Cracking Exhaust manifolds
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Cadillac Allante Forum Discussion, Cracking Exhaust manifolds in Past Cadillac Vehicle Discussion; After about six months of searching I located and purchased an 89 Red with Black Allante in pretty good shape. ...
  1. #1
    Ozark Caddy is offline Cadillac Owners Member
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    Cracking Exhaust manifolds

    After about six months of searching I located and purchased an 89 Red with Black Allante in pretty good shape. There are cracks in the exhaust manifolds. I noticed these same cracks in several of the Allante's that I checked out in my search and yet I find nothing on any of the Allante Web Sites or forums about this problem. I found today that I can order a set of new manifolds for just under $1000 and that may be the fix. The car is worth it, I am just wondering how other's may have dealt with this?

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    Allante North *'s Avatar
    Allante North * is offline Banned
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    Re: Cracking Exhaust manifolds

    Thats a new one on me. $1,000.00 seems a little high priced to me. Your source seems alful proud of there product(must be the General himself). You might try looking at some junkyards to see if you can find some that will fit off a wrecked Caddy with the same engine. Perhaps someone else will chime in with more knowledge than me, but I think that manifolds will interchange relatively easy.

    Good Luck and let us know how thing turn out.

  4. #3
    carnut is offline Cadillac Owners Master
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    Re: Cracking Exhaust manifolds

    This sub frame and basic engine were from an 87 to 92 Eldo or Seville. Called E body by wrecking yards. I would think these manifolds would be the same. My '88 manifold welds look like they are cracked but are in fact, not. The type of welder?used gives the appearance of cracks at the welds but is just overlap at the individual tubes. Try a wrecking yard first and report back. I would think for less than a $1000.00 you could have a certified welder repair both.

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    Ozark Caddy is offline Cadillac Owners Member
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    Re: Cracking Exhaust manifolds

    You may be right, they may not actually be cracks. Nearly every one that I looked at during my search appeared to have cracks and if that were the case I am sure there would be talk about that on the forums? I will investigate further and let you know what I find. Thanks,

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    Ozark Caddy is offline Cadillac Owners Member
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    Re: Cracking Exhaust manifolds

    I went back and re-examined the manifolds. They are cast units with no welds on them. The crack lines look like cracks? So I will blow a harmless smoke in the tailpipe and see where it comes out?

  7. #6
    Ozark Caddy is offline Cadillac Owners Member
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    Re: Cracking Exhaust manifolds

    I got the right manifold off today and the crack in it is hardly visable but the left manifold is severly cracked. Unfortunately it is also very difficult to get off. I am still working on it. I also discovered that neither manifold has a gasket between it and the head? I can't find anything in the shop manual concerning gaskets but the local auto parts dealer listed one for it. So I will put the manifolds back on with gaskets. Also a few of the bolts were loose and exhaust was blowing by the manifold. I don't know if this is the result of somebodies poor work in the past or if it is original?

  8. #7
    El Dobro's Avatar
    El Dobro is offline Cadillac Owners Connoisseur
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    Re: Cracking Exhaust manifolds

    GM didn't use exhaust gaskets on that series engine. The mating surfaces were sprayed with Goodwrench graphite spray p/n 12345268.

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    Re: Cracking Exhaust manifolds

    Correct, no exhaust manifold gaskets on the 4.1/4.5 engines.

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    Ozark Caddy is offline Cadillac Owners Member
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    Re: Cracking Exhaust manifolds

    Yes, I have confirmed through a couple of service manuals that there are no gaskets, My question now is what will be the result if I add gaskets? Dick at Allante Source says that he too has seen many cracked manifolds. With only 18lbs of torque on the bolts, as soon as the manifold cracks, it is no longer square with the head and it leaks. Brazing or welding the manifold will only make any out of square worse requiring the surface to be machined. If they are prone to crack (for unknown reasons) what would prevent it from happening again? This is not a simple job and I don't want to do it again. Gaskets are looking good at this point unless there is a major reason not to use them.

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    Ozark Caddy is offline Cadillac Owners Member
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    Re: Cracking Exhaust manifolds

    I finally got the manifold off the right side of the engine. Here is a picture of the back side of the manifold, this crack nearly went all the way around.
    Attached Images

  12. #11
    globetrotter is offline Cadillac Owners Member
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    Re: Cracking Exhaust manifolds

    I have crack very similar to the ones you photographed about the same location on my R-Manifold in spark #6 position. I found about 50 scrapyards with these exhaust manifold available price ranging from $45 to a max. of $100. Wonder what conditions they will be in.

    http://www.car-part.com/cgi-bin/search.cgi
    Hope this helps

  13. #12
    globetrotter is offline Cadillac Owners Member
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    Re: Cracking Exhaust manifolds

    I am replacing the R Exhaust Manifold with a used one from a junkyard. Should I use gasket or spray when installing to ensure no leakage from the used manifold being installed.

    Thanks

  14. #13
    Ozark Caddy is offline Cadillac Owners Member
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    Re: Cracking Exhaust manifolds

    I used gaskets, but let me explain. I did some research into this issue and it was a big problem for Cadillac on these models. The "no gasket" graphite spray was an attempt to get a more even heat between the head and the manifold. The graphite with the light torque allowed the manifold to move with respect to the head with expansion and contraction. I believe that the cars that have this cracking problem will probably all be found in areas where the ambient temp is subject to going below the freezing level. Those in dessert areas and deep south probably won't be as common. A new gasket was developed that has a wide aluminum band on the lower part of it. Most of this band is exposed when installed and acts as a heat fin. This is the gasket that I used and I used a torque of 22 ft lbs. Only time will tell if I truly have a fix or not. I can tell you this, it sounds great. It was a real trick getting the manifold out. One has to remove both exhaust pipes that go from the engine to the converter as well as heat shields and such and it is a very tight fit, but it can be done. Remove the oxygen sensors before you begin so as not to damage them, and be sure to disconnect the negative side of your battery before beginning. Lots of liquid wrench is also helpful. Good Luck.

  15. #14
    rbtclark is offline Cadillac Owners Member
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    Re: Cracking Exhaust manifolds

    I replaced the right exhaust manifold on my '89 Allante a couple of months ago and used a gasket. All is working well so far. The junkyard manifold I used was from an '92 Eldorado which uses a new design that includes a gusset on the cylinder head side of the casting to give it more strength. I recommend that anyone going through the difficult process on an older model uses the newer design manifold. I don't know what year that the design changed, but the new design has to be stronger than the older style. The job took me 12 hours to complete and I don't ever want to have to do it again!

  16. #15
    Donmgx is offline Cadillac Owners Member
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    Re: Cracking Exhaust manifolds

    I had the "header" tubular type manifolds welded well over a year ago and everything is fine. There are no gaskets and I used the graphite spray, but I've never seen the use of a gasket hurt anything. Now, my opinion of why they crack. I think Allantes have some kind of stress on the manifolds. From where? Maybe weak motor mounts?, bottoming out over bumps? Maybe the weight of the exhaust system? There are a lot of cars out there with tubular exhaust or headers that never have a problem. I don't buy the heat theory, especially with the front manifold being right behind the radiator. 200 degree air is like airconditioning for an exhaust header. Just my thoughts.

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