PDA

View Full Version : Soft Pedals?



JohnnyO
10-17-2010, 05:52 AM
Hey guys, I need some expert opinions.... 66 midget, mk2, ....after I drive it for about 30-40 minutes with lots of stop and go, shifting and such, it seems my brake pedal gets very soft, to the point where I need to pump my breaks. The clutch pedal seems to get a bit week too, and doesn't seem to shift so smoothly and effortlessly as it does when it's first ran. I have bled my clutch and breaks with the handy dandy EZ bleeder so the lines are air bubble free. I haven't noticed any leakage around the bleeder valves on the wheel cylinders. I haven't taken off the drums on rear to see if there's any leakage inside. So do you think it might be the Master Cylinder??? Or something else? Or is this just something akin to our little cars?

JPSmit
10-17-2010, 06:24 AM
how fresh are your fluids? DOT3 absorbs moisture - may be that

abarth69
10-17-2010, 06:42 AM
What type of fluid are you using ?

We had the same sort of stuffing going on with a old car after talking with Dow they told us there are a bunch of different blends and they are all not the same, Some of them the viscosity is not the same and will give you soft pedal. If you have no leaks the master is fine switch brands.

Cheers

Mark

Guest
10-17-2010, 09:30 AM
how fresh are your fluids? DOT3 absorbs moisture - may be that
What type of fluid are you using ?

Some of them the viscosity is not the same and will give you soft pedal. If you have no leaks the master is fine switch brands.

Cheers

Mark


I agree, time to flush. I word of warning, a car with an old master cylinder (m/c) is sometimes prone to m/c failure after pumping the pedal with pedal travelling to the floor. Trash builds up over time behind the seal's normal path of travel. When the seal goes past that point (i.e pedal to the floor), it runs over that trash and scars the seals. If that happens, the pedal will never get firm even though you have clean fresh fluid with no air in it. It won't build pressure due to the ruined seals. It's worth a try to change the fluid, but you may already need a new m/c, however; it'll never build pressure v.s loosing it while hot like yours is doing so you may be o.k too.

Flush it and let us know.

Billm
10-17-2010, 10:27 AM
Possible help is to change the Dot3 fluid for Dot4 which has a higher boiling point (which sounds like the problem here).
BillM

JohnnyO
10-17-2010, 01:19 PM
I am using Dot4 fluid. I guess I'll try flushing.

JohnnyO
10-19-2010, 08:45 PM
Well, I flushed my brake fluid. Have all new fluid, 475 degree dry boiling point, the highest I could find on the shelves of local auto parts store. Went for a little drive today, noticed some change, still not satisfied with the results. Thinking about replacing the Master Cylinder. Anyway here's a little video of my drive, didn't buffer the mic on this little cheap camera so the wind noise gets a little irritating after a bit, you might have to turn the sound down after a bit.

<object width="480" height="385"><param name="movie" value="https://www.youtube.com/v/0EZ8dERw5OI?fs=1&hl=en_US&rel=0"></param><param name="allowFullScreen" value="true"></param><param name="allowscriptaccess" value="always"></param><embed src="https://www.youtube.com/v/0EZ8dERw5OI?fs=1&hl=en_US&rel=0" type="application/x-shockwave-flash" allowscriptaccess="always" allowfullscreen="true" width="480" height="385"></embed></object>

JohnnyO
10-19-2010, 08:45 PM
Well that didn't work, try this

https://www.youtube.com/watch?v=0EZ8dERw5OI

mightymidget
10-20-2010, 12:03 AM
a bad brake line ?expanding under load

JohnnyO
10-20-2010, 12:49 AM
Bad break line??? Yeah, never thought of that, how would I find out which one if any? Although one time while at a stop and foot on the brake pedal, the pedal just depressed, lost pressure, I pumped it up and it seemed to work fine after that. But that pedal just giving way makes me think master cylinder. I know there can't be any air in the lines, I pushed 2 quarts of fluid through the system, till I was sure everything ran clear and bubble free.

smaceng
10-20-2010, 12:58 AM
If the pedal initially is firm, but goes to the floor when constant pressure is applied, that is a sure sign that the master is leaking internally or even externally. That assumes that there are no external leaks.
Scott in CA

JohnnyO
10-20-2010, 03:18 AM
I don't see any signs of leaks on the outside, and the fluid level is always at the top. So do you think a rebuild kit with new seals and stuff would do the trick or do I need a whole new M/C?

JPSmit
10-20-2010, 06:21 AM
It's always worth trying to rebuild first - it's easy and WAYYYY cheaper, so, even if it doesn't work you're not out much.

Brake hoses wear out from the inside and if they are more than a decade old or original, it is time to change them.

Have the brakes themselves been done recently? Don't want to turn this into a complete "might as well" project, but, remember MG's motto - Safety Fast. Brakes are intimidating (to wienies like me at least) but not difficult or particularly costly

JohnnyO
10-20-2010, 08:53 AM
yes, brand new pads on front, rear shoes still have plenty of wear left on them. Front lines were replaced recently, not sure about rears. I'm going to rebuild and see how that goes first.....

Guest
10-20-2010, 09:50 AM
Johnny, FWIW, I hate doing things twice and you can never spend too much money on brakes. IIWM, I'd change EVERYTHING and you won't have to worry about it for a good while. Last place you want to worry about brake system integrity is approaching a stop light. If you piece meal it, you'll run yourself ragged. Just my $.02.

JPSmit
10-20-2010, 02:38 PM
Go for rear hoses and don't forget the third hose from the hardline under the body to the hardline on the axle.