Hi

Have a problem with my xtype 2.5v6 auto. Noticed about 2 weeks ago braking had become very spongy most of the time, but sometimes normal braking. Fluid was about 1cm from max fill line so topped up. Problem continued. About a week later the fluid resovoir was empty. Filled again. Problem getting worse, as sometimes no braking at all, but more often spongy. Mechanic says he cannot see a leak anywhere. Suggested replacing master cylinder.

Any ideas or advice greatly appreciated.

Thanks

 

suavegarve, the mechanic is more than likely correct. You can confirm this by simply removing the vacuum line that runs from the top of the intake to the brake booster. You can then take say a Q-Tip or the like and swab the inside of the line. If you are getting a clear fluid out of that line, odds are, it is brake fluid and this will confirm their diagnosis.

The other trick I would have you try is to get inside the car and stand on the brakes as hard as you can with the vehicle parked. Hold the pedal for say a minute or so. If the pedal reaches the floor, let it come up and then stomp on it again. The big thing is to apply as much pressure as you can (don't go Hulk on this) and keep it applied. You can then look at each of the rims for signs of fluid and also do another look at the vacuum line from the brake booster. Probably wouldn't be a bad idea to look at the ABS module (behind the passenger head light). If you see fluid, odds are your leak is right in that general area and this will atleast give you a good place to start looking. Remember, fluid will pretty much travel straight down and you can normally follow the fluid line back to where it is starting at.

 

Thermo{ read my post on: OFF TOPIC, You will like it.

 

Thanks, I'll get to work checking those out. One thing though, do you have to replace the master cylinder and the booster, or is it likely to just need the master cylinder replacing?

 

Suavegarve, you normally buy the two as a pair. They are often used interchangeably for each other when they are a combined unit. Odds are, you would only need to replace the master cylinder as the brake booster is really nothing more than a big rubber diaphragm that gets vacuum applied to it that adds force to the operating shaft of the master cylinder.

 

Hello Suavegarve ,

If brake fluid has entered the booster , and I agree with Thermo that it may have done ,
you need to know that because the recommended brake fluid is DOT 4 , it is a GLYCO based fluid , and unlike the rubbers or seals in the brake master cylinder it is NOT compatible with the rubber Diaphragm in your booster .

The Diaphragm will soon swell and deteriorate , for this reason you must replace or repair the booster assembly at the same time you replace the Master cylinder .

Cheers ,

 

Thanks guys for the advice. Just remembered something else the mechanic said. He mentioned that you cannot bleed the system without connecting it to a computer, assuming he meant the service/fault finding machine he has in the garage. Would this be correct, as I was hoping to do everything myself?

 

suavegarve, you can vent this system without the use of a computer. I have done it more times than I care to admit to. This car is not any different than any other vehicle you may have worked on. If you replace the master cylinder/brake booster, you will be draining the whole system (no way around it). All you will do at that point is fill the reservoir with new fluid and let as many air bubbles come out as possible. Top off the reservoir. Next find the tire furthest from the ABS unit (this should be the driver's side rear tire for you). You will open the bleed port and vent the brake caliper like you would any other. Refill the reservoir. Next vent the passenger rear. Refill. Vent the driver's side front. Refill. Vent the passenger front. Top to the proper level.

The big thing is at first making sure that you are keeping the reservoir from getting empty. If this happens, you have to pretty much start the venting process all over again. Having a second person may be helpful as they can ensure the reservoir remains adequately filled.

 

Thanks again and sorry for all the questions. When you say vent, do you mean bleed? And will the system drain just by removing the master and servo, or do i need to open each brake port as well.

 

suavegarve, vent/bleed, same thing. You are removing the air from the system.

The system will not vent/bleed itself. You have to move fluid from the reservoir to a vent port to push the air out of the system to make it work properly.

 

The system won't drain by removing the brake master cylinder

But you do need to " bench bleed the M cylinder " , it can also be done on the car
once assembled .

This will make it much easier when you do the final bleed at the calipers .

cheers

 

Finally got my hands on a master and servo, I'll be attempting this at the weekend so prepare for more messages. Thanks to all for the help so far.

 

Hi, what does bench bleed the m cylinder mean

 

It means to use a vice or similar device to hold the new master cylinder, then add fluid and press the piston into the bore to remove air from the master cylinder prior to fitting it to the vehicle.

 

Exactly what NBCat said .

Air trapped in the M Cylinder can not be bleed out via the Caliper

It's easy enough to do , if you need help just ask .