How often should the PM pump run?

I

im4darush

Member
Joined
Jun 26, 2007
I was coming to a stop the other day and noticed that my pump was running longer than usual. Of course the light came on soon thereafter. I went ahead and replaced the accumulator the next day. Pump runs about 10 seconds with ignition on and turns off. No light on the dash, brakes feel fine. I'm not sure if I am paranoid now, but I hear the pump run quite often. Not every time I touch the brakes, but probably every 2-3 for sure. When it does turn on, it will run for a few seconds and turn off. I know it is designed to run in short durations, but how often? It seems every time I come to a light or have to use the brake pedal more than once, it comes on for a few seconds. The accumulator I put on was taken off a brand new PM unit from kirban.

Also, where should my fluid level be? Is too much fluid bad for the PM? Currently, it is close to the top and even on both sides.

Thanks!
 
Updating my thread. Well I went back and this time the pump would not turn off at all when I turned the ignition off. Not exactly sure why. It worked well in the morning when I put the accumulator on. Now it runs non-stop. I can see it getting sucked down but it won't stop. I also replaced the pressure switch and same thing. Can anything else cause the pump to not turn off? It would turn off even with the old accumulator and now it just keeps going with any one I try. As well as both switches. Very strange.
 
It doesn't make any sense that the motor runs with the key off. The schematics say the motor is connected to power in key on or start only.
 
Either the pressure switch is bad, or system pressure has dropped below 510psi and the pump can't reach the required 675psi to shut the pump off. Could be internal leakage or external leakage. Check for leaks around the master cylinder, and don't forget to look up in the cabin under the dash where the pedal rod enters the cabin
 
To check for internal leaks, turn key off after a short pump run cycle, place a short piece (6-12 inches) of flexible clear plastic tubing (aprox. 1/4 to 1/2" diameter) over Port A in the inboard reservoir. If leakage is occurring, fluid will rise in the tube. Place the same plastic tube over Port B. If leakage is occurring the check valve is the issue.
What is port A and B you ask?
On the inboard side of the reservoir, if you look down into the fluid you will see two holes/ports. The rear one is Port A, and the one forward of that is Port B.
 
Ok so pump running non stop (key on) can be either the switch, or the fact that it can't reach needed pressure required for the switch to turn off the pump due to internal leakage. I assumed it was my accumulator when I first heard it run too long and swapped it out. It then worked ok for a few hours. After I parked it and went back to it, the pump would not turn off. Much more going on than just the bowl I guess. I have a complete PM from kirban that I pulled the bowl and switch from...time for the whole assembly to go into the car. Second time doing this job...first was on a 16k mile car, and now a 29k mile one.
 
These kind of bad luck stories are unfortunate. If you're not the original owner it's hard to tell what kind of maintenance, or lack thereof, that it received over the years.
Both my GN's still have their original PM's. One with 177,000 miles and the other with 150,000 miles.
 
Switched out the entire PM for a new one. Brakes work fine now and the pump turns off as it should. However it does turn on almost all the time. When it does turn on, it goes off in a few seconds. So back to the original question, when working properly, is it ok for the pump to run 3-4 seconds every time you apply the brakes? If not, can bleed quality play a role here? I bled everything and the pedal feels ok but not perfect. If there is a bit of air somewhere in there, can it affect the frequency of the pump running?
 
im4darush said:
Ok so pump running non stop (key on) can be either the switch, or the fact that it can't reach needed pressure required for the switch to turn off the pump due to internal leakage. I assumed it was my accumulator when I first heard it run too long and swapped it out. It then worked ok for a few hours. After I parked it and went back to it, the pump would not turn off. Much more going on than just the bowl I guess. I have a complete PM from kirban that I pulled the bowl and switch from...time for the whole assembly to go into the car. Second time doing this job...first was on a 16k mile car, and now a 29k mile one.
Click to expand...

The only thing I would have done is use a new pressure switch with Dennis's reman unit.
Those switches had their issues in Gen 1.
Had a recall (or a TSB?) in 87 and I do believe it also included an improved switch, in addition to the changing from a cast iron to a brass valve. But I could be making things up - cant remember that far back.

Sounds like it is fine, so in all likelihood, the pressure problem was not in the switch, but in the internals, like TurboDave was getting at with the check valve.
But I still like the idea of a fresh switch on a reman unit.
They are also prone to sprouting leaks and dousing your expensive PM motor (and cowl / chassis / driveway) with brake fluid.
 
The entire PM assembly is new. I tried pulling parts from it in the beginning but that did not work as the issue was internal leakage causing the pump to run forever. I pulled the entire unit and installed a new one from kirban.

I just want to know if it is ok that it runs for a few secs every time i press the brake pedal.
 
im4darush said:
Switched out the entire PM for a new one. Brakes work fine now and the pump turns off as it should. However it does turn on almost all the time. When it does turn on, it goes off in a few seconds. So back to the original question, when working properly, is it ok for the pump to run 3-4 seconds every time you apply the brakes? If not, can bleed quality play a role here? I bled everything and the pedal feels ok but not perfect. If there is a bit of air somewhere in there, can it affect the frequency of the pump running?
Click to expand...

I believe the specs call for it running every other brake application.
 
You must log in or register to reply here.

Similar threads

S
Need help
Replies
4
Views
703
SuperStud28
S
turbobuick
Relay for the Powermaster motor.
Replies
1
Views
184
AN/GSC-52
AN/GSC-52
RezVek
Powermaster Issues
2 3
Replies
54
Views
5K
RezVek
RezVek
E
Fuel pump relay or bad ecu
Replies
0
Views
302
Eddie M
E
NoVA_87_GN
Bleeding Front Brakes
Replies
4
Views
821
NoVA_87_GN
NoVA_87_GN
Top