Air leak under boost???

[speedy1320]

Something is going on under boost and I cannot figure it out!

I posted this a few weeks ago and I am looking for some more ideas from the turbo pros again.....

I replaced my water pump,timing chain and gears awhile ago. When I put the car back together and took it out for a spin.....i heard a noticeable HISS under boost.

I thought this was simply a loose IC hose....but NO CIGAR!

I've looked for vaacum leaks and all.....still no luck!

The funny thing is.....the car runs STRONG....it doesn't seem to be losing boost ?????

Could it be an exhaust leak? Why did this happen after installing the chain/gears ??

Thanx

Tom

87 WE-4
3" DP
ATR exhaust,3" cat.
ATR IC
Testa Chip
Walbro pump
Hot wire
green-top inj.
K&N 14"
160 Therm
Adj FP Reg, Adj wg

 

[1970gsx]

Mine is doing the same thing. I check all my little plastic vacuum check valves and all are bad. I'm thinking boost is blowing through these and making the hiss somewhere like the cruise control unit under the hood.

 

[speedy1320]

Check Valves???

Hey......GSX 70........Are you referring to the plastic vaacuum manifold that bolts on top of the throttle body?? Or something else? I cannot place what a "check valve" is.....that is under the hood and is attached to any vaacum lines.....Please be more specific!

But what you describe sounds VERY similar! This is a high pitched HISS only under boost......and it is proportional to the amount of boost......for example, as the boost increases, so does the Hiss..


By the way, Nice car {70 Buick} We are two of a kind.....I also own a 70 Chevelle SS 396 4-speed Totally restored and garaged!

Annnnnnnd a 68 Charger RT 440Magnum auto. ditto ditto ditto!

Thanxs in advance for the help here!

Tom

 

[turbosam6]

The check valves he's refering to are the white and bluish/black disc shaped things, probably about as big around as a quarter and should be located inline on a few vacuum lines, more visibly on the drivers side. They are supposed to only flow one way, so check them. Check the IC hoses real well, they can be cracked and not look like it. Check for vacuum leaks as well, like around the intake, plenum, TB, etc.

 

[speedy1320]

Ahhhh

Ok, I know what you are talking about now. I can at least remember one of those on the drivers side......How can you check them, is it as easy as "blowing" through each side of it? Or do I need a vaacuum/pressure tool?

The IC lines were ALL replaced as were the Turbo lines when I first started hearing this HISS sound.

Thanks....I;ll check those valves.......wonder if you can still get em new???

Tom

 

[1970gsx]

Speedy1320, just blow trough them from each direction. Air should only pass through in one direction. If it goes both ways, it's bad. Yes, I believe they are still available,I've just been to lazy to order mine. Are car collections are similar, except my Mopar has a Hemi....opps, my fingers were on the wrong keys...I meant a 225 6cyl

 

[speedy1320]

Hmmmmmm vaacuum line goin nowhere

OK, now get this......as I am checking those damn little check valves....I am also taking GREAT notice of ANY and ALL vaacum lines on the car.

Well....how about this......I follow one line off the ECM going back towards the firewall.....then it kinda goes over towards the mastercylinder....and fianlly turns back towards the front of the car by travelling down the fender .......THEN I notice it goes down by the Vaacum canister and it FRICKING ENDS !!! just an OPEN line sitting there!!! I put a vaacuum tool on it and it's DRAWING like 18-20LBS of vacuum at Idle!!! What the hell is this??

I looked everywhere and I cannot find where it goes!

The charcoal cannister/vacuum cannister are all hooked up.

Any ideas?

{By the way, I plugged this puppy up and took the car for a ride.....MUCH better Spool up/Throttle response, but car is STILL making HISS !

don't you LOVE vacuum lines!!!!!!!!!??

Tom

 

[1970gsx]

Check to see if you have any open ports on the cruise control unit up on top of the d/s fenderwell.

 

[REDS HOT AIR]

the line you spoke of sounds like the one that goes inside the car to the heater controls to change direction of airflow thr the vents.

a drop of super glue when putting vacuum lines on makes a big difference..

you may want to pull the i/c and get it pressure tested ....it is very hard to find a pinhole in one.

when my buddys started hissing we looked everywhere and couldnt find anything and finally had his i/c pressure tested at a radiator shop and found 4 pinholes in it and even knowing where they are we cannot see them by eye.

 

[Joe 1320]

You could also have a bad PCV valve, a leak around the exhaust side of the compressor housing, or a hole in any of the multitude of lines.

 

[speedy1320]

Hmmm

70GSX.....Good thought about the cruise control....It's roughly close to where I found the line.....well.....sort of. The vaacum line runs further down the front of the car.....I mean Past the alternator....??

And Reds.....I hear you.....but I really doubt this line was supposed to go to the heater/vent control panel. Again.....it leaves the EGR heading Towards the Firewall.....then....it turns by the master cylinder....and does a "U" turn back towards the front of the car. A friend asked me if it was possible if it came off the factory Air-box......another possiblility since I now have an ATR 14" unit on there!

Thanks guys!

According to sources the CHECK VALVES are still available!

Oh and I had the HISS with stock IC, put on an ATR 1 1/2 IC and still have the Hiss...doubt it's an IC issue!

Should probably look for leaks in the exhaust area too??

Tom

 

[TurboDave]

My bet would be that, that is the vacuum line that is supposed to end up down on the vacuum reservoir. Round ball under the car, directly below where the charcoal cannister sits, but under the inner fender, gotta crawl under and in front of the tire to see it. It's a round plastic ball about the size of a softball.

 

[FRANKIEz28]

Daaam! you said it first

Originally posted by TurboDave
My bet would be that, that is the vacuum line that is supposed to end up down on the vacuum reservoir. Round ball under the car, directly below where the charcoal cannister sits, but under the inner fender, gotta crawl under and in front of the tire to see it. It's a round plastic ball about the size of a softball.

Thats what I was going to say.

Good Luck
FRANKIEz

 

[timothydog]

I was thinking that same thing. The vacuum pod. Only mine is under the passengers side by the headlight (?) I'll have to look at lunch time.

My question is: How can you hear this hissing sound over the wooosh of the turbo and the rrrrrrr of the engine?

 

[speedy1320]

RE

The vacuum "POD" as you guys are calling it would be THE FIRST thought......However......I relocated it and the Charcoal cannister for the 14" K@N filter........and I KNOW I hooked it back up.

But just to second guess myself....I did recheck it under the front of the car.....and ALL lines are where they should be.

doesn't this just Suck?

I have a buddy at a local garage that May be able to bring up the vacuum lines on his computer.......

Thanks again!

Tom

 

[1970gsx]

All this talk about the vacuum pod I noticed mine is missing! Does anyone know the purpose of the "pod", and from where the vacuum line runs? I can't seem to find an open vacuum line anywhere...

 

[speedy1320]

70GSX You probably HAVE the "Pod" and just cannot see the damn thing. It was right under my factory air-box before I relocated it with the charcoal cannister to accomodate the ATR 14" filter Kit. Keep looking!

As far as I can tell......all it does is "store" reserve vacuum..

Any other takers?

Tom

 

[salvageV6]

The factory setup includes a Y that takes the vacuum supplied from the brake switch line through the firewall out to the vaccum pod. and to the cruise control module via the Y. They should be paralleled out there.

I would double check all the connections and make sure any splices or joints for the extension of those lines are still in place.

The charcoal cannister has a similar line as you know.

If the questionable line leaks at least plug it up while driving.

 

[Dan Thompson]

Just for reference I am getting about 18# of vaccum in park just after I start the car.

When its in gear I get about 14#-15#.

 

[speedy1320]

I am getting similar vacuum readings from this line.....and yes I did plug it...and got noticeable performance in doing so.

Thanx

Tom