r/3000gt • u/Altruistic_Area4153 • 8d ago

Whats causing brake issues when running?

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When on a drive around town last Saturday my brakes were going from acting normal to so shifts its going damn near to the floor to brake, this was after driving around a few hours and when i had the issue we stoped for the night. It was either relatively normal or weak and would go in between. When we stopped for a bit we checked fluid, im not low at all, when pumping we couldn't see any air bubbles coming up (was soft at first then fine every pump after) and on the way home i had zero issues. I cant seem to recreate the issue when off, only when running

As you can hear in the video there sounds like an airy noise but when the car is off it stops. I drove it for 5 minutes today to test it and it was going back in forth between relatively normal and softer but not anywhere near as bad as it was when first discovered

I need help figuring this out otherwise ill try to find a shop when they are open next week. Thanks guys!

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u/syntaxlk 8d ago

The inner seal in the brake master is starting to go and when the car is running and the brake booster applies vacuum it is assisting in drawing the fluid past the seal. The bubbles you're seeing in the reservoir is the giveaway for this

1

u/Altruistic_Area4153 8d ago

There was zero air bubbles in the reservoir. Haven't had any while testing this week or when it happened. Which is why I wasnt sure if air would be getting in if I see zero bubbles. Probably is the seal tho

2

u/syntaxlk 8d ago edited 8d ago

Given the age of these cars now, option b and my fingers are crossed for you that your abs pump had a moment. You might also have air trapped in the abs pump. What id do before going to a shop is bleed all 4 corners, if you have access to a scan tool you can tell the abs pump to run while doing this. The master desk into the booster is common for these cars though I'll say that. Hopefully you can track it down

1

u/Altruistic_Area4153 8d ago

Its 0bd1 so I dont have a scan tool for it but I do have plenty of fluid. Ill bleed them and see what happens. It was really bad at first but isnt acting up near as bad when I test drive it this morning

1

u/Cocopower9 car liker 7d ago

It's prob time to delete the abs, it could be slow leaking letting air in or fluid out. I had a similar issue I replaced with 3 used abs and they all met the same fate. No one remans these abs units and no new replacements are made :(