Fading brakes and a turbo question

[elconquestador]

Well, the brakes on my 89 were working fine, until recently. They now are not nearly as responsive. The pedal travels a lot further before doing anything, and they are just weak. Don't stop nearly as well as they should. Also, when I pump the brake pedal a few times while sitting, the car almost dies. Could be a vacuum leak at the master maybe?

 

Turbo question... The fins on my intake wheel are bent up pretty badly. It still boosts, but it is sluggish and makes a lot of noise without doing a whole lot. I have a spare stock turbo I want to swap out with it. It looks to be a pretty simple job, but do those of you who have done it before have any advice? Thanks!

[Indiana]

You may just have air in the system have you tried bleeding it? If that doesn't work you need a new master cylinder. Too many times you push the pedal down the piston moves the brake booster doesn't know this and it lets that stored up vacuum out and it just can't recover at idle if you do that quickly over and over.

[elconquestador]

No, I haven't tried bleeding the brakes yet. I'll do that this weekend. I am hoping that's all it is, but it just randomly started doing it one day. I am gonna give it a shot and see. Is it hard to swap out the master on these cars?

[monkeywrench]

No, I haven't tried bleeding the brakes yet. I'll do that this weekend. I am hoping that's all it is, but it just randomly started doing it one day. I am gonna give it a shot and see. Is it hard to swap out the master on these cars?

 

Flush all the old fluid and bleed the system with some new stuff. Water in brake fluid will cause it to boil. No brakes! There's a hose from the booster to the manifold that gets pretty crusty too. A leak there and there will be problems.

[mikec]

A brake master cylinder with a blown rear piston will have a lot of pedal travel, with little force/resistance in the pedal, until the pedal is pushed half way or so... then the rear piston smacks into the front piston and you start getting front brakes - and a firmer pedal. Normal master cylinder operation is:

* You push the pedal... the rear brake piston starts moving. This shoves brake fluid to the rear brake calipers. The rear calipers & pads start moving.

* Once the rear brake pads actually touch the rotors and thus fluid doesn't flow so easily the fluid in the master cylinder, between the rear and front pistons, starts pushing on the front piston too. It's still pushing on the rear brakes but now it starts pushing the front piston... so your front brakes start working.

 

This dual-piston setup in the master cylinder assures the rear brakes "engage" before the fronts - something necessary when drum brakes were the normal rear brake setup. Drum brake shoes "rest" away from the drums so it takes a fair bit of brake fluid movement to push the shoes to the drums. Once the rear drums engaged, the brake fluid pressure builds up pushing on the front brake piston in the master cylinder. Even though StarQuests are 4 wheel disc brakes, they use the same style master cylinder setup to assure REAR brakes before FRONT brakes. In the event of a fluid leak or other problem with the rear brakes, the physical size of the pistons & master cylinder & pedal travel is designed such that the pistons will physically touch and push on each other if all rear brake fluid is lost. A blown rear brake piston (actually a bad rubber piston to master cylinder body seal) lets the pressure ooze past the piston instead of going to the brake lines. Usually you'll see brake fluid leaking down the front of the power brake booster. Any bubbled paint on the booster?

 

mike c.

[elconquestador]

I haven't noticed any bubbling paint, and I checked the level of the fluid and it has not gone down. Fluid is a little brown, but nothing excessive. I'll bleed out the whole system and go from there.

[elconquestador]

For those of you who have done it before, how much time should I plan on taking to swap out the turbo? The fins on my compressor wheel are pretty torn up. Have been since I got the car. It still builds boost, but not like it should. I have a spare stock turbo and am gonna swap it out. How difficult of a job is this? Thanks

[Indiana]

Might take you an hour. First drain about half gallon of coolant out of the radiator the valve is on the driver side in the back at the bottom. Loosen the two banjo bolts for the water lines one on each side of the cartridge and remove those bolts careful not to lose the crush washer that's on the cartridge side as you pull the bolt out it will fall off. Loosen and remove the oil feed line from the top using a flare nut wrench so you don't round off the corners of the fitting and can't get it loose. Squeeze and slide both the clamps of the drain hose to the middle off each end and remove the hose. Take the 10mm nut off the V band clamp and remove the bolt, take a screw driver and pop the clamp off just stick it between the ends of the clamp where the bolt was and pry. The cartridge now comes out. When you swap in the other cartridge, you can leave your old turbine housing alone and on the manifold do not remove it, make sure the groove/ring where the cartridge seats to the housing to get all the rust out so that it seats completely. Crank the motor so you get oil back up the feed line off before you let the engine start. Take the ECI fuse link out that kills the fuel pump and you can pull the coil wire off the coil and lay it on the negative battery post and just let it crank over and over for about a minute then you'll be sure the oil is pumped up and in the cartridge, make sure you can easily spin the turbo then put all your hoses/pipes back on.