Strange brake issue and ?

[DA BIG ONE]

When cold the hydro boost does a wonderful job braking can actually feel that little effort is required to brake. However, as I drive a little the hydro boost seems to get weak requiring more effort to brake. Could this be a sign of failing hydro boost, or?

I have in my scanner a device controller to calibrate brakes to larger tire diameter but have no idea whatsoever how to do it. Scanner is carcode obd2.

[rustyk]

It does sound like there's some bypass in the pump (which accounts for the reduced performance as the fluid heats up and thins out). The HydroBoost in my motorhome stops my 8-ton motorhome (with all-disc brakes) right now.

[DA BIG ONE]

It degrades fast even though there is a cooler. I wonder if having a hydro winch will cause this to happen?

Anyway, I need to learn how to diagnose this?

[Robyn]

If your steering is doing fine then the hydroboost should respond as normal too

The issue is probably a worn out hydrobooster. The valveing and other components get worn and start bypassing fluid and the result is poor braking.

Good luck with the issue

Robyn

[DA BIG ONE]

Needing a new hydro boost is it safe to go w/higher rated unit for more braking, or?

Thinking the cooler line w/coiled fins that is stuck into chassis rail may not be up to the task because of the hydro winch too.

[DmaxMaverick]

There is no "higher rated unit". The differences are fitment related.

Your winch will only be an issue if it is causing a restriction, or bypasses fluid volume/pressure beyond what is needed for brake operation. Same for the cooler. Having a cooler inline is good, but it must be rated for flow at or above what is needed. If your steering is fine, like Robyn said, your braking should also be fine. Unless your setup is reducing pressure or volume, your HB unit may be on the way out.

The PCM calibration for tire size will have no effect whatsoever with brake assistance. It is only for ABS calibration. The HB side of your brake system is a dumb circuit. Meaning, it does what it does, regardless of what the PCM or ABS does.

Try removing the cooler and winch from the circuit, temporarily, and duplicate the conditions. If the problem goes away, then you need to redesign them to be friendly with the system. Perhaps a supply and bypass that actuates only when you need the winch?? It wouldn't be that hard to do, manual or electric.

[rustyk]

If your steering is doing fine then the hydroboost should respond as normal too

The issue is probably a worn out hydrobooster. The valveing and other components get worn and start bypassing fluid and the result is poor braking.

Good luck with the issue

Robyn

I agree with the sentiment, but IMHO, the steering is less sensitive to issues with the system than the brakes, requiring less boost. In any event, the entire system should be checked; if it were I, I'd replace both the pump and the HydroBoost, and flush everything to clear the system. If one or the other consumes itself, the particles won't do the other any good.