieve great performance with the components that are already in there. I'd hate to replace a good, working part with many more years of dependable service if I don't have too.

If they begin to fade again, I'm only out the cost of the brake fluid. However, "fool me twice" and I'll start replacing components and do the whole thing in one shot... New Master Cylinder, brake booster, lines, calipers/cylinders, fluid, pads, shoes, springs (and anything else that looks ancient).

CADforce69
05-06-11, 07:28 PM
I understand your point of view. When we have recently bought a classic car frequently there is a lot of things to do and a limited budget. Hope itīs just air in the lines. Just in case you need it, you can find these parts at a low cost in www.rockauto.com

cadillac_al
05-06-11, 08:15 PM
CADForce69,

I agree with the theory of replacing calipers, cylinders and lines and start with a relatively clean slate. But I think I'm going to just bleed them first and see what happens. I might achieve great performance with the components that are already in there. I'd hate to replace a good, working part with many more years of dependable service if I don't have too.

If they begin to fade again, I'm only out the cost of the brake fluid. However, "fool me twice" and I'll start replacing components and do the whole thing in one shot... New Master Cylinder, brake booster, lines, calipers/cylinders, fluid, pads, shoes, springs (and anything else that looks ancient).

I agree, the theory is nice but I am always worried that I'm replacing a perfectly good wheel cylinder with some cheap chinese rebuild that could fail in 2 months anyway. It's a tough call so I usually wait until they leak or I break the bleeder off.

69Chateau
05-09-11, 11:51 AM
Good news.... I sprayed each bleeder with Sea Foam Deep Creep (shameless plug) on Friday afternoon. Saturday evening I put it up on jack stands and prepped for the brake bleeding. After some trouble with the initial bleeder bolt (right rear), I was able to slowly progress around the car bleeding fresh fluid through each cylinder or caliper. The brakes now work flawlessly taking about 1" - 2" inches of pedal travel TOTAL! Also, eliminating the side-to-side diving that occurred while I initially applied the brakes. Stops nice and straight with a firm pedal!

One thing I learned.. I would initially loosen the bleeder bolts with a socket wrench (3/8") rather than jump right to the box end wrench. Once it was loosened with the socket, the box-end wrench would work fine for opening/closing the bleeder bolt.

Also, it took a little OVER 1 qt. of brake fluid. So if you're going to do a full flush it would be wise to have an extra little bottle just in case. Luckily, I did!

69Chateau
05-09-11, 11:56 AM
I agree, the theory is nice but I am always worried that I'm replacing a perfectly good wheel cylinder with some cheap chinese rebuild that could fail in 2 months anyway. It's a tough call so I usually wait until they leak or I break the bleeder off.

Good point!

My neighbor had this discussion this past weekend. The parts that were manufactured in this country (USA) 40+ years ago may continue to be far superior to anything you can purchase new today. There's little to be gained, and perhaps something to be lost, by replacing them if they are operating properly.

Thanks for all the help everyone!

69Chateau
05-09-11, 12:03 PM
Also, I should mention that I purchased a replacement Balkamp master cylinder gasket and installed that before beginning the bleeding process. This perhaps was the source of where I drew in air during my initial spring brake testing and was certainly in need of replacement based on appearance alone.

CADforce69
05-09-11, 09:10 PM
Iīm glad to read the problem is solved easily. Probably that gasket was the trouble source. Now you can enjoy your caddy safely:thumbsup: