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Just read through, you do the rears last. I think you need to re-read the procedure
P38A Braking System Problem on P38a - Pedal Travel Question and What to do Next?
- Thread starter teflongrasshopper
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tomcat59alan
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Correct, after the THREE on the master cylinder., with the ignition off then on to the rears with the ignition on. That's from memory but I would recheck if I had to do it again.
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That's a good call. Or if soneone has clamped the flexible hose it might have delaminated inside.
That brake modulator can be an utter bar steward to get all air out if you've had it out and drained. That's where I found the Ezibleed kit useful, for pushing a litte of fluid through it and displacing all the bubbles.
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I think you can do the modulator on the nanocom fronts 1st then rears then fronts again I seem to Remember
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Not on a 1998 GEMS you can't. I tried it earlier this year !! Only works on later ABS ECU.
I found for filling the system, a vacuum bleed is better than eezibleed. Just remember to keep topping up !!
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Thanks I stand corrected
Gord Wedman
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Not sure if it is for the correct year but there is a pretty good YouTube video on bleeding the P38 system posted by the Norwegian fellow.
teflongrasshopper
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Hello All,
A quick update. Blocked bleed nipples was a great idea, unfortunately both are clear & can blow through them.
When bleeding I followed the rave so:
1. Depressurised
2. Bled at the front bleed screw on the master cylinder
3. "Bled" the front calipers. This is where no fluid came through or & there was very little pedal travel
4. Tried bleeding at the other valves on the master cylinder with same issues as the caliper (tried without and with pressure, I think the RAVE said ignition on for this step)
5. Gave up!
I am assuming that the pedal should go right to the floor in step 3 as the circuit is open at this point.
Is there anything in the pump/accumulator unit that could be blocking the flow of fluid to the calipers. I know there is a pressure switch. Is there a way to bypass this for testing?
A quick update. Blocked bleed nipples was a great idea, unfortunately both are clear & can blow through them.
When bleeding I followed the rave so:
1. Depressurised
2. Bled at the front bleed screw on the master cylinder
3. "Bled" the front calipers. This is where no fluid came through or & there was very little pedal travel
4. Tried bleeding at the other valves on the master cylinder with same issues as the caliper (tried without and with pressure, I think the RAVE said ignition on for this step)
5. Gave up!
I am assuming that the pedal should go right to the floor in step 3 as the circuit is open at this point.
Is there anything in the pump/accumulator unit that could be blocking the flow of fluid to the calipers. I know there is a pressure switch. Is there a way to bypass this for testing?
tomcat59alan
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I've removed bleed nipples in the past and found them clear but gently pressing on the brake pedal dislodged a lump of crap that was blocking the gallery.
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Yes, pedal should go all the way to the floor when bleeeing.
Pre-98? Modulators had plastic washers inside that have been known to break up. Odd that both fronts would break together though. And you said the pedal went all the way to the floor for the rears?
tomcat59alan
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From memory there are three bleed nipples on the brake modulator that have to be bled in order, follow Rave to the letter and you can't go wrong.
Datatek
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Pedal should go to the floor.
Datatek
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The is no reason to bypass the pressure switch, something is blocking the fluid flow, that is what needs sorting.
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Correct Alan 3 on modulator
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Collapsed flexi pipes to calipers maybe?
teflongrasshopper
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Hello All,
So got it sorted, it was the master cylinder.
The pedal travel was the thing that bothered me and everything else seemed to check out. I spoke to a friend who has done some car dealing that asked around for me. His sources said that issues with a valve in the pump unit were common which led me onto testing all the relays and electrics. After that I couldn't really avoid the inevitable so got stuck in with the master cylinder.
Once I had them both out and on the floor (with fluid drained) it was clear the old one was goosed as with hand pressure I could not push in the rod from the brake pedal. With the replacement I could push it in a good way quite easily. I suspect it's something that has ceased inside the unit. Its not obvious how to take the unit apart however if I get a chance I will try and get into it over xmas and feed back if there is anything interesting to report.
The car is transformed, there clearly has been an issue since I have had it and the difference in the way the break pedal works now and pre-master cylinder replacement is massive.
Thanks again for all your help on this, I really have found it helpful to see your comments. I have been surprised by thee obvious thing popped up that I didn't even think to check!
So got it sorted, it was the master cylinder.
The pedal travel was the thing that bothered me and everything else seemed to check out. I spoke to a friend who has done some car dealing that asked around for me. His sources said that issues with a valve in the pump unit were common which led me onto testing all the relays and electrics. After that I couldn't really avoid the inevitable so got stuck in with the master cylinder.
Once I had them both out and on the floor (with fluid drained) it was clear the old one was goosed as with hand pressure I could not push in the rod from the brake pedal. With the replacement I could push it in a good way quite easily. I suspect it's something that has ceased inside the unit. Its not obvious how to take the unit apart however if I get a chance I will try and get into it over xmas and feed back if there is anything interesting to report.
The car is transformed, there clearly has been an issue since I have had it and the difference in the way the break pedal works now and pre-master cylinder replacement is massive.
Thanks again for all your help on this, I really have found it helpful to see your comments. I have been surprised by thee obvious thing popped up that I didn't even think to check!
brianp38dse
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Glad its all sorted the p38 brakes do work well when all is right
the p38 brakes do work well when all is right
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It is years since I looked but I recall a disc shape with an Allen key in it? It required a hell of a lot of force to undo it.
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Is that the one that needs to be marked so it's screwed back in to exactly the same position?
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Er, dunno. I had an old unit lying around and wanted to know what was inside so attacked it!
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