Brake Pedal to floor!

Wouldn't you know it? Now that I have it running, I can barely stop!

Anyway, I was cruising around this afternoon and while leaving the post office, I'm waiting for traffic to ebb, when I feel my right foot slowly moving toward the floor. I pumped the brake pedal and it came back, but at the next stop, same thing. Took a few back roads home and checked the MC. The pic below shows the inside of the cap and the resevoir. In researching other posts, I see where "Mick & Susan" experienced something similar.

Seems that the seal just turned into a tar like gooey substance. I suspect it has also found itsway (kind of like the Blob) into my fluid as it appears darker than it should.

So, my question is, would this lack-o-seal cause the spongy, fading brakes? I have new brake line all around and had my wife pump the brakes while I looked for leaks. Nothing showed.

I know I'll have to bleed the system, but really want to know whether not having a seal in the cap could cause this or should I look elsewhere?

Also, would mixing types of brake fluid have this result? The brake lines and bleeding were done at a repair garage back in August.

Bill

Change the fluid and bleed the brakes. That fluid looks dark. The seal on the lid is not causing soft brakes. No leaks, wheel cylinders, master cylinder? If bleeding does not help then the master cylinder is suspect.

Did you replace or rebuild the master cylinder? It could be that the master needs bleeding but more likely than not, it needs a rebuild/replacement. Sorry. Basil

Don't go back to that repair garage, they should have known better. That brake fluid should have been changed.

Its true! The seals in the MC probably look like the one on the cap too! :-(

I was afraid of that. So, mixing different types of brake fluid could cause this? Now, I'm thinking that the wheel cylinder cups and any other rubber parts in the calipers may be turning to goo. Your thoughts on that?

I'm not knocking the garage that did the work as they might not have known which type to use.

In looking at the Moss catalog (pg 54 of the MGB/C)(nearly memorized) I can get a MC, dual line, non-servo, for $275.95. But then there is mention of a "Switch & Body" assembly, pressure failure, for $374.95. Do I need both at this stage of the game?

I did check the brake pedal and sure enough, the metal portion has a nice coating of fluid on it and there's a tad on the floor mat as well.

Is there a Master Cylinder "Jimmy or Jeff" on the forum?

Any other sources or recommendations welcome.

I take it this type of replacement is not for amateurs.
Bill

Sounds like brake master to me, talk to Gordon at the Bhive, I just bought one from him two weeks ago. www.bhive.tierranet.com/

Just buy a new one. From what I've read, new generally last a lot longer than rebuilds. Plus your core may not be rebuildable, and you don't really know until it's in pieces. Plus, it's a PITA, and a bit messy.

Talk to a Chris, or a Tony, and have them hook you up with a new M/C from Moss for cheap.

I am a rank amateur, and I replaced mine last winter with a helper (for bleeding). The helper only cost a case of beer. The trickiest part is getting all the hoses off without twisting them. The next toughest part is having them not drip bits of fluid on your paint. Be prepared to take off the whole pedal box assembly. It gives you a chance to clean it up, and give it a coat of paint. My pedals and whole pedal-box are sporting a nice shiney coat of black Rustoleum.

Age does that to the rubber. Mixing DOT3 with DOT4 is OK. Go with Castrol DOT4 when filling the system.

I was told once that mixing DOT3 & DOT4 are ok since they are made from the same glycol base and the only difference between the two is DOT4 having a higher boiling point. Is this correct?

DOT3 and 4 should never be mixed with DOT5 since 5 is a silicone base.

I Just checked my invoice from the garage and they used DOT 4. I have a new can of Castrol GTLMA which should be OK. I suppose it's possible that the previous owner at one time replaced DOT 3 or 4 with Silicone. That would be somewhat ironic.

So, is this just something that happens with age? And more importantly, just affecting the MC?

Also, need to know whether to order both the MC and the Switch & Body Assembly.

Thanks folks,
Bill

Sounds like some fluids got mixed and created that sludge which is common when using the DOT5. Switching back and forth only compounds the problem.

You could try just a rebuild before dropping a bunch of change on a new MC.

Read this:
http://www.xs11.com/tips/maintenance/maint1.shtml

If you need a new MC, I've been getting new TRW units for $165 plus shipping. PM me if interested. Basil

Why would you ever want to stop? Just keep driving. Paul

Paul,
Probably just stop to get it washed now and then! LOL.

Too much traffic in the Philly Metro area to avoid stopping once in a while.

Just engine brake then ebrake... :)

Just buy the O-ring kit to repair the switch and body assembly. Its not too complicated - just a couple of O-rings. The nbew replacement ins completely unnecessary!
As for the MC, just replace it. Many of us have rebuilt ours - several times - and the rebuilds just don't last!

well a good shop should know better than to mix dot 3 and 4 with dot 5 brake fluid......and lets hope they didnt put ps fluid or soemthing else in there by mistake then youll end up changeing everything that has rubber in the brake system. Ive seen it happen and totally messes everything up I would bleed the whole system till the fluid runs clear and go from there and also you can pull the cover from around the MC and see if the rubber boot where the rod goes is damp if it is the MC will need replaced or rebuilt

<<So, mixing different types of brake fluid could cause this? Now, I'm thinking that the wheel cylinder cups and any other rubber parts in the calipers may be turning to goo. Your thoughts on that?
>>

No. Dot 3 and 4 fluids are all compatible with each other. Dot 5 is the one that is not but no commercial shop would use it as a matter of course.

The best way to replace the fluid is to use a 2 ounce/60 cc (approx) plastic syringe with appropriate tubings, suck out the MC and discard, fill syringe with new and push it in at the RR wheel cylinder. Then suck out and discard what's in the MC, Refill syringe with new fluid, and push it into the LR. empty MC, Refill syruinge and push into RF, empty MC, refill and push in LF

Fluid should now be cleer in MC. If it is not, suck it out and discard, add more by pushing into one of the wheels. once you've got a little in the MC (over the holes) you can then fill conventionally.

do it this way and no bleeding will be required. Easily done by one person.

It could be the fluid, but it definitely sounds like the master cylinder. The same thing happened on my Jaguar. After then master cylinder was replaced, everything was like new. Castrol LMA is the best.

peace, Kyle

What's the Moss part number on that car wash? :)

smirkinwill Wrote:

I had a similar problem on my '67 B a couple of weeks back. Pedal to the floor. I bled the old fluid out until it ran clear with Castrol LMA. It stops okay now, good pressure on the pedal, but nowhere near as good as my '80 B. The pedal on the '67 seems spongy and not as crisp. The '80 got new rotors and pads last winter. Do I just need to do the same on the '67?

Hi Basil,
I was wondering if I could take you up on the offer you made Smirkinwill of a Brake MC at $165?
I've got that job in my near future for my '70B.
Let me know if you have one for me at that price and what shipping would be to:
Greg Moors
96 Church St.
Stouffville, Ontario Canada
L4A 4T8.

Thanks!
Greg.

There is more to the differences in Dot-3 vs. Dot-4 than just a difference in boiling point!!
It has more to do with different formulations due to the difference in materials used in the hydraulic sistems.

The reason is that unlike the american/Japanese/German auto industry that used synthetic rubber in the brake system seals, the English in their infinate wisom used "natural rubber. With the synthetic rubber brake seals you can pretty much use what ever type of brake fluid you choose (just don't mix types). With the natural rubber seals you have one choice and that is the Castrol/Girling DOT-4 LMA type... Reason is that DOT-3 will literally DISOLVE the natural rubber seals as it is formulated to operate with the synthetic rubber seals. I have seen this happen within minutes of contamination. I have also seen the results of a driver not realizing it till he HAD to stop, only to find that he had ZERO brakes! Most major auto parts store stock the Castol LMA fluid and if not can normally order you some from their local supplier.
Just don't let them or anyone else try to tell you that anything else will work just fine.

I had an experiance a couple years back, I needed some Castrol LMA fluid for my Rover 2000TC as I was going to rebuild the rear calipers..... stopped into an auto parts store in Spokane Wa. looking for some Castrol fluid.... they had zilch and the counter person told me that the regular Dot-3 would be just fine...lolol.... What suprised me was that the mechanic from the brake shop next door happened to be there...and tryed to tell me the same thing!! (and this was a major brake chain!!)

So just remember to double check anything you have done at a brake shop and make sure they understand that the only fluid you will accept id the Castrol LMA!!

Michael