I’ve got a bit of a weird one here.
First, let me set the scene. I live in a rural farming community, & while most of our roads are bitumen, they’re a narrow ribbon of tar that threads in & out of a patchwork of fields & impenetrable jungle. So very narrow & twisty, with limited vision. I was taking my 67 Daimler out for a run yesterday, just to keep things lubed up. It needs a fair bit of work, which has been on the back burner lately, for financial reasons. But it runs ok, & I exercise it around once a week.
There are some tricky one lane bridges on my road, with very limited vision of what’s coming at you. And on the trickiest bridge I had to brake hard to avoid running head on into a Concrete Mixer, who filled the bridge. When I came to the T intersection where my road ends, I dabbed the brakes, only to have the pedal go right to the floor, with no slowing to be felt. I negotiated the intersection alright, but I then had around 2klms of a steep & narrow twisty road before the road levelled out enough to stop the car. How I didn’t end up wedged into the jungle (which was an option I was thinking of) I don’t know. But I made it, & so did the Daimler,
I thought I must’ve blown something in the hydraulic circuit. But as we loaded it on the recovery truck, I noticed there was no brake fluid anywhere. And when I got it home & looked at the brake reservoir it was full. So I had another jab at the pedal, & it initially had some resistance (raising my hopes momentarily). But on the 2nd jab it went straight to the floor, & continued to do that. The rod that connects the pedal to the master cylinder is still in place. I need to disconnect it & pull the master cylinder off its body mount, to see how that connection is. But I suspect that’s where the problem will be. I just thought I’d check in with the brains trust here, to see if anyone’s had a similar problem

 

First thought is that the brake fluid may have needed changing as it can absorb moisture from the air, get aereated and them boil up when used hard. When racing bikes I used Dot 5 synthetic brake fluid and flushed new fluid through the front calipers before going out onto the track every time, otherwise the lever would come in to the bar after a few laps of spirited use in hot weather.

I only use Dot 4 mineral brake fluid on the road and have no problems here in the UK. If it were my Daimler, I'd just strip and check the master cylinder and try it again - maybe a bit cautiously..It used to be that you can't mix Dot 4 and Dot 5 fluids without cleaning the whole system out but Dot 4 is quite adequare for the road...

Ray.

 

Thanks Ray. It has been a while since the fluid was changed. Looks like it’ll be first cab off the rank. I’ll let you know how it goes.🤞

 

No brakes at all would suggest the master cylinder or possibly the servo. It makes a change from the more usual problem, but less frightening problem, of the brakes sticking on.

 

I think your master cylinder needs to be rebuilt . If your servo was bad you would still have some braking capacity and your brake fluid reservoir would probably be empty.
Good luck !
Schmitty

 

Yes, it is the master cylinder. Years ago I had the same issue (brake pedal to the foot, zero stopping power) while going downhill towards a busy cross street (!). The cause? Deteriorated rubber in the cylinder unit.

 

Thanks for the input everyone 👍. i knew it’d have to happened to someone here. There’s just too much experience encapsulated here. Well done! I’ll book in to a brake specialist on Monday.
Off Topic: sov211’s post above about loosing his brakes on a steep hill, while heading towards a busy cross road, reminded me of a chicken game we played when I was young teenager at high school in Melbourne. Our pushbike ride home took us down a steep hill, which crossed a busy arterial road, & we’d dare each other to see who could cross it the fastest, without touching the brakes. Nobody died! In fact I don’t remember anyone getting hit. But oh the follies of youth! I’m truly amazed that I survived them.😜

 

Greetings scatcat,

Arr . . . I recall those roads around Atherton and Mareeba, but aren't you lucky to be spared the signature of the Bruce Hwy potholes?

Yep, master cylinder it is, but don't just let the shop fit a kit of seals. Have them check the condition of the m/c bore and, if necessary, re-sleeve with either brass or ss, then rebuild.

The most dangerous car I ever drove was a Series1 E-Type in the 80s, rarely driven and in showroom shine compared to ours which looked almost as great but was well driven and well maintained.. As mentioned, brake fluid is hygroscopic (attracts airborne moisture) which accumulates in brake lines and, if so rarely driven that it never boils off, will slowly corrode from inside out. That other E-Type blew a rear brake line (also downhill) and the more I pumped, the faster that car went. Miraculously, the car survived unscathed, as did my underwear, but the memory lingers on!

Cheers and best wishes,

 

Oh well, if you know the country. I live on Middlebrook Rd, & the road I turned right onto is now called The Beatrice Way (previously The Old Palmerston Hwy) I finally came to a halt around 200m across the Beatrice River Bridge. Check it out on Google Earth.

 

Our little roads and lanes here in East Anglia are quiet but the villages are all quite close together due to the productive farm land. Several of us used to do a lot of trail riding on old British bikes many years ago, which involves the trails crossing lots of minor roads as well as the main highways. We used to make our way to a pub on the coast, about fifty miles away, by keeping off the tarmac as much as possible..

Our mate Horry always swore blind it was safe to hammer across an asphalted lane without shutting off because the odds of hitting something crossing your path was negligible if you were going quick enough. I watched him do it on his old BSA M20 many times and maybe he was right but I never took a chance on it. He survived this Russian Roulette to pass on in a nursing home a couple of years ago.

Ray.

 

As everyone agrees, the master cylinder needs looking at and new seals. One thing I've noticed with rubber seals in hydraulic systems is that they can survive for decades so long as they are never exposed to air, but, once they are, old ones can fail quickly. It's certainly what I've experienced with the clutch slave and master. Given that, after you've done the brake master cylinder be aware that the servo might start to misbehave in the following weeks. If it doesn't go wrong in that time, it'll probably be OK.

 

LOL.

I did have to Google to refresh my memory of FNQ roads on the Tableland. That would have been a hairy ride with no stoppers. However, back to the issue at hand . . . and I agree with Peter's experience of the air to brake fluid interface which leads to both hygroscopic penetration of water vapour and deterioration of rubber seals.

My theory (and while logical, it is unproven) is based on competition experience vs road use . . . competition produces such high brake system temps that air vapour, even water itself, is boiled off and rarely endures to become a problem . . . generally, not so on everyday road cars . . . but worse still, those prima donna, showroom shine, never driven, but 40 year old pristine Princesses can have so much water dilution and internal brake system corrosion they are potentially lethal.


My worry is that looking for a spongy pedal is not an exclusive test . . . but running out of brakes is no fun. I was reminded of this recently when an ABS bleed of my 2006 X-Type was required. Needed quite some fluid to purge the entire system, but now have a rock hard pedal again.

Cheers and best wishes.

 

Thanks Ken, last name Oath?😜 (a little Oz Humour for a fellow antipodean)
On Topic: That’s why I’ll hand the job to a specialist. i want the job done properly, with all air locks banished. & you can’t beat the machine they have for bleeding the lines. It’ll be after Easter before I get a booking, so the old girl can sit safely in the shed until then.
Thanks again to everyone who contributed. The lack of any visible brake fluid leak had me baffled. But it makes more sense now. I’ll let you all know how “on the money” you were when the job’s done

 

I have had brake fluid problems before. Before replacing anything, my suggestion would be start with bleeding brakes properly with new brake fluid.

 

I know everyone here knows it, but there seems to be the odd 'professional' that doesn't. Properly bleeding (or changing brake fluid) begins with removing old fluid from the reservoir and filling it with fresh fluid.

 

Absolutely, Peter,

and, as an ex medical scientist, can I add that the first tool I reach for is a 20ml (or better, 50ml) disposable plastic syringe. Don't want that brake fluid dripping onto the body paint!

Cheers and best wishes,

 

After a working lifetime in the motor trade, mostly running my own truck repair business, I discovered many years ago that there are often up to several proper ways to do a job, as well as numerous wrong ways. Normally, everyone has an opinion..

Ray