Lee Posted January 9, 2004 Report Share Posted January 9, 2004 It isn't running like it's loaded though, it growls up....then down. Errrrrrit/aherrrrrrr, over and over. It dims the lights like a pulse. I shut the car off and restarted. The motor sounded like it should for a few seconds and then once the system was charged it started the cycle up/down thing again. Note: For at least 1/2 a year the pump was running for one second or less at just about evey pedal use. Have to check the fluid level yet but it was fine two weeks ago. I'm at work and can't get out to check under the hood. Sounds like a final on the accummulator, yes? Pressure switch, hope? Quote Link to comment Share on other sites More sharing options...
TGPilot Posted January 9, 2004 Report Share Posted January 9, 2004 I am not an expert on PMIII's. I was lucky with my TGP and replacing the accumulator had it working like a charm for the entire time I owned the car. It does sound like your accumulator has met it maker! Chris A would most likely be able to give the "that's definitely it" nod or point you in the right direction... 8) Quote Link to comment Share on other sites More sharing options...
Lee Posted January 9, 2004 Author Report Share Posted January 9, 2004 I don't know Chis A's handle so I'll hope he sees the post. I'm wondering if fluid level alone could do it. I looked close enough to see that there are no leaks around the brakes and only the minimal seepage that I'm used to around the resivour cover. Wish the boss was off today. Hope to check it anyway before heading home. I have to hussle though to get to my 7 yr old son's bus drop. I'm not keen on driving it with the fuse out and the motor not running. I have to get 35 miles home today, then I'm off until Tuesday night shift Quote Link to comment Share on other sites More sharing options...
jheiv Posted January 9, 2004 Report Share Posted January 9, 2004 I had a problem a little similar to this, my PMIII would just keep pressurizing, to the point it would whistle as it escaped from the overpressure valve?? Anyway, for me, it was my pump relay, it was stuck open, so even when my car was shut off it would continue pumping. This might or might not be your problem, however... Chris A has a great website about TGPs and a great deal of PMIII info is included... http://aldridgec.home.att.net/TGP/brakes/powermaster.htm I believe Chris A's handle is oddly enough... Chris A. I know it is on the TGP board but not positive about the w-body board. Hope it helps Quote Link to comment Share on other sites More sharing options...
PaPaPooh Posted January 9, 2004 Report Share Posted January 9, 2004 I believe Chris A's handle is oddly enough... Chris A. I know it is on the TGP board but not positive about the w-body board. Hope it helps yes it is the same here!! Quote Link to comment Share on other sites More sharing options...
Chris A Posted January 10, 2004 Report Share Posted January 10, 2004 Well, your right it is Chris A, but maybe I should change it to PMIII God! He he.... Anyway. I assume the pump doesn't run when the car is off otherwise you'd be telling us dead battery stories. Probably not the accumulator. The pump would still pressurize and turn off even if the accumulator is bad. There would be no reserve pressure available though and the pump would run frequently. The up and down noise is probably the pressure bypass valve. My guess would be the pressure switch is bad. The best check would be to unplug the switch and see if the motor still runs. If it turns off then thats the problem. ALSO! Since IIRC the switch controls the relay ground (it gets its ign feed from the ign switch fused via the ABS fuse in the glove box) so its happened before that a bad wire or harness has shorted out and got it stuck on. But still, pulling the plug on the switch should tell. Since GM probably wants your left kidney for one, let me know I probably have a few. Chris Quote Link to comment Share on other sites More sharing options...
Lee Posted January 10, 2004 Author Report Share Posted January 10, 2004 Thanks Chris, your site on the PMIII made me think of the pressure switch first but I knew the pump had been running for 1/2 to 1 sec intervals when I used the brake: so I wasn't too confident. Yeah, the pump shuts off with the key or pulling the Glovebox ABS fuse. At start up, it pumps up normaly. The (regular) dash brake light goes out, the pump quiets a bit as the pressure tops off, then the cycle begins. It works the same if the fuse was out then replaced. I installed a full digital cluster and haven't seen the ABS light blink or light up since. May be burnt out. I drove it home with the fuse in and out, depending on when I wanted the brakes to work well. They do fade over a 13 minute period of time. Longer lasting than I expected. Anyway, I'll verify the pressure switch location in my shop manual tommarow and unplug it. Question: With the P. switch unplugged (at car start up), I'm expecting the motor to run up to full charge in the accumulator then shut off? Is that right? or: Is the car running/ABS motor running and I unplug the P. switch and the ABS motor stops? I'm thinking this is what you mean. That would point to the Pressure switch, yes? Sorry, to be a pest, I just want to get it right. Wife's already telling me to get a different car, doesn't want me to spend money on my car. Confuses me, it's always been a good car. She doesn't understand that a car with 180k is still a nice car but things wear out. I've had it 7 years. She's a 30k to 78k owner. SO...Yes I'd be very interested in one from you if that is the trouble. Thanks again, Lee Quote Link to comment Share on other sites More sharing options...
Lee Posted January 11, 2004 Author Report Share Posted January 11, 2004 I couldn't locate my manual. must be at work somewhere. Pressure switch: From the pic on your site it looks to be on the very bottom of the unit, horizontaly mounted, facing forward. Do you know how big of a socket that is? GM wants $28 just for the socket. I can get big sockets at work. Haven't tested yet, just figured out the switch placement. Son's been on me all day to play. Man there are alot of electrical connectors going to this unit :shock: Quote Link to comment Share on other sites More sharing options...
Chris A Posted January 11, 2004 Report Share Posted January 11, 2004 Yeah, its all the way on the bottom between the accumulator and the motor. I don't know what size it is I just grab something until I can get it off, be it big pliers a socket whatever. But getting it off won't do any good till you have a replacment so you could size it up then. Most likely the connector will have a lock on it so you will have to remove that before removing the plug. Good luck! Chris Quote Link to comment Share on other sites More sharing options...
Lee Posted January 14, 2004 Author Report Share Posted January 14, 2004 Chris A, I pulled the elec. connector to the pressure switch while the pump motor was running in the up/down cycle. The pump shut off as you described. I noted that it did not start up again 2 hours later when pressure had bled off, (until I plugged it back in). I assume the point was just to make sure the pressure switch had control of the motor. So the switch is bad then, yes? If so, I'd be interested in the cost of one of your extras, shipping to Osseo, WI 54758. Thanks for the very accurate help. It looks like alot of brake fluid will pour out when I remove the switch. Should I be trying to drain it down some before removal, (when the time comes). I'd like to just do a fast swap before alot pours out but it looks like a big hole and in an inconvenient place. Quote Link to comment Share on other sites More sharing options...
Chris A Posted January 14, 2004 Report Share Posted January 14, 2004 yeah, it sounds like the switch is stuck closed and keeping the motor running. The threads for the switch are large, but the hole for the brake fluid isn't so you shouldn't loose but a dribble. I wouldn't stress it. It should be easier to get to on your car since you don't have a turbo in the way. I'll get a switch ready for you and let you know. Chris Quote Link to comment Share on other sites More sharing options...
Jeff M Posted January 14, 2004 Report Share Posted January 14, 2004 Sweet job BrakeMaster 8) Never had to deal with a pressure switch issue so thanks for the learned info too! Thinking about introducing a few dribbles and the resulting few air bubbles in the area reminds me of an accumulator replacement, that can be followed up with an accumulator bleed procedure if wanted. When all done/part swapped, get into the car, hammer the brake pedal 5 times, cycle the ignition key to on, let the pump motor run till it (now!) stops, shut off the ignition key, hammer pedal 5 times, cycle ignition key to on till pump stops running, repeat a few times for good measures, if this sounds good oh BM. Jeff M Quote Link to comment Share on other sites More sharing options...
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