dr bob

Steven--

Sucking the fluid through with the MitiVac doesn't do much more than pushing it through with the pedal or the power bleeder. The key is to actually remove the air before you allow fluid in. So, vacuum pump on the MC side of the ABS unit (multiple ports). Lines from the wheels have been filled from the bottom and are sealed with the vacuum hose stubs and the hemostats. Use the vacuum pump to pull the air out of the ABS and the fluid little catch tool. I'm not sure the little hand pump is sufficient to get pressure low enough, but give it a try; any air you don't get out with the pump is going to still be in there when you allow fluid back in. Anyway, only after the air is out, gently push fluid into the ABS from the wheel ends, using the garden sprayer in my case. Very low pressure on the sprayer needed, since you have vacuum above. Connect the end of the sprayer wand to the hose, purge air from that section, connect to the stub of the vacuum hoes outside the hemostat clamp. Then release the hemostat so fluid can flow into the ABS unit. Repeat 2x for the other circuits.

I really regret not making a picture guide when I did this. It was a frustrating effort as I tried different methods and hookups, finally getting good results after several false starts and failures.

Mrmerlin

Steven if you will follow the suggested bleed I posted ,
then repost back what you have found .

NOTE dont use any of the pump type devices use a helper

yardpro

merlin,

I will try yours out tomorrow.

i tried with pumps and vacuum today but had no success.

i have questions about your method..

when opening the Mc lines, i see no bubbles....

today i pumped fluid in from the wheels cracking the high nut at the battery box for the rear then at the abs...

then the MC nuts... I would have thought that would have gotten anything out...

i still get about a half a travel first stroke then it firms right up..

once hard they are not very spongy.

Captain_Slow

Steven - I hope you get this sorted out soon. If it's any consolation, you are providing a very informative thread on how to bleed the brake system.

Stan/Dr. Bob -
Are the procedures you are prescribing here typical, or are they called for only when there is stubborn air in the system? Attaching the pressure bleeder at the wheels is unfamiliar to me.

I have a PowerBleeder and typically alternate between the Gold and Blue ATE fluid so I can see when new fluid is flowing out the bleeder valves. I attach the cap at the reservoir, pump it up to whatever PSI it states on the PowerBleeder and then go around bleeding from farthest corner to the nearest. I think I recall bleeding the MC before moving to the corners. Without the special tool (that thing about the size of a bread box that Sean brought to Frenzy) I typically cycle new fluid through the ABS unit on a nearby gravel road.

Is the above fine, or do I have some homework to do?

Mrmerlin

Jon reread post 12, it has the answers you seek.

NOTE your bleed sequence is backwards from that posted in the WSM

the ideal is to not let the system run out of fluid ,
as this greatly increases the possibility of trapping air in the lines.

NOTE with the ABS cars if your swapping in a new master,
I also suggest to swap in a new pressure valve onto the ABS unit,
these get corroded inside and simply dont function as they should.

Captain_Slow

Thanks Stan. What are the symptoms of the ABS pressure valve you mentioned malfunctioning due to corrosion?

dr bob

Stan's method is what 99%+ of the cars need.

There's always that stubborn exception, and when you get to that one, more extreme measures are called for. I ended up with a very small amount of air that seemed to be hiding in the ABS unit. The car drove OK with it, but it wasn't perfect. Nicole had shared with us the slightly more severe problem she'd had, and her quest for the solution. Bill Ball had noted that he'd been DQ'd from a driving event when a guest instructor wasn't comfortable with the feel of the pedal in his car. In my case, I managed to ge the air in there during a routine power flush and bleed when I let the bleeder get low on fluid. When it came time for a full brake system maintenance (rebuild calipers, new hoses/pads/rotors) at around 100k, it seemed a good time to go after the problem. I tried the usual methods, including gravity bleeding, pedal bleeding with a helper, vacuum bleeding with the hand pump, pressure bleeding from the caliper ends. It didn't get better, but I did end up with a lot of interesting tools, pipes, hoses and fittings. And the slightly low, slightly soft pedal. Finally, the "full-vacuum then fill" method was what worked for me.

Try Stan's way first. There's a much higher chance of success, and without disassembling the system and making a mess.

Mrmerlin

the symptom is how long has this part been installed on the ABS unit ,

if over 25 years then replace it.

I will guarantee its corroded inside,
you will only find this out after taking it apart.

NOTE once this is done the seals will be damaged thus making it a "You need for a new valve"

Ad0911

Is it wise to take the MC apart to chek for corrosion if the thing is out if the car and not been used for a ouple of years? Is it possile to put it together again if all is ok?

Mrmerlin

AD if you try to take apart the MC your probably going to damage it permanently.

They are made to not be taken apart, maybe the very early unit can be taken apart but the snap ring used in the later models is not removable.

That said if you have a questionable MC chances are very hi that the bore is damaged by corrosion and thus its pitted,
the pits will quickly chew up the fresh seals if you can find seal kits even if you hone the bore.

Get a new MC the brakes are the most important part of this hi performance machine that must work perfectly every time.


NOTE the other part of the MC that must be inspected are the tank grommet bores ,

these bores will corrode from the grommets holding water.

NOTE to combat this issue on a new MC,
remove the grommets and coat them with Dow Corning 111,
this will prevent moisture from touching the bare metal of the bores

Ad0911

Thanks,
It was a fresh MC before taking it from the car for some paintwork, but it was stored a couple of years.
I noticed the rust in the grommet area and cleaned it out. The flat bottom surface was clean. I hate to ditch a good part but in this case...

yardpro

follow up on the saga.

finally got the brakes fixed.

i was just not persistent enough....

looks like air was in the calipers.... got it out of the back bleeders today..... boooooyaaaaa