Brake psi question help

Good evening all,
I have a problem I'm trying to solve and looking for help, particularly if you have an Areoforce gauge(s) so you can read the psi. I replaced my brake master cylinder with a Terflex big bore master cylinder, replaced the Booster (master cylinder was leaking into it) and I have new SS brake lines. After install my brakes light were stuck on after I parked a few times. This lead me to look at the brake psi. I found that my brake psi, would stay at 5-9 psi, but would sometimes spike to 16, 23, 30 and even 33 psi. I found out that when the brake pressure was high the brake lights were "stuck" on. The brake pedal was not fully resetting, the booster was removed and adjusted to reset the pedal. High psi and brake lights still on. The brake light switch was reset, it was a little better, but still happening. Replaced the switch, still happening. I am thinking that the high psi means brakes are slightly applied. Auto shop swears that the calipers, master and booster are all working properly.

I readjusted the new switch and I think I "fixed" the brake lights staying on, but not the psi.....

1. Does anyone have a gauge to read brake psi? I want to compare readings, I never looked at psi before my brake issues. Maybe the jumpy psi is normal?

2. Any ideas what else could be happening?

I'm $800 into the install and attempts to fix the issues and I'm out of ideas.

did you disconnect the battery (ground) for about 15-20 minutes to reset everything? Another thing you may try it to disconnect both terminals of the battery wait a minute then touch the neg and pos ends together..just the wires nothing on the battery- this also resets - wait 15 minutes then hook the battery back up.

Sometimes it'll a few start/stops and drives before everything clears out and back to normal.

Also, I'm not sure on the 2008, but did they bleed the brakes and ABS? some models require the ABS be bled as well.

I have not tried the battery reset, but I will.

The brakes were bled and then re-bled along with ABS, the brake did feel better after that, but no luck with the psi.

Thank for the battery reset idea, it can't hurt....

Felix 13

I have the gauges (two) and the reading is always 2psi w/o any pressure on the brake pedal. You definitely have an issue.

GoBig said:

I have the gauges (two) and the reading is always 2psi w/o any pressure on the brake pedal. You definitely have an issue.

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THANK YOU, that will verify what I thought and will let me know when it is fixed..... Back to the shop and see what they say

Felix13 said:

THANK YOU, that will verify what I thought and will let me know when it is fixed..... Back to the shop and see what they say

Click to expand...

Please give us an update on what you find.

After waiting for UPS to deliver and setting up a day I could get it to the shop, success....I think. p.s.i. holding steady at 5. I had to replace the booster, which was confirmed as not working properly and it appears that the master was "weeping" fluid, so I replaced that as well. Brake pedal feels better, very excited to be back up and running.

Interesting! The reason why it reads 2 is because of the pressure at the caliper being below the master cylinder. Not sure why you are reading an addition 3-psi. But, you've definitely improved from where you were!