• The Roadster Factory Recovery Fund - Friends, as you may have heard, The Roadster Factory, a respected British Car Parts business in PA, suffered a total loss in a fire on Christmas Day. Read about it, discuss or ask questions >> HERE. The Triumph Register of America is sponsoring a fund raiser to help TRF get back on their feet. If you can help, vist >> their GoFundMe page.
  • Hey there Guest!
    If you enjoy BCF and find our forum a useful resource, if you appreciate not having ads pop up all over the place and you want to ensure we can stay online - Please consider supporting with an "optional" low-cost annual subscription.
    **Upgrade Now**
    (PS: Subscribers don't see this UGLY banner)
Tips
Tips

TR6 Brake Pressure Problem

SherpaPilot

Jedi Hopeful
Country flag
Offline
1972 TR6, stock brakes: I recently flushed my brake system and replenished it with Castrol Dot 4 fluid. Each corner was properly bled with great results and good pedal pressure. After installing each wheel and putting the car back on the ground, I started the engine and warmed the car up. With the engine running at normal idle rpm, my brake pressure seemed to drop considerably. After shutting the engine down, my brake pressure returned to normal pressure. So, I am now thinking something is wrong with the booster. All vacuum lines are new with no obvious leaks. I believe this drop in pressure is due to a faulty booster but it doesn't make any sense to me. One would think that the loss of the booster would make the pedal more difficult to depress and not the opposite.

Does anyone have any experience with this happening? I am not sure what my next move will be with this brake system. Could this be vacuum related???? Maybe I need to plug the vacuum line and see if there is any change without the booster..
 

TomMull

Darth Vader
Silver
Country flag
Offline
If by "brake pressure seemed to drop" you mean that it becomes easier to push the pedal, that's what the booster is supposed to do. If the pedal does stop at some reasonable point above the floor and holds there, I'd say you are good enough to test drive at least and you may find that it will stop fine.
Tom
 

poolboy

Yoda
Country flag
Offline
What's normal is "feeling" the brake pedal drop a bit when the engine first starts up and after a pump or two "feeling" the pedal rise a bit when the engine dies..
"feeling" meaning resting, not pressing your foot on the brake pedal.
If you don't feel those movements, that's usually an indication of a problem with the servo.
 
OP
SherpaPilot

SherpaPilot

Jedi Hopeful
Country flag
Offline
Hey guys thanks for the responses. I have owned this car for about 30 years and had always thought the brakes could be a bit better. The reason I dove into this brake issue was because I flushed my brake system and re-serviced with Castrol. The bleed process went well (did it twice). It just seemed to me the pedal distance (from static to floorboard) decreased when the booster was energized with vacuum just like Poolboy stated. But it also seemed that brake effectiveness did not occur until the pedal was pretty close to the floorboard. With the engine off and obviously no vacuum, it felt more like normal. I don't know, maybe its just my imagination but then again, this booster is the original from 1972. Maybe I just need to replace the booster. I wish Triumph had eliminated the power boost system and designed a simple dual master cylinder instead. If I had extra cash, I would upgrade the system, but other things are more pressing. Thanks again for your comments, they are appreciated.
 

malbaby

Jedi Warrior
Country flag
Offline
Strange symptoms.....Firstly, it would be interesting to see what the outcome is by disconnecting the vacuum line to the booster.
Another consideration is the length of the push rod connecting the booster to M/C.
 

TomMull

Darth Vader
Silver
Country flag
Offline
Another consideration is the length of the push rod connecting the booster to M/C.
Good thought and I think that is adjustable.
Tom
 

TomMull

Darth Vader
Silver
Country flag
Offline
On our Honda, the brake pedal goes down when you start the car. It's normal.

Yes, I tried to indicate that in my initial reply but there is a limit that the pedal should safely "go down" when vacuum is applied. From what SherpaPilot seems to be saying is that his pedal goes beyond that limit "pretty close to the floorboard".
Tom
 

malbaby

Jedi Warrior
Country flag
Offline
Must be a master cylinder rubber seal problem, it is not booster related.
Fit a new M/C or have yours reconditioned.
 
Similar threads
Thread starter Title Forum Replies Date
6 E-Type brake light pressure switch location Jaguar 5
B TR2/3/3A Bubbling in brake reservoir. No pressure in lines Triumph 5
AHS TR2/3/3A Residual brake pressure valve - how much front wheel drag? Triumph 18
Gerry M TR6 Brake warning light & oil pressure light stay on Triumph 2
TomChar TR6 '74 brake failure / oil pressure / ARV wiring question Triumph 19
R Vanishing Brake Pressure Austin Healey 18
smaceng TR6 TR6 brake pressure balance valve Triumph 2
jhorton3 Brake Pressure Sensor Options Spridgets 3
B T-Series MGB Brake Pressure Switch MG 2
P Changing Brake Fluid & Brake Pressure Switch Austin Healey 17
S How to test a Brake Pressure Failure Switch Triumph 7
S homemade brake pressure bleeders Triumph 9
hondo402000 TR6 71 TR6 Brake warning light and oil pressure light Triumph 6
X T-Series Brake pressure failure switch MG 4
JodyFKerr Spitfire Brake pressure sensor leaking ['78 Spitfire] Triumph 6
X T-Series Brake pressure failure switch MG 3
glemon Brake Pressure Switch Wiring Triumph 2
Johnny What does "excessive brake fluid pressure" mean? Austin Healey 21
Randy Harris Brake Lights Work Only With Heavy Pedal Pressure Austin Healey 12
jjbunn T-Series Brake Pressure Warning Switch MG 10
weewillie brake pressure warning lamp Spridgets 12
angelfj1 TR5/TR250 TR-250 Brake Differential Pressure Valve/Switch Triumph 3
cutlass29 Spitfire spitfire mk3 '70 brake pressure switch pdwa Triumph 1
Woodie brake pressure failure switch Spridgets 15
ecurie_ecosse Brake pressure failure switch. Spridgets 8
S TR2/3/3A brake pressure switch tr3 Triumph 3
T brake pressure switch assembly Spridgets 6
F Disc Brake Shimming Austin Healey 8
PDIGIO_6x3 TR6 BRAKE TUBING KITS Triumph 6
L Red Rubber Brake Grease Austin Healey 2
Martinld123 Emergency Brake Doesn't Release Austin Healey 9
71TR6 TR2/3/3A Aftermarket brake and clutch master cylinders - black extension? Triumph 6
petnatcar Aluminum Brake Fluid Reservior Austin Healey 5
M Brake Servo Austin Healey 2
E TR4/4A What Flare to put on a TR4 Brake Line Triumph 2
scottkilpatrick TR4/4A TR4 Rear Brake Drum Removal - Basic Question Triumph 16
T Spin-On Oil Filters for Cars with a Brake Servo Austin Healey 3
J MGB BRAKE VALVE ? MG 11
G Brake Light Switch Failure Austin Healey 24
B Rear Brake Cylinders Austin Healey 4
K TR2/3/3A Brand new brake caliper question... Triumph 8
K TR2/3/3A Front brake hub removal to access Vertical Link bolts(screws) Attached pictures. Triumph 1
K TR2/3/3A How to remove the front brake hub from the brake disc? Triumph 11
J TR2/3/3A Brake Line Flares Triumph 8
Frameman 1949 Brake Bleeding Austin Healey 0
Racer-X- Frame mounted power brake pedal/booster/master cylinder kits for RHD cars? Restoration & Tools 1
Chrisc9 TR6 TR6 brake light Triumph 6
L T-Series Another brake prob. ? MG 12
S TR2/3/3A brass fitting from a steel brake line Triumph 2
Sopwith_Camel MGB pulsing brake pedal MG 10

Similar threads

Top