I read that the fluid takes up water over time but already two places refused to change the brake fluid saying that is unlikely to cause squishy pedal feel since it's a closed system that hasn't been messed with, and changing it can cause new issues like breaking the bleed nipples.

My fluid is likely original (15 years old), the last mechanic said some cars go 30+ years on the same brake fluid, no reason to change it.

Thoughts?

 

Spongy feel is because something is giving in the braking system. Usually it is air. If a lot of moisture has gotten in the fluid, it may have boiled, and this gas also can cause spongy feel. Finally, if the rubber hoses have deteriorated, they can expand with pressure and cause the same feeling.

Hoses are easy to diagnose, look at the hose while someone stands on the brake pedal. Expansion should be very minimal on all four.

If the fluid has never been bled, the bleeders are probably fine. What gets people in trouble is if during bleeding some mechanic monkey torques the bleeders - then next guy usually has trouble.

I would change the fluid carefully. If a bleeder is really stuck, don't try too hard to loosen it without considering ramifications if it breaks. At 16 years old, it could probably use new brake lines anyway - and to do the brake lines you need to be able to bleed.

At 16 years your brake fluid likely looks like stout. It should be light amber clear. The deep color is from rust from moisture in the system.

-Mike

 

find some better mechanics/places. what they said is 100% BS. it is not a fully closed system since it's vented and 15 years old brake fluid is at least 10 years too old

 

If a shop is refusing to do a brake flush because it's a "closed system" then they're either afraid to work on a car with a cat on the hood, or don't know what they're doing. I suppose the bleed nipples could break like TXE said, but only if they're severely corroded or someone overtightened them in the past.

The only other thing I could think of is that I've read on some cars with ABS the module needs to be accessed to lock the abs solenoids "open" in order to encourage bleeding of the ABS unit itself. I think this is mostly only needed in a new empty system or if there's air in the ABS module, if doing a flush by pushing out the old fluid with fresh fluid it shouldn't be needed (?).

Fluid does deteriorate, mine is going a bit green and in need of replacement. You can pull the reservoir cap and take a look, if that's green or dark colored then the rest of the system is probably not better off. Make sure to use DOT4 fluid and not DOT3 if you or a shop are doing the service.

 

All good and valuable info - thank you

So the likely culprits are bad fluid or old stretching brake lines?

The pep boys website says Master cylinder, but their shops tend to be the biggest rip off joints - any likelihood of that? How would you know if it's the master cylinder causing this? The power brakes certainly still work when you apply more pedal force...

 

Given the age of the fluid, I'd start there, but check the brake lines first anyway - it's easy.

I doubt it is the master cylinder. Power brakes have nothing to do with it, it just provides an assist and it is provided by the vacuum booster, not the master cylinder.

-Mike

 

A few years ago I blew a factory stainless steel brake line on my 03 XJR win Brembos at a car control school. I elected at the time to move to rubber lines and I was able to retrofit factory rubber lines in place of the SS lines.

It took a couple of weeks to figure out what to do and source parts. In that time, the brake system drained completely via the disconnected lines (master cylinder reservoir bone dry). Got the new lines, reassembled everything and filled the fluid using my pressure bleeder. Filling went quickly and no issues - no need to cycle the ABS pump or anything.

On my previous BMW E36 street car that I drove at the track, and my E36 race car, I bleed/change the fluid the same way and I've never cycled the ABS pump.

I don't think this "cycling" is required because plumbing starts at the master cylinder and routes to the calipers through the ABS unit. Any air in there is going to get pushed out by the bleeding process. I also don't recall "abs cycling" instructions in the JTIS CD.

-Mike

 

You've read correctly that brake fluid (DOT3/4) is hydrophilic but for some reason, the misconception above is way too common. Sad to hear a mechanic is so misinformed.

I restore vintage cars as a hobby and I wish I had my money back for every used brake caliper, master cylinder, wheel cylinder, clutch master or slave cylinder that I've opened up and found to be too far gone. Besides the reservoir not being sealed against atmospheric humidity, water can still get in through the calipers too. An interesting design consideration is that on some older cars, the caliper piston seals were flared like a skirt around the piston such that the fluid pressure expanded the seal against the cylinder wall, thus holding the fluid in. However, driving through puddles with the brake pedal relaxed, water could actually be siphoned into the system by a warped rotor pumping the piston back and forth with no pressure behind it to expand the seal skirt. They started in the 80s to change to tighter tolerances and o-rings, but if water gets in past the dust boot, then it can still get siphoned into the system, just not near as bad as older designs.

Your problem very likely is air in the system as mentioned. If its the original fluid or very old, then the bores of the master cylinder and/or calipers will have rust pitting. Tiny little bubbles of air can get in as the piston seals move back and forth across the pits. Not to mention water becomes a gas when it boils and those brake calipers can get pretty hot. You may say well I don't see it leaking, but a single drop of fluid escaping is hardly noticeable compared to big effect on pedal feel you get from a single drop of compressible air getting in.

If you're not going to DIY, then you may need to have a shop dismantle and inspect the master cylinder and calipers. If the pitting is not too bad, then they may be rebuildable by simply honing the cylinder bores and replacing the o-ring and dust seals. If the pits are too large, then the standard operating procedure is to replace the parts. On antique cars for which new parts are unavailable or very expensive, we'll have a machine shop bore them out larger and either use a larger piston or press in a stainless steel sleeve, the later being the ultimate solution for longevity.

The recommended service interval for most cars with DOT3/4 brake fluid is two to three years. The system should be flushed on schedule religiously to prevent corrosion. You can try just having the system flushed. I suspect it will help a whole lot, but the question is for how long. Being a safety concern tho, I'd get it checked out.

 

Brake fluid recommended to be changed every 2 years, I'd certainly start there and see how it goes
Jim

 

Every 2 years regardless, even if the car has only done 10 miles.
I'm frankly shocked a mechanic has said he'd be happy to have brake fluid in the system for 30 years!

 

Yep me too Stu, I get the impression that his wife's mother's best friends auntie may be married to a mechanic and that's where he's getting the info from.


Jim

 

Mechanics in NYC tend to be like Cuban mechanics, whatever the heck method keeps the car on the road is good enough, lol, for better or worse - frequently you get much less costly repairs than anywhere else in America, but lower work quality too.

 

There are a lot of Mechanics on Long Island that won't even LOOK at my car. They won't go anywhere near Jags.
Hence: I've become pretty good at fixing most stuff my self with the help from my "Friends" on this forum.
I've lost count of how many times my friends on this forum have helped me.

As the song goes "I get by with a little help from my friends"..............

 

In my XJR things were spongy after my last brake job (and fluid change) until I did the whole "point the bleed bib at the sky" trick. The calipers have a bleed port that placed slightly below an area that catches and traps air. You have to remove the caliper and rotate it slightly to get the last of the air out...

Or at least, that's what worked for me... I remember getting the car all buttoned up and bled and it was still spongy. I went nuts trying to bleed them, then I read a post somewhere here on the forum mentioning the air pocket.

Pulled everything apart, pointed the little bleed bibs at the sky, bled out the last of the air, and she's back to tight.

 

Shop #3 just said the same thing, sigh, went as far as saying this car never needs to charge brake fluid unless it is contaminated, and changing it can end up causing damage to the master brake cylinder (not sure how, from the pumping/pressure??) Sounds absurd to me, is there any truth to this at all?

The prior shop #2 mentioned if the bleed nipple breaks you may need to change the whole caliper - does that sound right??

 

If the brakes are bled using the two man method, where one guy pushes on the brake pedal the MC seal can be damaged if the brake pedal is pushed to the floor because the piston is pushed deeper into the bore than normal and that part of the bore may be rough. The solution is easy, use a pressure bleeder or just don't push the brake pedal to the floor.

I can see a broken nipple causing a trashed caliper. I broke a brake line off in a caliper because the previous mechanic monkey torqued it. Could not get it out without trashing the caliper. Replacing a caliper is not the end of the world. If this happens, source a used one and move on. This is what I meant in my first reply that if a bleeder is particularly tight to have contingency plans before going at the bleeder with more force. In most cases, the bleeder will come out intact.

Who knew NYC mechanics were such pansies. I can't believe I'm suggesting this, but if all you want is a brake fluid flush, perhaps try the Jaguar dealer. It is only an hour's labor and even at Jag prices, the fluid can't be that bad. I would at least ask.

-Mike

 

My dealer does it for $150 .. take in on old car Wednesday and it's cheaper. The DOT 4 in the Jaguar -- every two years. The DOT 3 can remain longer. Most Japanese cars call for 5 years -- most USA cars don't include it as a maintenance item. I ran a bottle of the Jag fluid through mine when I did the rear pads. Some dealers suck the tank -- fill and bleed out the lines -- others use the BG flush machine.

I have a pressure flusher -- I have been using the 4e in my other Jag -- that's the MB recommended fluid.

 

My brakes were spongy for almost two weeks after replacing pads and rotors, now they are grabbing real nice. I was about to yell at the shop who did the job and ask them to flush the system, but my laziness did a great service to me again :-)

 

. . . over time, some of the air in the line will bleed out naturally -- or the brakes could fail and you get killed. Get the brakes bled correctly by a pro.

. . . by now, I have my wife's right foot deftly trained to as she yells, "pumping, pumping, HOLD!" At HOLD, her foot goes no lower (took a lot of time and yelling to get her to understand why that was really important). Over and over again until no more air squirts out.

 

I'd be happy that the fluid was still there after 30 years, and immediately flush it, but yeah, that's dumb.

Every 2 years. $10 worth of Valvoline DOT3 (good compromise for wet and dry BPs, and easily available) and a friend/relative with a beer ($1-5). Same goes for hydraulic clutches, 2 years.

It's amazing how long brake parts last when they're exercised at least a little, and the fluid changed on the 2 years.