Am I the only one terrified by my weak brakes?

At highway/road speeds, the braking is just fine.

But when the truck is at idle, I feel like I have to give it all I got just to get it to stop when it feels like it. It's scary off-road.

I just did new pads, turned the disks, and new dot 4 synthetic fluid, and it's just as it was before.

Thoughts?

Max

 

Only if I'm in front of you.

If you are saying that the brake pedal is hard, you either have a vacuum leak or your booster is going bad.

If the pedal is spongy and you have poor braking performance after doing what you mentioned (and did it all properly), it's likely you have a bad (rubber) brake line somewhere. If you have someone stomp on the brakes while you're under there you'll likely be able to see it bulge.

What you are describing is in no way normal or typical of a DII.

 

It puts this little excursion into a whole new perspective...

 

The pedal is hard. I'm thinking it is a booster issue. When there's lots of vacuum (highway driving) it's fine. So, where do I start?

I've never done much with vacuum, forgive my newbness.

 

Yeah, I can tell. Because you have it backwards. Vacuum DECREASES with engine load.

Which makes what you are saying not make much sense, unless you just aren't noticing the harder braking when at speed because you aren't trying to come to a full stop then.

The easiest way to test for a leaking booster is to put a vac gauge on the motor. There is a port on the upper intake manifold on the passenger's side in the middle.

- Start the truck, let it idle and note the reading.
- Shut down, disconnect the vacuum like going to the booster. Plug it on the manifold side. Start the truck and take another reading.

Is that second reading higher? Replace the booster. Is it the same? Continue.

- Reconnect everything. Have someone sitting in the truck. Have them press the brake pedal while you are watching the vac gauge. Have them keep their foot on it.

If it returns slowly to the original level (before you hit the brakes) you have a collapsed or blocked vacuum line or a bad 1-way valve (I believe it is a "non return valve" in Rover-ese). If it doesn't return (chances are good you will hear a hiss or a hum from the booster as well) its a bad booster. Replace it.

 

DarylJ,

Thanks for all that. I will get a gauge and check it out tomorrow.

Would you mind dropping a little more knowledge on vacuum? Why does it decrease with engine load? I've always thought it was created by air moving through the intake manifold. More engine speed = more air = more vacuum. I'd love to know how it actually works.

Thanks!

MAx

 

There are two types of vacuum created by the motor; Manifold Vacuum and Ported Vacuum. Manifold Vacuum is created by the movement of the pistons drawing in air. Ported Vacuum is caused by air rushing past a "port". Manifold Vacuum is usually used to perform work - like the Brake Booster. Ported Vacuum is usually used for control devises such as Canister Purge, etc. Ported Vacuum increases with engine speed and Manifold Vacuum is greatest at idle (closed throttle) which is why a check-valve is placed in-line to the Brake Booster, to maintain vacuum in the Booster when the Throttle is open.
Hope I did not give too much info.

 

What RPM are you idling at?

 

Rover brakes are good but not great. It's a heavy vehicle. Do not expect sports car style braking in these things....

 

First, you never re-surface Rover rotors, because of the material the factory used and because now your rotors are under sized from being cut.
Who's brake pads are you using?
By the way, a little of what you experience is normal, Rover corrected some brake issues when they brought out the 03, with different calipers and master cylinder.