p38 brakes just failed, poo nearly came out.

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cljcars

Active Member
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I have just nearly wiped out a corsa that stuck its nose out of a junction on the way home from work.
Stopped at shop and noticed a the hydraulic brake pump was still running, a bit quieter than usual and at the same pitch. Went the shop, got back in and drove off, tested brakes and noise stopped. Then corsa stuck it nose out, I slammed on and peadal went nearly to the floor and had no power all the lights on the dash came on. Hand brake, tc and brake warning light.

Seems I have lost brake power. What could this be, any idea. Looks like I may have to buy a nanocom early. Overdraft is getting bigger, dam it.
 
You've just experienced a burnt out pump motor.

The black siemens relay in the fuse box melted and kept your pump running and this has now burnt out. You have no pressure in the braking system and at best after motor has run out you have 30 good applications. However as you switched off the system depressurised anyway.

New Wabco pump and new relay needed easy job but not cheap...next time pull the ABS fuse or Black relay as quickly as possible.

I always keep a spare relay in the glove box.

Good luck.
 
Jeeeeeez! Glad you come out of that unscathed! My old tdi had abs probs, would be fine then I'd be coming up to a junction and it would grind and carry on, overshooting, then the light would come on. Pulled the fuse in the end, light was permanently on but it was safer to drive!! :(
 
aerofabrique, just pulled the relay and gave it a sniff, doesn't seam burned. Got a new fuse box just before I bought it.

Turned the ignition on and the pump, a bit noisy with bonnet open, pumped up in about 20 seconds then cut off. Brake pedal hard but lights still on. Tc went out but when I pressed it it came back up.

Strange?

That moment when the brakes fail scared the Crap out of me, had to weave out narrowly missing the on comming cars.
 
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cljcars said:
aerofabrique, just pulled the relay and gave it a sniff, doesn't seam burned. Got a new fuse box just before I bought it.

Turned the ignition on and the pump, a bit noisy with bonnet open, pumped up in about 20 seconds then cut off. Brake pedal hard but lights still on. Tc went out but when I pressed it it came back up.

Strange?
Click to expand...

It wont smell burnt.. Open it and you'll see a melted/fused contact point. Little silver blob on the switch arm. Fuse box isn't the problem it's the relay - well documented fault, doesn't happen often.

After full depression (as you experienced) it should take around 45-60 seconds to fully repressurise. It could be your accumulator may need changing also as it's weak. Only way to tell is to get the system pressure tested.

It's odd that your pump is still running though after running on when you switched off. It's probably not completely gone but on the way out hence the 20 second charge it offered. That small charge could also be why you had a hard brake pedal. If your ABS, Brake Warning and TC light is on don't drive it.

Just sucking eggs.. check under your car for any obvious brake fluid leaks, and slave cylinder if its a manual. See if any of your calipers are wet to see if you have a fluid leak. Whats the level in the brake fluid reservoir with the engine running?
 
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Right, pulled the relay apart, definitely the offending item.

The pump took about, 30 45 seconds i reckon. the level in the brake fluid reservoir is normal with engine off.

IMAG0304.jpg


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What do you think? replace the relay and try it?

This must have been sticking and then releasing when hot cold, holding the pump on off? is that correct. Hopefully I caught it before any lasting damage happened?
 
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I had the same problem, turned out to be the pressure switch in the pump. They do give up eventually.

Difficult to see from your pic of the relay's buggered. You really need to test it with a multimeter... Unless you can definitely see fused / melted contacts that aren't obvious in the pic.

I know that Emmotts have some pumps in (or did a few weeks ago) at £130, if that turns out to be the issue. They separated a pressure switch from a pump for me and let me have it for £45 - good, because you can't get them anywhere else!!

Search for my recent thread on ABS failure - might help you.
 
The contact looks like it has been stuck together and then cracked apart. Sorry the pics are pants, looked ok on the phone. You can see its melted and fused.

I will check your thread out clarky cheers.
 
Not easy to just swap out the ABS relay as I believe it's different to all the others? Best way is to put 12v through the coil and see if it switches, then you'll know for sure it's knackered. If it works, then do the following test - depressurise the brake system by pumping the pedal about 30 times (ign off). Pedal should go soft and have increased travel. Switch ignition on and listen for pump running. It should run for around 30-60 secs to repressurise the system, depending on what state your accumulator is in. If it doesn't run with the ignition on, get a length of wire and ground the switched side of the relay coil (the large pin directly opposite the 1 smaller one). If the pump then runs, it means your pressure switch is most likely the culprit.
 
If the relay has gone it's likely the pump isn't far behind. Conversely RAVE mentions if the pumps to be replaced so should the relay.

It's the most expensive relay on the board at about £30 a pop and a Siemens part, but definitely worth it for having brakes. If it is fused and cracked which I think it looks like then best get a new one, because either way you'll need one. There are americans who claim to use 'higher rated' relays here for the same problem, but i'll let you draw your on conclusions.

Second hand pumps (with accumulator) are a good bet especially if you can get it with a 3 month warranty or similar. I paid £99.99 from a P38 breaker who did just that. Nicked 2 of his relays to and probably unknowingly sold those to me for 1p.
 
Right Thanks, I will change the relay and see where that gets me. Do you know where the best place to get one is? Preferably quick?

I think the pressure switch must be still working, because it did switch of the last time I checked it. I must admit, I am near my overdraft limit at the moment after just rebuilding the engine and various other bits and pieces so could do without another £100.

Could I have damaged anything with the pump over running, Not looked at any diagrams yet but don't most hydraulic systems have Safety Valves in case of over pressure, or does it just burn the pump out? It has only just started running sticking on!
 
Rimmer (not affiliated) do them that's one of the only places online I've seen. Quick shippers.

Other than that Google the relay number from the case and see what you come up with. Depending where you are find your local scrappy and see what they have in P38 wise and see if you can blag one as a temp fix.
 
Someone in the LZ for sale section announced yesterday he's scrapping his P38 if anyone interested in spares
 
Well all, looks like that relay malfunction has knackered my abs pump. Its just seized and wont run, brakes are spongy as if no pressure. lights are on, on the dash. swine.

Probably the accumulator causing the pump to stop start, ruined the relay, and knackered the pump. Chicken and egg.

What makes it worse is the bloody vapourizers are right next to the abs pump so it will be a swine to take out.
 
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The pump isn't that hard to do - RAVE doesn't give a clear procedure as I think it forms part of another. I think there's three or four mounts on the pump, undo your hoses it won't leak a great deal but have a jar/jug handy then the banjo bolt at the back of the pump is fairly easy but just be careful of any residual pressure. Depressurize the system fully before starting of course.

All the above assuming you have your new/nearly new pump and relay and accumulator :)

Good luck!
 
Thanks for the info chaps, changed it this afternoon. 145 quid for a pump and relay, if it didn't work I could have taken it back, Off a local scrappy. Bled through the bleed nipples on the block, followed rave. Left out bleeding all the brake calipers. Worked a treat, brakes better than ever and no lights on at all.

Cheers all.
 
Since reading up on the brake system and how it works I thought it best to invest in a new acumulator for my new second hand pump. The pump currently runs for 40 seconds on start after sitting overnight but then runs again near enough after the second brake push. So just to be sure I will change the accumulator for a new one and bleed the system. I will keep the second hand one for emergencies. Along with that little spare relay which is now sitting in the glove box.
 
Just a quick update, put new accumulator on, went from 2 brake pedal pushs between pump runs to 6. Result. Just need to give it a dam good bleeding.
 
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