I have a 98 Dodge Stratus 2.4L with a spongy brake pedal that goes almost to the floor.
This car doesn’t have ABS, it does have the ES package with 15 inch wheels, although all the brake parts are apparently for the 14 inch wheels.
The rear cylinders were leaking and air got into the system.
I changed the cylinders, flexible lines, and shoes, the drums are OK and recently replaced.
While I was at it, I also checked the front and replaced the half worn pads and slightly warped discs.
I bled all the lines and the brake petal is still spongy and goes almost to the floor.
Without the engine running the brake pedal is firm.
We brought the car into a local repair shop and they power bled the brakes to no effect.
The repair shop said the master cylinder must be bad, so we put in a rebuilt master cylinder.
We bench bled the master cylinder before we installed it, bled the system again and the brake pedal is still the same.
The front calipers are not leaking and moving freely.
The rear adjusters are working and the emergency brake engages about halfway.
We then took the car into the local Dodge dealer, they said they couldn’t find anything wrong and that the pedal movement was normal.
The brakes engage within about 1/2 inch from the top of the brake pedal and go basically to the floor under pressure.
Can the proportional valves have anything to do with this?
Is it possible that the synthetic brake fluid is more compressible than the original brake fluid?
We have paid the repair shop to power bleed it, and the dealer for giving an estimate to fix it.
I’m at a loss, I was going to give this car to my sister but I don’t trust the brakes.
I’m thinking if the porportioning valve was bad you would/should be getting a warning light on the dash. You probably already know this but when you start the engine vacuum builds in the brake booster and works to assist you in applying the brakes. I suspect there might be a problem with the brake booster, or with the fitment between the master cyl. and the booster, or the adjustment rod that actuates it. I had a parts house sell me a master cyl. one time that looked correct in all ways except the piston was recessed 1/2 to 9/16 inch more into the cylinder bore than the original one was. This master was for a different model booster and it required a longer rod, but it bolted right up and all the ports were in the correct positions. This caused an adjustment problem and a low pedal because the rod wasn’t long enough to be a compatable length for the recessed piston. I would double check the master cylinders. Look at them together and measure the depth from the mounting point to the bottom or the recessed hole where the rod sits. They should be exactly the same.
What bothers me is that the Dodge dealer said they couldn’t find anything wrong and the pedal movement was normal. Going to the floor is NOT normal…
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UPDATE !!!
There is a post on another page where a GMC product is expericencing the exact same complaint as on your vehicle. It has a firm pedal without the eng. running & vacuum booster asisting , BUT the pedal is spongy & goes all the way to the floor when the engine is running and the vacuum booster is asisting.
THE FINAL DIAGNOSIS ON THAT VEHICLE WAS SPLIT BETWEEN NEEDING A NEW MASTER CYLINDER BECAUSE IT WAS BYPASSING… HOWEVER THEY HAD ALREADY TRIED 2 NEW MASTERS AND 2 REBUILTS IN A WEEK WITH NO POSITIVE RESULTS.
THE OTHER DIAGNOSIS WAS: THAT SYSTEM REQUIRES THE BRAKES TO BE BLED BY THE GM DEALERSHIP WITH “SPECIAL EQUIPMENT”. I didn’t recognise the name of the item he said was required to do this, but it wasn’t a pressure or powwer bleeder.
I know you said that the Dodge dealer checked it, but I don’t see where you said that Dodge bled the brakes. I’m thinking that before you spend any more time on this, that it might be worth a call to Dodge and ask them if your system "requires special equipment to properly bleed it.
ALSO FROM WHAT THEY SAID OVER THERE, YOU CAN DISREGARD MY ADVICE IN THE FIRST PARAGRAPH ABOVE WHICH I HAVE NOW DELETED THAT REFERRED TO THE HYDROLICS BEING OK IF THE PEDAL WAS FIRM WITHOUT THE VAC. BOOSTER ASSISTING. THEY SAID THIS PROVES NOTHING. NORMAL CHECKING PROCEDURE IS ALWAYS WITH THE ENGINE RUNNING AND THE VACUUM BOOSTER ASSISTING. SORRY FOR THE MISINFORMATION… Keep us posted…
Try applying brake hard and with the brake applied ratchet the hand brake on and off several times. This will adjust rear drums brakes if you have rear drums.
Also check rear brake flex lines. There is a clamp that bends around the line, and if rust builds up between it and the line it can squeeze it closed. This is unlikely though because it would have been be hard to bleed the lines
Synthetic brake fluid? If you mean silicone brake fluid, the rubber components in the brake system are not compatible with silicone brake fluid. If silicone brake fluid was added to the system, you’ll never get brake pressure as the seals are damaged from the silicone brake fluid.
Tester
Unfortunately, I don’t have the original master cylinder to compare against.
The rod has an adjustment, and we adjusted it so that when we install the master cylinder, the rod hits with about a 1/4 inch of brake pedal movement.
We removed the brake lines and put plugs into the master cylinder, and the brake pedal barely goes down, and just stops, with no give at all even with the vacuum assist.
When we install the rear brake lines the brake pedal goes down about an inch and is slightly spongy, but not bad.
When we put the front brakes lines back on, the brake pedal goes nearly to the floor under pressure, and is spongy all the way down. This is with the vacuum assist.
The brake pedal doesn’t come up any when pumping the brake pedal
The brake fluid is valvoline synthetic, says compatible with all DOT2 and DOT3 brake fluid.
The rear flex lines are new.
Unfortunately, I don’t have the original master cylinder to compare against.
The rod has an adjustment, and we adjusted it so that when we install the master cylinder, the rod hits with about a 1/4 inch of brake pedal movement.
We removed the brake lines and put plugs into the master cylinder, and the brake pedal barely goes down, and just stops, with no give at all even with the vacuum assist.
When we install the rear brake lines the brake pedal goes down about an inch and is slightly spongy, but not bad.
When we put the front brakes lines back on, the brake pedal goes nearly to the floor under pressure, and is spongy all the way down. This is with the vacuum assist.
The brake pedal doesn’t come up any when pumping the brake pedal
EXCELLENT DIAGNOSIS PROCEDURE THERE TPB. You have already done what I was going to suggest next (plugging the ports and isolating front from rear), labor intensive, but good thinking and a good start…
It seems you have isolated the problem to the front 1/2 of the brake system. At this point I think it has got to be a leak in one of the calipers, OR the flex lines are expanding. Watch the flex lines while someone starts the vehicle and applies the brake on and off so you can see if they are expanding and contracting. Also please make sure they don’t run over you. If they do not expand, can you isolate the left front from the right front caliper? If it turns out to be one of the calipers leaking, then eventually you should see some external leakage showing up somewhere, unless the fluid is bypassing the caliper piston seal and then when you release the pedal it is bypassing back the other way) although I don’t think this is possible because of the pressure differential. Keep us posted…
UPDATE !!!
There is a post on another page where a GMC product is expericencing the exact same complaint as on your vehicle. It has a firm pedal without the eng. running & vacuum booster asisting , BUT the pedal is spongy & goes all the way to the floor when the engine is running and the vacuum booster is asisting.
THE FINAL DIAGNOSIS ON THAT VEHICLE WAS SPLIT BETWEEN NEEDING A NEW MASTER CYLINDER BECAUSE IT WAS BYPASSING… HOWEVER THEY HAD ALREADY TRIED 2 NEW MASTERS AND 2 REBUILTS IN A WEEK WITH NO POSITIVE RESULTS.
THE OTHER DIAGNOSIS WAS: THAT SYSTEM REQUIRES THE BRAKES TO BE BLED BY THE GM DEALERSHIP WITH “SPECIAL EQUIPMENT”. I didn’t recognise the name of the item he said was required to do this, but it wasn’t a pressure or powwer bleeder.
I know you said that the Dodge dealer checked it, but I don’t see where you said that Dodge bled the brakes. I’m thinking that before you spend any more time on this, that it might be worth a call to Dodge and ask them if your system requires special equipment to properly bleed it.
ALSO FROM WHAT THEY SAID OVER THERE, YOU CAN DISREGARD MY ADVICE IN THE FIRST PARAGRAPH OF MY FIRST POST WHICH I HAVE NOW DELETED THAT REFERRED TO THE HYDROLICS BEING OK IF THE PEDAL WAS FIRM WITHOUT THE VAC. BOOSTER ASSISTING. THEY SAID THIS PROVES NOTHING. NORMAL CHECKING PROCEDURE IS ALWAYS WITH THE ENGINE RUNNING AND THE VACUUM BOOSTER ASSISTING. SORRY FOR THE MISINFORMATION… Keep us posted…