535i shaking like crazy - Brake related

[OMP]

Hi.
Finally I got my 535i from the shop after spending there the last few months.
Just as a reminder, I bought this car this past summer ( way cheap) and I started by doing the basics ( Oil, Battery...very basic stuff), and the it when thru a complete front end suspension arms kit replacement, then radiator, new plugs, belts, some gaskets here and there and so on.

I did had the chance back when I bought it to drive for about 100 Milles and I had episodes of the car shaking like crazy that would start some time ( maybe 10-15 minutes) after start and driving steadly on the highway....IT was just plain dangerous as I had the feeling the tires would just let go ( I did post on this I think back then).

So, because I will be keeping the 535i ( and the Toruing is now for sale), I decided to just get rid of all the "small" issues and come up with the solution for this ( and other minor) culprits.

So, back on the issue: Back in the summer, I did have episodes where my brake pedal had completely different feel. Sometimes it would be very hard and set at the top of its travel and ( I would say) in normal situation, the pedal would be just "fine" with inital travel and smooth braking assist.

At this point, sometimes, coming out from the highway, and coming to a stop and go traffic situation, slightly uphill ( very slight but noticeable), I would just feel that the car would not inmediatley back down ( it felt like an uphill start assitant from modern cars)......and the pedal was hard as a rock, very little travel and very hard.

So, into the shop the car went and I just picked up on hour or so ago....And here is the update on the issue related elements:
- Like said, new front suspension arms kit
- New brakes lines ( rubber section of course), as the mechanic said that old rubber lines might not "open" as quickly ( as they are harden) as new ones because of the lack of flexibility in them, and so, pressure would still be at the end ( calipers) even if the pedal is not in use.
- Wheels and tires: Tires are about 5000 milles ( Toyo Winter) and wheels are the std that are perfectly in everyway ( they were refurbished to new about 3 years ago and same as the tires, 5000 milles).
- Alignment and balancing are OK, as they also been done.

So, I took the car from the shop, which is about 15 milles away from home and it just fetl great....brake pedal ( for me ) a little on the "mushy" side, light pressure on initial travel and getting more "pedal feel" from mid travel onwards, but OK....

I took 2 highways, one for about 7 milles or so and the following another 8 milles. When getting into the first highway, no issues, car run as smooth as it can get....no shakes, no nothing, just plain perfect....then, about 5 milles afterwards, I start sensing just a little shake from what felt the front end ( wheel, tire)....but I didn't really gave much importance ( maybe the road itself)....then I take the second highway and after 5 minutes of driving, without touching the brake fro anything, I start again feeling some shaking......but 3 minutes after that, it was getting worst and worst.....I was just about to get to my exit, and the car was now just freeking dangerous....shaking like crazy....This was at about 60 mph, but no matter what the speed was ( got it to 85 mph but same thing), it would just shake......luckily, I was on the exit ramp.....Then I go for the brakes, and first contact with the brake and the pedal was just hard like a rock and no or little travel before braking, with a very uncomfortable feel.....

Anyway, since the exist ends in a roundabout, and after getting to a compelte stop and having the pedal back to a fluffly feel again, I decided, to go back to the highway just to see if, effectivelly, it was brake related.....And bang!!!! I go back to the highway and again, smooth as it can get.....

So, back in the summer, the mechanic told me that it could be suspension arms related, maybe tires ( it another, older set back in the summer), but not anymore.....It is just plain brake related....

I have searched around teh forum and checked a post about an M5 have its calipers seized....But, I don't know if this would be the same as the calipers seem to be just fine, but it is like having some sort of "back pressure" or some leakage from the system.....I am really puzzled and pi**ed off as I thought everything was going to be just marvelous after so many months, but it is not.....


Any ideas or past experiences??

Thanks
Regards

[moroza]

Are the brakes dragging? You could have a sticking master cylinder.

[fo3]

Booster or one way valve? Check the 1 way valve and vacuum hoses first. That would explain the high and hard pedal, but not vibration though.

When I had my manifold off I replaced the brake booster line, got it all together and tried the brakes. Pedal was rock hard and no boost assist. I thought I'd just not got the hose on right because the booster adapter got pulled off with the old hose and I just pushed the adapter back in the best I could earlier on.

So I pulled the adpater out, lubed it to try work it back into the booster and tried again - no boost. So I thought I had the 1 way valve on the manifold on the wrong way, reversed it and tried again - no boost.
Not suprised because I swear the valve was the right way around.

Took everything apart again and put it all back together carefully and it worked fine. To this day I don't know if it was the hose adapter, the little plug on the valve (I plugged it with sealant maybe you're not supposed to so I cleaned that out)

Anyway it sounds like the booster from my BMW experience (hard and high pedal). Usually when it's the master you have a low soft pedal as it leaks internally.
BTW it's a common thing with aussie ford falcons - booster plays up and applies brakes constantly leaving you with hot and warped rotors with vibration.

Jack the car up and check for dragging brakes. If one drags it could be that caliper. If they all drag it could be the master or the booster. I guess the booster since you lose boost.

[OMP]

Are the brakes dragging? You could have a sticking master cylinder.

Hi Moroza....I don't feel brakes are dragging as when I start driving, car just feels perfect.......I'd say ( without any detailed brake system expertise ) that, or some reason, there is some sort of "back pressure" ( don't know how this would apply to the brake system ) that would be building up while the car is running...It is just so strange......As, again, first touch to the pedal is hard and this hard feeling is on top of the pedal travel......Then, coming to a stop, brake pedal goes back to its "natural" feel and then the car would be fine again.....

[OMP]

Booster or one way valve? Check the 1 way valve and vacuum hoses first. That would explain the high and hard pedal, but not vibration though.

When I had my manifold off I replaced the brake booster line, got it all together and tried the brakes. Pedal was rock hard and no boost assist. I thought I'd just not got the hose on right because the booster adapter got pulled off with the old hose and I just pushed the adapter back in the best I could earlier on.

So I pulled the adpater out, lubed it to try work it back into the booster and tried again - no boost. So I thought I had the 1 way valve on the manifold on the wrong way, reversed it and tried again - no boost.
Not suprised because I swear the valve was the right way around.

Took everything apart again and put it all back together carefully and it worked fine. To this day I don't know if it was the hose adapter, the little plug on the valve (I plugged it with sealant maybe you're not supposed to so I cleaned that out)

Anyway it sounds like the booster from my BMW experience (hard and high pedal). Usually when it's the master you have a low soft pedal as it leaks internally.
BTW it's a common thing with aussie ford falcons - booster plays up and applies brakes constantly leaving you with hot and warped rotors with vibration.

Jack the car up and check for dragging brakes. If one drags it could be that caliper. If they all drag it could be the master or the booster. I guess the booster since you lose boost.

Hi fo.
What you say makes much sense. From what I am experiencing, it has to do something with the booster or cylinder for sure.
The feeling is that one of the front calipers ( I wouldn't say both of them ) gets some sort of pressure while driving for some time without touching the brake...Again, as if ( as you say) some leak would definetely would make system pressure....Again, I am not a brake expert and I cannot see how this could happen.

However, fo, now that you mentioned that, it is true that when things are OK ( starting the car), the pedal feels much mushy...Pedal travel is somehow longuish and feels mushy and there is some dead travel before brake power is there....from the middle of the travel downwards....

So, again, really strange things, but I am sure something around the booster and / or cyclinder is not correct....I'll try to drive the car around these days see if I can find a cause/effect on it.

Thanks
Regards

[OMP]

OK, so I might have some valid news...
On teh dragging brakes....Well, I am not 100% sure yet but I think I just might have some back brake dragging.

Here is the thing. I took the car yesterday for a spin and went to see a friend of mine ( a mechanic ). I told him about this and right away he asks me about how much travel do I have on the hand brake...And, to be honest, there isn't much....In fact, it feels very tight. He tells me that he once had a situation at his shop where a customer had the same symptoms and culprit was on the hand brake.

OK, so I went back home and I disn't really think THAT would cause such a mess in the driving....but then I found a post talking about dragging brakes that would make this comment reasonable. I am quoting : ..."When the now dragging brake warms up the fluid expands and with nowhere to go presses the piston out of the caliper further dragging the brakes."

So, I went to a bar near my house and I took the car for another spin....And I tested ( as far as I could ) the hand brake...And in fact, yes, it has very little travel before it feels engaging.....Without it, in a flat surface, just making the car move slightly, the car, when coming to a complete stop, I felt like it "stopped" instead of just "laying"......I hope to see what I mean.
So I took the car, and in the garage ramp, letting the car go backwards very slightly, I went for the hand brake, and I feel only ONE of the 2 rear wheels had some hand brake stopping action....I tried several times, and you can just feel the car kind of "tipping" to one side, and this, with the first "clik" of the hand brake....barely lifting the hand brake an inch or so...maybe not even an inch.

So, bottom line, I might just have a rear dragging brake.........But then again.....Why wouldn't I smell anything if I do have a dragging brake? Wouldn't I just smell burnt somewhere? Would this eventual rear dragging brake make all this mess ( shaking like crazy)?
And, why when I do have this crazy shaking, and come to a complete stop, the car would be just perfect after that. I could take it to any speed without feeling any anything until past sometime?

Crazy thing....

I keep reading you guys.
Thanks

[OMP]

Hi, I keep giving some ( I think ) valuable information.
Keep in mind that I have just driven the car since I bought it ( June 2019 ) about 120 milles, no more and I got it back from the shop it went in July just last thursday.
Anyhow, I have just returned from running some errands and while parking, I got the "brake Pad - Please check owner's manual" message.
Brakes were just revised ( there hasn't been any brake service done - yet). However, there "something", independently or not to my problem, going on with the brakes ( or at least the pads).

One other element that could help : Prior to buying the car, it had run barely in the last few years, and when I did start it, it sat for at least 8 months ( although people that have seen the car think it was more like 1 year and 8 months......so, quite some time). Just telling if it helps.

Regards

[fo3]

I'd jack the car up front and back (so all in the air), and test each wheel to find a grabbing brake. The brake fluid could have been decades old and the pistons are corroded causing dragging. On top of that it could be like a falcon - a failing booster applying brake pressure and being funny with dropping boost too.

The handbrake is a separate issue as it's just a shoe in the hat. Not related to hydraulics and you would have thought it would just wear the shoe down rather down or smell those old old shoes, rather than overheat the disc caliper.
If the rears are dragging remove the rear calipers and recheck. Still dragging then inspect the shoes - could be cracked or loose. If they look good then adjust them off a bit. Refit without the caliper and test or continue adjustment.
Shouldn't change much when you put the rear calipers on.
If front wheels or the rear calipers are dragging then you could unbolt the master cylinder from the booster and see if that changes anything (stops applying force to the m/c) with the wheels while it's up in the air. It shouldn't make a difference because the booster isn't supposed to be pressing on the master. So if it does, something wrong with the booster or ?

Dunno mate, it's brakes. Kind of important and seems like they need an overhaul. Start with adjusting the park brake yourself while also doing a caliper clean and lube looking for signs of corrosion. Then flush with new brake fluid with vacuum line, 1 way valve, brake hoses and pads or rotors as required. You may end up replacing the booster and master because it's brakes, kind of important.

If you're not comfortable with disassembling everything maybe you could buy the parts and find a brake/hydraulic specialist or your friend the mech to go through everything. Might be some bias valve or abs problem as well.

E: My handbrake was very tight as well. No more than 2-3 clicks when I bought the car. I didn't like that so I adjusted it to 5 clicks when I replaced the rotors and pads a year ago. But it didn't cause any problems in braking back then. The only issue I had which I mentioned earlier was recently when playing about with the booster. I think I didn't get the seal right into the chamber.

But it sounds like you have multiple problems, dragging brakes, heat, worn pads, eith no boost or a bad pedal when the booster is working. You need a complete overhaul of whats on the axles just as a starting point. Then diagnose a booster or MC whatever problem.

[OMP]

Hi fo.
Thanks a million for the tips. I didn't know the hand brake was on its own ( as on E39s), so I'll have to pass that one, although it surely needs of some adjustment.
Tomorrow or tuesday I'll take the car to the mechanic as I have an A/C leak from when I bought the car, and while the car is there, I'll them him to go throught the brake booster and master cylinder.....Maybe from a "visual" inspection or some basic checks something can be figured out...
I'll let you know about any progress....

Thanks!!
Regards

[moroza]

+1 to the above. When I overhauled my handbrake (replaced cables, shoes, rotors and hardware), I had excellent results following the adjustment procedure in the Bentley manual.

[OMP]

Ok, latest news on the problem.
Yesterday morning I took the car to run an errand at about 15 milles away from home and most of the trip on highways....I wanted to feel again the brakes behavior and keeping more data on that.
Anyway, After about 10 minute drive and the risk of having that hidious brake thing, on open Toll highway, with no traffic, I wanted to "check" the brakes....As I was driving, I kept feeling the brake pedal with my left foot and it was getting harder and harder....at one point, I decide to give a few pumps so could expect the brake to loose some of that hard feeling.....BUT BOY!!!!! After 2-3 pumps......Front brakes got to dragging, and the car just started to stop even though I wasn't even touching the brakes any more....The car tipped to the front ( shocks are busted so it felt more critical), and this lasted for about 3 seconds or so...Then, gave another good pump to the brakes and they got loose.....Thank good at that time ( mid morning) and on the Toll highway no one was around, but it freaked me out...Anyway.....Got back and took the car to the guy close to my house, and first thing checked was the one way valve from the intake manifold which is just fine....He told me about something "else" wrong on the Servo or maybe even the ABS unit...he told something about uneven pressures, but I didn't really understood....Also, of course, pistons are to be checked as well as pads......
I hope to have some news by tomorrow....Will keep you posted.
Regards