Power Steering Fluid Temps

[BMWTurbo]

GTSBoy :- I Was thinking along the lines of insulation, but a water spray might be a simple test.

Dale :- The Vacuum booster won't fit in there with the 2j.

I have stumbled accross a thread where a BMW tech had the same issue, did the following :-

-Rebuilt both front calipers
-Flushed fluid, and replaced hoses
-Replaced pads and rotors. It needed them anyway
-Changed Pentosin (this is the fluid in the resevoir that later models used instead of trans/PS fluid)

but unfortunately the thread doesn't contain a resolve. Another thread talks about no change after replacing his hydraulic booster with a new unit.

[RB30-POWER]

i'll laugh if i read this thread in 12 months time and it turned out to just be the master cylinder requiring reco/replacing.

didn't you say the car was fine for the last two years with this setup?

fark i've never heard of a hydraulic booster until i read this thread, always some cunt over complicating things in the auto world. vacuum works fine for everyone else.

[BMWTurbo]

If I can't correctly ID it over hte next week or two, the MC will be replaced along with the hydraulic booster.

Not a good feeling when your brakes are sticking to the point that maintaining steady speed requires 80% TPS and 19psi boost

[Greg Rust]

So by the looks of the diagram there must be a servo piston in the master cylinder that applies a hydraulic force once the port is uncovered by pushing the pedal, sometime in autotransmission the servo pistons can stick or even get minute particles that can block or jam ports and also varnish from fluid degredation can stick pistons.

Pull the master cylinder out and clean that servo out.

[BMWTurbo]

I can confirm it's either sticking master or booster ( you might be on the money RB). I drove around until the brakes stuck on, jacked the front and wheel was tight, gave the master cyl a touch with the wooden handle of a hammer and it free'd the wheel.

Will have to work out how to ID if it's the master or booster. Only way I can think is to blank the pressure feed to the booster and see if it still does it.

[nutwood]

Sounds like the master cylinder. 70C is not hot enough to cause some exotic problem. The BMW would have been engineered for far higher under bonnet temperatures and eventually everything under the bonnet comes up to much the same temperature.
As for the fluid, ATF runs comfortably at well over 100C

[BMWTurbo]

I'm still trying to come up with way to correctly ID if it's the booster or master cylinder.

The thing leading me towards booster is that when it happens, the brakes are fine, I release the pedal and the next touch of the pedal, it's like pushing against a rock.

The pedal locks up instantly through the pedal travel as soon as you touch it and there's no freeplay.

Now I've never had a master cylinder stick on me so might be wrong, but if the master stuck, wouldn't the pedal have free-play until the actuation rod reached the stuck position of the piston?

So althought the brakes are hard, the pick-up point would be further through the brake pedal travel?

[Gammaboy]

Yeah, from having stuck a master before, I'd agree with your booster diagnosis.

[BMWTurbo]

Looks like I'm trying to rebuild this jiggah...



http://bmwe32.masscom.net/maxf_websi..._breakdown.htm

[RB30-POWER]

you need to check the bore very carefully for any weird grooves in the process. this is the part that is always cactus when the brake guy we use at work can not rebuild them, which is atleast 70% of the time i reckon.

[BMWTurbo]

I'm grabbing some second hand units to 'rebuild' ie change what O-rings and seals I can get as replacements. There might be no issues with the used ones (but I can't test to be certain) so I think for peice of mind it can't hurt to open them up.

I may as well do the BMC and the Booster at the same time as change them as a single unit.

There will be nil chance of finding replacement seals for 'B' Servo Piston, so I'm hoping the bore is all good.

Do you rebuild BMC's RB30?

[RB30-POWER]

i don't build them personally, no, although i would have a go if a kit was available for my own car and a replacement was out of the question due to either cost or availability.

first port of call for you would be to find out if a rebuild kit is available to suit the master i guess? unless someone has to match the seals up manualy, but that could be risky for someone untrained. factory manual might have spring lengths to confirm if they are ok as well.

the main seals could be teflon coated although being that vintage couldn't say for sure.

you could just try a deemed to be good, secondhand one, if you can find them, but if a rebuild kit is reasonable might as well attempt to do it properly, but if it very expensive, just try the master, if it works, well and good, if not you can fit the old one and not be down as many dollars.

[BMWTurbo]

I could fit the used items i get I guess.

Car did the lock brakes this afternoon and hammer at the ready free'd it, but it didn't take too long to start to stick again, so temp related and can't rectify by force

I'll inspect replacements for leaks before fitment.

[BMWTurbo]

Rebuilt the hydraulic booster the other weekend, all I could do was replace all the O-rings as the bore/pistons/springs etc all seemed perfect.

Learnt that you can tightent the 'spring' on oil seals, by twisting the spring apart (anticlcokwise), triming a small section off and then twisting it back together (clockwise) to form the ring and slip it back over the sealing edge.

I also had a new PS HP feed (restrictor fitted this time) and a flexible booster feed line made up and fitted them too.

PS noise seems to have all but gone, brakes feel fine and with the replaced supra water pump, underbonnet and temps in the fluid etc seem to have dropped dramatically and the car feels stronger due to less heat soak.

Now if everything else would stop breaking for a while I might be able to enjoy it for a bit.
Appears to have resolved the problem.

*EDIT* Fuckin thing partially stuck last night on the way home, nothing like it used to, but I could feel it was jsut starting to do it and then free'd up again.

Will do another brake flush and bleed tonight - entire system. I have one adjustment I can make to the booster freeplay also, that I'll do and if no joy, back to looking at the BMC as suggested right at the beginning of this thread...

I'm about ready to cube the fuckin thing.