Carbon build up on the intake....
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Cadillac Seville / Cadillac Eldorado Forum Discussion, Carbon build up on the intake.... in Past Cadillac Vehicle Discussion; Last nite I cleaned the TB on my 98 STS that has 130,000. The stuff was an 1/8" thick on ...
  1. #1
    Guy,mn.usa is offline Cadillac Owners Fanatic
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    Carbon build up on the intake....

    Last nite I cleaned the TB on my 98 STS that has 130,000. The stuff was an 1/8" thick on the back side of the throttle blade and a 1/8" thick rim of the crap behind the throttle blade!!! Looking down the inside of intake it looked as bad if not worse! So I cleaned the TB up to the intake and boy did the throttle responce pick up when I test drove it!
    Is the paper air filter doing a good enough job keeping the dirt out? Why is this happening? Too much blow by? My car does not use hardly any oil either...
    I'm going to clean the intake too....as there must be a ton of power robbing gunk in the intake....a clean intake will flow so much better I can only imagine how much more the engine will pick up some hp's and run better!!!!Can someone who has removed an intake from the Northstar give me a heads up to how much work this is and what envolved?
    Thanks
    Guy

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  3. #2
    JimD is offline Cadillac Owners Connoisseur
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    Re: Carbon build up on the intake....

    Forget about the crud on the inside of the manifold; it is only harmless unburned petroleum products that is common to all "dry" intake manifolds (there is no gasoline spray to wash it off). Continue to keep the throttle blade clean every 40,000 to 50,000 miles to prevent a sticky throttle condition at off-idle.

  4. #3
    mikeay's Avatar
    mikeay is offline Cadillac Owners Fanatic
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    Re: Carbon build up on the intake....

    I did this about a month ago.
    I used a plastic scraper to remove the build up. There was so much of it that I could actually stick the scraper in the "cake" and it would stay there. I (as you did) notice the intake was also full of it too. I purchased the gaskets for the throttle body and replaced the intake gaskets as well (they are reusable as well), I just did not want to be stuck without them when putting it back together (if worn) which they were.
    Cleaning the intake was a choir. There is no easy way to clean the inside. TB cleaner only did so much, scraping it was the only way and that was inpossible, unless you have tooth picks for arms. I think it would have been easier to have it hot tanked. Maybe look around for a shop that can do it for you. Take the intake to them. If I knew then what I know now, that's what I would have done.

    Anyways, I just used Spray Nine, let it sit for 5 minutes then rinse with hot water. Did that about ten times. Used compressed air to get most of the water out, and let it sit over night. By morning it was bone dry.

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    Guy,mn.usa is offline Cadillac Owners Fanatic
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    Re: Carbon build up on the intake....

    My clean tank has non flamable cleaning solution or simple green would work. I think it would increase flow if it were cleaned up. I would never put down a intake that is this bad on my 68 gto....it would kill my port/port match work that I have done to the RPM intake I use. I think my N* would really pick up if it were clean...what causes this to happen to the intake?

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    Guy,mn.usa is offline Cadillac Owners Fanatic
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    Re: Carbon build up on the intake....

    I have a really long tappered bristle brush...pickup a hardware store. I used it on my RPM after I ported it. I think hot tanking it might warp it. Maybe I'll port match it since I have it off already.

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    Guy,mn.usa is offline Cadillac Owners Fanatic
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    Re: Carbon build up on the intake....

    Mike how did the run after you cleaned the intake?

  8. #7
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    Re: Carbon build up on the intake....

    interesting post. Where are the throttle blades located and do you have to remove anything to get to them?

  9. #8
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    Re: Carbon build up on the intake....

    Pay attention to JimD. What you are seeing in the intake is coming from the PCV. Clean it and it will be back in short order. Don't waste your time. Clean the TB yearly and it will be much easier.

    Blackfrontier,
    I assume you are talking about a Northstar, you don't say, (4.9 is a little different). You need to remove the intake ducting and MAF sensor. Throttle plate is inside the TB bore (much like the lower portion of a carb). Do a search. It has been discussed many times. I think there are some posts with pics in the Tech Tips section.

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    Re: Carbon build up on the intake....

    Thanks RANGER. I was talking about a Northstar motor in my 95 STS.

  11. #10
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    Re: Carbon build up on the intake....

    Guy,mn.usa
    Honestly, I did not notice a difference (performance wise). The TB was sticking, thats why I started to clean it, and didn't stop. I did also notice the (see attached) red arrows on the left were almost pluged from the inside. I did not see the restrictions from outside with the tubes pulled off, pipe cleaner did the trick there. This is what I observed.
    The arrow on the far right - this is a spring loaded flap. It was extremely "caked" up. I'm not exactly sure what it does but, it's in fine flapping order now.

    I did notice there was no more puff's of smoke coming out the exhaust when I floored it.

    It also appears to excelerate smoother.

  12. #11
    Ranger's Avatar
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    Re: Carbon build up on the intake....

    Those tubes you indicated are where various vacuum lines are connected.

    The flapper you talk about at the front is an over pressurization valve. Basically a spring loaded trap door. In the event of an overpressurization (backfire), it is forced open and the pressure is relieved rather than blowing up the intake.

  13. #12
    mikeay's Avatar
    mikeay is offline Cadillac Owners Fanatic
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    Re: Carbon build up on the intake....

    Ranger
    Thanks for the clarification.

    Would it make sence that the various vacuum line connections on the intake would become pluged? I do recall using a flash light to see if I could "see the light at the end of the tunnel", but I was unable to. I guess over time this would be possible without proper maintenance. I think now that I have it cleaned up, the WOT's would now be part of my preventitive maintenance schedule to stop this kind of build up in the future. I don't think (aside from my cleaning efforts) WOT's or fuel additives would have cleared that out. Am I wrong?

    Appologies, not my post, but I think it's relevant.

  14. #13
    Ranger's Avatar
    Ranger is offline Cadillac Owners Member
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    Re: Carbon build up on the intake....

    I have never heard of the vacuum ports becoming clogged and would not expect it as the inside of the manifold is usually nothing more than an oily residue.

    Remember, the WOT proceedure is to clean out the combustion chamber. It does nothing for the intake manifold or TB.

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