Brakes

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Thu, 08/11/2007 - 22:05
BIBERSG
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Joined: 09.01.2006
Location: SOMERSET

Hi just a quick question my 300gd has just failed it's mot on spongy brakes.So i've gone and bled them starting at the wheel furthest away from the servo, but they are still spongy. I also think the vacum pump is on the way out because it's taking longer to switch off, would this affect the brakes as i believe a pipe goes from the pump to the brake booster.
Many Thanks bibersg

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Fri, 09/11/2007 - 13:49
#1
fixwin38
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Joined: 09.07.2006
Location: northern ireland
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Re: Brakes

Hi try your brakes with the engine not running..then start the engine and try the brakes both times with the vehicle stationary repeat until you you can compare the pedal feel.if there is little or difference then your vacuum system may have a leak or a faulty vac pump.what is the condition of the brake fluid in the reservoir clear and slightly golden is good dark and opaque/muddy means it is contaminated with moisture if so flush the complete system including wheel cylinders and calipers and replace with .4 spec fluid

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Fri, 09/11/2007 - 17:57
#2
mgrays
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Location: Aberdeen Scotland
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Re: Brakes

To find out if Servo is not working .. stop engine, pump brakes until they are hard (ie use up the vacuum) .. then with your foot on the brake start the engine .. you will feel your foot sink as the servo operates.

Spongy brakes is air in the system or rubber hoses that are really dead (you would see them really swell by twice if you had perforated inner tubes and this would fail rapidly so is unlikely) .. bleed fast and low pressure then close down bleed nipples at wheels and bleed slow and under pressure.. then do little more fast/low pressure.. finish with another slow/high pressure. The speed/flow at low pressure may move stuff, the high pressure will cause the air to collapse to close to no volume and hence drag it out of hard places to bleed from (ABS systems are bad for this). Might as well use the 1 litre of fluid you bought.. it quickly absorbs water sitting on the shelf..

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Fri, 09/11/2007 - 18:15
#3
Michael
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Joined: 08.04.2006
Location: SNODLAND
Re: Brakes

I had the same thing on my 300gd(1983) pull the pipe off the master cylinder start the engine and put your thumb over the end of the pipe it should be sucked in, or put some engine oil down the pipe it should be sucked down the pipe and into the vacumn pump. You can also check the motor swich off the same way. Get someone to start the engine you put oil down the pipe to cause a vacumn seal then turn the engine off - it should stop straight away and not run on. ( I assume you have already checked the pipe seal at the joints by using washing up liquid)
Hope this helps

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