I have been having problems with my brakes boiling and I know the problem has got to do with air being trapped in the lines and the shop I go to not knowing how to get the air out.

I have a 1994 LT1

I keep hearing about a special ABS bleeding procedure, but I looked through my entire service manual and searched for it online. I only see people saying there is a "Special" procedure but never is it explained. Does anyone know anything about this?

The shop is getting a new bleeding machine that replaces the fluid as it drains it so they are waiting until it gets in to try that. but as for this ABS thing. is there anyone out there that could enlighten me on this?

Thanks.

 

Boiling the fluid sounds more like not using a fluid that can withstand the high temperatures found in aggressive braking. What fluid are you using? What sort of braking is involved to boil the fluid? I would suggest going to a DOT4 fluid. Fluids from ATE or Motul would be a huge improvement over a standard DOT3 fluid.

There is nothing special about a simple bleeding process. Have the shop look up the procedure in AllData or follow the procedure in the FSM.

Bleeding the ABS unit is "special" in that a GM Tech 1 or 2 will be needed. To bleed the ABS pump, it has to run and that's what the scan tool will do; run the pump. IIRC, there is a valve on the side of the pump and it is opened to let the fluid pass out of the unit.

 

How does "air" in the lines lead to a boiling problem? typically, when there is air in the system, you feel it in either a spongy, or low peddle..

Unless you change out the brake (ABS) modulator, there shouldn't be any reason to suspect air between the high pressure pump/accumulator, and solenoid valves.

What are your symptoms, and how are you driving the car?

 

When the car idles too long, like when I am in traffic and there is no air flow i lose brakes. Its a sudden loss. The brake pedal will get a little bit soft, the car will continue to get hot, and then bam, all of a sudden my peddle goes straight to the floor and I get nothing. no brakes. I will pull over and sit for 15-20 min to allow the car to cool off. A few pumps of the brake peddle and my brakes are as good as new. It happens like clock work.

It happened after I had my engine rebuilt.

No one can figure it out and I've been through this many times with many people. It is very frustrating. The best I can come up with is there is air in the lines or the fluid is vaporizing and not allowing any compression.

It makes sense that the fluid is vaporizing/boiling with the fact that the loss of brakes is directly related to heat, and it happens instantly (as the fluid hits its boiling point). As to why the fluid is overheating we do not know. I am not driving the car hard, again, this happens while the car is NOT moving. When I am moving and the air flow is good, the brake lines stay cool enough and it is not a problem. It is only a problem once I hit traffic or try and go though a drive through.

I do not know what to do next except to go up to a dot 4 or dot 5.1

Also the temperature of the car stays at a constant 182 degrees while moving, but at idle or rest it will climb into the 220-230. I've never overheated. and the car is not running rich. Someone asked if my headers ever get red hot, and the answer is no. They are long tubes so they are much closer to the ABS lines than stock headers. I put some header wrap around those lines and I was able to improve its resistance to boil by 10-15 degrees or so.

 

Since it only occurred since your engine rebuild, I really doubt if there is air in the lines. Underhood temps I think have gone up and are causing problems. I would go over how everything is routed underhood and check exhaust temps using a laser temp gun. How hot do the headers get near the brake booster? Maybe make a heat shield like others have done where they are near to it.

Take the temp readings and find someone with a stock C4 and take their exhaust manifold temp readings - compare the difference. Also check the routing of the complete exhaust system as opposed to the brake lines. Good luck.

 

You might be on to something here with heat radiating from the exhaust, the stock manifolds have a full wrap around heat shield, with an air gap between the cast iron, and the shield it-self.

Here is a chart showing the boiling temperatures of brake fluid. Note the difference between "Dry" and "WET" boil. [Dot] 3 standard is 284°f [w] and 401°f [d]

http://www.lelandwest.com/brake-flui...ison-chart.cfm

here are a couple shots from my 95..







I would shoot the brake lines with an IR gun when the episode occurs..

 

How old is the fluid?

There's nothing special to doing the brakes on these cars. I used the $30 hand pump from Harbor Freight to do mine. Works like a champ.

 

A "special" procedure is merely a bleeding sequence order.
Some swear by it , others not.
You talk about temps and wrapping lines.
Nothing said about flushing, yet. So we'll assume you have fresh clean fluid. Yes?
Mileage? History?
At this point it sounds more like a bad master cylinder.

 

I noticed my fluid looks a little murky when I stuck my finger in the reservoir. Will need some new brake fluid to flush system. Will get some dot 4 synthetic from AMS oil.

 

If you only drive on the street, you only need a DOT3 or 4 fluid. You need to just gravity bleed/flush the brakes. You should be fine after this. If you still have an issue, then you have an open in the system sucking air.