W124 brake upgrade

[aprilsunncuba]

Hi, I'm new to this forum and I'm interested to know if anyone on here has ever upgraded their brakes on a W124. And if so, what are the options out there?

Many thanks
George

[CraigB]

See if you get responses from others with more knowledge, but I think the ultimate bolt on is 400/500e brakes, but they are a bit thin on the ground locally. These may be the same or similar to R129 500sl brakes and while still rare, might be easier to find. You don't say in your profile which W124 you have, but I think your later m104 cars might have bigger brakes than your earlier M103/2.

[aprilsunncuba]

Thanks Craig, I'll patiently wait to hear from others. you mentioned the R129 model, I did see something about that a while back now but I can't remember where.
BTW my W124 is a 300D, have had it for over 7 years now and wouldn't trade it for anything in the world.

[CraigB]

So I would imagine the later model brakes could be an upgrade on yours - what year is it?

And are your brakes giving you trouble? Could be other issues? I just say that having used heavier models than yours on the track, I would have thought what they had originally would work pretty well.

[aprilsunncuba]

It's a 1990 model, the issue I have is that on some occasions I'll apply the brakes and it will feel like there's nothing there unless I apply more pressure.
this is an intermittent issue, most of the time they're perfect.
I have a new set of 17" wheels that I will be putting on the car and thought with the extra weight, might be the right time to upgrade the brakes as well. I can access a set of R129 SL500 calipers but I'm not sure if they'd be a straight bolt on fit, I'd have to do some research on that.

[CraigB]

That's a brake problem though, my brakes never ever do that. Perhaps sticking pistons or master problem. When did you last change your fluid and flex lines? Fluid should be changed every few years and attracts water. That water can corrode and damage things, compresses more than the fluid and if you get them hot, can boil and lose brakes altogether.... always guaranteed at a 'come and try' track day that at least one white faced driver will have had the pedal go to the floor and spear off the track!

But the flex lines, should have about a 10 yr life, lose their internal structure and can act like a valve. Those times you hit the brake it could swell and block the fluid getting through - I learnt this one many years ago when a caliper would jam on and it was the hose stopping fluid returning. Hoses you can usually find for about $20 locally, with a fluid change and regardless you are in a better position even if still not happy ie. you would want to fit new flex lines with new calipers anyway. I always feel like brakes are something I don't want to risk and caliper kits are also cheap and dust seals can go and get corrosion in calipers. A quick clean up and pop new seals in calipers and you are set for many years of trouble free use. That's assuming you can do the labour yourself.

[Bartman4800]

Funny how people directly think of an upgrade, when they do not realize the OEM setup is not working properly.

Don't go overboard. As Craig said, check the calipers for free moving pistons, install new flex lines if suspect. Refresh the brake fluid, this needs done every 2 years. Ensure your brake booster works well.

And put some good brake pads on the car while you are at it. If done properly I am sure the OEM setup is sufficient for Oz speeds and more.

Bart

[CraigB]

And I should have said, on the outside this dodgy brake line I had looked completely normal, but when you tried to blow air through it you could tell the restriction. They have different layers within and can be gone without realising. Also from what you said, this is happening some times and not others, so that internal part can be moving and blocking some times and not others. All of them have a date stamped on them too, but they tend to be a part that is forgotten. I can't quote anything, but 10 yr life is what I have always heard. Of course they last longer and these could be the originals, but for the money and being brakes.... and in 20+ years of forums its one of those things that has come up a lot as a solution when brakes do weird things.

[aprilsunncuba]

Thanks for the re-assuring advice guys, the brake fluid was flushed and changed late last year but I don't believe the brake lines were ever changed.
The rear brakes are due to be changed at the next service, I'll have them replace the brake lines and check the overall operation of the whole system.

Cheers

[Christo C]

Brakes and tyres are the most important safety aspect of driving any car if you value your own life and the lives of others; if you are experiencing brake problems take your car to a brake specialist and be HAPPY TO PAY WHATEVER IT COSTS. Do not compromise. There is nothing special about the brake system that requires a “Merc specialist”.
In my opinion the W124 series brakes are great if kept in peak condition.

[CraigB]

Only saying this based on gut feeling - if it is significant you can feel that resistance in the brakes, then I think its more likely to be the front where the issues are. Labour wise (which is what counts when paying for people to work on your car), then I would say not much more time to undo and replace the fronts too. Trade price he might get cheaper but if not they are $22 for German Meyle ones on ebay and in australia with free postage. The system will be drained to do rears anyway, so only a few spanner movements to do fronts too. Also though shouldn't take long to look over the whole system, push back caliper pistons and check for free movement etc. Even a brand new oem master cylinder is only $200 - there's not much else in the system to go wrong.

[tsharkey]

so only a few spanner movements to do fronts too.

Getting the hoses off the hardline at the chassis is a right old PITA. I soak in WD-40, heat than rapidly cool the nut, use a flare spanner but often still can't crack them - Any tips ?

[CraigB]

I can't claim to have done a million of these, but I can't remember a failure. I don't have top quality flare nuts and maybe others are ok, but on those small sizes I don't trust them. I have many open end spanners, good quality but some are just that fraction tighter than others. I reckon its an old sidchrome one that has a tighter fit. Important to have a spanner on the hose, but sure your doing that... just mentioning though with this being a record others could look at. Sounds good what you are doing. One product that sometimes works well is 'Freeze release'. I find it a funny product that works well in some cases but often disappointing. The brake thing springs to mind though recently when trying to get pistons out of a seized caliper. I have a wreck with master in it with all but one line blocked off and set up to fit a caliper to direct. I bled it and tromped on the pedal but couldn't budge. I then sprayed some of the freeze release all around the perimeter and walked away for an hour or so. When i came back I couldn't believe it had popped out by itself. Didn't make total sense because it must have held some pressure to push it out - I would have thought pedal off and no pressure. Anyway, later using compressed air (I give that a go first rather than bleeding and fluid etc.) I tried a soaking with the freeze release after it didn't move and once again it moved. So nothing conclusive but I reckon its a good product to have on the shelf. The other one I only tried recently was auto trans fluid and acetone. The item in question did move, but I'm not totally convinced based on the evidence, but enough people rave about it that I am sure there is something in it, and another trick to have up your sleeve. I think there is a youtube video that experiments different fluids. That's just a brain dump of what comes to mind.

How do your flare nut spanners go and what brand are they? Its one of those tools that doesn't get used a lot, but can be critical, and have thought about good ones if they were a tight fit.

[Bartman4800]

If my flare spanners fail, first I try with the Snap on open spanner, which occasionally has more grip than the flare spanner.
It also helps to hit the fitted join with a hammer, while the back is supported by something heavy. This can break the frozen join.

Then it is usually my one-way Snap-on adjustable pliers.

pliers.PNG

These offer tremendous grip, but only one way.

If that does not work, and by that time I know I have to replace nut and brake line, I use the map gas torch and maybe the vise grips.

Bart