Another pre-service issue brakes this time

[Guest]

Another question everyone:
I've felt for a little while that my brakes were getting a bit soft, so
I tried some emergency stops last night and discovered that I was
running out of servo before I locked up the wheels, in other words I was
hitting the "hard" feeling you get when you are doing all the work on
the brake pedal yourself. We still stopped pretty rapidly, and we had a
smallish unbraked trailer on the back at the time, so it's not dangerous
(yet), but clearly I have a potential problem since I would expect to be
able to lock up the wheels on a dry road and force the ABS to cut in.
to a vacuum reservoir reserved for the brakes, with also a minor pipe to
run the a/c and p/s "idle up" actuators. The latter two don't seem to
be doing much, which suggests to me either that the pump is getting
tired or that I have a leak somewhere. I also remember a previous
correspondence a while back about the non-return valve at the top of the
vacuum reservoir failing, but the brake servo seems to hold its vacuum
when left for several days so I don't think it's that.
Does anyone have any advice to offer?
Christopher Bell
Devon, UK
1996 1HD-FT
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[Guest]

when you press the pedal can you push it all the way to the floor? or only half way and then it firms up?
have you checked the vacuum pump- i do it by pulling the hose off the servo and stick my finger on the end- you should feel a reasonable vaccum being created.
when did you last change the fluid- this made a HUGE change with my brakes- flushed the fluid out a few times as the first change the fluid was dark brown. i use my local garage to power bleed my brakes as for some reason they get a far firmer pedal than i can using traditional methods.
> Subject: [ELCO] Another pre-service issue: brakes this time
> Date: Thu=2C 1 Oct 2009 10:02:28 +0100
> From: [Email address removed]
> To: [Email address removed]
>
> Another question everyone:
>
> I've felt for a little while that my brakes were getting a bit soft=2C so
> I tried some emergency stops last night and discovered that I was
> running out of servo before I locked up the wheels=2C in other words I was
> hitting the "hard" feeling you get when you are doing all the work on
> the brake pedal yourself. We still stopped pretty rapidly=2C and we had a
> smallish unbraked trailer on the back at the time=2C so it's not dangerous
> (yet)=2C but clearly I have a potential problem since I would expect to be
> able to lock up the wheels on a dry road and force the ABS to cut in.
>
> >From what I can make out it has a vacuum pump that sends its main "suck"
> to a vacuum reservoir reserved for the brakes=2C with also a minor pipe to
> run the a/c and p/s "idle up" actuators. The latter two don't seem to
> be doing much=2C which suggests to me either that the pump is getting
> tired or that I have a leak somewhere. I also remember a previous
> correspondence a while back about the non-return valve at the top of the
> vacuum reservoir failing=2C but the brake servo seems to hold its vacuum
> when left for several days so I don't think it's that.
>
> Does anyone have any advice to offer?
>
> Christopher Bell
> Devon=2C UK
> 1996 1HD-FT
> ____________________________________________________________
> Electronic mail messages entering and leaving Arup business
> systems are scanned for acceptability of content and viruses
>
> --
> European Land Cruiser Owners Mailing List
> Further Info: http://www.landcruisers.info/
=0A_________________________________________________________________=0AWith Windows Live=2C you can organise=2C edit=2C and share your photos.=0Ahttp://clk.atdmt.com/UKM/go/134665338/direct/01/

 

[Guest]

James
Thanks for the ideas.
The pedal does indeed firm up about half way down, but if I pump it
repeatedly when at idle I can exhaust the servo assistance, ie use the
vacuum faster than the pump is delivering it. So the pump is definitely
delivering a vacuum, but I'm not sure that it is enough, or perhaps it
is getting lost en-route. I haven't attempted any hands-on diagnosis
yet but I'll do some serious hose checking this weekend.
Fluid was last bled about 3 years ago, and I've asked them to do this
anyway. I've no doubt that this will help - apart from anything else if
it reduces the brake pedal travel it will use less vacuum. I don't know
if they have a power bleed system, but I'll ask.
CB
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[Guest]

Sounds like you might have a leaky pipe somewhere. Best way to check is to test the feel of the vaccum at the pump end of the pipe and the servo end of the pipe. If you have a leak vacuum will develope far quicker at the pump end than the servo end.
> Subject: RE: [ELCO] Another pre-service issue: brakes this time
> Date: Thu=2C 1 Oct 2009 10:21:16 +0100
> From: [Email address removed]
> To: [Email address removed]
>
> James
>
> Thanks for the ideas.
>
> The pedal does indeed firm up about half way down=2C but if I pump it
> repeatedly when at idle I can exhaust the servo assistance=2C ie use the
> vacuum faster than the pump is delivering it. So the pump is definitely
> delivering a vacuum=2C but I'm not sure that it is enough=2C or perhaps it
> is getting lost en-route. I haven't attempted any hands-on diagnosis
> yet but I'll do some serious hose checking this weekend.
>
> Fluid was last bled about 3 years ago=2C and I've asked them to do this
> anyway. I've no doubt that this will help - apart from anything else if
> it reduces the brake pedal travel it will use less vacuum. I don't know
> if they have a power bleed system=2C but I'll ask.
>
> CB
>
> ____________________________________________________________
> Electronic mail messages entering and leaving Arup business
> systems are scanned for acceptability of content and viruses
>
> --
> European Land Cruiser Owners Mailing List
> Further Info: http://www.landcruisers.info/
=0A_________________________________________________________________=0AWith Windows Live=2C you can organise=2C edit=2C and share your photos.=0Ahttp://clk.atdmt.com/UKM/go/134665338/direct/01/

 

[Guest]

<James wrote>

Sounds like you might have a leaky pipe somewhere. Best way to check is
to test the feel of the vaccum at the pump end of the pipe and the servo
end of the pipe. If you have a leak vacuum will develope far quicker at
the pump end than the servo end.
I'd sort of worked that out for myself. It's annoying that I don't have
a vacuum gauge because subjective measurement via a finger tip is going
to be tricky unless, as you say, I have a significant leak. I thought
of making a manometer out of water, and then remembered that one
atmosphere =3D 32 feet thereof ... tricky! I suppose something like a
balloon stretched over a small funnel might do.

CB

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