Vacuum leak

[Marlboro_Man]

Got the car running tonight with the new setup, BUT it has a vacuum leak somewhere


It'll start and run, It pulls about 10 in of vacuum at first (@ 800 rpm), and will pull 20 (@ 2000 rpm). But it will slowly lose vacuum. It only takes between 2-5 minutes and the vacuum will zero out and the motor will die.

I've isolated the vacuum tree, since all it sends vacuum to is my brakes and boost/vacuum gauge, and that made no difference. Isolated the PCV valve, no differance. The only other thing with vacuum is the AFPR and it didn't seem to make any differance when i dissconected it either.

I pulled the upper intake off to make sure no wires got caught in it or that the gasket didn't get messed up, Everything looked perfect.

I let it idle and sprayed carb cleaner around the front lower seal and the rear lower seal and it didn't seem to change the idle any.


I went over everything i could think of short of pulling the lower intake off. I can't hear anything that sounds like a leak, But my intake and exhaust is pretty loud lol.

With the PCV hose and the hose from the TB to filler neck dissconected the valley shouldn't have any vacuum unless the lower intake gaskets are leaking, correct?

Anyone have any ideas where i could be losing vacuum?

 

[Black1987Stang]

Got the car running tonight with the new setup, BUT it has a vacuum leak somewhere


It'll start and run, It pulls about 10 in of vacuum at first (@ 800 rpm), and will pull 20 (@ 2000 rpm). But it will slowly lose vacuum. It only takes between 2-5 minutes and the vacuum will zero out and the motor will die.

I've isolated the vacuum tree, since all it sends vacuum to is my brakes and boost/vacuum gauge, and that made no difference. Isolated the PCV valve, no differance. The only other thing with vacuum is the AFPR and it didn't seem to make any differance when i dissconected it either.

I pulled the upper intake off to make sure no wires got caught in it or that the gasket didn't get messed up, Everything looked perfect.

I let it idle and sprayed carb cleaner around the front lower seal and the rear lower seal and it didn't seem to change the idle any.


I went over everything i could think of short of pulling the lower intake off. I can't hear anything that sounds like a leak, But my intake and exhaust is pretty loud lol.

With the PCV hose and the hose from the TB to filler neck dissconected the valley shouldn't have any vacuum unless the lower intake gaskets are leaking, correct?

Anyone have any ideas where i could be losing vacuum?

What exactly is ur new combo, what did u just put on/replace? (change just the upper and lower? etc. )

BTW if u messed with the valve train, that has to do with how much vacuum the motor has. 10 inches is pretty low, but it pulls 20 at 2,000rpm? u mean in neutral or revving it up or driving, as soon as u put a load on it or give it gas its gonna drop below 20 in a heartbeat anyways.

So it loses All vacuum after 20 minutes? thats pretty weird, can u explain that some more

 

[Marlboro_Man]

What exactly is ur new combo, what did u just put on/replace? (change just the upper and lower? etc. )

BTW if u messed with the valve train, that has to do with how much vacuum the motor has. 10 inches is pretty low, but it pulls 20 at 2,000rpm? u mean in neutral or revving it up or driving, as soon as u put a load on it or give it gas its gonna drop below 20 in a heartbeat anyways.

So it loses All vacuum after 20 minutes? thats pretty weird, can u explain that some more

Installed a TFS1 cam, AFR 165's, new timing chain, water pump, balancer, lifters, PR's, RR's, 24# injectors, pro-m.

10 inches at idle after i first start it, then it will slowly drop to zero and will die out. If i hold the RPM at 2000 it will pull 20 inches of vacuum. My vacuum gauge is surging a little, like 1-3 inches of surge.



Does this really sound like a problem associated with the valve adjustment???


Oh and not 20 minutes, it will lose all vacuum within 2 to 5 minutes.

 

[Black1987Stang]

Is ur vacuum gauge surging but ur idle staying the same??? if it is then that would make me think its something with the valves or drivetrain...do u have any codes? sometimes my car likes to bug out after it idles for about 20 seconds like at a light, it will idle normally at like 12-13 inches, then once the sensor or w.e goes out of range or whatever it drops down to like 8-9 inches and gets a real bad lope and will buck when i drive...Have u set ur timing yet? where is it and do u have any codes? Most of all tho the vacuum shouldnt be varying if the idle is staying the exact same...n normally thats a valve problem or some type of valve train

 

[Marlboro_Man]

Is ur vacuum gauge surging but ur idle staying the same??? if it is then that would make me think its something with the valves or drivetrain...do u have any codes? sometimes my car likes to bug out after it idles for about 20 seconds like at a light, it will idle normally at like 12-13 inches, then once the sensor or w.e goes out of range or whatever it drops down to like 8-9 inches and gets a real bad lope and will buck when i drive...Have u set ur timing yet? where is it and do u have any codes? Most of all tho the vacuum shouldnt be varying if the idle is staying the exact same...n normally thats a valve problem or some type of valve train

It seemed like the idle was staying pretty much the same but the gauge was surging, untill the vacuum got real low then the idle would lower and eventually die.

I will try to pull the codes today and post the results afterwards.

Timing is at 14* spuot out.

 

[Marlboro_Man]

I just noticed that the RPM's are acting kinda funny also, like it revs to 4k when it should only be at like 2k. wierd?

 

[Marlboro_Man]

video of the car running



http://video.tinypic.com/player.php?v=2jez6ew

 

[Marlboro_Man]

Update

I changed the distributer and that solved the Bouncy RPM's.

I set the idle, TPS, and timing and took it for a spin around the block and it drove OK. But still seems to have a vac leak.


Then i noticed that my serp belt was getting eaten up. I had installed a new water pump and sure enough the WP pulley is off a bit.

The flange on the new WP shaft is .365 thick and the flange on my old WP is .343 thick. So i have to figure out how to make the belt work.

Then i'm going to run the KOER and cylender balnce test. I will also probably have to redo the rocker adjustment as thats probably whats causing my poor vacuum.

Heres a vid of how it was running last night after the dizzy swap.
http://video.tinypic.com/player.php?v=3029axc

I'll keep ya'll updated and if anyone has any ideas please feel free to post them.

 

[Marlboro_Man]

Still seems to have a vac leak. I'm out of ideas. so far i have.

Redone the rockers.

Replaced vac lines.

Redone the lower intake 3 times.

pulled the KOER codes and got 91 (Hego sensor), sefi balance test showed good.

Compression tested warm motor= 140-150 psi on all cylenders.

I don't know what to do. To me it only leaves the TFS1 cam, the valves/valve seals, rocker adjustment to blame.

I just really don't think it's the lower itake leaking. The last time i did it i used alot of rtv on both sides of the gaskets. I could see on the old gaskets where the intake had sealed.

I'm at the point where i'm ready to say fu ck it and take it somewhere to have it checked out, and i've never had to do that with any car/truck of mine.

 

[90_Red_LX]

Find a shop that has a smoke machine and have them hook it up for ya. It will find a vacuum leak very damn quick as it fills it up with smoke. We got one at my dads shop and it is awesome. Expensive, but it's great when you do repair work for other people.

 

[HISSIN50]

In the old days, if it was thought to be an intake leak: Disco' all the vac lines to the intake and plenum except one, which gets a vac gauge hooked to it. Disable the ignition and fuel system and crank the engine. It should read 3-9" hg of vacuum while cranking. If not, there's a leak or one of the ports you sealed up is leaking (always check user error items first).

The smoke machine would be easier.

Good luck.

 

[Marlboro_Man]

I'm going to call some shops monday and see if anyone has a smoke machine and what they want to check it with it.

Could i use any type of smoke that could be pumped in??? Like could i take one of those mosquito foggers and hook it up to an intake vac line and then just look for smoke to come out?

At this point would it be time well spent to do a "leak down test" ?

 

[90_Red_LX]

I have no idea. All I know is that our smoke machine uses either this stuff that came with it or baby oil or w/e it is, that clear crap thats really slick. It found my cousins exhaust leak in just a matter of several seconds. Once the smoke filled the exhaust, it came out of the seams in the muffler. No way in hell the naked eye could have seen that w/o an aid such as that.

 

[Marlboro_Man]

I have no idea. All I know is that our smoke machine uses either this stuff that came with it or baby oil or w/e it is, that clear crap thats really slick. It found my cousins exhaust leak in just a matter of several seconds. Once the smoke filled the exhaust, it came out of the seams in the muffler. No way in hell the naked eye could have seen that w/o an aid such as that.

So it doesn't pressurize at all, it just fill with smoke. right.

 

[Marlboro_Man]

Ok

Did a compression test, 145psi on # one and two cylenders. Then set the rockers to zero lash only. 150 psi on those two cylenders.

Set all rockers to zero lash only. Put it all back together and tried it. Still the same, no better, no worse. According to my friends vac gauge it's only getting 8 in. hg when my gauge says 9-10, thats at idle, at 13-1400 rpm it gets 15-16 in. hg.


So i borrowed a leak down tester and an air compressor from a friend today. Next thing to do is a leak down test and go from there.

Pending those results, I think I might just tear it all down again. Take the heads to the machine shop and have them pressure tested and all the valves and valve seals/guides and so on checked out. At the same time pay my friends grandfather to come over and index the cam for me. And in the mean time i will port match the cobra lower to a 1250 gasket so it will line up with the ports in the heads better.

I really don't know what to do. I can only think that it has to do with the cam phasing or the valvetrain, as i think i've exhausted all other possibilities.