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99 Pontiac grandam SE V6 has alot of miles on it! OK the car does show a knock sensor service engine code but i don’t think that would cause these problems? there is a knocking noise coming from under the hood on the right driver side of the engine kinda towards the trans mission lowers engine or the back of the engine cant really tell for sure. the car knocks when i turn the key to the on position but do not crank it over to fully start it and it will stop when you push the break. The knocking noise will also start when you start the car all the way and start driving the car around town it will knock also and sometimes comes and goes someday it will knock and someday it wont knock but when it is knocking it will always stop knocking when i push the break to stop and when i let up on the break to go it starts knocking again? the car makes the knocking noise when i am parked with the car on and when i am driving around also but the knocking noise always stops when i push the break peddle down it will do this when the car is hot or cold. OK also if i have the car parked in a parking lot or stopped at a red light and start pumping the breaks fast the cars RPM will start slightly jumping up and down as i keep pumping the breaks the cars lights will start getting dimmer and brighter kinda flickering but the car does not die or stall. 🙁
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It is probably the A.B.S. control box. Some of the vehicles from around that year had a brake system that had to be bled with a computer to activate the A.B.S. pump and force the air from the system. I would recommend that you take the car to a mechanic that you trust and have them give you an estimate for the repairs. When it comes to the brake system you don’t want to take chances. Hope this helps.
If you suspect an ABS issue, you could remove the fuse and see if that issue goes away. If it does, then you will need to have the ABS diagnosed as stated above.
Keep us posted.
I removed the ABS fuse yesturday and been driving around all day and there is no knocking noise anymore I think that was the problem thank you
Good call Dreamer. I was thinking along those lines too. Many ABS systems have an electric pump that runs to pressurize the system on start up. Since the noise was happening when you did this and the engine wasn’t running it made the most sense. You can run without ABS, you may consider this because ABS parts can get expensive. Your regular brakes should still work just fine. You might want to do a good visual of the ABS components however, perhaps they’re just loose on their mounts.
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