90 brake issues
Thread Starter
Safety Car
Joined: Oct 2008
Posts: 4,689
Likes: 4
From: Yucaipa CA
90 brake issues
90 brake issues
Pedal goes almost all the way to the floor, abs light always on from time key is turned on. there is a sensor on the master cylinder that is broken yet brake light does not come on (does come on when parking brake applied) .... Brakes are very weak to say the least .... does this just sound like a bad master cylinder or something more? Can a bad master cylinger cause this service abs light to stay on?
Pedal goes almost all the way to the floor, abs light always on from time key is turned on. there is a sensor on the master cylinder that is broken yet brake light does not come on (does come on when parking brake applied) .... Brakes are very weak to say the least .... does this just sound like a bad master cylinder or something more? Can a bad master cylinger cause this service abs light to stay on?
Thread Starter
Safety Car
Joined: Oct 2008
Posts: 4,689
Likes: 4
From: Yucaipa CA
Thread Starter
Safety Car
Joined: Oct 2008
Posts: 4,689
Likes: 4
From: Yucaipa CA
Drifting
Joined: Jun 2010
Posts: 1,853
Likes: 8
From: Westerly RI
The C4 master cyl is quite sensitive to fluid level. Try topping the reservoirs off, and see if you feel a difference in the pedal. You will likely have to bleed the brakes as air could have gotten into the lines, but you may well feel a difference in the pedal before doing that. If this brings the brakes up, I would look for a fluid leak, examine all the brake lines, etc., for a wet spot. Keep an eye on the fluid level for a while, and if it goes down, there is a leak somewhere, including into the booster. If the fluid does not go down again, your low pedal and low fluid was probably due to pad wear.
In any case, the abs light might be due to the low fluid or damaged sensor. You can read the code that is set (in the ccm, not ecm) without equipment as the car will self-diagnose.
In any case, the abs light might be due to the low fluid or damaged sensor. You can read the code that is set (in the ccm, not ecm) without equipment as the car will self-diagnose.
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Le Mans Master
Joined: Jul 2007
Posts: 5,043
Likes: 7
From: Tampa Florida
Even out the amounts in both cups - work the brake pedal then pay attention to the amounts in the cups to see if there is a change in the levels....fluid could be moving from 1 cup to the other.....internal master cylinder issue.
The ABS sensor/connector on the MC that is not connect is more than likely the source of the ABS warning light.
The ABS sensor/connector on the MC that is not connect is more than likely the source of the ABS warning light.
Safety Car
Joined: Jan 2004
Posts: 3,759
Likes: 8
Even out the amounts in both cups - work the brake pedal then pay attention to the amounts in the cups to see if there is a change in the levels....fluid could be moving from 1 cup to the other.....internal master cylinder issue.
The ABS sensor/connector on the MC that is not connect is more than likely the source of the ABS warning light.
The ABS sensor/connector on the MC that is not connect is more than likely the source of the ABS warning light.
Le Mans Master
Joined: Jul 2007
Posts: 5,043
Likes: 7
From: Tampa Florida
What ever you want to call it the OP called it a "sensor on the master cylinder that is broken" so this is what he knows it as - I did add the "/connector" term to it in my post....anyway - so how about in non technical speak - it is the "do-dad thingy" that lights up the ABS indicator light on the gauges when you hit the brake pedal "hard"....the OP is going to want to take a look at getting that taken care of as a first step in getting the ABS indicator light to quiet down.
Thread Starter
Safety Car
Joined: Oct 2008
Posts: 4,689
Likes: 4
From: Yucaipa CA
Yes that is the sensor that is broken on my car as is the pigtail that plugs into it.
The brake fluid level has been like this since I bought the car two years ago. So it's not a leak that is my issue.
I was more curious if the abs light on could be causing the horrible brake issue. Basically when I do pump the pedal the brake pedal will stay up for a split second then will drop to about maybe two inches from the carpet (might even be closer)
Caliper issues could be a problem to since this car has been off the road since about 2006. The pedal feels different when the car is runing verses not running so the booster must be working correctly.
I will read my fsm and see how to pull abs codes that issue I'm wondering if could be related to no brake fuse being in the car since there are no tail lights currently in the car.
The brake fluid level has been like this since I bought the car two years ago. So it's not a leak that is my issue.
I was more curious if the abs light on could be causing the horrible brake issue. Basically when I do pump the pedal the brake pedal will stay up for a split second then will drop to about maybe two inches from the carpet (might even be closer)
Caliper issues could be a problem to since this car has been off the road since about 2006. The pedal feels different when the car is runing verses not running so the booster must be working correctly.
I will read my fsm and see how to pull abs codes that issue I'm wondering if could be related to no brake fuse being in the car since there are no tail lights currently in the car.
Safety Car
Joined: Jan 2004
Posts: 3,759
Likes: 8
What ever you want to call it the OP called it a "sensor on the master cylinder that is broken" so this is what he knows it as - I did add the "/connector" term to it in my post....anyway - so how about in non technical speak - it is the "do-dad thingy" that lights up the ABS indicator light on the gauges when you hit the brake pedal "hard"....the OP is going to want to take a look at getting that taken care of as a first step in getting the ABS indicator light to quiet down.
The OP needs to look elsewhere with regards to the service ABS light.
Le Mans Master
Joined: Jul 2007
Posts: 5,043
Likes: 7
From: Tampa Florida
Pulling ABS codes from 1990 vette without a scanner:
Enable flash code diagnostics, by jumping pin H of the diagnostic link connector (DLC) to pin A or a chassis ground and then keying-up. The Service ABS light will come on for 4-sec., then start blinking two digit DTCs. Each digit is signified by half-second-apart flashes. One second separates the digits. Codes are flashed three times with a 3-sec. pause between. Each sequence is bracketed by code 12, signifying the sequence's start and finish.
Pro
Joined: Oct 2003
Posts: 506
Likes: 12
From: Savannah GA
Does the 90 give codes? I thought 90 was the last year for the Bosch ABS 2. It needs the special equipment/tester. If you have the FSM you can do most of the troubleshooting with a DMM.
I bet you have 2 problems. Pedal to the floor is a hydralic problem. ABS is an electronic/sensor problem
I bet you have 2 problems. Pedal to the floor is a hydralic problem. ABS is an electronic/sensor problem
Thread Starter
Safety Car
Joined: Oct 2008
Posts: 4,689
Likes: 4
From: Yucaipa CA
The service ABS light issue has been fixed. I replaced 3 fuses that were pulled because of no tail lights in the car.
Brake fuse
turn/backup fuse
stop fuse (I think)
Anyways one of these fuses what was causing the problem since the service abs light has never come back on. The light does come on though during ignition on prior to starting so the system appears to be working correctly now.
Brakes still suck though !!!!! Will be ordering stainless brake lines and new pads and rotors and a master cylinder and that should resolve the last issue. I will be putting ZR1 replicas on my car so have been considering a C5 brake upgrade as well.
Brake fuse
turn/backup fuse
stop fuse (I think)
Anyways one of these fuses what was causing the problem since the service abs light has never come back on. The light does come on though during ignition on prior to starting so the system appears to be working correctly now.
Brakes still suck though !!!!! Will be ordering stainless brake lines and new pads and rotors and a master cylinder and that should resolve the last issue. I will be putting ZR1 replicas on my car so have been considering a C5 brake upgrade as well.
Burning Brakes
Joined: Oct 2009
Posts: 773
Likes: 2
From: Minneapolis MN
That should solve your problem.Make sure you get that broken sensor & a new pigtail for it.For people that don't know,to check for a bad master cylinder-first you bleed all 4 wheels throughly until fresh/new brake fluid is in brake system(master cylinder).If no change go to step 2.Second install a hose crimper tool or a vise grip on each brake hose(meaning install one tightly to block brake fluid travel on all 4 brake hoses) being careful not to damage hose(s).Install a cloth on hose first if using a vise grip so you don't damage hose.Get in vehicle & press down brake pedal.If brake pedal is hard as a rock(it should be if master cylinder is working properly),master cylinder is fine & problem lies somewhere else.But if brake pedal still sinkings to floor or is not stiff,master cylinder is bad(assuming clamps on brake hoses are installed properly thus blocking brake fluid travel to caliper).Hope this helps.On some vehicles above test could mean ABS hydralic unit could be the problem but in my experience it normally is an accurate test for master cylinder diagnosis
Drifting
Joined: Jun 2010
Posts: 1,853
Likes: 8
From: Westerly RI
IMHO, I would not trust brake hoses that have been pinched as suggested in the previous post. In a panic stop, there is considerable pressure in those hoses, and I would be afraid that they would be compromised. Since the brake system is closed, the only two conditions that would cause the pedal to sink to the floor are a leak in the system or a bad master cyl. If you have this symptom, it is relatively easy to find a leak, whether in a line, caliper, etc. If you don't find an external leak, you can conclude that the master is leaking internally.