Brake failure.....nearly

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Well there is an "switch" in the STC2778 or ABS Pump Master Cylinder and apparently this switch is prone to fail.. for P38 below the year 99

I will have to order a new one and yep you have to spend at least 1500GBP to get a new one...

My problem is different and I am apparently not the only one to have it (As describe here below)



Please read all P38 owners up to mid 1999(brake modulators) - Page 14

The cheapest way is to get one from a scrapper, but it will fail unless you rebuilt it.
 
If the Hydraulic Boost pump isn't running - wouldn't that throw a fault with the ABS Modulator Block thingy also, as this isn't getting the required pressure??

If the ABS Block is duff, all you would get is loss of Antilock and traction control, you should still get brake pedal pressure and good braking....??

If you have no hydraulic pressure in the system (due to knackered pump or pressure switch) you would get soft pedal and no braking efficency surely??
 
Saint.V8 said:
If the Hydraulic Boost pump isn't running - wouldn't that throw a fault with the ABS Modulator Block thingy also, as this isn't getting the required pressure??

If the ABS Block is duff, all you would get is loss of Antilock and traction control, you should still get brake pedal pressure and good braking....??

If you have no hydraulic pressure in the system (due to knackered pump or pressure switch) you would get soft pedal and no braking efficency surely??
Click to expand...

That's about right as i understand it.:)
 
Just do the test as detailed by Clarky, could be the relay but almost certainly the pressure switch. Even if it's the pump itself you don't need the whole braking assembly for £2K, just a pump. I'm sure Emmotts can oblige.
 
Again, many thanks to all especially Clarky

Phoned breakdown - I have recovery - and going to take the easy route, will just need to wait around Sunday for them to turn up.

Unless anyone knows a breaker with 10 miles of Kendal?

Will get over to Emmotts next week and see what they have. Will give me the chance top remove the pump etc and make sure I get right part (are there variations depending on model/year?). Might even buy some extras :)

But first will try to get some cable to jump the relay, in case I can find even a second hand relay locally. Let's hope the site warden is friendly :)

Again many thanks for clear instructions and support
 
8994071 part number for SAAB abs pressure switch which will fit P38 range Rover

I believe the above part no for a SAAB abs pressure switch will fit and work for the P38.I have not tried it myself but got the info from some one who has done so successfully.
 
JohnP38 said:
8994071 part number for SAAB abs pressure switch which will fit P38 range Rover

I believe the above part no for a SAAB abs pressure switch will fit and work for the P38.I have not tried it myself but got the info from some one who has done so successfully.
Click to expand...

Tried that route myself, John, a few months ago - rang a couple of Saab dealers who said the entire company no longer had any stock!!
 
Thought a quick update was in order .... and thanks.

Got recovery to bring me & caravan home Sunday. Today tried a local breaker on the off chance (he gives 30 day return and has always been ok with me) and he had a P38 breaking. Unfortunately not much left but did have the abs pump etc. £85 for pump, relay and a pair of headlight wiper arms (mine are missing).
Picked up, home 5.20, old one out, new one in by 6.30.
Been for a test drive and all seems perfect and in good working order.

The forum working at its best - a potential scrapper if I'd listened to the garage and their bill. Fixed for £85

Cheers
 
Trevt said:
Thought a quick update was in order .... and thanks.

Got recovery to bring me & caravan home Sunday. Today tried a local breaker on the off chance (he gives 30 day return and has always been ok with me) and he had a P38 breaking. Unfortunately not much left but did have the abs pump etc. £85 for pump, relay and a pair of headlight wiper arms (mine are missing).
Picked up, home 5.20, old one out, new one in by 6.30.
Been for a test drive and all seems perfect and in good working order.

The forum working at its best - a potential scrapper if I'd listened to the garage and their bill. Fixed for £85

Cheers
Click to expand...

Nice one! Good to hear the result:D
 
Sorry to hi jack this thread but after searching the site for topics on "ABS failure" and other brake related threads, I just wanted to confirm some things and see if I get can some expert guidance.

Yesterday, late afternoon, between 6 & 7, whilst on a 60 mile trip, on two occasions after cruising (50-60mph) I went to brake when coming up to a junction and the pedal was soft. A quick second press and the brake pedal was ok again.

Yesterday the weather was fine and in the mid to late twenties.

I have no warnings on the dash etc and didn't get any at the time either.

The rest of the journey was fine.

Any ideas/guidance on why this happened?

It's a 1995 4.6 auto.

I have carried out the following checks.

1) With the ignition off - pressed the brakes pedal 20+ times to de pressurize the system. Then turned the ignition on and the pump ran for about 20 secs then stopped. Pedal tested and was hard.

2) I have tried putting a wire to ground from the relay (85) but that doesn't seem to kick the pump into life. What position does the ignition have to be in? Radio on or dash lights up ready to fire? I'm not even sure I have it grounded correctly but need to get the ignition bit correct first!!

3) Brake fluid level checked - between min and max, but nearer min.

4) Relay cover taken off and condition checked - no damage/melting found.

5) checked for leaks - cant see anything and nothing on ground from overnight.

Thanks
 
If it works similar to how the Classic works, you won't need the ignition switch on.....on the Classic, a common fault was the relay sticking and burning out the pump motor - even with the ignition switched off (happened on my 3.9).

If you can, jump the pump to the battery (breifly - don't want an over pressure a few seconds will do) to see if the pump is actually functioning.

I would say the pump is knackered - if the pump runs when jumpered, suspect the pressure switch or accumulator.
 
Right,

Just tried jump wiring the pump by connecting a wire from the relay point 85 to the battery ground.

It does not make the pump work whatever position the ignition is in.

However, when I put the ignition into pos 2 to start the car, the pump fires up and pressurizes the system for approx 25 secs.

Can it be the pump? As it seems to work when I go to start the car.

Thanks
 
steve, if the pump works with ignition on, there is nothing wrong with the black relay. If it was, it wouldn't work. Usually if broken, the relay sticks in the ON position (actually welds its contacts together internally), so the pump is working all the time (even with the car turned off and key removed), thus frying the pump.

My guess would be that you're grounding a wrong pin. I tested the pump using a short wire and put it in the contact slots where the relay pins go in. Fat pins, IIRC.

Saint, yeah, the same problem occurs in P38's... ask me how i know :)
 
If it works when the car starts, the pump seems fine....

25 seconds is a little ecessive in my opinion - so could be the accumulator is knackered - this little dome contains a diaphram with Nitrogen pressure on one side and the brake fluid on the other, when the pump runs, it pressurises the brake fluid which pushes against the Nitrogen causing an increase in Nitrogen pressure, this is then used to maintain pressure in the hydraulic system - as you press the pedal, the Nitrogen pressure reduces and after about 10 or so pedal pushes, the pressure needs re-building and the pump runs again.

With the car running, after the pump has pressurised - press the brake pedal a few times - if the pump runs after one or two pushes, the accumulator is knackered, after about 5-7 pushes the accumulator is tired...it is runs on and off with out any pedal pushes - the accumulator is totally shot and maybe a tiny pressure leak in the system somewhere....
 
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