Soft Brake problem
Re: Soft Brake problem
Biggest problem with brakes after a vechicle has been sitting is rust on the rotors, longer it sits, the more builds up, and enough the dust and build up on the pads, till it gets work off.
example, mine has been down over a month while I have been working on a single aluminum driveshaft from the 2 piece steel, now I have no more flex discs and not more center carrier bearing.
but the rust has built up on the rotors thicker, and first drive, had to push hard on the brake and petal went alot farther down, due to having to push alot harder on the petal, but after easy driving on my back roads, going easy on brakes not to heat or much pressure, just doing a self cleaning, while doing some light testing brakes kept feeling better and better, now, good as they where before, throw you in the windshield.
you can also get a test gauge and take out a bleeder, and screw the test gauge in the bleeder to test pressure and for bleed off.
power assisted brakes can build pressures upto 1400 psi.
example, mine has been down over a month while I have been working on a single aluminum driveshaft from the 2 piece steel, now I have no more flex discs and not more center carrier bearing.
but the rust has built up on the rotors thicker, and first drive, had to push hard on the brake and petal went alot farther down, due to having to push alot harder on the petal, but after easy driving on my back roads, going easy on brakes not to heat or much pressure, just doing a self cleaning, while doing some light testing brakes kept feeling better and better, now, good as they where before, throw you in the windshield.
you can also get a test gauge and take out a bleeder, and screw the test gauge in the bleeder to test pressure and for bleed off.
power assisted brakes can build pressures upto 1400 psi.
Re: Soft Brake problem
Try this, engine OFF. pump the brake several times to bleed off the vacuum assist.
Now press the pedal to see the unassisted pedal feel. It should be solid and unyielding.
It should also not drift, go to the floor or other odd thing.
Has the brake fluid gone down?? have lid on when pumping brakes or expect a fountain to erupt.
Let us know, WDY
Now press the pedal to see the unassisted pedal feel. It should be solid and unyielding.
It should also not drift, go to the floor or other odd thing.
Has the brake fluid gone down?? have lid on when pumping brakes or expect a fountain to erupt.
Let us know, WDY
Re: Soft Brake problem
Circling back on this. I did this and found the brake pedal to be very firm and what I consider normal when the car is turned off. When running however the pedal goes back to being soft. Do those finding indicate what might be wrong between air in the lines or master cylinder? Brake fluid level is very normal and no signs of leakage.
What one person calls a soft pedal another may say is fine. We have no way of comparing two or more cars if they are not side by side.
Last edited by onehundred80; 04-29-2018 at 01:45 PM.
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Re: Soft Brake problem
Yes, would love to hear a solution for this everlasting problem. Where do you get the gauge that is referred to that measures the pressure in the brake line. I guess that could tell us if we have a master cylinder that has a bleed off problem at the seal, or if a brake caliper is having a bleed off problem. Let me know about this. A firm pedal, like that on the American made cars and the Japanese imports is what I feel is desirable. My wife has a Subaru and the pedal on that barely moves and the pedal starts getting firm. I had a Chev. HHR until recently and the brake's were great on that car, too! Very nice brake feel!
I solicit any helpful information.
Jim
I solicit any helpful information.
Jim
Re: Soft Brake problem
Yes I know what ya mean , I don’t remember my Crossfire having that much brake pedal travel before this year ! That’s why it felt so strange when I brought it out last week for the 1st time ! My Stang & my Tacoma brakes are so much better ! Hoping I get some answers from MB this week I hope ! Thinking of having them do a brake fluid flush 1st because never been done ! Hope that helps out with both problems !
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Re: Soft Brake problem
Yes, would love to hear a solution for this everlasting problem. Where do you get the gauge that is referred to that measures the pressure in the brake line. I guess that could tell us if we have a master cylinder that has a bleed off problem at the seal, or if a brake caliper is having a bleed off problem. Let me know about this. A firm pedal, like that on the American made cars and the Japanese imports is what I feel is desirable. My wife has a Subaru and the pedal on that barely moves and the pedal starts getting firm. I had a Chev. HHR until recently and the brake's were great on that car, too! Very nice brake feel!
I solicit any helpful information.
Jim
I solicit any helpful information.
Jim
Yes I know what ya mean , I don’t remember my Crossfire having that much brake pedal travel before this year ! That’s why it felt so strange when I brought it out last week for the 1st time ! My Stang & my Tacoma brakes are so much better ! Hoping I get some answers from MB this week I hope ! Thinking of having them do a brake fluid flush 1st because never been done ! Hope that helps out with both problems !
.
Re: Soft Brake problem
I do not see how a pressure gauge would help, the pressure is proportional to the force applied to the pedal and you would have to keep a constant force on the pedal to see anything, if the system was leaking a little and you kept a constant pressure you would not see the gauge needle dropthe pedal would go down though with or without the gauge.
So if the pedal goes down you have a leak in the system somewhere.
Just after I started driving a car I had a sudden total failure of the brakes when I was stopping behind a bus, the pedal went to the floor and automatically I started pumping the brakes. There was a guy looking at me from the rear of the bus and he must have seen the panic on my face. Fortunately the bus moved as I was about to ram it, I turned around and pumped the brakes furiously all the way home, I can still remember where that incident happened some fifty five years ago.
Re: Soft Brake problem
My 05 roadster has been sitting several months and I am experiencing the same "soft pedal" issue that you have been discussing. I have tried the "pumping while not running" approach, and haven't seen any appreciable improvement. I am going to try bleeding the brakes next. My question is what fluid to use. Should I go ahead and pay the extra money for the MB dot 4 plus, or will off the shelf dot 4 from one of the parts stores be safe to use? Here is the spec from the manual:
Brake Master Cylinder Use brake fluid approved to MB 331.0, or a DOT 4 brake fluid with: minimum dry boiling point (ERBP) 500°F (260°C), minimum wet boiling point (WERBP) 356°F (180°C), maximum viscosity 1500 mm2 /s, conforming to FMVSS 116 and ISO 4925.
Standard dot 4 specs show lower minimum ERBP (230C) and WERBP (155C). Is this really going to make a difference?
Brake Master Cylinder Use brake fluid approved to MB 331.0, or a DOT 4 brake fluid with: minimum dry boiling point (ERBP) 500°F (260°C), minimum wet boiling point (WERBP) 356°F (180°C), maximum viscosity 1500 mm2 /s, conforming to FMVSS 116 and ISO 4925.
Standard dot 4 specs show lower minimum ERBP (230C) and WERBP (155C). Is this really going to make a difference?
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Re: Soft Brake problem
donsxfire - I bought my brake fluid from Rob at Needswings. The reason being that I was also buying other brake parts at the same time. His is a dot 4 fluid and since it was recommended by him, I felt safe. He has both the "race" fluid and the "street" fluid. Of course, get the "street" fluid.
An open question for all here. Has anyone replaced the master cylinder with a new one, not a rebuilt, and noticed any improvement? Has anyone replaced the calipers and noticed any improvement? Like 180 said, he, and a lot of us, have replaced the fluid and bled the system only to find no appreciable improvement. I didn't think of it until 180 mentioned that the gauge wouldn't help, but I agree with him. I don't think it will reveal what we are looking for. I'm one who just refuses to say "that's the way it is". There has to be an improvement somewhere. If American, Japanese, and other European cars can have a good brake pedal feel, we can too! It might take all of us to find the answer but we have to keep trying. I put "Wildwood" calipers on a street rod, two in fact, and was very happy with their performance over run of the mill calipers. I also used their complete brake system on a race car. Wonderful brakes!
If anyone has some more ideas, lets hear them.
Thanks,
Jim
An open question for all here. Has anyone replaced the master cylinder with a new one, not a rebuilt, and noticed any improvement? Has anyone replaced the calipers and noticed any improvement? Like 180 said, he, and a lot of us, have replaced the fluid and bled the system only to find no appreciable improvement. I didn't think of it until 180 mentioned that the gauge wouldn't help, but I agree with him. I don't think it will reveal what we are looking for. I'm one who just refuses to say "that's the way it is". There has to be an improvement somewhere. If American, Japanese, and other European cars can have a good brake pedal feel, we can too! It might take all of us to find the answer but we have to keep trying. I put "Wildwood" calipers on a street rod, two in fact, and was very happy with their performance over run of the mill calipers. I also used their complete brake system on a race car. Wonderful brakes!
If anyone has some more ideas, lets hear them.
Thanks,
Jim
Re: Soft Brake problem
Thanks for the feedback Jim. I looked up the fluid from your dealer, and it exceeds the temp specs, so it should definitely be OK. FYI to everyone: Ebay has the Mercedes Benz dot 4 plus fluid, 1 liter for $15, free shipping, and a free bottle of windshield washer fluid. I'll probably go with that, just to be safe. I'll report how it works out.
Re: Soft Brake problem
Thanks for the feedback Jim. I looked up the fluid from your dealer, and it exceeds the temp specs, so it should definitely be OK. FYI to everyone: Ebay has the Mercedes Benz dot 4 plus fluid, 1 liter for $15, free shipping, and a free bottle of windshield washer fluid. I'll probably go with that, just to be safe. I'll report how it works out.
That is meant as a joke, some might get irate at such a post as humor seems to be going the way of the dodo.
Re: Soft Brake problem
Bleed each cylinder until new fluid shows, it is easier if you use fluid of a different colour.
Bleed left hand drive cars in this order, R/rear, L/rear, R/front and L/front.
Re: Soft Brake problem
Drain all the fluid you can from the reservoir, refill with the new fluid and then bleed the brakes. This will rid the system of the old fluid quickly.
Bleed each cylinder until new fluid shows, it is easier if you use fluid of a different colour.
Bleed left hand drive cars in this order, R/rear, L/rear, R/front and L/front.
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Re: Soft Brake problem
Thanks Jeff. I just talked to a German Import specialty garage near me. They specialize in European Imports, particularly Mercedes and BMW. They told me that to do the job properly they have to use a scan tool to properly bleed the brakes. They said that's the only way to COMPLETELY CLEAR ALL FLUID from the system. I've never heard of that before but I'm not a German car Specialist. This shop comes highly recommended and I guess that all one can do is try them once and see. If it's a rip, I can sure let a lot of people know. If it's good, I can also relate my experience here. I will keep everyone posted on the results. It may take a week or more because they are busy enough that I can't get in for a week. Hope that's a good sign.
Jim
Jim