Generally not a reasonable probability. Type three and four brake fluids are compatable and type five is both expensive and still pretty rare.

Now when you first purchase an old used car sometimes it pays to check that there is brake fluid in there. I have heard of car flippers putting the wrong fluids in transmissions and brake systems.

The most likely probability is a replacement caliper that was defective and is leaking. Still it is all too subjective until the point the system is leaking at is found.

This is over done. Buy a power bleeder, slap it on, pressurize the system, remove all 4 wheels and look for leaks.

Brake pedal method might be useless since the MC is shot from going to the floor.

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1998 Ford Escort ZX2 5 speed - 279,000 miles My Daily

1992 Mercedes 300D 2.5 202,000 - Pure junk
2000 Mercedes E320 Black - 136,000 miles - Needs repair

Don't forget to grease the screw and threads on the spring compressor.

My friend had me look at his brakes because they where soft, a shade tree recently did their brakes and he finished at night.

Well what do ya know, the banjo bolt to the caliper was loose, tightened it up for them. I explained their MC was possibly shot and at the very least(and best case) needs to be rebled, they had a proper mechanic take care of it.

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1998 Ford Escort ZX2 5 speed - 279,000 miles My Daily

1992 Mercedes 300D 2.5 202,000 - Pure junk
2000 Mercedes E320 Black - 136,000 miles - Needs repair

Don't forget to grease the screw and threads on the spring compressor.

If you live upnorth in the salty snow areas then a hard line giving away is also a chance, when it happens you will lose one brake circuit as the fluid is expelled away from the open line.

Check under the whole car to see any wet areas.

if the lines are corroded - replace with hand made nicopp lines and not the steel lines mercedes installed at the factory. Nicopp is easier to work with and dont corrode.

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2012 BMW X5 (Beef + Granite suspension model)

1995 E300D - The original humming machine (consumed by Flood 2017)
2000 E320 - The evolution (consumed by flood 2017)

Hard line failure = will not be in the open most likely. It is most likely against the body and especially under the clamps. "...look for the wet spot "

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The OM 642/722.9 powered family
Still going strong
2014 ML350 Bluetec (wife's DD)
2013 E350 Bluetec (my DD)

both my kids cars went to junkyard in 2023
2008 ML320 CDI (Older son’s DD) fatal transmission failure, water soaked/fried rear SAM, numerous other issues, just too far gone to save (165k miles)
2008 E320 Bluetec (Younger son's DD) injector failed open and diluted oil with diesel, spun main bearings (240k miles)

1998 E300DT sold to TimFreeh
1987 300TD sold to vstech

It turned out to be a leak in a hard line in a place that would be difficult to detect. Coincidentally, the the low fluid lamp was not working initially...but mechanic got it working again.

To those of you who thought it was obvious that the mechanic screwed up on the previous brake job...well, perhaps a little less dogmatism in the future would be wise.

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14 E250 Bluetec 4Matic "Sinclair", Palladium Silver on Black, 154k miles
06 E320 CDI "Rutherford", Black on Tan, 172k mi, Stage 1 tune, tuned TCU
91 300D "Otis", Smoke Silver on Tan, 142k mi, wastegate conversion, ALDA delete

19 Honda CR-V EX 61k mi
Fourteen other MB's owned and sold
1961 Very Tolerant Wife

been there with the corroded brake line fiasco more than I wish to recall. I have replaced quite a few of them now. My lesson from it was that if one line has let go. All lines should be replaced no matter how long it takes. They are all equally aged and corroded as the one that just failed.

Nicopp material and new fittings with a nice flare tool makes easy work of this.

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2012 BMW X5 (Beef + Granite suspension model)

1995 E300D - The original humming machine (consumed by Flood 2017)
2000 E320 - The evolution (consumed by flood 2017)

Where exactly was the leak?

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2004 F150 4.6L -My Daily
2007 Volvo XC70 -Wife's Daily
1998 Ford F150 -Rear ended
1989 J-spec 420SEL -passed onto its new keeper
1982 BMW 733i -fixed and traded for the 420SEL
2003 Volvo V70 5 Speed -scrapped
1997 E290 Turbo Diesel Wagon -traded for above
1992 BMW 525i -traded in
1990 Silver 300TE -hated the M103
1985 Grey 380SE Diesel Conversion, 2.47 rear end, ABS -Sold, really should have kept this one
1979 Silver 300D "The Silver Slug" -Sold

Actually you are mostly right. If a brake line rusts out up here in the north. The other brake lines on the vehicle should be at least examined for their condition.


In the north rust belt even just brushing on a coat of grease helps extend their life if done when the car is purchased. Do not forget to do them in the engine bay as well. Plus the parts of the fuel lines that are metal. A half inch brush does it well.

I will go one step further. On more modern cars there are a lot more lines. So protecting them to some extent is worth the effort.

In line that goes to ABS module.

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14 E250 Bluetec 4Matic "Sinclair", Palladium Silver on Black, 154k miles
06 E320 CDI "Rutherford", Black on Tan, 172k mi, Stage 1 tune, tuned TCU
91 300D "Otis", Smoke Silver on Tan, 142k mi, wastegate conversion, ALDA delete

19 Honda CR-V EX 61k mi
Fourteen other MB's owned and sold
1961 Very Tolerant Wife

Im going to assume "from the ABS module" as the only lines going to the ABS pump are from the master cylinder.

The wheels (slaves) have lines going from the module and yes they do rust right at the junction where they make a 90 degree turn under the car.

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2012 BMW X5 (Beef + Granite suspension model)

1995 E300D - The original humming machine (consumed by Flood 2017)
2000 E320 - The evolution (consumed by flood 2017)

I sent a Buick in decent shape other than it needed all new brake lines to the wreckers. There where a pile of brake lines. . Older Buick but only 80 thousand miles. Fully optioned as well and was decent on fuel consumption. I wanted to give it away but the young fellows around here cannot even put new brake lines on today it seems.

Some manufacturers use far better sacrificial coatings on their brake lines than others. If you are trying to get the maximum time out of cars it is ultra important to get some petroleum based material on the exposed steel. At least in the rustbelt. Actually with brake lines your safety is also involved.


A rusted out fuel line pressurized by a pump in the fuel tank could produce quite the issue. Although I have never heard of one.

Thanks for the update.

It is absolutely critical that son understand that a when a half of a dual circuit system loses fluid, he will still have half braking capability. The peddle will go " to the floor " but there will be braking if he pushes hard enough , like hold onto the steering wheel and push.

If he does not understand this and has a brake leak in the future, he may crash because he is convinced he has " no brakes " rather than " reduced brakes "

For those playing the home game, see posts 2 10 12 14 17 22 26

Gee, still searching Google for a reply to the real cause of the brake failure? Perhaps you can team up with OJ and find the real killer. . .

Well look on the bright side, you found an honest mechanic!

__________________
1998 Ford Escort ZX2 5 speed - 279,000 miles My Daily

1992 Mercedes 300D 2.5 202,000 - Pure junk
2000 Mercedes E320 Black - 136,000 miles - Needs repair

Don't forget to grease the screw and threads on the spring compressor.