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Technical How do you find an exhaust leak.....

Discussion in 'The Hokey Ass Message Board' started by rockable, Apr 20, 2014.

  1. rockable
    Joined: Dec 21, 2009
    Posts: 4,429

    rockable
    ALLIANCE MEMBER

    That you only hear under acceleration.

    I just had a totally new exhaust system put on my 455 Buick engine in my 49 Buick. I have what sounds like an exhaust leak but I see no soot at any of the joints or around the manifolds. Admittedly, I can only see the tops of the manifolds, due to the OEM design. They hug the block closely.

    I have used a stethoscope. I hear no mechanical noises and no exhaust leaks at idle. The noise is only apparent when the engine is under load but I can't replicate that in the shop. How do I figure this out?

    Thanks for your help.
     
  2. A long length of Rubber Hose, Hold one one at your good ear and start covering the total system with it running. When you find it you'll hear it puff in the hose.
    The Wizzard
     
  3. Phil Stevens
    Joined: Mar 24, 2002
    Posts: 391

    Phil Stevens
    Member

    was just gonna suggest the same thing, just don't breath in too much of it
     
  4. sdluck
    Joined: Sep 19, 2006
    Posts: 3,185

    sdluck
    Member

    Plug the tail pipe with a rag and broom stick the exhaust leak will almost whistle and get louder.
     

  5. rockable
    Joined: Dec 21, 2009
    Posts: 4,429

    rockable
    ALLIANCE MEMBER

    Now, that's what I'm talking about! That, coupled with the rubber hose ought to expose it. Thanks for the suggestions! I'm open to more.

    PS - I'm really concerned I have a cracked exhaust manifold. I'm told these engines have a history of that.
     
  6. squirrel
    Joined: Sep 23, 2004
    Posts: 55,934

    squirrel
    Member

    Can you describe the sound? It could be something besides an exhaust leak. Sometimes intake air noise at WOT sounds like exhaust. Or is it possible that it's pinging?
     
  7. My thought is if you just had a new exhaust system installed and you have a leak take it back to the muffler shop and let them fix it...HRP
     
  8. The powder idea needs the fan disabled or it gets messy quick !! HRP has the right fix. JW
     
  9. Rusty O'Toole
    Joined: Sep 17, 2006
    Posts: 9,657

    Rusty O'Toole
    Member

    I agree with taking it back to the shop. When I was in the muffler business years ago, we would occasionally make a mistake. If the customer brought it back right away we could usually fix it in a few minutes, for free.

    To check for leaks we would put the car on the hoist, start it up, and one mechanic plug the exhaust with a rag while the other looked for the leak. Usually it was a matter of tightening a clamp or something equally simple.
     
  10. 55 Ford Gasser
    Joined: Jul 7, 2011
    Posts: 698

    55 Ford Gasser
    Member

    Run a little ATF through the carb. Watch for the smoke. Plugging the tail pipe will help also. I use this method alot.
     
  11. 50dodge4x4
    Joined: Aug 7, 2004
    Posts: 3,534

    50dodge4x4
    Member

    Also check around the heat riser, they like to leak at the bushings on each side of the exhaust manifold that has the heat riser in it.
    I had a 350 Buick that had a cracked head, sounded just like an exhaust leak when it first cracked. Gene
     
  12. rockable
    Joined: Dec 21, 2009
    Posts: 4,429

    rockable
    ALLIANCE MEMBER

    I had a leak before I took it to the shop, HRP....but it was evident. Perhaps there were more. My deal with the shop was that they didn't touch manifolds other that to connect the pipes. I just need to find the leak first, then decide the course of action. Truthfully, I cannot see where the new system is leaking.......which is bad for me.
     
  13. If you have a crack in the manifold or other exhaust leak, sometimes you'll see a light gray trace of soot at the crack site. It may take some looking though.

    When I was doing exhaust work, the rag over the tailpipe was a good way to find the leak.

    Bob
     
  14. Well perhaps it is on the under side of the manifolds, or something else.
    If you are not certain its a leak or ping you might want to have a trained ear take it for a spin. You could try retarding the timing a touch and see if the noise lessens to flush out a ping.

    Ping is knock and pre detonation and it can ruin your engine, which also only happens under acceleration. There are some easy things to prevent/cure it.
     
  15. rockable
    Joined: Dec 21, 2009
    Posts: 4,429

    rockable
    ALLIANCE MEMBER

    Well, I have good news and I have bad news.

    First, the good news is that the rag in the tailpipe and rubber hose together worked well. I found the leak and it does not appear to be a cracked manifold.

    The bad news is the leak is between the exhaust manifold and head on the number one cylinder. God only knows how long it's been like that but the bolts in that manifold look like they've been in it for decades.

    I'm going to drive it until it gets too hot to drive it during the summer. Then, I will take the intake and heads off as a unit, do a valve job and put it all back together. I know that I will screw up if I start trying to get that manifold off by itself. Then, I will just wind up pulling the heads anyway. May as well plan on it and do it right. Probably will have a burned exhaust valve anyway.

    Thanks!
     
  16. Bigchuck
    Joined: Oct 23, 2007
    Posts: 1,159

    Bigchuck
    Member
    from Austin, TX

    Not to mention baby powder sticking to all the grease and oil.
     
  17. 54vicky
    Joined: Dec 13, 2011
    Posts: 1,599

    54vicky
    Member

    I would not use starting fluid on exhaust as verde742 suggested if you like your hair and eyebrows works for intake but not exhaust
     
  18. rockable
    Joined: Dec 21, 2009
    Posts: 4,429

    rockable
    ALLIANCE MEMBER

    I agree!
     
  19. k9racer
    Joined: Jan 20, 2003
    Posts: 3,091

    k9racer
    Member

    Marvel mystery oil works very well..
     
  20. stimpy
    Joined: Apr 16, 2006
    Posts: 3,546

    stimpy

    everyone wondered why we had cheap stogies at the shop for years , we used to light one up and use the smoke for a tell tail , later we used the smoke machine we used for the new cars to find leaks it was easier and less addicting , and cheaper too ( cigars went up in price)
     
  21. Am I missing something?,it sounds like you have a blown exhaust manifold gasket.

    No time like the present to repair it. HRP
     
  22. rockable
    Joined: Dec 21, 2009
    Posts: 4,429

    rockable
    ALLIANCE MEMBER

    It is...but I'm really worried that I would snap one or more of the exhaust bolts off trying to remove them. Then, I would have a era problem, as there is not much room to work in that area. It has bolts instead of studs and they are pretty well known for breaking off.
     
  23. tommy
    Joined: Mar 3, 2001
    Posts: 14,757

    tommy
    Member Emeritus

    A 3 foot piece of rubber fuel hose. You will be able to determine which side of the joint is leaking not only the joint. A pin hole in a weld?... you can easily spot it with the hose trick. We kept short pieces on each lift just for this purpose in my muffler shop. Shop air hose works well if you have a damaged air hose. Leaky header? get some fuel hose.
     
  24. 50dodge4x4
    Joined: Aug 7, 2004
    Posts: 3,534

    50dodge4x4
    Member

    Rock, If you have a manifold gasket blown, running with the blown gasket may damage the head surface where the gasket is suppose to be. The hot exhaust blowing through the opening acts like a torch and will melt away both the manifold and the head.

    I've seen it happen many times through the years. Its not fun when you have to build up a cylinder head and an exhaust manifold up with a welder, so you can get it resurfaced so it won't leak. It may already be to late to simply replace the gasket to fix the leak, but I promise in 2-3 months it WILL be. Gene
     
  25. Ulu
    Joined: Feb 26, 2014
    Posts: 1,775

    Ulu
    Member
    from CenCal

    Yeah, exhaust gas erosion is a bummer. Especially on an aluminum head/block!

    But even cast iron melts under those conditions.

    I have an aluminum block engine that has erosion between the block & steel exhaust seat. Just the tiniest 0.001" crack between seat and block was enough to start the channel of molten aluminum that blew out the tailpipe.
     
  26. RussTee
    Joined: Mar 25, 2008
    Posts: 1,241

    RussTee
    Member

    a squirt of desiel down the carb and a rag over the end of the pipe always shows it up
     
  27. A little OT, but, I had a slight exhaust leak one morning on my OT Cherokee. Pulled away from a curb under hard acceleration later and it got LOUD. Found out some SOB cut halfway through the exhaust with a battery powered sawz-all to try to steal the cat.
    Life in the big city!
     
  28. 54vicky
    Joined: Dec 13, 2011
    Posts: 1,599

    54vicky
    Member

    so true what a hell of away to start your day would be nice to catch them at it pour gas on them then ask do you smoke.light them up say now you do
     
  29. rockable
    Joined: Dec 21, 2009
    Posts: 4,429

    rockable
    ALLIANCE MEMBER

    Thanks, Gene. It may be too late. I'm going to have to wait until I know I have time to tackle the worst case scenario before I try for best case.

    These are cast iron heads, not Aluminum. They will still erode. I know.
     
  30. 327Eric
    Joined: May 9, 2008
    Posts: 2,116

    327Eric
    Member

    If you hadn't already thought of this, starting now, when you come home from a drive, with a warm engine(a few minutes after shutdown) spray each of the bolts with your favorite penetrating oil, This will cause the inconvenience of smoke when you fire it up for the next ride, but it goes away quickly. Keep doing this until you do the repai, and hopefully you will have enough oil on the bolts as not to snap them. This assumes it is not your daily driver. If it is, you definately don't want to do it daily, more like weekly.
     

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