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635 bmw brake botheration bollox


Crispian_J_Hotson

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So I'm ripping most of this out because weird shit is happening with me anchors.

 

post-24545-0-82604100-1515346124_thumb.jpg

 

Considering it's been bolted together for 32 years it came apart quite well, maybe because it's been leaking fluid for 30 years... Probably. 

I haven't been here yet so obviously it's gonna break but this car does strange things. I'll rebuild it all as much as I can, paint it up, clean the body down reassemble and bleed and you know what?... It'll be worse than before because that's how this car rolls.

So whats the problem? The brakes lock on when the engine gets hot. It uses a fandangled pressure system from the power steering and I'm not an expert on this, I know the small stuff like depressurising to check the level of the power fluid but I don't know what those 2 pressure switches are for exactly or why it locks the system when it's hot, I left it idling for an hour the other weekend, didn't even touch the brakes and sure enough, locked solid. Hopefully replacing all the bolt on stuff might cure it but I'm sceptical.

Has anyone any other ideas or is there a person who spent 30 years solely developing BMW boosted hydraulic brake systems? 

 

post-24545-0-86132700-1515347053_thumb.jpg

 

In the pic above I did find the seal from the bottom of the power fluid filter had come adrift and was floating around the bottom of the can, don't think that could be causing the issue but stranger things have happened. If the seal was to interrupt the flow then gawd knows what could happen.. and only when hot???? Other than that, bar some yonks old weepy sealing it all seems still operational.

 

Of course, old tin likes to throw a few problems at you and true to form I noticed my carpet was wet... Again! Then I found this...

 

post-24545-0-11434100-1515347732_thumb.jpg

 

FFS... A drop of water ON the inner sill... welder out next week then... 

 

I had already dusted the inside with powder last time and after a massive rain storm there were no marks!

In may last year when I laid this up due to the brakes, I got a maccy D's on the way home from work which was lucky because I put the spare napkins in the door pocket to use as snot rags later. These were wet and I managed to just notice a water stain down the door panel coming from the door mirror area although I'm not discounting that the door seal is buggered too.

Inner sill is fubard too for about 10 inches with crispy holes found under the panel sealer.

 

So, any help with the brake issue would be gr7 I'd also like to find out if anyone knows someone who knows someone who has a hidden stash of parts for it. I will post up a bit later that I fear is made from unobtainium!

 

But all is not bad news, a plane done this in the sky:

 

post-24545-0-76320500-1515349007_thumb.jpg

 

Cheers.

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The cross linkage bell cranks seize on their shafts - I've taken apart, cleaned and greased a few. But more than that, I've found cold brakes that seize when hot are caused by fucked front flexies that don't allow fluid back. The pads get hot, then very hot, then so fucking hot the front brakes lock on.

 

The hydraulic booster also plays up, causing the above issue.

 

E24's are lovely to look at, generally quite awful to own now they are old. Been there, done that.

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The booster arrived on the E23 in '77 and it was always wonky and nowhere near as progressive as the vacuum servo set up on lesser models. You can in fact convert an E24 or M30 E28 to a 520i/525e vacuum servo and do away with this hydraulic shit. Very early E32's had it (as do all 750i's) but after a year, a vacuum servo replaced it.

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 I've had this for a few years as a daily. It's not long been grounded because 100 miles a day commuting was too much for it - my wallet. When it works it's proper gangsta but when it goes bad it's a world of trickery and financial pain where no-one has an answer.

If I don't fix it this time I'll fuck it off to some other poor sod.

 

I'm on big coupe but it's a ghost town there sometimes and I forget about it. 

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The Reverend Bluejeans, on 07 Jan 2018 - 6:26 PM, said:

cold brakes that seize when hot are caused by fucked front flexies that don't allow fluid back.

 

I was going to post exactly that, they delaminate & collapse inside. It's a common fault with old hydraulic hoses.

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Flexis aren't the issue here though right? It may be useful to know that when they started seizing in traffic, finding a empty stretch and opening it up for a mile or so completely saw the issue gone. It's a gradual thing until it's all locked up. It's definitely related to the heat of the engine/ fluid around it. I didn't even use the things the other week and it still done it. The flexis to the calipers are old and crap. Could this delamination happen to the big flexis supplying the power fluid? Suppose I'd loose steering power though... And I'd notice that as hanging a left would snap my arms off trying to turn the steering wheel.

 

I have a new sphere and other metallic shit to go on in replacement and check anything that remains. I'm gonna look for some info on that conversion because all this stuff is an effin joke.

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I think the problem is the ram between the bastard cylinder and the bulkhead - something happens to them under pressure from the PAS pump and they just apply the brakes.

 

About three years ago I did a major overhaul on a 1986 D plate 628CSiA for a mate - replaced the shagged autobox, flexy hoses, ABS trigger rings, brake bomb, cam spray bar, heater fan............they are such needy cars and require never ending fettling. I had three - a very early 1976 R reg 633CSi, a later one from 1979 and then a white A reg 3.5 that was supposedly Tom Jones' old one. That was in 1995.  :shock:

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So I'm ripping most of this out because weird shit is happening with me anchors.

 

attachicon.gifIMG_20180107_110809187_HDR.jpg

 

Considering it's been bolted together for 32 years it came apart quite well, maybe because it's been leaking fluid for 30 years... Probably. 

I haven't been here yet so obviously it's gonna break but this car does strange things. I'll rebuild it all as much as I can, paint it up, clean the body down reassemble and bleed and you know what?... It'll be worse than before because that's how this car rolls.

So whats the problem? The brakes lock on when the engine gets hot. It uses a fandangled pressure system from the power steering and I'm not an expert on this, I know the small stuff like depressurising to check the level of the power fluid but I don't know what those 2 pressure switches are for exactly or why it locks the system when it's hot, I left it idling for an hour the other weekend, didn't even touch the brakes and sure enough, locked solid. Hopefully replacing all the bolt on stuff might cure it but I'm sceptical.

Has anyone any other ideas or is there a person who spent 30 years solely developing BMW boosted hydraulic brake systems? 

 

attachicon.gifIMG_20180107_113934473.jpg

 

In the pic above I did find the seal from the bottom of the power fluid filter had come adrift and was floating around the bottom of the can, don't think that could be causing the issue but stranger things have happened. If the seal was to interrupt the flow then gawd knows what could happen.. and only when hot???? Other than that, bar some yonks old weepy sealing it all seems still operational.

 

Of course, old tin likes to throw a few problems at you and true to form I noticed my carpet was wet... Again! Then I found this...

 

attachicon.gifIMG_20180107_132651547.jpg

 

FFS... A drop of water ON the inner sill... welder out next week then... 

 

I had already dusted the inside with powder last time and after a massive rain storm there were no marks!

In may last year when I laid this up due to the brakes, I got a maccy D's on the way home from work which was lucky because I put the spare napkins in the door pocket to use as snot rags later. These were wet and I managed to just notice a water stain down the door panel coming from the door mirror area although I'm not discounting that the door seal is buggered too.

Inner sill is fubard too for about 10 inches with crispy holes found under the panel sealer.

 

So, any help with the brake issue would be gr7 I'd also like to find out if anyone knows someone who knows someone who has a hidden stash of parts for it. I will post up a bit later that I fear is made from unobtainium!

 

But all is not bad news, a plane done this in the sky:

 

attachicon.gifIMG_20180107_144657291.jpg

 

Cheers.

Oof! A 'hole' in the ozone layer... Now where is a penis when you need one?

 

TS

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As for your brakes, when hot, the Master Cylinder piston fails to return fully, leaving pressure in the brake system, which is a phenomenon

predominantly seen on RHD examples, since only they use a cast iron MC, which is hilariously expensive to replace nowadays.

 

So when it happens, it should create a 'dead spot' at the top of the pedal travel, followed by a 'click' as the pedal firms up part way through

the stroke, as the pushrod contacts the rear of the piston again.

As you wait for it to cool down, the shaft will eventually return to its normal position and the brakes free off.

Others have reported that they sometimes hear a distinct 'click' as the system cools off and this accompanies resumption of 'normal' braking.

The fault appears to be that the phenolic spacer/shaft guide at the rear of the MC swells over time, probably with oil or brake fluid contamination,

to the point that it starts to bind on the shaft, but only when hot.

 

 

I bet you anything that's it. I know my old shitbox BMWs and thus gave up driving them 25 years ago.

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That shaft is sticky during operation, I was dicking about with it but surprisingly there was no leakage of fluid in there or from the MC. There is supposed to be grease on it which has turned to crust tho. The MC is ally if we're talking about the same unit, and I nearly threw it out the engine bay upon removal expecting it to be heavier! That was before the obligatory 'push the end in to see if it works and shoot yourself in the face with brake fluid' happened. Would all that partially seize even without depressing the brake pedal, just purely letting the engine heat up? That's the bit that's got me stumped...

 

I haven't noticed a click from the brakes at all whilst shitting myself in traffic with a rock hard pedal. I think we're in the right area though... I hope... but with the 635 it could be the indicator relay causing the brake problem.  :mrgreen:

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Would all that partially seize even without depressing the brake pedal, just purely letting the engine heat up? That's the bit that's got me stumped...

 

 

 

That's the peculiarity of the hydraulic servo system. With a vac servo, you'd have to stomp on the pedal to make the brakes stick on,

with the hyd system, the car does it for you, although this also hints to slightly leaking piston seals in the MC.

If I were you, I'd take the MC out, clean everything properly, install a seal kit and whack everything back together not forgetting

to lube the shaft (stop snickering, ffs!) with high temp moly grease.

 

Lucky dip you don't have the iron one, m8, which makes me believe it has been replaced at some stage.

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E24's are lovely to look at, generally quite awful to own now they are old. Been there, done that.

 

 

Yes. Mine has spent most of last year as an ornament. I am finding that they were probably built very well with high quality parts, so it all lasted a long time and survived the ravages of neglect but everything is expiring now within months of each other, I have replaced most things, some of those replacements have been replaced since! They are a beast to own at this age, not very rewarding either and then there's the rust that still refuses to stop. If I wasn't so stubborn, this motor would have gone years ago. What would I get if I outed it though? Another P.O.S no doubt. On the flip side, owning this makes owning the Discovery a feckin breeze!

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That's the peculiarity of the hydraulic servo system. With a vac servo, you'd have to stomp on the pedal to make the brakes stick on,

with the hyd system, the car does it for you, although this also hints to slightly leaking piston seals in the MC.

If I were you, I'd take the MC out, clean everything properly, install a seal kit and whack everything back together not forgetting

to lube the shaft (stop snickering, ffs!) with high temp moly grease.

 

Lucky dip you don't have the iron one, m8, which makes me believe it has been replaced at some stage.

 

Good info. Rebuild kit is in a box under the kitchen table. Can't wait for that to be wrong! I'm still amazed that when these cars fuck up it's not a case of ripping a dead bit out and sellotaping new stuff in, you literally have to become an expert in the field of whatever component has blown up! It makes a 5 mile drive to a petrol station very rewarding... because the thing is moving!

 

The 635... certainly not for the faint hearted!

 

The first breakdown this car had was random shifting through the gears, gearbox warning light, cutting out, intermittent radio and other strange occurrences as well as absolutely fine running. One horrid day on the M11 though she died, then started and then died again... limped it to a services and left running I opened the passenger door, released the bonnet catch and slammed the door shut... the engine then cut out. Starting it up again, I repeated the door slamming technique and sure enough, the engine cut out again. I got it towed home. 2 days later I went to go butcher it and pull wiring and looms and shit out to find the gremlin and upon first going to disconnect the battery found that the earth terminal was loose and rattling about... 3 people had looked over the car ffs! Then a year later the same thing happened but this time it was the main relay that shat itself, took a week to find that as it worked when it felt like it, it was only fitting that bridging doobry that found it.

The electrics are ruined in it too which I will come to if I fix this brake problem. The previous owner paid half a bag to have a BMW electronique specialist fuck the electrics up when it refused to start and I'd like to sort them. No one on any other forum has had an answer for me yet but I suspect it will involve me replacing the internal wiring...

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I must have been lucky with my '83, apart from the rust. All I mostly did was change the oil and filter every 4500 miles, and the pads and discs when they expired. The brake fluid was DoT5.1. Wiring was never messed with. Only thing that ran down was air conditioning; I hardly ever used it and the gas eventually leaked out.

 

Did use it as daily driver for work for a few years - it was fifty quid a week in super unleaded, but could be claimed back via expenses. Did revert to leaded fuel if ever I came across anyone selling it.

 

Cylinder head renewed at 130,000 miles when hairline crack discovered. New casting was £250.

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That is the problem, they are unlike any other car in every respect. Here is a list of breakdowns/ failures since purchase and over the last few years of daily running to 200 odd thousand miles:

 

Terminal rot everywhere- welded

Snapped exhaust bracket on the 3/4 tonne rear box- Welded new get up onto it

Rotted fuel tank- welded

Fuel pump assembly fell off- replaced mounts

Super wash inoperative- ripped it all out and got rid of those stupid headlamp wipers

Rotter rear back plates for handbrake- welded

Rear beam bushes fucked- replaced with poly

Borked front wheel bearings - replaced

ABS working when it feels like it- disconnected

OSF back plate detached due to rot- welded

Loose battery terminal- Recovered home- fixed

Wobbly rotten headlamps- rebuilt

Main relay intermittent- Recovered home- replaced relay after swapping out everything else with no success

Front top mounts disintegrated- replaced

Heater motor seized, screaming in pain- replaced

Rear diff mount collapsed - can still drive it, just very lumpy rolling- replaced

Rear damper exploded (my fault- over enthusiastic rally driving)- replaced

Buggered dizzy cap/ rotor - replaced 3 times

Front lower arm bushes - of course- replaced with poly

Front top mounts again - It's lowered- replaced again

Shit HT leads- replaced with expensive racing crap

Most ball joints- replaced

Boot lock failed to operate and open boot- drilled it out (had my lunch in there)

Leaking cold start supply loosing fuel over hot engine- replaced valve and hose from a tractor shop which disintegrated- replaced again

Starter motor died- replaced (what a fuck about!)

Fuel pressure regulator weak- still in use, replaced for a second hand unit which was worse so swapped back

Leaking vacuum hose to manifold- replaced all with silicone

Exploding air flow meter- Shocking problem to diagnose- replaced in the end

Steering play (obvs)- Twiddled the setting nut a bit- all ok

Brakes locking up- currently on the kitchen table being overhauled

 

See, it's not that bad.

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..... list of breakdowns/ failures since purchase and over the last few years of daily running to 200 odd thousand miles:

 

Terminal rot everywhere- welded

Snapped exhaust bracket on the 3/4 tonne rear box- Welded new get up onto it

Rotted fuel tank- welded

Fuel pump assembly fell off- replaced mounts

Super wash inoperative- ripped it all out and got rid of those stupid headlamp wipers

Rotter rear back plates for handbrake- welded

Rear beam bushes fucked- replaced with poly

Borked front wheel bearings - replaced

ABS working when it feels like it- disconnected

OSF back plate detached due to rot- welded

Loose battery terminal- Recovered home- fixed

Wobbly rotten headlamps- rebuilt

Main relay intermittent- Recovered home- replaced relay after swapping out everything else with no success

Front top mounts disintegrated- replaced

Heater motor seized, screaming in pain- replaced

Rear diff mount collapsed - can still drive it, just very lumpy rolling- replaced

Rear damper exploded (my fault- over enthusiastic rally driving)- replaced

Buggered dizzy cap/ rotor - replaced 3 times

Front lower arm bushes - of course- replaced with poly

Front top mounts again - It's lowered- replaced again

Shit HT leads- replaced with expensive racing crap

Most ball joints- replaced

Boot lock failed to operate and open boot- drilled it out (had my lunch in there)

Leaking cold start supply loosing fuel over hot engine- replaced valve and hose from a tractor shop which disintegrated- replaced again

Starter motor died- replaced (what a fuck about!)

Fuel pressure regulator weak- still in use, replaced for a second hand unit which was worse so swapped back

Leaking vacuum hose to manifold- replaced all with silicone

Exploding air flow meter- Shocking problem to diagnose- replaced in the end

Steering play (obvs)- Twiddled the setting nut a bit- all ok

Brakes locking up- currently on the kitchen table being overhauled

 

See, it's not that bad.

 

That is pretty extensive. I had mine from about 93000 to 205000 miles. ZF4HP22 (ordinary non-switchable) had fluid and filter changes every 25000 miles.

 

Comparing notes, out of your list, I think I had:

 

- rust (too much in the end, and mostly in rear arches plus offside roof behind sunroof opening

- intensive wash restored by correct relay early on; never a problem afterwards

- exhaust was mostly stainless steel so I never worried about it

- there was a new front subframe early on, and the control arm bushes were replaced by Meyle E32 750iL ones so I never had the 55mph vibration thing

- headlamps were converted to the later Highline ellipsoid ones with all plastic mounting frames and I kept the wiper arms and washers that came with them as they didn't obstruct the lens.

- suspension was from M635CSi, hence Bilsteins all round - again never a problem (apart from my lower back not appreciating the harder ride)

- indicator stalk didn't self-cancel (broken return spring), but I always cancelled manually anyway - good training for later Citroen CX!

 

I put reflective foil in the tail light clusters to try to improve the light output. Not totally successful so converted to LEDs - much better. Decided to live with the "bulb out" warning on the Check Control, and the MoT testers never counted that as a fail.

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My intensive wash system was rotten, wasn't even worth a save. Unusually though, the rear arches on mine are bang on, inside and out. History doesn't suggest any replacements/ repairs but it's business as usual around and under the rest of the car. The back end has been blown over on both rear 1/4's up to the roof which has mostly worn off/ faded out- *character because patina. When I first got this car I stripped it and went all over it looking for crap body repair and nothing shows on the arches on either side. Found plenty of bubble wrap and isopon in the wings and sills though! Can only fathom that it's had proper insurance rear 1/4 panels on it at some point and blown over with shite paint. No history for any of it though... and I have a big lever arch file for it.

 

It was first registered in Wales for some seemingly upper class in mining who's name escapes me right now- it's proper posh. On it's first service it was marked up with scrapes and dents on the body so the owner was probably a bit of a shaky driver.

I bought it down the cafe and dragged it off a driveway in the darkest depths of London where it had been festering for a while, the only view I got of it was one night in the rain with no keys, I decided there and then it was the car for me and drove it 30 miles home... moss and all! Proper shitter retrieval. 

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I was okayish with mine. The first one was a 1984 A plate 635CSi Auto (reckoned to be Tom Jones' white one - can't recall the reg) but that was bought for peanuts in 1985 when it was 11 years old. Already had new front wings but it had four new Avon Turdospeeds and it wasn't old enough to be the fucking awful dropping to bits wanked old E24. 

 

The 1979 633CSi however, certainly was. If there's anything worse than a fucked 635, it's a fucked 633 as they were E12 based and everything is that much older/badly designed/fucked. In 1996 it was 15 years old and just on the turn. Twin hydraulic remote servos, old L Jetronic and as pretty as it was (gold with beige velours and 7x14 Alpina wheels) it was a right turd. It had an endearing habit of cutting out in traffic, later traced to a broken coil winding in the distributor.

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That is the problem, they are unlike any other car in every respect. Here is a list of breakdowns/ failures since purchase and over the last few years of daily running to 200 odd thousand miles:

 

Terminal rot everywhere- welded

Snapped exhaust bracket on the 3/4 tonne rear box- Welded new get up onto it

Rotted fuel tank- welded

Fuel pump assembly fell off- replaced mounts

Super wash inoperative- ripped it all out and got rid of those stupid headlamp wipers

Rotter rear back plates for handbrake- welded

Rear beam bushes fucked- replaced with poly

Borked front wheel bearings - replaced

ABS working when it feels like it- disconnected

OSF back plate detached due to rot- welded

Loose battery terminal- Recovered home- fixed

Wobbly rotten headlamps- rebuilt

Main relay intermittent- Recovered home- replaced relay after swapping out everything else with no success

Front top mounts disintegrated- replaced

Heater motor seized, screaming in pain- replaced

Rear diff mount collapsed - can still drive it, just very lumpy rolling- replaced

Rear damper exploded (my fault- over enthusiastic rally driving)- replaced

Buggered dizzy cap/ rotor - replaced 3 times

Front lower arm bushes - of course- replaced with poly

Front top mounts again - It's lowered- replaced again

Shit HT leads- replaced with expensive racing crap

Most ball joints- replaced

Boot lock failed to operate and open boot- drilled it out (had my lunch in there)

Leaking cold start supply loosing fuel over hot engine- replaced valve and hose from a tractor shop which disintegrated- replaced again

Starter motor died- replaced (what a fuck about!)

Fuel pressure regulator weak- still in use, replaced for a second hand unit which was worse so swapped back

Leaking vacuum hose to manifold- replaced all with silicone

Exploding air flow meter- Shocking problem to diagnose- replaced in the end

Steering play (obvs)- Twiddled the setting nut a bit- all ok

Brakes locking up- currently on the kitchen table being overhauled

 

See, it's not that bad.

 

 

Now I understand why BMW bought Rover.

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That is the problem, they are unlike any other car in every respect. Here is a list of breakdowns/ failures since purchase and over the last few years of daily running to 200 odd thousand miles:

 

Terminal rot everywhere- welded

Snapped exhaust bracket on the 3/4 tonne rear box- Welded new get up onto it

Rotted fuel tank- welded

Fuel pump assembly fell off- replaced mounts

Super wash inoperative- ripped it all out and got rid of those stupid headlamp wipers

Rotter rear back plates for handbrake- welded

Rear beam bushes fucked- replaced with poly

Borked front wheel bearings - replaced

ABS working when it feels like it- disconnected

OSF back plate detached due to rot- welded

Loose battery terminal- Recovered home- fixed

Wobbly rotten headlamps- rebuilt

Main relay intermittent- Recovered home- replaced relay after swapping out everything else with no success

Front top mounts disintegrated- replaced

Heater motor seized, screaming in pain- replaced

Rear diff mount collapsed - can still drive it, just very lumpy rolling- replaced

Rear damper exploded (my fault- over enthusiastic rally driving)- replaced

Buggered dizzy cap/ rotor - replaced 3 times

Front lower arm bushes - of course- replaced with poly

Front top mounts again - It's lowered- replaced again

Shit HT leads- replaced with expensive racing crap

Most ball joints- replaced

Boot lock failed to operate and open boot- drilled it out (had my lunch in there)

Leaking cold start supply loosing fuel over hot engine- replaced valve and hose from a tractor shop which disintegrated- replaced again

Starter motor died- replaced (what a fuck about!)

Fuel pressure regulator weak- still in use, replaced for a second hand unit which was worse so swapped back

Leaking vacuum hose to manifold- replaced all with silicone

Exploding air flow meter- Shocking problem to diagnose- replaced in the end

Steering play (obvs)- Twiddled the setting nut a bit- all ok

Brakes locking up- currently on the kitchen table being overhauled

 

See, it's not that bad.

So it's nearly as bad as a modern BMW.
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