Brake Pedal Does Not Return When Pressed

[DonWheeler]

I own GT40 MKII P2171.
I have approximately 2500 miles on it.
When I press down on the brake pedal it does not return to its normal position; and it appears as though its stopping power ability has deminished.
I have examined to pedal assembly and do not understand how the brake pedal is suppose to return to its normal position. The gas pedal has a spring as a return mechanism.
Could some one please tell me how/what makes the brake pedal return; and provide some clues as what I need to do to correct this problem.

Thanks,
Don in Maine

 

[Jack Houpe]

Check your fluid level under the front bonnet.

 

[Ian Clark]

Hi Don,

Things to consider:

a)fluid level - without the entire system full from above the master cylinders to the calipers there's no way for the natural "pull back" of the caliper pistons to return fluid to the masters, thereby restoring the brake pedal to it's initial position.

b)piston bind in caliper bore, long shot but does happen, causes same effect as above.

c)gross misalignment of brake bias bar on master cylinders, well covered off in other threads.

d)friction, deflection or binding in the pedal tray. Something to check over, although I cannot advise on SPF specifics.

Any combination of these could be going on, don't fool around with brakes, call the factory or bring in a local race car prep guy.

Cheers

Ian

 

[Randy V]

The guys are right on here...

Also -

Check for some crap fouling the balance bar assembly.. If it does not float freely, it will bind up and not retract all the way.. One of the reasons I absolutely hate floor mounted pedals on racecars...
And I'm not too fond of them on street cars either...

 

[DonWheeler]

I removed the front clip to discover where the two brake master cylinder reservoirs are. I am however puzzled to determine just what the proper level of fluid should be.
There is a brass rim that with treads on it for the caps to screw into. The fluid in one reservoir is approximately 3/4" below the bottom of the brass rim. The fluid in the other reservoir is approximately 3/8" below the bottom of the brass rim.
Two Questions:
1. How is some one suppose to know what the proper fluid level is?
2. Assuming the level in one or both is low, what specific type of brake fluid should I add?

Most every thing about this vehicle is new territory for me; thus the reason for asking some basic questions, and asking for help.

Thanks,
Don in Maine

 

[Seymour Snerd]

1. How is some one suppose to know what the proper fluid level is?
2. Assuming the level in one or both is low, what specific type of brake fluid should I add?

1. Most cars have a marking on the reservoir. With the SPF/Original-GT40 arrangement, that's essentially impossible since their sides are not exposed. Even so, you'd think the user manual would cover that, wouldn't you? But, these being honest-to-God Girling resevoirs, whatever it says in your old '60's XKE/MG/Healy/Lotus/Lamborghini manual will probably work. .

2. The SPF user manual does say "If the reservoir needs to be topped up, use DOT 3 or DOT 4 Brake and Clutch Fluid."

 

[Rick Muck- Mark IV]

1/2 inch below top of canister is about right......

 

[DonWheeler]

I haven't made too much progress determining my brake pedal issue.

I added (topped off) the brake fluid to the level discussed earlier in the forum. This did not cure the brake pedal from returning.

I removed the four bolts that secure the pedal assembly and moved it forward enough to thoroughly clean (vacuum) the area/footprint where the pedal assembly resides. The area was relatively clean and free of any significant debris. This did not cure the brake pedal from returning.

I altered (adjusted) the brake bias bar settings to a few different places because I felt it may have vibrated out of its original setting. This trial and error procedure did not help so I put it back in the original spot.

While cleaning the area under the pedal assembly I found the pin that is depicted in the image below. This is most likely a long shot, but I am curious if this pin may have some thing to do with my pedal issue. Although it does seem to be a coincidence that this pin was found in the location where I am having a problem. The pin, or whatever it is, has cuts on each end that look like they were cut with cutting pliers. The pin also has little tick (penny) markings on it like ordinary nails have that depict their size. The pin is 1 5/8 inches long and its diameter is about the size of a ball point pen refill. It's interesting that it is shiny on one end and darker on the rest of it. If this thing has nothing to do with the brake assembly, I wonder if it is a portion of a rivet. Any, or please comment on this?

Again, please understand that I have little experience dealing with problems of this nature. Thus, my time consuming struggle to determine the problem.

Thanks,
Don in Maine

 

[Rick Muck- Mark IV]

That item is the "shank" from a Pop rivet. The "nicks" are from the jaws of the puller and you can see where the shank broke from the head insert of the rivet. Just trash left in the car.....

 

[Seymour Snerd]

d)friction, deflection or binding in the pedal tray. Something to check over, although I cannot advise on SPF specifics.

I think you could do a simple test that would determine whether the problem is in the mechanical front end, or the hydraulics: disconnect the pedal from the rod that goes into the master cylinder, and then see if the behavior is different. If the pedal then returns freely the problem is not in the pedal tray, etc., but is in hydraulic system.

If on the other hand it still mis-behaves you need to look for the source of friction or binding in the pedal and its attachment.

 

[Steve C]

Don,

I believe I can solve your problem.

Give me a call tonight >9:30 @ 781-273-3105.

Steve

 

[Seymour Snerd]

I believe I can solve your problem.

Steve -- what's your theory?

 

[Seymour Snerd]

... Just trash left in the car.....

I may start an online fastener store with the stuff I've found. I'm wondering about the bags of white powder though....

 

[Steve C]

A I discussed with Don during ph call yesterday AM:

Assuming this condition has developed over time (was originally OK)

Brake pedal bushing to cross shaft in need of lube.

Disconnect brake pedal from master push rods and flush out the bushing with WD40.

Fixed it for me but, as an added precaution I flushed out old brake fluid and added a return spring to the brake pedal.

Works great.

Steve P2125