Strange Slow speed brake shutter & fluid flow noise. Once per engine start. What???

Not sure how to describe this.

2004 Double Cab. 4x4 w/ manual hubs. AT. Tundra brake upgrade. 3" lift with aftermarket brake lines. Otherwise the rest of the brake system is stock. Whole front end including spindle bearings were replaced about 2 years ago.

Once per engine start-up i get a brake fade and shuttering noise from the front brakes only when the truck is under 2-3 mph. More like right at the very end of stopping. The lasts 1 second until the truck stops. It happens only once per engine start. Never twice and not every time. Probably 80% of the time. Otherwise the brakes feel and perform like normal. No other symptoms and in no way does the truck feel unsafe otherwise.

It is ALWAYS accompanied by what i can only describe as a fluid flow sound or pressurization sound. Almost like brake pressure drops and the system is trying to boost again. This sound ALWAYS happens when i start the truck and has always been there. I liken it to the brake booster or steering pump pressurizing. The peddle does not drop or anything.

This brake fade started this weekend immediately after i replaced the upper control arms and got an alignment. I did not touch the brake system other than slight tugs on the brake lines while doing the upper A arms. I also re-torqued the rack & pinion mount bolts. I am not loosing fluid anywhere.



Any ideas?

 

Is the shuttering noise from the front brakes the ABS triggering? That's apparently a common issue with some vehicles when they are almost at a complete stop. If that sounds likely to you, start by inspecting the abs sensors. Remove all four and clean them with an electrical contact cleaner. Peek inside and ensure the tone rings are free from debris. Inspect the length of the wiring to the sensors as well, checking for any signs of wear through the shielding. I'd also suggest disconnecting the other end of the harnesses the sensors are connected to, and spraying them with contact cleaner, and applying some dielectric grease. It could be that the sensors are fine, but over the years fine dust or water has made it into the clips. If you were replacing the upper arms, you at least had to touch the abs wires leading down to the sensors on the front.

I'd also inspect the brake booster and ensure that the vacuum line is not cracked, and properly connected. My brake booster made a slight hissing sound when it started to go bad.

 

Interesting. I do not know what it feels like when ABS kicks in but i did remove both ABS sensors from the spindle to route the cables on the new upper A arms so maybe they got dirty or are not seated right.

What would the fluid flow or pressurization sound then be if it were ABS. When ABS kicks i imagine the brake booster has to react so maybe this is the brake system adjusting? Hmmm....

 

If you've ever hit a speed bump while holding down the brake, you know what ABS feels like. That always gets it to kick on, makes that rumble sound that you can hear and feel especially in the pedal.

Hearing fluid though, that's a mystery to me...I would double check your ABS sensors since you said you had removed them at one point

 

Another suggestion for activating the ABS is to drive (it should really do it any speed, but you don't need much) on a loose surface (dirt, gravel, snow, etc...) and abruptly step on the brake pedal. The tires should slip and the ABS should step in to help you come to a stop.

It's not so much that the brake booster is reacting- it's actually rather passive, but you'll feel (and hear) the abs modulate the pressure in the lines through the pedal.

If the brake booster is an issue, I suspect it's unrelated to the replacement of the upper arms. The FSM does have a procedure to check for proper operation of the booster. It's a pain to replace though. Gotta remove the master cylinder, which means lots of brake bleeding, etc... and from what I recall, it was generally a huge PITA to get the old one out, and new one in.

 

The fluid sound is like something charging, Building pressure. Only happened up till now when i started my truck in the AM. As soon as i start to drive off this sound has always been there. It is very easy to hear from inside the cabin even with the radio on. Sound like fluid flowing to build pressure. Lasts no more than a second. Is this not normal? (Wonder if I can attach a sound file?)

I always figured it was the power steering but now i am not sure. I rebuilt my brake MC about 3 years ago. Did not mess with the booster. Have never done anything with the steering other than replace the rack bushings.

 

I've heard that a heater core starting to go out can make a gurgling sound from behind the dash, but that would present other symptoms as well like your heat not working, smelling coolant in the cab, coolant leaking, etc.

 

Thank you @eon_blue . No issues like that. Heater works great and no smell or leaks. It is not a gurgling sound. It is a high pressure fluid sound. I will try and capture the sound and upload it somewhere...

 

Check booster hose and check valve as previously suggested.

 

Follow-up on this. The issue is still there and happens usually once per drive cycle and usually with-in the first 5 stops of the drive cycle and never again which i find strange.

This is for sure the ABS kicking in and i am sure it is either the sensor or cable. I have re-seated both sensors a few times now. Betting when i did the upper A arm replacement i damaged something but i do not have spares to swap out and have not bought anything to fix it yet.

 

Before the "just delete the ABS" crowd rush in, here is a link to a video that describes the FSM procedure for diagnosing the ABS system:
https://www.youtube.com/watch?v=dGQtEDfnATM

If you do have a damaged cable or sensor, this should help you pin point the issue.

 

Thank you Andy and for sure i would not remove ABS. Heck when i did my 4x4 conversion i purposely made sure i kept it. I know i am on the road far more than off the road.

 

Folks are on both sides of the ABS fence- That's it's either safer to have it or not in either on-or-off road circumstances. My preference is to maintain the ABS if possible, while others find it easier to just remove it for whatever reason they see fit.

 

I like having ABS for driving in traffic on slick roads...can save your bacon in a panic stop situation. On loose surfaces or snow, proper tires do far more to reduce stopping distances.

In any case, there must be an ABS fuse that you could temporarily pull to see if the noise goes away.

 

I believe the ABS "fuse" is a relay under the fuse block, which you have to remove to access.

 

Thanks, Andy.
-Andy

 

I'll take that as a compliment! For now, I'll just aspire to accumulate the level of knowledge that @Andy01DblCabTacoma brings to the forums.