Tough vacuum question, who can answer??
04-29-2003, 08:42 PM
#1
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Tough vacuum question, who can answer??
Okay, this ones gonna be hard to explain but I will try my best.
First of all my car is a 79 and im not sure what other years have this same setup. I think I have seen this on cars in the 80's but am not sure.
Over the last few weeks I have been going through the top part of the motor redoing vacuum lines because the old ones were hard and far the most part all of them leaking a bit. I pretty much pulled the intake and was able to replace all lines under it. I did not pull the throttle body and fuel distributor housing because of time constraints. That will come at a later date.
I put everything back together and using the vacuum diagrams that I got from the manual everything went back together good. No problems with anything. The car runs good.
My question is: there is a vacuum point on the intake plenum, its on the drivers side between #7 and #8 intake ports I believe. This vacuum has kinda a V-Tee made out of plastic with a reducer of some sort built into it. (basically two lines enter, one of those lines has a reducer in it, both lines end up going into the intake through one hole) One side of the "V" goes to the brake booster (I understand what that is for) but the other line which has the reducer built into it routes around the front of the intake and T's into the Auxillary air supply line which is located on the passenger side of the car near the decel vacuum valve. That line is tied into the bottom of the air box prior to the throttle body. What is this vacuum for?? It seems to do nothing except route air around the throttle body assembly. Which to me would mean that, that is a vacuum leak. Maybe a controlled vacuum leak but a vacuum leak non the less.
All diagrams that I have seen clearly indicate that this is the correct routing and I have everything put back together the way it came apart and that it matches all my diagrams.
Does this vacuum thats being pulled through a small orifice help pull vacuum for the brakes?? Its confusing to me what this vacuum is for.
Maybe when the Auxillary air valve is closed (engine warm or hot) the air needs to escape and that is what its for.
Im lost. Anyone an expert in vacuum lines on early cars.
Thanks
First of all my car is a 79 and im not sure what other years have this same setup. I think I have seen this on cars in the 80's but am not sure.
Over the last few weeks I have been going through the top part of the motor redoing vacuum lines because the old ones were hard and far the most part all of them leaking a bit. I pretty much pulled the intake and was able to replace all lines under it. I did not pull the throttle body and fuel distributor housing because of time constraints. That will come at a later date.
I put everything back together and using the vacuum diagrams that I got from the manual everything went back together good. No problems with anything. The car runs good.
My question is: there is a vacuum point on the intake plenum, its on the drivers side between #7 and #8 intake ports I believe. This vacuum has kinda a V-Tee made out of plastic with a reducer of some sort built into it. (basically two lines enter, one of those lines has a reducer in it, both lines end up going into the intake through one hole) One side of the "V" goes to the brake booster (I understand what that is for) but the other line which has the reducer built into it routes around the front of the intake and T's into the Auxillary air supply line which is located on the passenger side of the car near the decel vacuum valve. That line is tied into the bottom of the air box prior to the throttle body. What is this vacuum for?? It seems to do nothing except route air around the throttle body assembly. Which to me would mean that, that is a vacuum leak. Maybe a controlled vacuum leak but a vacuum leak non the less.
All diagrams that I have seen clearly indicate that this is the correct routing and I have everything put back together the way it came apart and that it matches all my diagrams.
Does this vacuum thats being pulled through a small orifice help pull vacuum for the brakes?? Its confusing to me what this vacuum is for.
Maybe when the Auxillary air valve is closed (engine warm or hot) the air needs to escape and that is what its for.
Im lost. Anyone an expert in vacuum lines on early cars.
Thanks
04-29-2003, 08:57 PM
#2
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That odd Y pipe is in fact a "venturi tube" the controlled vacuum leak rushing past the specially shaped tube increases the vacuum that the booster sees for more assist in braking .
04-29-2003, 08:58 PM
#3
Nordschleife Master
It's not a leak, but a "by-pass", similer to the throtal by pass, or the a/c by pass. A leak would add unmetered air to the system, this is bad. A by-pass allows air to go around the throtal, BUT still be mettered.
I belive it's designed to allow for additional vacume for the brake booster. As I understand it, you most need the brakes at low throtal, when the throtal possion is closed. Under that condition, the air rushes through the by-pass, and goes through a "extractor". This is somewhat similer to the cheap, commpressed air powered vacume pumps they sell. Result, when you are at low throtal, the unit ups the vacume of the car by like 2-5" Hg, IIRC. Thats a little bit more power for your brake booster, and thas a good thing, right?
I belive it's designed to allow for additional vacume for the brake booster. As I understand it, you most need the brakes at low throtal, when the throtal possion is closed. Under that condition, the air rushes through the by-pass, and goes through a "extractor". This is somewhat similer to the cheap, commpressed air powered vacume pumps they sell. Result, when you are at low throtal, the unit ups the vacume of the car by like 2-5" Hg, IIRC. Thats a little bit more power for your brake booster, and thas a good thing, right?