tgage

Sorry to repost an issue on the C4 hydraulic pump, but I could use some methodical help! I have not driven my car in a while.....

I replaced the hydraulic pump with a used pump and also replaced the pump relay 96461513500 with a new part as it appeared that the reason it failed in the first place was the pump stayed on.

The system does not appear to be pressurizing as I get the warning alert shortly after startup.

I primed the pump initially at the pump using a short hydraulic line attached to a hand vaccuum pump. I know the pump is running as it quickly will fill the reservoir for the vaccuum pump. I did not bleed any of the lines downstream of the pump and I don't have a hammer. I've tested the voltage at the pump at it is 13.6 with the motor running

Any diagnositc suggestions (I'd prefer to not go down the path of just replacing parts).

Many thanks,
Tom

Indycam

Did you crack open the bleeder nipple on the bomb ?
If you disconect the battery , run a hose from the bomb nipple to the top of the brake fluid res , turn on the key , then touch the battery cable to the battery post . You can watch the fluid run out of the bomb into the res and stop the pump from running by the battery cable .

tgage

Indycam... thank you for the advice!

last night I took your advice and:
* Disconnected the battery
* ran some plumbing between the bleeder on the bomb to the resevoir
* Opened the bleeder
* Connected the battery
* Saw great flow.. ran for about a minute
* Closed the bleeder (while still running)
* Stopped the pump (disconnected the battery)

As soon as I close the bleeder, the pump starts to making a vibrating sound (which does not sound right). When I start the car, I'm still getting the hydraulic failure buzz. I was trying to determine if the system was being pressurized or not (I wanted to know if it is not pressurizing, or is a sensor issue), so I tried testing if I had to use normal force to stop or extra... it appears that I don't have pressure based on this method.

So... should I just let the pump run for a while (and if so, for how long).... I stopped after a minute as I sure don't want to burn out another motor.

Thoughts?

tom

Sten

Did you have the connector plugged back on the pressure warning switch? Pin 1 of the switch is connected to ground. Whilst there is no hydraulic pressure contact is maintained between pins 1 and 4, which feeds ground to terminal 85 (pin 2) of the Pump Relay R51. With the ignition in the first position, +12V is supplied to terminal 86 (pin 7) of the relay and it energises, feeding +12V from fuse number 15 via terminals 30 (pin 3) and 87 (pin 5). If the pump fails to make the pressure, the contact never opens in the pressure warning switch and the pump will run all the time. The pump should reach working pressure in less than a minute, mine usually takes about 20 seconds to put the light out after the car has been stood for a week. The pressure warning switch is a known weak point, they often fail the other way and the pump won't run at all. Under 'normal' circumstances, if you get the lights and warning horn while you're out driving, there should usually be enough residual pressure to pull up safely. If you've got no pressure, you need a right leg like Hercules to stop!
sal965 bought a switch recently, I think it was about £180?

Indycam

I got a good beer on , bad pump .
Flow but no pressure , pump runs and runs and runs , cause it never gets up to the cut off pressure .

tgage

....and my blues guitar has a broken string...

you are a hoot.

Indycam

You have a good pump head from the old pump
and a good motor from the new pump .
If you put the two together , does that get you back on the road ?

And sorry to hear about your geetar .

tgage

I'm back up and running!

Indy: Bleeding the line at the bomb for a few minutes did the trick for the pressure (I could feel the brakes had pressure), and I used Stan's advice to figure out that the pressure sensor was bad... so swapped it out with the original pump..... Had to make another run over to Automobile Atlanta for some more super blue.

But what a great day.... spent the day replacing brakes and rotors on the other car, and was just about to pack it in when I thought, lets give it a try. Ran around the block. I really don't know what you guys do that live up north and park your cars for the winter. I go through serious withdrawals!

tom

Sten

Glad you fixed it. Enjoy!