Delco ABS pump won't stop running

[Russ91SE]

The brakes were working OK, but it is time for a fluid change, and the hose from the reservoir to the pump was sweating fluid. Since I put it all back together and bled the fronts, now the pump isn't working properly. It runs non-stop.

Here's what I've done so far:

I removed the old fluid from the reservoir using a Mityvac hand pump, sucking it out of the front and rear chambers. I cleaned out the interior where there was some crud clinging on.

I removed the old hose running from reservoir to pump and replaced it with a translucent hose. This made it easy to see the clean fluid going in when I filled the reservoir.

I have the Delco brakes manual and started the bleeding procedures as described. Fronts went OK, clean fluid coming through. Again I used the Mityvac system at the bleed nipple, rather than the brake pedal pumping method.

At the step where you're supposed to pressurize the accumulator before moving to the rear brakes, the pump never shut off, and because I had the translucent hose I could see that the fluid wasn't moving. The hose was only about half full of fluid, and had air at the pump end. I had the thought that the pump was cavitated and worked the hose to get fluid to the pump input, and tried again, but no good.

I pulled the hose off the pump end, plugged it and sat it off to the side. then I hooked up another translucent hose and hung it vertically down to the pump, filled with fluid and turned the key. No movement on the fluid. I can hear the pump running, but there is no suction. I even hooked up a tire inflator and tried to put some pressure on the fluid. It moved forward, but when I shut it off, it came right back to the same level it started. I tried with the pump off and pump on with the same results.

Apparently the pump isn't moving any fluid, so I'm left with the thought that either the pump has gone bad internally, or there's some blockage downstream from the pump (to, or in, the accumulator?) preventing and fluid movement.

I thought about trying vaccuum pressure (rather than the positive pressure that I tried) on the pump but I'm not sure if that can help or just make it worse. I've also thought of opening the nipples at the rear brakes and trying to get fluid through the system that way. I would appreciate any inputs. It's kind of frustrating because it was working before I started, and I didn't think changing the hose would cause such a problem.

BTW, the translucent hose wasn't brake fluid compatible and started sweating after 4 days, so I switched back to black EPDM. Seemed like a good idea, but didn't work out. It was worth a try and it let me see that the fluid wasn't moving.

Thanks for any thoughts or experience you can share.

Russ

BRG91SE

[PaulEspritGT3]

Have you tried this (from the Lotus Service notes) ......

Pump Runs Continuously

IMPORTANT: This procedure is to be used if the pump runs for more than 60 seconds.

1 . With the ignition off, de-pressurise the accumulator by FIRMLY applying and releasing the brake

pedal up to 40 times. A noticeable change in brake pedal feel (to a hard pedal) will occur when the

accumulator is completely discharged.

NOTE: In the following steps, use a suitable container and/or shop towels to catch the brake fluid

and prevent it from contacting any painted surfaces.

2 . Loosen but do not remove the two tube nuts from the master cylinder front chamber (for the left and

right hand front brakes).

3 . Press the pedal to its fullest extent. Fluid should run slowly from around the tube nuts.

4 . With the pedal depressed, tighten both the tube nuts.

5 . Quickly release the pedal and re-apply using a jabbing (sharp and rapid) motion with full force.

6. Turn on the ignition and allow the motor to pressurise the accumulator.

7. Assess brake pedal feel, and road test-as in steps 16 & 17 of ‘Manual Bleeding’.

IMPORTANT: If the pump still runs continuously, refer to ‘Hydraulic Diagnosis’

Paul.

[Russ91SE]

Thanks, yeah I've been through those steps too. Forgot to mention. I may give that another shot though.

[sailorbob]

Eliminate a switch or relay fault by disconnecting the pressure switch connections and the ABS pump relay in turn.

[Russ91SE]

Follow up. I tested the electricals and they seem OK. I don't know how the pump is set up internally, but I put some suction on the feed side and nothing came out. I'm at a loss for any more "simple" cures, and don't have time to take it all apart in the coming weeks, so it's going off to the shop. Perhaps a real mechanic with some GM experience can fix a GM brake system.

[dodge1979]

Have you read my post in this section on getting the delco brakes working correctly? Give it a read and follow the methods...tried and proven. If you cant get it working the way ive written then ill get the grey matter thinking....where abouts are you btw?

[Vulcan Grey]

Here's Dodge1979's thread about the Delco ABS.

http://www.thelotusf...fully-and-well/

[Russ91SE]

Yeah, I read that thread a couple of weekends ago when I got started. Almost took the whole weekend to read it! It's good stuff; thanks for posting it. If I had more time available I would continue to tackle this. Unfortunately, I need to have it running for LOG, and between work and a couple of out-of-town trips coming up starting this week, I'm just running out of time.

On the bright side, one of the trips is to London and I've scheduled a visit to Hethel. Definitely looking forward to that.

Oh, and I'm near Pensacola, Florida.

[dodge1979]

Well its a shame, its a system that does take getting your head round..but its worth it in the end. Like many things...do it.right and it makes such a.difference. Are you bringing the esprit over to london on your trip too!

[wohlmeyer]

RUSS:  This is EXACTLY the problem I am having right now with my brakes.  I changed the master cylinder and was doing a complete flush.  The pump runs constantly and is getting fluid but wont push it to the rear brakes.  What was the solution???  my mechanic is stumped right now.

[dodge1979]

http://www.thelotusforums.com/forums/topic/50411-delco-brakes-get-them-working-successfully-and-well/

[Russ91SE]

Sorry for the delayed reply.  What I thought was a fixed system has turned to dismay and frustration.  Too long a story to type all the details, but basically I replaced the pump with a used one that I bought.  I also used the pressure switch that came with it, but that turned out to cause intermittent running of the pump.  So with my original brake system, original pressure switch, new accumulator, and used pump installed, it all worked.  For two months. 

 

I drove the car probably 4 times with about 10-12 hours of highway and city driving and it worked great.  Then with the bad weather of December it sat in the garage for the whole month.  Unfortunately, when I started it up last week, the pump ran continuously again and both lights came on.  Espritmon gave the Low Pressure code, but I haven't had any further time to work on the troubleshooting. 

 

So that's where I'm at.  Pretty much back where I started.  At least now I have more time to work on it since I'm not looking at a LOG deadline.  (Not until August anyway)

[ramjet]

Sticking relay?

[wohlmeyer]

Sorry for the delayed reply.  What I thought was a fixed system has turned to dismay and frustration.  Too long a story to type all the details, but basically I replaced the pump with a used one that I bought.  I also used the pressure switch that came with it, but that turned out to cause intermittent running of the pump.  So with my original brake system, original pressure switch, new accumulator, and used pump installed, it all worked.  For two months. 

 

I drove the car probably 4 times with about 10-12 hours of highway and city driving and it worked great.  Then with the bad weather of December it sat in the garage for the whole month.  Unfortunately, when I started it up last week, the pump ran continuously again and both lights came on.  Espritmon gave the Low Pressure code, but I haven't had any further time to work on the troubleshooting. 

 

So that's where I'm at.  Pretty much back where I started.  At least now I have more time to work on it since I'm not looking at a LOG deadline.  (Not until August anyway)

Damn Russ that sux.  My pump is currently being rebuilt.  Ill let you know if that does the trick.

 

Bill

[J400GED]

Sticking low pressure switch?

[wohlmeyer]

I wasn't going to say anything until it was all done but I got the pump back yesterday and installed it last night. Turned the key on and it immediately pumped fluid. I am hoping I can get them bled tonight but if not then it will be on sunday. I will let you know.

 

I was very excited when it pumped.