I have a 1994 LT1 6spd, with only an x-pipe and magnaflow mufflers modified to the exhaust. I've had this problem for a while, probably since i bought the car over 2 1/2 years ago....but noticed it 2 summers ago. What happens: when the car gets up to normal operating temp and it's hot outside (90-100+), it feels as if my car isn't pulling as hard, and sometimes the engine feels like it's under more of a load than it should be. The brake pedal also feels very stiff, and not nearly as responsive. When I floor it above 4k rpms in any gear it seems, the red BRAKE light comes on in my dash, which is the light signaling to get my brakes checked. Also when I slowly roll to a stop, it feels as if the brakes are engaged slightly, so instead of gently gliding to a seamless stop, it slows quicker into a jerked stop. If i'm at a slight incline and my foot is not on the brake pedal, my car doesn't move. Not sure what the cause of this is.... I found in another post about headers that someone said,

I suspect that my cats are clogged also, because i smell the rotten egg smell when the car is warmed up, and the inside of the car seems to get abnormally hot, near my shins and feet. Also there's the slight loss of power, and slight hesitation on acceleration. What does he mean by the brake booster "popping open"? Could the high heat from the cats be effecting the brake booster in messing with my brakes in this case? Basically my question is...should I go get my brakes inspected...or should I get some new cats? (I was thinking of getting some LT headers w/ high flow cats very soon) thanks for any advice and input.

 

Can't help with the brake issue(s). Things I'd think about are: master cylinder, brake booster, abs, air in the brake lines (altho that would seemingly cause less braking power, not more), low fluid, crimped lines, etc. How do your brakes smell after a long run? Like the pads are cooking? Very hot to the touch (wheels only)?

But the rotten egg smell isn't necessarily a sign that the cats are clogged. They may still be, but to my knowledge that isn't the definitive sign that they are.

And, how're you gonna pass Calif. emissions with LT headers? None are CARB legal.

 

I have a 90 and it maybe different but in the 90 FSM that light will come on in a few circumstances:

If you step on the brake & light comes on = possible air in sys.
If the light flickers under heavy accleration = possible vacuum diaphram failure.
If the parking brake has an adjustment problem.
If the brake light switch is not adjusted correctly.

Check up under the dash at the spot where the rod comes thru the firewalll & look for fluid leaks. That's the easiest check to do. Oh, another symptom of a booster going south is that the pedal seems unusually firm but the brake effect is not quite up to snuff.

I would also do the parking brake adjustment test because it sounds like your parking brakes are sticking. I'm about to look into that myself as my P/B sometimes doesn't want to release...sorry I don't have much to share on the brake issues as I'm just starting down that road.

On the CAT thing if you know someone with a tail pipe sniffer you could do a tail pipe sniff test and see what's coming out. That with a scan may tell you what's up.

Tom

 

Thanks for the advice Tom, I'll look into it. I don't know if my parking brake is sticking, because when the car is cool, the car runs fine, and the brakes aren't seemingly engaged. Or do you mean once it gets hot? Only when the car and outside temps are hot, under heavy acceleration the brake light comes on for 1-3 seconds then goes away, and also when I hit the brake pedal it's very stiff with very little response, you really have to put your foot on it.

* I just went out and took a look at it, there is no wetness or fluid leaks under the dash on the rod where it goes thru the firewall. Under the hood, I moved the ECM which was over the brake booster, tried to inspect the vacuum lines around it, but it's a tight fit...hard to see... but I didn't find anything. Maybe it's what you said...a vacuum diaphram fracture? you mean inside the Brake booster right?

and LT4CompYell, as for passing cali emissions, i'm going to try and wing it..see if they notice... if they ask, i'll give them a legal number for some shorty headers... worse comes to worse i'll swap it out 1 1/2 years from now.

Thank you for all your input...all help is greatly appreciated.

 

There is a possibility that the adjustment rod out of the brake booster is not adjusted properly. If the rod is to long it will depress the piston on the master. The rod may need to the screwed in to shorten the length. Also with heat as you run the car, the tolerances close and the problem can get worse.

Many ways to check for this but this is one easy way. Jack one wheel up and see if it is dragging. If it is, loosen the bolts on the master to relive the pressure and see if it clears the problem. If adjustment is needed, take bolts off and pull back master, leave fluid lines on.

As for your brake light lighting on acceleration, add some fluid as see if that clears it up. These masters like to be real full and acceleration can make it give a false light. I had this myself. Good luck, hope you have a simple fix.

 

Ditto about checking the master cylinder rod length. I had this problem where in hot weather the brakes would just almost seize. It took a while and lots of money to figure out the master cylinder operating rod was adjusted too long. When I replaced the master cylinder some time before I never checked it because I thought what the hell it's a GM part so it should be spot on, right? Don't assume anything, verify!

 

THank you both very much for the advice. My dad suggested I may need to change the master cylinder, but I'm not ready to do that quite yet. I will check the rod tomorrow morning when it's light out. I checked the brake fluid, and it was noticably lower than maximum, so I filled 'er on up

 

.....despite what it says under my forum name I'm no senior anything! I've had my C4 for 2 yrs, so I'm a rookie.:o

Yes, about the diaphram in the power brake booster. You might also see if you can just change the check valve on the vacuum line that feeds the booster. On my LT5 it's the big hose on the inboard side about at the mid point on the face of the booster body. I've never heard of one of those failing...but ya never know.

In truth, I would be inclined to listen to the other guys about the rod lenght and check that. The only thing that sticks in my mind about that is if the master or the booster were never out of the car then how does the rod lenght come out of adjustment? Anyway I'm sure that those guys know a lot more than me....last vette I had was a 72!!! My C4 is like working on the space shuttle compared to my LT-1...it didn't even have power brakes...such a simple car compared to what I now own!

I got sooo much to catch up on with a C4. I'd be interested to hear what was the root of the brake situation & the eventual resolution!


Tom