Help - Brake line squeal and low idle

2003, V6, 5spd, 193,000 miles.

1) I first noticed that when at a stop light (drive-thru, etc) I would hear a squealing sound (sounds like: eeeeeeeeeeeee) coming from under the hood. I could pump the brakes and it would change pitch and volume. My brakes don't really feel mushy, and the pedal doesn't really go to the floor, but sometimes it feels like it is creeping ever-so-slightly...a small enough amount to make me question whether or not I'm imagining it doing so.

I've also noticed that my brake performance is as good as ever. However, I've also noticed that if I run down the interstate for a few miles and don't hit the brakes, that the first time I press on the brakes, there seems to be a significant amount of resistance...then the feedback seems to normalize.

2) I then noticed (not that it necessarily came later, but it started happening at about the same time) that when sitting at a stop, engine idling, that my RPMs were about 550. Typically, with no extra load (PS pump strain or A/C) the truck used to idle at 680 RPMs and with the A/C load, it would kick up to about 780 RPMs. Now, it idles at about 550.

Lastly, both #1 and #2 are inconsistent. It happens when I first start the truck sometimes and sometimes it doesn't. It happens when its hot in midday and even in the cool of the evening. I can't deduce a pattern on when it tends to do either one.

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So what I tried the other night just messing around was to squirt some water around some of the vacuum lines and connections around the intake and brake booster. I did hear some sucking and replaced that hose. It did seem to be less frequent, however it is still happening.

I still believe it is vacuum related. A friend told me to use some carb cleaner (it tends to change the idle when it makes its way into the intake). Anyone seen this before. Am I on the right track checking for vacuum leaks.

Thanks in Advance.

 

Anyone?

 

Definitely on the right track. Sounds like a vacuum leak to me. Best thing i can tell you is to recheck all the hoses from tb/brake booster and all and make sure you dont have a very small crack somewhere.

 

Update: A buddy and I were messing with the truck trying to narrow down the source of this issue. We were working in the parking lot at work, so we weren't really wrenching on it.

We noticed that if we tugged on the master cylinder (almost applying a leveraging force to the brake booster) that we could change the pitch greatly. I'm not sure if it is one of the lines on the master cylinder or if it is internal to the booster.

When I get some time I'm going to try to leak check all of the easy, external parts, hoses, fittings, etc.

I've searched this forum and others and really can't find any significant brake booster failures (which I'm praying it isn't...$500+).

Any thoughts?

 

Update: Confirmed that the brake booster is leaking.

I've looked for part-out trucks and in the Marketplace on here and haven't found anything. Anyone got an old (functioning) brake booster laying around or know of someone who is parting out a Taco?

Any help is much appreciated as Toyota is wanting $550 for a new one and I refuse to buy anything from AutoZone or Advance Auto Parts. If nothing works out in the next few weeks, I'll spring for the Toyota one. I've found some on eBay and may end up going that route but would rather give someone on here the money rather than an eBay unknown.

TIA.

 

Have you tried rockauto.com? Their prices are good...actually alot better than a dealer or autozone.

 

No, unless it is for performance (lift, bumper, etc) I typically won't install non-Toyota parts.

Although, I pulled up the FSM last night and decided to not allow the dealership to confirm my paranoia. I went out and got the truck to make the squealing noise again. I started spraying some WD-40 around all of the suspect spots. I finally sprayed where the master cylinder meets the booster and it instantly started making a sucking sound. Since then (150 miles later), no squealing. Additionally, after doing that, I decided to perform the test the FSM recommends. According to that "On-Vehicle Inspection," my booster isn't the culprit.

I think my next order of business is to order the gaskets for booster removal and keep them on hand. I think I'm going to check torque on everything and just keep my eye on it.

I'm a vacuum engineer, so I should be pretty good with leaks (??). It has been my experience that 50% of the leaks you deal with are never as initially expected. However, I will also admit it is rare to see leaks "come and go."

Right now, I'm as lost as last year's Easter egg...

 

I still haven't done squat about this and was wondering if anyone else had the same issue. I've also noticed it only when it is hot and humid.

 

I decided to update this post. Back in the summer I bought a used booster off of a Tacoma on eBay and replaced it (15 minute job by the way) and that was the issue. I bet the stats of bad boosters on Tacomas is virtually non-existent.

 

You were lucky and hit the jackpot with yours.