Total Loss of Brakes

[nz_overlander]

Hi all,

My '95 4.6 p38 lost all brakes from the pedal while on an offroad track yesterday. I can't remember if the ABS engaged and then I lost the brakes or if it happened while I was pressing down on the pedal, but it definitely happened while in use. I managed to drive home using engine braking and the handbrake.

There feels to be no pressure on the brake pedal and it travels all the way to the end with no resistance. No matter how hard I press, there are no brakes. Also on the dash I have the 3 amigos lit up, and I have a full reservoir of brake fluid with no visible leaks.

There seems to be power getting to the pump as with the ignition ON there is a constant buzzing/humming/whirring sound coming from it that doesn't stop unless ignition off - YouTube link here: P38 Loss of Brakes - Sound from Engine Bay - YouTube (https://youtube.com/shorts/tNUvjlSGTH8?feature=share)

I am aware it may be the plastic spacers giving way, however it doesn't seem like TOTAL loss of brakes is a symptom. The pump sounds as though it isn't doing anything towards pressurising the accumulator, so either the fluid is being pumped but instead of pressurising the accumulator it is just circulating it for some reason or it isn't pumping, just spinning. Is this a symptom of failed spacers?

The photo on the left is the faulty p38 and the right is a functioning p38, both early GEMS models. The difference is Pressure Switch 1 and 2, and the difference in the Pressure Valve values, although not drastically different.
182375

[Tins]

Can't have been fun. You may find something here while you wait for the P38 gurus to chime in:

P38 three lights and NO BRAKES - Land Rover Forums - Land Rover Enthusiast Forum (https://landroverforums.com/forum/general-range-rover-discussion-archived-19/p38-three-lights-no-brakes-28935/)

[nz_overlander]

Definitely wasn't fun but thankfully it happened on a 4wd track and not coming up to a stop light!

Cheers for that link, there is a lot of useful info on that thread. However the main difference seems to be that I have absolutely zero brakes no matter how hard or far I push on the brake pedal, which I am uncertain that it will be fixed using their method. Nevertheless, they talk about some good testing tips for me to try this weekend so I guess that's progress.

[Tins]

More reading. These threads are old so some of the info about parts supplies will be obsolete.

P38 Total Brake Failure! (https://www.aulro.com/afvb/p38a-range-rover/179589-p38-total-brake-failure.html)

P38 Brake failure timely reminder (https://www.aulro.com/afvb/p38a-range-rover/107093-p38-brake-failure-timely-reminder-4.html)

All p38 owners up to mid 1999 please read. (https://www.aulro.com/afvb/p38a-range-rover/53794-all-p38-owners-up-mid-1999-please-read-10.html)

[prelude]

Did you check the brake pedal is correctly connected still?

No brakes at all whatsoever usually points to the brake distributor, which is also the ABS modulator in our cars, to be fried. The plastic washer thingy inside is definately suspect since. What seems to happen is that your brake "signal" (though it is purely mechanical) does not reach the distribution points and that the pump can't build up pressure since the oil path are falsely interconnected internally.

Since you will want to replace the washer with a metal one at any rate, I suggest pulling that unit out and apart to begin with. Once you have that off, test if the pump works and holds pressure and take it from there.

Lastly, if the ABS is somehow really borked I guess it could keep a valve open and allow oil te bleed back into the reservoir, releasing brake pressure but on 4 wheels? that is a bit of a stretch imho.

Good luck finding the bug and thank god you are safe mate. I would certainly been using some non AULRO words at that point...

-P

[Borgy]

It's scary when it happens. It happened to me going down a hill with a set of lights down the bottom. I was lucky I always leave a huge gap from the car in front but shifting down through gears and using handbrake and looking for a soft tree to nudge just in case, I eventually stopped.
Similar symptoms to mine but strange thing is when I turn off car and restart the lights dissapear and brakes work as normal then after a few minutes the ABS and RC light come on and pedal sinks to floor. Stop car switch off and restart and lights stay on and still no brakes...do the restart 2 or 3 times and the lights decide to stay off and the brakes work again properly for a while, sometimes 15 minutes and 10kms of driving go by sometimes after only a few corners. Empty back roads of course..
I changed accumulater. Put in a new battery and alternator as I heard even a slightly weaker charge plays havoc with the electricals.
Am stumped..
Good luck finding an answer. Keep us in the loop if you do.
Cheers
Borgy.

[bowlink]

(I am the OP, I had the wrong account enabled)

Ok so update:


I haven't managed to switch any parts out yet, but during some more testing something interesting happened. I noticed I was getting very little brake pedal movement (only approx 55mm) and when I pressed as hard as I could, and held it, with two feet it felt like something "gave way" after a slight boom sound and suddenly I got all 100+mm travel from the brake pedal. I could pump the pedal and generate some pressure in the system to stop the car moving. This sounds like the hydraulic system is working. I was able to use these brakes a couple of times before the pedal jammed up again and only travel half distance.


Interestingly, the pressure reading on my nanocom has gone from 192 to 226 however the pump is still constantly buzzing.


I have reached out to get some new SS spacers from Russell so I will update when these have been installed. Thank you all for your input so far

[Tins]

It's scary when it happens.

Yep! Happened to me in the Adelaide hills somewhere near Woodside while approaching a level crossing in a "little" semi. Prime mover was a MB 2238. This lovely thing had air brakes, sure, but it had a hydraulic master/slave system that operated them. Guess which hose blew. The old trailer ( full to the brim with pot plants ) did not have spring brakes ( had to be parked on level ground or chocked or both ) so no emergency brakes for Tins. The AULRO swear filter would have a meltdown if I tried to replicate what I was shouting.

Train services are infrequent up there. Just as well.

[Tins]

Good luck with it. No harm done, which is the main thing.

[prelude]

Be sure to follow the instructions to the mil mate. Mine must have gotten ever so slightly off and it looses pressure quite quickly. Nothing to worry about since the brakes always work but it needs to rebuild pressure way more often than I would like to see/hear. Also, when parked for a day or more it takes a full 30 seconds to build up pressure again.

I think this is because the "plunger" shall I call it? connected to the brake pedal is slightly misaligned internally in the block.

Cheers,
-P

[bowlink]

Update on this issue.


I finally found some time to pull the modulator out following Russell's instructions that came with the stainless steel washers and what I found wasn't good... Unfortunately, part of the plunger is bent with chunks gouged out of it (hopefully the photo uploaded) and was jammed in there with the large spring. It has also caused scouring on the chamber walls. The only sign of the original plastic washers are small bits of black plastic scattered throughout the chamber.


Luckily there is a Pick-A-Part in my city with a p38 there so I'm off to get that modulator, fit the replacement washers, and install that unit. Hopefully this will be the end of the issue.

Photo of the plunger in case the upload didn't work: https://www.rangerovers.net/cdn-cgi/image/format=auto,onerror=redirect,width=1920,height=192 0,fit=scale-down/https://www.rangerovers.net/attachments/img_8691-jpg.308033/

[prelude]

bloody h... That is quite the catastrophic failure. Glad I replaced them before they went. Be very accurate in putting it all back together though, my modulator is slowly leaking internally. Not enough to ever be a safety risk but over night almost all pressure will go and during long trips I can hear the pump run every now and then. My guess is that I have a very small error introduced when I put it back together.

Cheers,
-P