Now here's a scary one. Yesterday I drove the jag pretty much all day in stop-start traffic. Used the brakes a lot (first trip like this since I got it).

Assuming the brakes get hot, I am getting intermittent no brake (pedal to the floor). If I pump it, I get brakes back after two pumps to full capacity.

When I let the car cool down brakes are back.

Master cylinder? I am thinking no because with a worn master cylinder, the condition would be repeatable on a hard stop and wouldn't be happening only when hot?

Water in fluid? I'm thinking unlikely since I flushed most of the fluid and refilled with new DOT4.

Any thoughts guys?

Thanks in advance.

 

I was ready to jump up and say "Contaminated brake fluid, contaminated brake fluid!" but you spoiled my opportunity :-)

I wouldn't do anything without a good visual inspect of calipers and hoses to see if anything pops out at you....although some faults might not be readily visible.

Lacking any concrete visual clues I'd go with a master cylinder. My experience is that m/c failure modes do not always follow my logic or anyone else's.

That said, and because spending money that isn't my own is always easy, it might be time to consider a full brake system overhaul. I've seen a number of old Ser IIIs still on original calipers, m/cylinder, and hoses. Just something to think about.

Cheers
DD

 

Thanks Doug. It does seem like it's contaminated fluid, but I'm skeptical since I flushed a lot of it out and replaced with new.

Today I drove the Jag to work (8km, 5mi) no problem, perfect brakes! Damn. The brake fluid level is slightly low and no leak I can find. Everything else seems fine.

I guess I could start the process of rebuilding the entire braking system.. M/C is as good a place to start as any?

 

Not my car but my 'generic' test of master cylinders is to press hard on the brake pedal with the engine off and see if the pedal slowly creeps down.

 

I would not dismiss contaminated fluid just yet. Oliver mentioned flushing a lot of it out.

That implies some old stuff still there.

So, would think of a MC bleed in situ. That would assure fresh fluid at the head of the system. Then selecting the caliper nearest the MC, bleed it and work ones way back to the last one. Watching for bubble free clean fluid all the way back and making sure the reservoir is full at each bleed. A power bleed would be nice if available. An assisted bleed by mitty vac would be my next choice. And, lastly, a bleed with engine running to provide boost at the MC.

And, I do not discount the bleed down check suggested or the physical outward inspection seeking obvious anomalies.

Now, if I can figure out why my repowered chipper throws a belt at startup....

Carl

 

As this symptom happened to me, I will tell you what it was for me. Many years ago in the mid 90s with a Series 3 I had a couple of instances of 'no/part pedal' and just ignored it, (very foolishly !!), until one day going down south to a holiday with my family near Bournemouth, on a steep hill found I had no brakes. A rapid pumping restored braking, but having got a brake back, I then turned into a garage a short distance ahead and stopped. On getting out of the car white smoke was pouring out of the rear wheelarches. I expected to have to be recovered home, but there was a mechanic present, (this was a Saturday, so unusual). They got it up onto a ramp, and soon told me I had a seized piston on one of the rear calipers. This had heated up the fluid so it boiled-up. When it cooled down, they managed to free-up the piston and I carried on to Bournemouth but fluid continued to leak all that week and I had to top-up every day. Outcome was I had to have the rear brakes rebuilt, and a new diff oil seal, the heat had fried everything. I think I got service exchange calipers, new handbrake calipers and parts etc.

So, you may have what I had. The rear brakes are notorious as they are so hard to get at that servicing tends never to get done until something fails, as happened to me.

 

Thanks guys. Fraser, I will give each wheel a good inspection on the weekend, specially the back. I did not notice any irregularity (i.e. smoke) on the day of the incident.

Steve, your test proves "negative"...

In any event, I have bought a master cylinder kit, so I will rebuild the master cylinder as a matter of precaution. Also, what I see at each wheel will dictate what I do next. I will also flush the fluid again when I do the master. This should hopefully eliminate any remaining contaminated fluid.

Needless to say, the problem has not resurfaced! Then again I have not driven it on that sort of long stop-start traffic trip since.

 

My experience is that things don't get better on their own. I had many weeks even months between "events". It was the last one that counted the most !!

 

I hate to say it, but I think you're playing with fire. Park the car until you can inspect the braking system and determine what is likely causing the problem! It's not worth hurting yourself or someone else. If everything at all four wheels checks out, I'd start with the master cylinder.

Another thing that has not been mentioned: These cars have the modern-style front/rear split braking systems. The front brake system and the rear brake system are largely independent. If you have a failure in the front brakes, your rear brakes should work, etc. If you had a total brake failure, there's a chance that one of your systems, probably the rear, has already failed or is badly compromised. If you had a little bit of brakes (not a total failure) then take a hard look at the front brakes first - they do the vast majority of the stopping.

BTW, just throwing it out there - any chance you hit the gas and brake at the same time, causing the car not to stop?

 

Hi FastKat,

I know the severity of the issue believe me. Nothing scarier than pushing the pedal and nothing happening!

The fact that there was no brakes at all on first pump makes me suspect (in this order):
1. Master Cylinder
2. Something seized (probably on the rear) and boiled the brake fluid

Don't forget that after two pumps, the brakes were back to 100%.

Strange. In any event, tomorrow morning I am inspecting at each wheel, rebuilding master cylinder and flushing the entire system, putting in new fluid.

 

My money would be on a seized rear caliper piston, maybe more than one.

 

Hi Guys,

That problem has not come back since the first time, however today I refurbished the master cylinder and inspected the rest of the brake system. The rear end (thank god!) seems to have been done recently enough before my purchase. Discs / Rotors still perfect, pads have a lot of life. Front end is fine, no leaks, discs/rotors ok, pads need replacing in the next 5,000km / 3000mi.

Master cylinder, the seals and rubbers were quite worn and it was leaking from the top seals by the reservoir. So let's hope I've resolved this issue.

Master cylinder is REALLY easy to remove, rebuild and refit.

Some pics:

1. Removal (2 bolts and the brake lines)


2. Removed (traces of some really old grease)


3. Rebuilt and refitted

 

Good work. In my early years, my cars had no or lousy brakes. I was good at down shifting, applying the pedal and the handle, etc. It wasn't until about 1950 that I finaly got a car with brakes that worked properly. A 41 Studebaker Champion tudor. It had hydraulic brakes all it's predecessors were rod or cable operated. The cable cars were the worst. Except for my first car, a 23 T. special techniques need there for the single band on the transmission. Oil impregnated webbing!!

But, that was a different world. Today, no way would I drive those cars on today's roads amongst today's drivers!!!

My 57 F150 blew a front hose at work on Wilshire Blvd in LA. Using my past skills, I managed to drive home in the San Fernando valley. surface streets, only. It's granny low trans allowed that to happen!!

Once, I drove my present Jaguar into the driveway and applied the brakes. Wowee, the PS and PB were out for just an instant!! Why, I dunno.

When I first got my jaguar, the braking was marginal. New pads on the front, because of a horrible growl and they were far better, but not on a par with my Jeep. Then the rear calipers started to weep. Replaced with rebuilts and the braking is now as good as it gets. It acts like ABS. No wheel lock up, it just squats and stops. I say a combo of discs all the way around in top nick and good tires at proper PSI's.

A far cry from the old days!!

OTH, at times things do fix themselves!!! I got out my 2 cycle leaf blower to work on patio revitilazation stage II. The pull cord would not behave!!! So, I used my trusty, but less energetic electric blower. Job. done. Then, I took the gas blower into the shop and put it on the bench to see how to access the recoil start mechanism. Oh, oh, buried good!! So, I tried it again. Wow, it is back in and working. Got it to fire and for good measure swept the shop and driveway, the easy way!! Probably my share for a decade or so of it fixed itself!!

Now, I am nursing a really aching back. I don't always realize I am no longer in my 70's!!

Carl