Discussion
Morning Chaps, following LM trip think that my brake fluid needs replacing / topping up - brake pedal now quite heavy.
Not having much experience in the spanner sector & feeling that I should do more to my own car is it straightforward to just top up? Apologies if the question's so obvious!
Cheers in advance.
TC
Not having much experience in the spanner sector & feeling that I should do more to my own car is it straightforward to just top up? Apologies if the question's so obvious!
Cheers in advance.
TC
Brake pedal just feels heavier than previously; only noticed it coming back from LM Classic so assumed it was connected to the journey & a symptom of having run in very hot conditions (104 degrees through Rouen), although whether this would contribute towards the problem I don't know.
No concerns over the stopping performance as such so not a pad / disk issue far as I can tell, hence thought fluid best place to start & work back.
Car had a check over prior to the trip & was fine, no probs noted against the brakes.
No concerns over the stopping performance as such so not a pad / disk issue far as I can tell, hence thought fluid best place to start & work back.
Car had a check over prior to the trip & was fine, no probs noted against the brakes.
I don’t think brake fluid issues would cause a heavy pedal unless perhaps you had fluid on the friction material reducing friction. Could be an issue with the servo not performing as it should. May be worthwhile getting them checked out again if your concerned, as a lot of driving in hot conditions can certainly find any weak points on a car.
Rob.
Rob.
Check the vacuum hose from the plenum to the brake servo. I has braking problems which I eventually found was caused by a split in the hose. The brakes became a bit heavier and harder to stop until one day I was getting very worried I wasn't going to stop for a junction.
Bad brake fluid would cause sponginess in the pedal due to the fluid becoming compressible. Also if it boiled (hard to do unless driving very hard or your brakes are locked on) then you would get the same effect although worse and quite suddenly.
Bad brake fluid would cause sponginess in the pedal due to the fluid becoming compressible. Also if it boiled (hard to do unless driving very hard or your brakes are locked on) then you would get the same effect although worse and quite suddenly.
orange_dodo said:
Check the vacuum hose from the plenum to the brake servo. I has braking problems which I eventually found was caused by a split in the hose. The brakes became a bit heavier and harder to stop until one day I was getting very worried I wasn't going to stop for a junction.
Bad brake fluid would cause sponginess in the pedal due to the fluid becoming compressible. Also if it boiled (hard to do unless driving very hard or your brakes are locked on) then you would get the same effect although worse and quite suddenly.
Cheers. Thanks for the comment on the fluid. Wasn't hard driving to & from LM Classic, more the outside (& car temp) that got me thinking along that line.Bad brake fluid would cause sponginess in the pedal due to the fluid becoming compressible. Also if it boiled (hard to do unless driving very hard or your brakes are locked on) then you would get the same effect although worse and quite suddenly.
Your comments re the hose sounds similar to the current issue so reckon your onto something there.
Sorry if it's obvious but where do I find that to inspect?
Ok, took car out this am, first time it's been out for a week or so.
Brake pedal's very spongy & needs pressing quite hard after it's travelled approx. 50% of the way down to make the brakes start working.
Listened for hissing as per advice above; can't hear anything & there's nothing obviously wrong that I can see.
Got to go to a wedding now so I'll do some more investigation tomorrow.
Brake pedal's very spongy & needs pressing quite hard after it's travelled approx. 50% of the way down to make the brakes start working.
Listened for hissing as per advice above; can't hear anything & there's nothing obviously wrong that I can see.
Got to go to a wedding now so I'll do some more investigation tomorrow.
If the pedal is spongy it probably isn't the servo - if the servo fails the pedal goes pretty hard although you have to stand on the pedal to make it stop.
Try holding the brake pedal down and starting the engine - it should go down I think when the engine starts if its OK.
Just be careful - we are talking about a braking problem here
Try holding the brake pedal down and starting the engine - it should go down I think when the engine starts if its OK.
Just be careful - we are talking about a braking problem here
Barkychoc said:
Try holding the brake pedal down and starting the engine - it should go down I think when the engine starts if its OK.
Almost there 
Correct proceedure to test servo;
Engine off, pump brake pedal until firm & hold pressure on pedal, start engine & you will feel the pedal creep away from you as the servo assistance works. No movement in the pedal indicates servo unit/supply issue.
If the pedal, under pressure, creeps away from you before the engine starts you may have a defective master cylinder as the fluid escapes past its internal seals.
If the pedal is spongy then you either have air in the system or the fluid has absorbed to much water & is boiling too early. DOT 4 fluid has a minimum boiling point of 155C.
Bodders
see here first...
http://www.pistonheads.com/gassing/topic.asp?h=0&a... Braking System for TVR S Series Cars Updated
and here:
http://www.pistonheads.com/gassing/topic.asp?h=0&a... FROM SAAB TO FORD SERVO /MASTER CYLINDER (summary)
then look on ebay and you will probably get the Master Cyl complete with Servo for not much more than a tenner...
K
http://www.pistonheads.com/gassing/topic.asp?h=0&a... Braking System for TVR S Series Cars Updated
and here:
http://www.pistonheads.com/gassing/topic.asp?h=0&a... FROM SAAB TO FORD SERVO /MASTER CYLINDER (summary)
then look on ebay and you will probably get the Master Cyl complete with Servo for not much more than a tenner...
K
Edited by ketvrin on Wednesday 15th September 12:19
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