fearofweapons Posted August 8, 2014 Share Posted August 8, 2014 ... after replacing all brake lines, hoses and rear cylinders/pistons. Frankly I think that the very shoddy brake performance before was masking the slow fall of the brake pedal when depressed. So am I looking at servicing or replacing the master or servo brake cylinders? Which would you say is the prime suspect here? The Servo is a NRC4775 Type 50 unit and the service kit is, I think, 18G8951L. It would seem there is a master cylinder repair kit, AEU3015, should I do that as well or instead? The vehicle is a 1989/90 110 SW TD. Just to be sure I have bled the brake system through two weeks/1,000 miles after the replacement work on the lines, hoses etc. many thanks, Rich Quote Link to comment Share on other sites More sharing options...
Adam001 Posted August 8, 2014 Share Posted August 8, 2014 It's the master cylinder, repair kits can be fine so long as there is no internal corrosion on the bore. Quote Link to comment Share on other sites More sharing options...
FridgeFreezer Posted August 8, 2014 Share Posted August 8, 2014 Check the one-way vacuum valve on the servo, a cheap fix if it's that. Quote Link to comment Share on other sites More sharing options...
fearofweapons Posted August 8, 2014 Author Share Posted August 8, 2014 Gents, many thanks for the replies. Re the vacuum valve - any suggestions on how to test it please? regards, Rich Quote Link to comment Share on other sites More sharing options...
cackshifter Posted August 8, 2014 Share Posted August 8, 2014 You're not going to like this... gently pull it out of the servo and see if you can suck air in through it. Alternatively, take it out of the servo and the pipe, and see if you can blow through it towards the servo (max 1 bar). I 've had them fail and it's normally obvious when you try. A servo/vaccum failure shouldn't produce a sinking pedal though, just a very hard ineffectual one. Probably master cyl. Quote Link to comment Share on other sites More sharing options...
fearofweapons Posted August 8, 2014 Author Share Posted August 8, 2014 ah OK - the pedal is not hard or ineffectual so I'll stick with the master cylinder service as a first step. Quote Link to comment Share on other sites More sharing options...
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