Power brake ans steering loss

[BSZ]

'02 Sierra 3500 Duramax 4x4, Allison, tow pkg

 

After sitting for one day, when I started it, it had no power assist in brakes or steering.

Immediately turned off and restarted...same...shifted through all the AT gears, rolled a few feet, backed up a few....then all of a sudden both worked fine. No message displayed before or after. At start, ABS light comes on, half second goes off after others.

 

What might have caused, reason for concern?

[GM-Tech]

Have not heard of that one. The p.s. pump operates both the steering and the brakes, that's about the only thing I can tell ya. Why it would have momentarily not put out enough pressure to operate both is anyone's guess.

[mmmikkke]

Check your ps fluid level. If it's ok when daily driven, but has this problem if it sits for a day, aireation might be the difference. If your ps fluid is low, the pump sucks some air along with the fluid. Low fluid gets aireated, which causes it to expand, giving you "enough" to run the system. But if it sits for a day, the aireation diminishes (bubbles rise to the top and escape to the air), and your fluid volume is less. Might have dropped below the critical level.

[BSZ]

But if it sits for a day, the aireation diminishes (bubbles rise to the top and escape to the air), and your fluid volume is less. Might have dropped below the critical level.

 

 

Interesting. I will check. Actually, I did. After it started working, I shut it down and checked the PS fluid level. It was in the cold range, but now that you mentioned it I did notice some bubbles in the resevoir. I will check it now that it has been sitting.

 

I would expect that I would still have some pressure, maybe highly reduced, but I had no pressure at all, then, instantly had pressure.

Does that still sound like low fluid level? I'll definitely check it in any case.

 

Thanks for the quick feedback.

[Shawn T]

I had problems with the pressure regualtor valve inside the pump resevoir itself. If it is sticking closed, it feeds the direct high pressure line to the brake booster. I had the same problem, changed the valve and it was back to normal. You will have to trace your lines, but if I remember correctly, the high pressure discharge (has the regulator valve) feeds the booster, booster returns through the resevoir, out to the steering gear, and from the gear back to the pump. I think. GM-Tech will know better, than me. But, those were my symtoms and my fix. The part was about $16 on GMPD.