Confused

[72 scorpio]

As I said in my other post, I have a truck we are building from the ground up”so to speak” I have been having issues with my brakes. I’m not losing fluid but If I turn sharp then brake pedal doesn’t react property. Wants to go to floor. If I attempt a hard acceleration then hit my brakes they act like the abs shudder but go to the floor. I actually came to a stop once and I could hear a whirring sound coming from engine bay around the brake booster area. Again it’s a 98 sierra 5.7
Thanks in advance.
When driving normal no issues

 

[Schurkey]

If I turn sharp then brake pedal doesn’t react property. Wants to go to floor. If I attempt a hard acceleration then hit my brakes they act like the abs shudder but go to the floor. I actually came to a stop once and I could hear a whirring sound coming from engine bay around the brake booster area.

98 sierra 5.7

2WD?
I'd be checking the front wheel bearings. Probably loose, maybe defective, almost certainly needing to be re-packed.

If this is a 4WD, the front wheel bearings could still be loose, but then it's a matter of replacing the hub(s), since there's no adjustment and no repacking.

Either way, loose wheel bearings can knock the piston back into the caliper, making for a low brake pedal on the next brake application. Generally worse around corners.

Low fluid level in reservoir?

Pull the wheels, inspect the brakes at all four corners including verifying that the pistons in the calipers aren't stiff/seized; there's no fluid seepage at the rear, the rear brakes are properly adjusted AND IF THIS VEHICLE HAS THE HORRIBLE 254mm LEADING-TRAILING SHOE DRUMS, THE PARK BRAKE WORKS and you use it frequently. Fix any leaks/seepage, and bleed the ABS with a scan tool (instructions attached) so that you have fresh, clean brake fluid at all four corners and in the reservoir.

A defective ABS could cause a low brake pedal, but it wouldn't be worse after cornering. Doesn't match your stated symptoms.

 

[72 scorpio]

2WD?
I'd be checking the front wheel bearings. Probably loose, maybe defective, almost certainly needing to be re-packed.

If this is a 4WD, the front wheel bearings could still be loose, but then it's a matter of replacing the hub(s), since there's no adjustment and no repacking.

Either way, loose wheel bearings can knock the piston back into the caliper, making for a low brake pedal on the next brake application. Generally worse around corners.

Low fluid level in reservoir?

Pull the wheels, inspect the brakes at all four corners including verifying that the pistons in the calipers aren't stiff/seized; there's no fluid seepage at the rear, the rear brakes are properly adjusted AND IF THIS VEHICLE HAS THE HORRIBLE 254mm LEADING-TRAILING SHOE DRUMS, THE PARK BRAKE WORKS and you use it frequently. Fix any leaks/seepage, and bleed the ABS with a scan tool (instructions attached) so that you have fresh, clean brake fluid at all four corners and in the reservoir.

A defective ABS could cause a low brake pedal, but it wouldn't be worse after cornering. Doesn't match your stated symptoms.

Thanks for the info. There’s a lot wrong with this truck but I bought it out of a field. In fact today my whole front suspension kit arrived. All my a/componets. We put my truck on a lift and we could shake tires left and right pretty bad. Working on ac now. Cept I cant get line off accumulator.
Would like to ask a question that I’m getting different viewpoints on. So my truck has bigger than stock pistons. What I’m wondering is cant I get a basic tune before headers and bigger exhaust. I bought 400$ for two 40series flowmasters. Supposed to be aggressive. If you take off on the throttle it sounds like glass packs. Was hoping maybe because of no headers or cats it was doing that? Or I got screwed on my flowmasters. My truck cuts off at 92. Another reason I want to go see my boy
Any thoughts would be more than appreciated. Thanks guys

 

[Schurkey]

In fact today my whole front suspension kit arrived.

You've never bothered to tell us whether this is 2WD or 4WD.

We put my truck on a lift and we could shake tires left and right pretty bad.

That's gotta change. Good thing you have a heap of new parts.

Be sure to replace the control arm bushings. Lotsa folks "forget" to even check them; and they're essentially guaranteed to be bad by now.

And the rag-joint on the steering column/steering gear is a high-failure item. Another "guaranteed to be defective" part.

Working on ac now. Cept I cant get line off accumulator.

You're going to replace the accumulator anyway, so worst-case is that you'll be buying hoses. You can MAYBE warm-up the nut in hopes of expanding it and getting it to break-free from the male threads...but you risk damaging the hose in the process. BE CAREFUL.

So my truck has bigger than stock pistons.

As in .010--.060 oversize?

Means nothing other than the cylinder walls are marginally thinner. There's enough adaptation in the OEM computer tune to account for the displacement increase. The bigger issue is whether or not the pistons are cheap-junk "rebuilder" pistons with .010- or .020-sabotaged compression height. These trucks were a bit shy on compression to start with, then the engine gets rebuilt with too-short pistons and too-thick head gaskets and all the quench/squish goes away. Then you need much more timing advance. Engine efficiency suffers.

What I’m wondering is cant I get a basic tune before headers and bigger exhaust.

Sure you can. Then you can buy another "tune" when you've made more changes. How many "tunes" do you want to buy?

Wild Guess with no evidence: If this engine isn't running right, you have something WRONG that needs to be fixed. A "tune" for more power and to eliminate the speed-limiter can come later.

I bought 400$ for two 40series flowmasters. Supposed to be aggressive. If you take off on the throttle it sounds like glass packs.

Flowmasters stink. This is coming from a guy who's put Flowmasters on his truck, his toy car, and his boat.

The 40-series are just too loud for the street. Might be fine on a race track.

MOST street cars have engines that sound like crap through 40-series mufflers. Mild engines do not sound good without sufficient muffling. Loud exhaust just amplifies their mildness; and it sounds bad. It's like telling everyone in a three-block radius that you have a weakling engine.

Was hoping maybe because of no headers or cats it was doing that? Or I got screwed on my flowmasters.

No, Flowmaster gave you exactly what you requested--the wrong muffler for a street-driven vehicle especially with a mild engine.

Put the cat(s) back on--the same number and in the same location that the truck was born with.

 

[Hipster]

Flowmasters stink. This is coming from a guy who's put Flowmasters on his truck, his toy car, and his boat.

The 40-series are just too loud for the street. Might be fine on a race track.

MOST street cars have engines that sound like crap through 40-series mufflers. Mild engines do not sound good without sufficient muffling. Loud exhaust just amplifies their mildness; and it sounds bad. It's like telling everyone in a three-block radius that you have a weakling engine.

Yep. Nothing sounds like all show and no go like a set of Flow 40's on a stock or even tuned stock engine.