Question about 1983 Ford F 250

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My 83 f250 makes a air leak sound under the dash when the brake pedal is compressed and even when not. is it a bad master cylinder?

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Sounds like the brake booster has a hole in the diaphragm .. You should be able to pick up a used one fairly cheap and they are easy to change out. You don't need to undo any brake lines just remove the master cylinder and prop it out of the way.

Posted on Jul 29, 2010


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1 Answer

No brakes..No leaks..Can physically grab pedal and it moves forward and back with no resistance...

look up under the dash where the brake peddle is hinged-there should be a rod that goes forward through the firewall to the master cylinder- check the pin that holds these together- Denny

Dec 12, 2013 | 1990 Ford F250

1 Answer


if a master cylinder is bad and you are sure you have all the air out and no leaks.pedal will go to floor , running or not. if booster is bad it will cause a hard pedal. but if master cylinder is bad it will turn on a brake light on dash if it works. make sure the wheel cylinders are not leaking. I beleive that the master cylinder is bad, or you have a leak somewhere. If the master cylinder is functioning properly, the brake pedal will depress to a certain depth and no further.

Apr 20, 2012 | 2000 Chevrolet Blazer

1 Answer

Clutch is loose at pedal. will not go in gear. Is the clutch bad or is there a fluid reservoir I need to know about?

Check the linkage under the dash to make sure it's not broken, then check the clutch master cylinder (on the firewall next to the master cylinder on the fender side) If it's low there is a leak, usually from the back of the master or at the slave on the bellhousing. (sometimes you can see the master leak under the dash where the rod goes in) The system is "sealed" like your brakes so any leaks must be repaired or the problem will continue even if you bleed it. Bleeding is done at the slave cylinder and the same method (hold pedal down open bleeder, close valve till there's no more air)
Usually a clutch slips noticeably before failing and since you did not mention that check what I said.

Oct 30, 2010 | 1993 Jeep Wrangler

2 Answers

Brake warning indicator lamp is on, brake pedal

Check for leaks under the car. Look carefully at the back of each wheel for dampness or wet areas that would identify where the leak is. If there is nothing evident, no spots on the ground where you park, etc, check under the dash where the master cylinder is attached to the firewall (INSIDE the car, not under the hood). Again, check for any evidence of leakage. If the master cylinder leaks, it can usually only be confirmed by looking under the dash, and because of the location, usually goes unnoticed. The fluid level may have gone down low enough to allow air into the system, which is causing the low pedal. Check this out asap, as this is too dangerous to drive. In an emergency situation, a panic stop wouldn't give you time to pump the brakes to stop.

Mar 25, 2010 | 2001 Ford Taurus

2 Answers

Brake pedal goes almost to the floor before taking effect. Checked for low hydraulic fluid and leaks. Found none. Fluid levels are normal. All else appears optimum.

you might have air in the system, if you have drums on the rear the slave cylinders could have a slight leak that is letting in the air, or, the master cylinder is doing the same, you can check to see if the carpet is damp inside under the dash where the brake pedal is, even if you are not loosing fluid it sounds like you have air in the system, if you are a diy person you might be able to bleed the air out but if you have a slight leak anywhere this will not make a difference as it will just get air back in the system again...hope this helps

Feb 19, 2010 | Chevrolet Venture Cars & Trucks

1 Answer

2004 holdern rodeo v6 clutch went to the floor was working all good before

The problem could come from the clutch master cylinder or the slave cylinder. The cause could be external or internal.

First check the fluid level in the reservoir. The reservoir could be independent of the brake system or using the same.

If the level is too low, air may have entered in the line and the hydraulic compression is affected. So first, adjust the level in the reservoir using recommended oil. (normally brake oil is ok).

Check for any oil leak starting from the clutch pedal following hydraulic circuit up to the transmission.
Your vehicule should have two clutch cylinders: the master and the slave.
The master cylinder is operated by your clutch pedal, it's located under the dash, fixed to the firewall and connected to the hydraulic line on the other side of the firewall. Check for any leak on the carpet, under the carpet and near the hydraulic connection. Pumping the pedal making that verification could help to detect leak. Then follow the hydraulic line going to the slave cylinder attached to the transmission making a visual inspection for leaks.
If for any reason some air entered the circuit, the line could be purged from air bleeding the slave cyclinder as you do bleeding brake component.
If there is no air, no leak detected then it's probably an internal problem that you can't see. Remove the cap from the reservoir, depress the pedal. If the oil is moving in the reservoir then the master slave is probably bad otherwise I would suspect the slave.
I'm not an Isuzu technician.
Some other Gurus could complement or correct my saying.
Hope it will help

Dec 20, 2009 | 2004 Isuzu Rodeo

2 Answers

Ford f250 diesel . front brakes come on when driving, don't have to use brakes. changed all calipers and hoses. if i bleed the calipers then they will start to release, sometime you can hear the brake...

sounds like a bad master cylinder, next time brakes are locking up , open bleeder screw and see if that releases brake at that wheel if it does then replace master cylinder, good luck.

Oct 13, 2009 | 2002 Ford F250 Super Duty SuperCab

2 Answers

Air/Hissing Noise from Brake Pedal

this noise is caused by a defective power brake vacuum booster, (big round thing behind the master cylinder) the diaphragm is leaking vacuum.

May 06, 2009 | 1995 GMC Suburban

4 Answers

Pedal goes to floor on 92 F250

I would strongly recommend checking your trucks R.A.B.S. (Rear Antilock Brake System) valve . It is located on the left frame rail just under where your left foot would rest . They can leak internally and exhibit the problems you are describing (loss of pedal , with no fluid loss) .
It is highly unlikely that a power booster would cause this , as a failed booster will show itself in these ways . 1) a hissing sound when you apply the brakes (indicates a vacumm leak) 2) rough engine idle/stalling when brakes applied (also indicates a vacumm leak) or 3) No power assist (brake pedal hard to push) .
If you do discover your hydraulic problem is in your RABS valve , don't forget to bleed it ,(there is a bleeder valve on it) and the rear brakes again after you replace it .
Hope this helps

Oct 31, 2008 | 1992 Ford F250

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