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| Academic question for the day [message #261232] |
Sun, 07 September 2014 19:46  |
Ken Burton
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Location: Hebron, Indiana
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At what vacuum (pressure) level will 70 degree F. water boil?
Here is the issue.
I installed new pads, rotors, and hoses on the rear of a 16 year old Blazer. the brakes have never been bled before and now I'm trying to do that by vacuum bleeding. There is a lot air in the system because it was opened up for days while I waited for new hoses to arrive from Rock Auto. So I put it all together and started to suck out all of the old fluid and air out of it. I get to about 20" of vacuum and I see clean fluid with tiny, tiny bubbles. If I go to 25" of vacuum I see very large bubbles. I have the bleeders teflon taped and they do not leak air when closed. When opened 1/4 turn I now pull fluid and air bubbles.
So Now I'm thinking that brake fluid is hygroscopic and that fluid in there probably has all kinds of moisture in it. I'm looking for the source of the bubbles and I'm thinking that maybe at 25" of vacuum I'm actually boiling off some of the moisture absorbed by the fluid.
BTW,
This thing will not gravity bleed due to the ABS and I do not have an adapter to pressure bleed it. (I may have to make one.) The correct method is to use a $2000 scanner and force the fluid through.
Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana
[Updated on: Sun, 07 September 2014 20:13] Report message to a moderator |
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| Re: Academic question for the day [message #261236 is a reply to message #261235] |
Sun, 07 September 2014 20:17  |
Ken Burton
Messages: 10030
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Location: Hebron, Indiana
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wally wrote on Sun, 07 September 2014 20:10Ken Burton wrote on Sun, 07 September 2014 19:46At what vacuum (pressure) level will 70 degree F. water boil?
He is the issue.
I installed new pads, rotors, and hoses on the rear of a 16 year old Blazer. the brakes have never been bled before and now I'm trying to do that by vacuum bleeding. There is a lot air in the system because it was opened up for days while I waited for new hoses to arrive from Rock Auto. So I put it all together and started to suck out all of the old fluid and air out of it. I get to about 20" of vacuum and I see clean fluid with tiny, tiny bubbles. If I go to 25" of vacuum I see very large bubbles. I have the bleeders teflon taped and they do not leak air when closed. When opened 1/4 turn I now pull fluid and air bubbles.
So Now I'm thinking that brake fluid is hygroscopic and that fluid in there probably has all kinds of moisture in it. I'm looking for the source of the bubbles and I'm thinking that maybe at 25" of vacuum I'm actually boiling off some of the moisture absorbed by the fluid.
BTW,
This thing will not gravity bleed due to the ABS and I do not have an adapter to pressure bleed it. (I may have to make one.) The correct method is to use a $2000 scanner and force the fluid through.
70 F water "boils" at .362292 psi absolute taken from Combustion Engineering's power system book. We used that kinda stuff for condenser performance in the power plant.
So,
Now I need to figure out the relationship between 25" of mercury and .362292 psi.
Thanks.
Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana
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| Re: Academic question for the day [message #261237 is a reply to message #261236] |
Sun, 07 September 2014 20:25 |
Ken Burton
Messages: 10030
Registered: January 2004
Location: Hebron, Indiana
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Ken Burton wrote on Sun, 07 September 2014 20:17wally wrote on Sun, 07 September 2014 20:10Ken Burton wrote on Sun, 07 September 2014 19:46At what vacuum (pressure) level will 70 degree F. water boil?
He is the issue.
I installed new pads, rotors, and hoses on the rear of a 16 year old Blazer. the brakes have never been bled before and now I'm trying to do that by vacuum bleeding. There is a lot air in the system because it was opened up for days while I waited for new hoses to arrive from Rock Auto. So I put it all together and started to suck out all of the old fluid and air out of it. I get to about 20" of vacuum and I see clean fluid with tiny, tiny bubbles. If I go to 25" of vacuum I see very large bubbles. I have the bleeders teflon taped and they do not leak air when closed. When opened 1/4 turn I now pull fluid and air bubbles.
So Now I'm thinking that brake fluid is hygroscopic and that fluid in there probably has all kinds of moisture in it. I'm looking for the source of the bubbles and I'm thinking that maybe at 25" of vacuum I'm actually boiling off some of the moisture absorbed by the fluid.
BTW,
This thing will not gravity bleed due to the ABS and I do not have an adapter to pressure bleed it. (I may have to make one.) The correct method is to use a $2000 scanner and force the fluid through.
70 F water "boils" at .362292 psi absolute taken from Combustion Engineering's power system book. We used that kinda stuff for condenser performance in the power plant.
So,
Now I need to figure out the relationship between 25" of mercury and .362292 psi.
Thanks.
Well that destroyed that theory
25 " of mercury = 12.7 PSI
Based on my calculations I would have to be over 29" to get it to boil.
Thanks
Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana
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| Re: Academic question for the day [message #261238 is a reply to message #261237] |
Sun, 07 September 2014 20:29 |
midlf
Messages: 2212
Registered: July 2007
Location: SE Wisc. (Palmyra)
Karma: 1
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I suspect your bubbles are disolved air coming out of solution.
Steve Southworth
1974 Glacier TZE064V100150 (for workin on)
1975 Transmode TZE365V100394 (parts & spares)
Palmyra WI
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| Re: [GMCnet] Academic question for the day [message #261240 is a reply to message #261236] |
Sun, 07 September 2014 20:32 |
emerystora
Messages: 4442
Registered: January 2004
Karma: 13
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Ken
Forget about mercury.
.362292 psi equals 10.22 inches of water.
However there are other factors at play than just the boiling point of water. In a hygroscopic mixture there are intermolecular attraction forces so even if water has that boiling point alone you are never going to get the pressure low enough to boil it off using a vacuum pump unless you have a lab pump which would set you back several thousands of dollars. Your best bet is to flush it out and put in new fluid.
Emery Stora
77 Kingsley
Frederick, CO
> On Sep 7, 2014, at 9:17 PM, Ken Burton wrote:
>
> wally wrote on Sun, 07 September 2014 20:10
>> Ken Burton wrote on Sun, 07 September 2014 19:46
>>> At what vacuum (pressure) level will 70 degree F. water boil?
>>>
>>> He is the issue.
>>>
>>> I installed new pads, rotors, and hoses on the rear of a 16 year old Blazer. the brakes have never been bled before and now I'm trying to do
>>> that by vacuum bleeding. There is a lot air in the system because it was opened up for days while I waited for new hoses to arrive from Rock
>>> Auto. So I put it all together and started to suck out all of the old fluid and air out of it. I get to about 20" of vacuum and I see clean
>>> fluid with tiny, tiny bubbles. If I go to 25" of vacuum I see very large bubbles. I have the bleeders teflon taped and they do not leak air when
>>> closed. When opened 1/4 turn I now pull fluid and air bubbles.
>>>
>>> So Now I'm thinking that brake fluid is hygroscopic and that fluid in there probably has all kinds of moisture in it. I'm looking for the
>>> source of the bubbles and I'm thinking that maybe at 25" of vacuum I'm actually boiling off some of the moisture absorbed by the fluid.
>>>
>>>
>>>
>>> BTW,
>>> This thing will not gravity bleed due to the ABS and I do not have an adapter to pressure bleed it. (I may have to make one.) The correct
>>> method is to use a $2000 scanner and force the fluid through.
>>
>> 70 F water "boils" at .362292 psi absolute taken from Combustion Engineering's power system book. We used that kinda stuff for condenser
>> performance in the power plant.
>
>
> So,
> Now I need to figure out the relationship between 25" of mercury and .362292 psi.
>
> Thanks.
>
>
>
> --
> Ken Burton - N9KB
> 76 Palm Beach
> Hebron, Indiana
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| Re: Academic question for the day [message #261241 is a reply to message #261232] |
Sun, 07 September 2014 20:58 |
Bullitthead
Messages: 1411
Registered: November 2013
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Ken,
Why can you not use the brake pedal to push fluid through? I know it really requires a helper with some skill to push the pedal slowly and repetitively, but that system should bleed with no problem with the key off and no power to the ABS as long as the prop valve has not been set to block off the rear system. If you see clean fluid at the bleeders, then that would be new fluid, right?
Terry Kelpien
ASE Master Technician
73 Glacier 260
Smithfield, Va.
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| Re: [GMCnet] Academic question for the day [message #261259 is a reply to message #261232] |
Sun, 07 September 2014 22:55 |
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USAussie
Messages: 15912
Registered: July 2007
Location: Sydney, Australia
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Ken,
Forget the science; I reckon you're sucking air in around the Teflon tape the higher the vacuum the bigger the bubbles!
Take one of the bleeders and drill a small hole straight through the angled sealing surface on the bottom. Replace the bleeder
furthest away from the master cylinder. Tighten it down completely so what's left of the sealing surface seals in the caliper. Then
pull a vacuum and let us know what you get.
Regards,
Rob M.
The Pedantic Mechanic
USAussie - Downunder
USA '75 Avion - Double Trouble TZE365V100426
AUS '75 Avion - The Blue Streak TZE365V100428
-----Original Message-----
From: Ken Burton
At what vacuum (pressure) level will 70 degree F. water boil?
He is the issue.
I installed new pads, rotors, and hoses on the rear of a 16 year old Blazer. the brakes have never been bled before and now I'm
trying to do that by vacuum bleeding. There is a lot air in the system because it was opened up for days while I waited for new
hoses to arrive from Rock Auto. So I put it all together and started to suck out all of the old fluid and air out of it. I get to
about 20" of vacuum and I see clean fluid with tiny, tiny bubbles. If I go to 25" of vacuum I see very large bubbles. I have the
bleeders teflon taped and they do not leak air when closed. When opened 1/4 turn I now pull fluid and air bubbles.
So Now I'm thinking that brake fluid is hygroscopic and that fluid in there probably has all kinds of moisture in it. I'm looking
for the source of the bubbles and I'm thinking that maybe at 25" of vacuum I'm actually boiling off some of the moisture absorbed by
the fluid.
BTW,
This thing will not gravity bleed due to the ABS and I do not have an adapter to pressure bleed it. (I may have to make one.) The
correct method is to use a $2000 scanner and force the fluid through.
--
Ken
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Regards,
Rob M. (USAussie)
The Pedantic Mechanic
Sydney, Australia
'75 Avion - AUS - The Blue Streak TZE365V100428
'75 Avion - USA - Double Trouble TZE365V100426
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| Re: [GMCnet] Academic question for the day [message #261262 is a reply to message #261259] |
Sun, 07 September 2014 23:54 |
Bullitthead
Messages: 1411
Registered: November 2013
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One more thing, ABS is an addition to a braking system, and must not interfere with normal brake operation when the ABS system is not functioning. Brake fluid will still flow to the wheels when there is sufficient pressure differential. The weight of the fluid may not be enough to generate that pressure, so gravity may take a long time to get fluid down, and any air bubbles in the lines will probably counteract any gravitational pressure.
If you want to make your own pressure bleeder, go to the boneyard and get another lid and gasket for the master cylinder. Drill a hole in it and install your choice of hose connection that you can hook up to a regulated compressed air source. Nitrogen would be even better. Fill up the M/C and put just a few PSI on it and go to the most distant wheel and let the fluid flow nice and slow until there are no bubbles, check your fluid level and go to the next wheel. Be careful when releasing any pressure in the M/C, no need to make a big splash of brake fluid on any paint!
Terry Kelpien
ASE Master Technician
73 Glacier 260
Smithfield, Va.
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| Re: Academic question for the day [message #261265 is a reply to message #261237] |
Mon, 08 September 2014 00:25 |
Ken Burton
Messages: 10030
Registered: January 2004
Location: Hebron, Indiana
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I got it fixed. I just went through a quart bleeding it, and bleeding it, and bleeding it until I got all of the air out.
Thanks
Ken B.
Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana
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| Re: Academic question for the day [message #261266 is a reply to message #261232] |
Mon, 08 September 2014 00:27 |
Chris Tyler
Messages: 458
Registered: September 2013
Location: Odessa FL
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Im with Emory, change the fluid. Its cheap.
I had a 98 blazer with ABS. Changed out the rear calipers and had no problem gravity bleeding the system. I changed all the fluid, using a turkey baster for the MC, gravity bled it to fill the calipers most of the way [BTW the bleeds are the high point, right?]and then the old mayonaise jar with 2" of old BF and vinyl line trick to bleed them.
I have found a similar problem using a mighty vac and leaking air at the bleeders. My 73 Vette was a nightmare to bleed.
Have had good luck with the Russell speed bleeders in that and several other vehicles..
76 Glenbrook
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| Re: Academic question for the day [message #261285 is a reply to message #261232] |
Mon, 08 September 2014 09:15 |
jhbridges
Messages: 8412
Registered: May 2011
Location: Braselton ga
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Now that the system is bled, go out on a gravel road and light off the ABS a few times, to get the old fluid out of it. I found this out on one of the Town and Country vans. Fortunately, it was the first year for ABS on them and they had some teething problems, so Mopar warranted the pump and hydraulic assembly for lifetime. I think I paid the dealer about 250 bux, they billed Chrysler somethiing north of 2 grand.
--johnny
Foolish Carriage, 76 26' Eleganza(?) with beaucoup mods and add - ons.
Braselton, Ga.
I forgive them all, save those who hurt the dogs. They must answer to me in hell
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| Re: Academic question for the day [message #261288 is a reply to message #261232] |
Mon, 08 September 2014 09:57 |
habbyguy
Messages: 896
Registered: May 2012
Location: Mesa, AZ
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I'm with Rob on this one - when I used my big honkin' vacuum pump to bleed my brakes, I could have put a gallon of fluid through the system waiting for the bubbles to stop. There was just no way I could get a seal around the bleed nipples. So what I did was to simply use the vacuum to pull enough fluid through to ensure I'd properly flushed the system, then used the "stomp the brake pedal and hold" method to make sure there was no air left in the system.
Mark Hickey
Mesa, AZ
1978 Royale Center Kitchen
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| Re: [GMCnet] Academic question for the day [message #261356 is a reply to message #261288] |
Tue, 09 September 2014 00:19 |
James Hupy
Messages: 6806
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Now you know why I am not a fan of vacuum bleeders. But, your results might
vary, (i kinda doubt it though).
Jim Hupy
Salem, Or. but presently in Kelonwa BC.
On Mon, Sep 8, 2014 at 10:57 AM, Mark wrote:
> I'm with Rob on this one - when I used my big honkin' vacuum pump to bleed
> my brakes, I could have put a gallon of fluid through the system waiting
> for the bubbles to stop. There was just no way I could get a seal around
> the bleed nipples. So what I did was to simply use the vacuum to pull enough
> fluid through to ensure I'd properly flushed the system, then used the
> "stomp the brake pedal and hold" method to make sure there was no air left
> in
> the system.
> --
> Mark Hickey
> Mesa, AZ
> 1978 Royale Center Kitchen
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| Re: Academic question for the day [message #261360 is a reply to message #261288] |
Tue, 09 September 2014 03:06 |
Ken Burton
Messages: 10030
Registered: January 2004
Location: Hebron, Indiana
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I had no air leak at the bleeders. I could hold 25" to 26" of vacuum on it for an hour. I think what I discovered is that you can not vacuum through the ABS. The ABS would not allow extra fluid to come through from the master cylinder. If I put a vacuum on it and pressed on the pedal, then more fluid would flow from the master cylinder and reservoir to the system and allowed me to purge all of the air. This also explains why they wanted me to attach a Tech 2 scanner and run he ABS pump to bleed the brakes.
Anyway, I got it done and bled it one more time tonight and with no more air. It is back on it's rear wheels and all I need to do is flush the fronts. The fronts should be easy because I have not opened up the hydraulic system. I have never seen black brake fluid before but this stuff was really black. I'll just bleed the fronts using the brake pedal until the new DOT4 comes through and the fluid turns clear.
Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana
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| Re: [GMCnet] Academic question for the day [message #261388 is a reply to message #261360] |
Tue, 09 September 2014 09:51 |
James Hupy
Messages: 6806
Registered: May 2010
Karma: -62
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Ken, when my son, who had a similar ABS system to yours, tried to bleed
down the system, he encountered the same difficulty as you are having. When
we attached the scan tool to his system, the ABS unit made noise like a
piston rapidly cycling. Upon closer inspection, I located bleeder screws on
the unit itself. I attached a bleeder hose onto those screws and the unit
bled itself with the scan tool connected. I don't know if there is a manual
way to do that function, though. We eventually prevailed. Good luck with
yours.
Jim Hupy
Salem, Or
78 GMC Royale 403
On Tue, Sep 9, 2014 at 4:06 AM, Ken Burton wrote:
> I had no air leak at the bleeders. I could hold 25" to 26" of vacuum on
> it for an hour. I think what I discovered is that you can not vacuum
> through the ABS. The ABS would not allow extra fluid to come through from
> the master cylinder. If I put a vacuum on it and pressed on the pedal,
> then more fluid would flow from the master cylinder and reservoir to the
> system and allowed me to purge all of the air. This also explains why they
> wanted me to attach a Tech 2 scanner and run he ABS pump to bleed the
> brakes.
>
> Anyway, I got it done and bled it one more time tonight and with no more
> air. It is back on it's rear wheels and all I need to do is flush the
> fronts. The fronts should be easy because I have not opened up the
> hydraulic system. I have never seen black brake fluid before but this
> stuff was
> really black. I'll just bleed the fronts using the brake pedal until the
> new DOT4 comes through and the fluid turns clear.
> --
> Ken Burton - N9KB
> 76 Palm Beach
> Hebron, Indiana
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| Re: [GMCnet] Academic question for the day [message #261396 is a reply to message #261388] |
Tue, 09 September 2014 11:53 |
Ken Burton
Messages: 10030
Registered: January 2004
Location: Hebron, Indiana
Karma: 10
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Thanks Jim.
That gives me a little more insight as to what that ABS system is doing. I have not driven it yet, but I think I have all of the air out now. My real problem is that I do not really understand what is inside the ABS control unit. I guess I ought to find one in a junk yard and take it apart. As if I really have time to do that.
Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana
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