PDA

View Full Version : Need a little help finding a hidden vacuum leak



Mike Puckett
10-06-2007, 06:15 PM
What is the best thing to use to spray around the engine bay to find a vacuum leak. I normally have about 18 inches of vacuum but it suddenly has dropped to about 8 and I can't find the leak after looking everywhere. I've gone over every connection and followed every hose and tube but can't find it. I read the post below after writing this one so I don't mean to repeat but of the ones mentioned, which one works the best, carb cleaner, brake parts cleaner, propane, or starting ether?

mywhite89
10-06-2007, 06:23 PM
What is the best thing to use to spray around the engine bay to find a vacuum leak. I normally have about 18 inches of vacuum but it suddenly has dropped to about 8 and I can't find the leak after looking everywhere. I've gone over every connection and followed every hose and tube but can't find it.

I know people use carbeurator cleaner. I seal up the throttlebody the best I can with an empty container of Gojo hand cleaner(works perfect for an 85mm throttlebody), hook up a air pressure regulator to check for leaks. If its sucking air in, it should push air out very noticeably.

Mike8675309
10-06-2007, 06:44 PM
Yep, carb cleaner, or starting fluid may work.

Mike Puckett
10-06-2007, 09:59 PM
I tried starting fluid and got mixed results. I'll get some carb cleaner and try it. Propane sounds a little scary. I might give the compressed air thing a try, sounds like an interesting idea.

deepbluesc
10-07-2007, 09:04 AM
Propane is the best choice.

95MTSC
10-07-2007, 10:02 AM
I like the compressed air method. I found that a 3" rubber compression plug from a hardware store will seal a 75mm TB just fine. Then add about 10psi from your compressor to an intake hose. Sometimes you can hear and feel the leaks. After you fix any of those, you can fill a spray bottle with some soapy water and spray all the suspect areas - if you see it bubble then it's leaking. It's really easy to spray those areas, intercooler piping connections, rubber hose connections, etc.

I didn't even think I had any leaks, but tried it anyway for fun. I found a cracked rubber hose on the intake plenum, and found that my lower IC connection was leaking too.

spetz01
10-07-2007, 10:24 AM
I did the air trick too, worked like a charm. I stuffed a coke bottle into the TB and duct taped it on. Just make sure to rinse the soapy water off. I didn't and it made a mess.

Mike Puckett
10-07-2007, 10:43 AM
Thanks for the idea, sounds interesting, I'll give it a try. I've got an 85mm TB which is 3 1/2" OD so I'll have to look for something big enough. I had the lower intake off and and replaced the intake gaskets and redid the the IC tube connections and it's still leaking somewhere even if it is a little better. It came and went at 1st and now it's leaking all the time so I'm thinking there's a split hose maybe. I zip tied all of the connections and that didn't help. I've just got to dig deeper.

Mike8675309
10-07-2007, 11:03 AM
Make sure the line for the boost gauge isn't leak. Bypass valve as well. They use a stiff line that I've seen crack but not be obvious.

Does it leak only under boost, or is the idle quality messed up a bit signifying a decent vac leak all the time? Maybe that fitting for PCV on the back of the inlet plenum?

Mike Puckett
10-07-2007, 02:27 PM
It appears to just be idle quality and drives Ok. It starts right up and wants to stall out at 1st but after a couple of minutes it'll idle w/o stalling. My a/f gauge will show a lean idle but if I rev it up it'll read normal to slightly rich and I've got normal boost. Every hose and tube I check looks Ok but it doesn't mean that it's not leaking.

90blkbrd
10-07-2007, 05:51 PM
Don't pressurize the engine. Disconnect the PVC system.

I've seen brake cleaner used.

Mike Puckett
10-07-2007, 05:56 PM
Well, I shot some carb cleaner into the air cleaner and it raised up the rpm so I knew what to look for when I did find it. I then sprayed everywhere on the intake, inlet tubes, hoses, fittings, couplings, sensors, and nothing. Squirted the IC connections and still nothing. Finally almost as an afterthought I sprayed the front of the intercooler and got a response. Hmmm, shot the bottom righthand corner and the rpm shoots right up. That's got to be it! The IC's got to be cracked right there. I'll pull it off and fill it with water and see if I can find the crack. Hopefully I can fix it with a layer of epoxy and not have to get it welded.

Mike Puckett
10-07-2007, 10:57 PM
The leak is hidden no more. Thanks for all the assistance. The crack is apparently worse than it looks. I couldn't fill the IC up with water in the kitchen sink it leaked out so fast. I hope that's the only leak. I think I'll get the whole bottom plate rewelded.

Mike8675309
10-07-2007, 11:02 PM
That is a very bad crack. Expect it to be much worse behind that weld. Pablon2 had a similar crack across the top of his IC. Had to be ground all the way down to the tubes before the whole crack was exposed and I still don't recall if it ever got fixed, as it cracked again after an initial fix.

victor malvar
10-07-2007, 11:58 PM
Hi we have these special vacuum testers in a 3" and 3.5" which we like a lot. NO need for any chemical spraying at all. It works with air pressure and some home products everyone has at home....It can be used for other leaks also. Hoses. Take a look at them they work great. I was able to find a crack behind the blower. I would have spent another month looking for this leak because it was one of the three tabs that broke from tightening to much I suppose??

We had these made specially for us and it is one of those tools you like to keep around. You can use a bicycle pump, compressor but take it easy on how much PSI or pressure you put into your system 10 to 12 PSI at most!!!
If I had a current picture on this computer, I would show everyone tonight. I will get one in sometime tomorrow.

Stay tuned for the picture and other information.

I also want to say hello to my friend Mike 8675309 and also Mike Pucket and 90BLKBRD, Deepbluesc as well as others I'm not sure l know you but I hope your all doing well :) !!!

Mike Puckett
10-08-2007, 07:02 AM
I'm glad to see that your doing and feeling better Victor. I've visited your website several times. Ocala's not that far from Atlanta either. I'd be interested in seeing your vacuum tester. I suppose I'd need the 3.5" with the 85mm TB. These vacuum leaks can be really frustrating to find at times and can really screw up the performance of the car.

victor malvar
10-08-2007, 08:24 AM
Hi Mike P.,

Thanks for the get well greeting!!!

I will post a picture of one in a minute. I have to wait for Diane to send it from my computer which she uses now and reads all my personal MY PLACE invitations:rolleyes::D:p my age was put it wrong I'm only 26 in My Place...If they only new. Actually it is a good one with music such as Spinningwheels album it's cool...... I'll have to post it also. I just want to finish this post that I started an hour and a half...Here comes the picture...I hope.

Oh we also have these on a special SCCoA member discount. You have to show your membership no. to get that price... I'm dropping the price so wait before any one buys one they are at $75.00 now. I'll charge $75.00 but this week only $60.00 ;):) I think I got it....Cool. Also we need cool car pictures and nice looking girls with some clothe on NOT naked...What a shame eh. For our 1st ever calendar this year you must be old enough to look at these calendars.Take care and good luck.

Victor........

Mike Puckett
10-08-2007, 09:36 AM
Victor, I've got a couple of photos that may work but no scantily clad girls in them. In fact I've got no girl at all unless we count my 6 year old granddaughter. She's a real cutie pie, though. Being single in my 50's has been tough! Women in their 50's can be really strange and the young ones don't want an old man like me since I'm not super wealthy.
After I get my IC rewelded and reinstalled if I've still got a leak, I'll get right back to you on the tester.

mywhite89
10-08-2007, 10:19 AM
Victor, I've got a couple of photos that may work but no scantily clad girls in them. In fact I've got no girl at all unless we count my 6 year old granddaughter. She's a real cutie pie, though. Being single in my 50's has been tough! Women in their 50's can be really strange and the young ones don't want an old man like me since I'm not super wealthy.
After I get my IC rewelded and reinstalled if I've still got a leak, I'll get right back to you on the tester.

congrats on the find Mike. Gotta love when a plan comes together. With compressed air you would have found that leak in a heartbeat.

Mike Puckett
10-08-2007, 08:05 PM
I just put the repaired intercooler back in, fired that baby up and viola, it voiks, it voiks!! My A/F gauge is back reading right and it idles right and didn't try to stall out. It was nice to see the A/F gauge light all the way across when the O2 sensor's heaters warmed up and then fall back to normal readings. My K&N A/F gauge may not give me pinpoint readings but it sure alerts me to danger and lets me know when it's right.
Thanks to all those who helped.

Young-SC-Owner
10-08-2007, 09:15 PM
glad you got it fixed Mike!,

Victor seems like your gettin better! I miss swapping stories with ya ol buddy!:D

victor malvar
10-08-2007, 10:57 PM
I just put the repaired intercooler back in, fired that baby up and viola, it voiks, it voiks!! My A/F gauge is back reading right and it idles right and didn't try to stall out. It was nice to see the A/F gauge light all the way across when the O2 sensor's heaters warmed up and then fall back to normal readings. My K&N A/F gauge may not give me pinpoint readings but it sure alerts me to danger and lets me know when it's right.
Thanks to all those who helped.

Awesome!!! It was good talking with you. You have very good ideas. I can't wait to see your SC and also that 440!!! It will do just fine. I'll send you the info on what we spoke about. He knows his stuff on muscle cars..

See you in a few months hopefully. :)

Victor......

victor malvar
10-08-2007, 11:22 PM
glad you got it fixed Mike!,

Victor seems like your gettin better! I miss swapping stories with ya ol buddy!:D

Hi Tony,

Some days are better than others. I hope your serious about flying school. I had my 1st supervised solo when I was 16 that's a LONG time ago. I did my 1st. solo in 11 hours of dual or with a CFI in a good old Cessna 150 call no's were N4186U Yellow and white. I love flying but can't fly anymore without another pilot on right or left seat. I can fly fine from either seat but I am sure I'm rusty and the landings might hop once or twice. I tried to call your you or your Dad but there was no answer and left a message.About then I got worse. I have only been feeling better since I stopped taking some medicine that was kicking my butt real bad. A good friend Ray G. from this club helped me a lot asking all the right questions of my Doctor (s) I feel better as the day goes on. It's not been this good in quite awhile. Call me if your still up if your with your girl friend?? I can wait if you can ;):D:p.
Please send my regards to your Mom and Dad.
Take care Tony,
Victor......