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-   -   Brake Line Theory (http://www.hotrodders.com/forum/brake-line-theory-12601.html)

Turbo2Sam 02-07-2003 09:49 AM

Brake Line Theory
 
I scrapped the ABS Brake System on my '90 Jeep (Tow Vehicle). Went to the Junk Yard and got a Vac/Booster/MC/Combo Valve from same car. Installed it but am having a tough time bleeding it. Installed a new MC, Bled the MC, then tried to bleed at the Brakes. Still have tons of air.

I've got a couple of Lines, one above the Combo Valve and one under, that loop up higher than the Combo Valve height so I'm thinking that these higher loops are retaining some air and I am just sucking it back into the MC.

QUESTION: When running Brake Lines, are all of the Lines, from the MC downward, all supposed to be lower and lower as they progress, or is it normally OK for some of the Lines to be higher than others?

QUESTION: I've also tried bleeding the Lines with one of those "SucALux" things at the Bleeders, but can't seem to get a good Vac on the Bleeder. Leaks air around the Hose. Any ideas on how to get a good fit from the SucALux hose to the Bleeder? (My son's getting tired of pumping the Brake Pedal).

Thanks, t2sam

meanmachine666 02-07-2003 09:54 AM

you can rent a pressure bleeder and try it that way. No pumping the pedal needed.
I use one mainly because when I am bleeding brakes no one is ever around to help.

HotRodMan 02-08-2003 05:39 PM

I have had some brake bleading problems that would drive you nuts. Here is what I did, and it worked great. Get a one man blead kit from the parts house. This consists of a plastic bottle with a magnet and about 3 feet of clear hose.($6.95) Hook up the hose to the bleader valve on the caliper or wheel cylinder. Here is the key. Bring your plastic bottle up high so that it is higher than the caliper or wheel cylinder. Keep your master cylinder full and pump the pedal up and down several times. You don't have to close the bleader valve each time you let the pedal up like you would with a hose and container on the floor. Within about 10 to 15 pedal pumps you should have all the air out of that line. I usually start with the longest brake line and work toward the shortest. This method has never failed me.

Dave E Shank 02-10-2003 04:07 PM

HEY TURBO: Bleeding brakes is right up there on the fun chart like busting your knucles <img src="graemlins/sweat.gif" border="0" alt="[sweat]" /> If you go to <a href="http://www.mpbrakes.com" target="_blank">www.mpbrakes.com</a> they have a good "help" section that might give you a hint. If you go to <a href="http://www.holley.com" target="_blank">www.holley.com</a> and then to Earl's Performance Plumbing and look up " Solo-Bleeds" they make a nifty check valve that allows air and fluid out but nothing in. I have them on all my cars and they are cheap and work well. I had a problem with air getting in system and found I had loose brass fitting at MC <img src="graemlins/spank.gif" border="0" alt="[spank]" /> GOOD LUCK DAVE

Turbo2Sam 02-12-2003 06:24 AM

So I'm two weeks into trying to get the Jeep Brake Lines Bled and still, no soap. This was the former ABS system that I replaced with a traditional Vac/Booster and new MC.

I re-ran some Lines so that they are all now, lower than the MC and the Combo Valve. Tried to do the SucALux Machine Bleeding at the Bleeders, but on the Rears, which have smaller Nozzles, was getting a lot of air around the Tubes.

However, as a test, I did some Pedal Pumping and after a couple of good pumps, noticed that the Rear Chamber of the new MC (this goes to the front brakes), was "fizzing" with Bubbles rising up from one of the two Ports into the Fluid after the Pedal was released.

I completely bled the MC so I know that there was no trapped air, but would the fizzing mean that I have an air leak somewhere and when the Pedal is released, I am sucking some air back into the system?

Also, as an Air Leak Tracking test, since the fizzing starts quickly after releasing the Pedal, could I assume that the Leak is close to the MC?

Thanks, Turbo2Sam

tm454 02-12-2003 08:53 AM

Brake problems can be a lot of FUN! I always expect to have problems with the brake system when I do any work on it. Makes the job easier if I do it right the first time!!


Todd :rolleyes:

HotRodMan 02-12-2003 06:56 PM

Here is a method I use to track down leaks in the brake system.

1. Cut a 2 X 4 so the length will wedge between the brake pedal and the seat with a good bit of pressure on the pedal. If needed clean the connections and brake lines of any brake fluid, oil, grease, etc.

2. Fill your master cylinder with fluid. Get the best high intensity light you have and a hand held mirror (to look at the back side of the line) and examine every inch of the brake lines and connections while the system is under pressure with your 2X4.

3. If you have a leak in the system this method will uncover it. If you have new fluid and a small leak it is harder to detect so you will need a really good light. I have seen some leaks that were so tiny I had to leave the system under presure for 15 minutes before they would show up.

4. If the fluid is leaking out, that also means you have air getting in, which will have to be fixed before you can blead the brakes.

5. If you suspect the master cylinder itself, try re-bleading the master cylinder seperatly first, then re-connect to the rest of the system. You can bench blead the master cylinder without taking it off the car. Don't assume if your master cylinder is new that it is good. I have seen plenty that were bad right out of the box. You will get bubbles continually when bench bleading if its bad. If you got all the bubbles out when bench bleading and then have them re-appear after you hook your lines up, you have trouble with the connections or lines going to the master cylinder.

4811 02-12-2003 07:59 PM

I had an air problem with a 72 corvette. Tried everything. New calipers, master cylinder, new lines. Finally after 2 or 3 years I gave in 7 took it to a corvette shop. They put on new rear calipers. The old ones were sucking air. The old ones I bought new from a brake supplier. They never worked from day one. The clue on mine was that they had fluid at the bleeder and after pumping the pedal they went dry. Now my brakes are fine.


Good luck!!

Dave E Shank 02-14-2003 11:46 AM

HEY TURBO: I had this same problem and it took FOREVER to find. Problem was MC is cast iron with rough threads. Brass bushing fittings were not making good seal against MC threads, EVEN THOUGH they were tightly bottomed out. I had to use teflon tape and sealant to finally get tight seal. What was happening was when pedal would pull back up it was sucking in small amount of air around fitting. You might try putting soap suds around brass fitting and see if you are getting any air movement. HOPE THIS HELPS..DAVE


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