P38A ABS Pump Failing

Went out to move my P38 this morning to check a few things. WTF no brakes - pedal to the floor. So waited for the pump to pressurise, but it never kicked on.

Gave it a few gentle whacks, and it started but definitely not sounding good. Anyone got one at a reasonable price ?

pwood999 said:

Went out to move my P38 this morning to check a few things. WTF no brakes - pedal to the floor. So waited for the pump to pressurise, but it never kicked on.

Gave it a few gentle whacks, and it started but definitely not sounding good. Anyone got one at a reasonable price ?

Click to expand...

You sure it's the pump and not the pressure switch? The switch is a much more common fail item than the pump.

That was my first thought. When I whacked it, the pump started but not sounding great. It seems to speed up & slow down quite a bit, and only occasionally runs steady. It was fine yesterday.

Looking at RAVE it seems I can simply bridge the pump relay to check if the pump runs properly. Will pump the brakes a few times to lower the pressure first though !!

pwood999 said:

That was my first thought. When I whacked it, the pump started but not sounding great. It seems to speed up & slow down quite a bit, and only occasionally runs steady. It was fine yesterday.

Looking at RAVE it seems I can simply bridge the pump relay to check if the pump runs properly. Will pump the brakes a few times to lower the pressure first though !!

Click to expand...

Dodgy contacts can cause variable speed. Jumping the relay should prove if it's the pump or not.

Update:

1. Pumped brake 5 time to reduce any residual pressure. Then bridged the relay contacts and the pump seems to run fine.
2. Borrowed the relay from project P38, and got same behaviour, so relay is probably ok.
3. With original relay back in, I tapped the pressure switch, and it started running intermittently. At same time I could feed the relay switching on & off.

So it does appear to be the switch. After about 30 seconds the pump started to run steady (ish), so it does sound like switch contacts, but I should probably check the connector after dinner !!

Cannot find any new available, only second had for £150 . At that price I might grab a complete used pump, switch & accumulator for £200.

Might even consider a 200bar pressure gauge for testing.

pwood999 said:

Update:

1. Pumped brake 5 time to reduce any residual pressure. Then bridged the relay contacts and the pump seems to run fine.
2. Borrowed the relay from project P38, and got same behaviour, so relay is probably ok.
3. With original relay back in, I tapped the pressure switch, and it started running intermittently. At same time I could feed the relay switching on & off.

So it does appear to be the switch. Cannot find any new available, only second had for £150 . At that price I might grab a complete used pump, switch & accumulator for £200.

Might even consider a 200bar pressure gauge for testing.

Click to expand...

The switch is a available new as a SAAB part and also for some Yank cars. There have been several posts about it.
Second hand is a waste of time IMO.

Pressureswitch replacement: ACDelco 25530882


ACDelco25530882 GM Original Equipment Brake Pressure Warning Switch(slutscomei.com)

Yes found various threads about the SAAB part, but cannot find it available anywhere.

That link does not seem to work. Browser says there's a typo ?

Amazon product

They seem available over the pond. Also Jag fitment to.

J

marjon said:

Amazon product

They seem available over the pond. Also Jag fitment to.

J

Click to expand...

That says currently unavailable when I click on it. Guessing most of these cars stopped production 20 years ago so parts are becoming rare.

Datatek said:

The switch is a available new as a SAAB part and also for some Yank cars. There have been several posts about it.
Second hand is a waste of time IMO.

Pressureswitch replacement: ACDelco 25530882


ACDelco25530882 GM Original Equipment Brake Pressure Warning Switch(slutscomei.com)

Click to expand...

Sorry about the link, seems the site has disappeared. Lots available in the USA if you Google ACDelco 25530882

Grrrrrr said:

That says currently unavailable when I click on it. Guessing most of these cars stopped production 20 years ago so parts are becoming rare.

Click to expand...

That was the first 1 I came across, We did this about a year ago for somebody else he managed to get 1 if I remember.

Try here

http://oemcats.com/oem-parts/25530882.html

It would also seem that Porsche use them too, But they have a price attached But they state "core charge" so you have to send the old 1 back for refurb



J

Spare (used) pump with accumulator & pressure switch arrived today. Pressure switch seems to be 36mm, but I cannot shift it with the only 36mm spanner I have (thin water pump spanner). 36mm socket will not fit because switch is too close to the pump.

Guess I need a better spanner, but got no transport until wifey gets home.

pwood999 said:

Spare (used) pump with accumulator & pressure switch arrived today. Pressure switch seems to be 36mm, but I cannot shift it with the only 36mm spanner I have (thin water pump spanner). 36mm socket will not fit because switch is too close to the pump.

Guess I need a better spanner, but got no transport until wifey gets home.

View attachment 296219

Click to expand...

That looks like a replacement switch, not the original.

Hopefully it works. The original has a slightly lighter green body after cleaning engine bay grime, but the threaded sections are same colour. Can't find any part number on either.

Bought a 36mm single hex socket, which just fits. Noticed the old switch has slight wobble on the pin sticking out the end. The replacement seems to not have this.

Have bled the the booster screw on master cylinder. Hopefully don't need to bleed the entire system.

Rain stopped play.

pwood999 said:

Hopefully it works. The original has a slightly lighter green body after cleaning engine bay grime, but the threaded sections are same colour. Can't find any part number on either.

Bought a 36mm single hex socket, which just fits. Noticed the old switch has slight wobble on the pin sticking out the end. The replacement seems to not have this.

Have bled the the booster screw on master cylinder. Hopefully don't need to bleed the entire system.

Rain stopped play.

Click to expand...

Pump the brake pedal 30 times as required for changing the accumulator. Should be no need to touch the booster screw.

Datatek said:

That looks like a replacement switch, not the original.

Click to expand...

Was about to say the same, plenty of spanner rash.

Bled it anyway. Got some bubbles for about four pumps. Then just fluid, so was def worth doing the booster bleed.

Looks like the eBay pressure switch is ok. Discharged the pressure a few times, and pump runs up to pressure when I put the ignition on. Brakes now working.

Downside is it runs every 3 hard brake presses, so accumulator might need doing soon. Will try the used one first, and buy another if required.

pwood999 said:

Bled it anyway. Got some bubbles for about four pumps. Then just fluid, so was def worth doing the booster bleed.

Looks like the eBay pressure switch is ok. Discharged the pressure a few times, and pump runs up to pressure when I put the ignition on. Brakes now working.

Downside is it runs every 3 hard brake presses, so accumulator might need doing soon. Will try the used one first, and buy another if required.

Click to expand...

I thought 3 hard presses was the trigger to cut in?

pwood999 said:

Bled it anyway. Got some bubbles for about four pumps. Then just fluid, so was def worth doing the booster bleed.

Looks like the eBay pressure switch is ok. Discharged the pressure a few times, and pump runs up to pressure when I put the ignition on. Brakes now working.

Downside is it runs every 3 hard brake presses, so accumulator might need doing soon. Will try the used one first, and buy another if required.

Click to expand...

Three hard presses is about normal.