2nd Gen Non-Engine/Transmission No brakes at startup

[AlFischer]

96 4WD. First thing in morning. Parked on sloping driveway. No brakes for 5-10 seconds after startup. Original owner sez always been that way. Is this normal?

 

[LSMITH]

Not normal at all. Not sure what it is but it should not do that.

 

[jeff95]

I have the same problem from time to time. When it does occur, it is only after it has been sitting overnight or longer. I'll definitely follow this thread.

Jeff

 

[ewcmr2]

You may have a vacuum leak. My '96 would not have any brakes (vacuum assist) after it had not been driven for a while with the heat/ac knob in certain positions. Bringing it in for the 7 year, unlimited mileage vacuum recall fixed it, but don't expect the dealer to "remember" that recall without some "prodding. "



Eric

 

[rrausch]

It is definitely not normal. My '95 started doing it about 6 months ago. OK... I guess it is time to get serious about it. The manual for my '95 says the booster can't be re-built--this one is a Delco! (I have gotten Delco booster's rebuilt before but that was on another car) However, there is a check valve on the front, pass side of the booster. Maybe the check valve is leaking and causing the booster to loose pressure. It's worth a try.





Mine will loose pressure overnight, but not if I park it for 2-3 hours.

 

[Thomas]

Recall 720?



TSB 24-16-96



Warranty Extension D-97-10

 

[rrausch]

The build date on mine is 3-95.

So that means I escaped the dreaded "no vacuum pump check valve" condition.



Apparently there is another check valve on the booster, that is the one I meant.

 

[illflem]

My '95 has lost the vacuum assist when using the brakes a lot at idle since new, the pump just can't keep up at low rpms. The recall made no difference.

Sam Peterson can get the rebuild kit for the booster.

 

[rrausch]

Illflem, I was hoping you would chime in here!



Under normal conditions, I believe the vacuum booster should be able to hold enough vacuum overnight to handle a couple of brake-pedal depressions first thing in the morning. All of my vehicles which have had P. B. could do that, including this truck for the first few years I owned it.



But this condition is different, because that ability disappeared suddenly. Hence I think it is a vacuum leak which is affecting the booster. The leak wouldn't be in the hoses, since there is a check valve at the booster to keep it charged, so I would think it has to be either in the booster diaphrams themselves, (rebuild time) or in the check valve on the front of the booster. I am going to try to replace that check valve and see if it makes a difference.

 

[rrausch]

Illflem, how can we reach Sam Peterson?

Is this a fairly simple re-build? Anybody ever done it?

 

[sam616g]

Originally posted by Al Fischer

96 4WD. First thing in morning. Parked on sloping driveway. No brakes for 5-10 seconds after startup. Original owner sez always been that way. Is this normal?

I just bought a 96 4WD automatic and it also does the same thing. I just noticed it because I usually let it warm up for a little bit before running it. But the other day I hit the brakes right away and had nothing. And like you said after about 5 seconds (usually by the time the "ABS" light goes out) I have brake power. I'm not sure if it has to sit over night before it looses boost though. I'll have to look into it.

 

[illflem]

Sam 360/357-4958

Got to thinking that maybe Sam was talking about the rebuild kit for the hydro boost not the vacuum. If I recall the kit was cheap, like $25. Not sure which system it was for but Sam will be the one to know. Let us know what you find out.



I know I don't have a vacuum leak at the booster, just pulled the hose off last week after the truck was parked for a couple days, had plenty of vacuum but nevertheless it's only good for about three times on the brakes at idle before the vacuum's gone. I'd say it's "normal" but not right. I think this is part of the reason DC went to hydro boost. DC offers a kit to increase your vacuum storage but it's a rip-off, over $100. I've seen add on vacuum tanks from other sources for as little as $10. Only other things you need are a little hose, a tee and a place to mount it.

 

[TFabian]

One thing I found last week when I replaced the oil seal on the back of the vacuum pump was the fitting on the side of the VP where the large hose connects to and goes to the booster was very loose. I don't think that is the descibed problem but I would recommend checking it. Would keep the pump from applying maximum vacuum.