Scary loud noises! Help!
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500, 472, 425, 368 Discussion, Scary loud noises! Help! in Cadillac Engine Technical Discussion; My '79 SDV with the 425 started randomly having this horrible sounding like screech/grinding noise and a burnt smell from ...
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    79Devil'Girl's Avatar
    79Devil'Girl is offline Cadillac Owners Member
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    Scary loud noises! Help!

    My '79 SDV with the 425 started randomly having this horrible sounding like screech/grinding noise and a burnt smell from the engine bay. The noise and smell happened as soon as I started the engine, it was fine this morning, drove it to work, came back,few hours later was leaving for a dinner, fired her up and ERRR mixed with a mechanical noise like something was moving around and grinding/hitting something else. Sorry I cant describe the sound that well, its nothing I've heard before, first sounding electrical and then those scary mechanical noises, screeching and almost thunking. The car supposively has 88k miles on it.. but now, I'm not too sure..
    I'm calling my mechanic tomorrow but if anyone has any ideas..
    Oh, forgot to mention I shut it off after a minute because I didn't want anything to explode!

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    deVille33 is offline Cadillac Owners Connoisseur
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    Re: Scary loud noises! Help!

    Sounds like you caught a cat in the fan.
    If you don't want to get dirty, put on a pair of work gloves and open the hood and inspect the drive belt and pulleys. Can you wiggle the fan back and forth? A little motion is alright, but more than a 1/4" is too much.

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    79Devil'Girl's Avatar
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    Re: Scary loud noises! Help!

    Poor cat. Lol.
    But would the fan be causing that burning smell? And.. Idk if it matters but the car smoked alittle more than usual - white-ish blue. Before it was just white and it would stop smoking as soon as it was warmed up. This morning my dad tried starting it to move it out of the driveway, it started only after 4 or 5 times (usually starts 1st or 2nd time) and he let it warm up for a bit before I heard it and ran outside to tell him not to drive it and it was dumping white/blue smoke. I'm starting to get scared.
    I'm not even sure if I should drive it to my mechanic's shop.. God what if it needs a engine rebuild!

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    YourMainParadox is offline Cadillac Owners Fanatic
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    Re: Scary loud noises! Help!

    it may be a simple thing like needing new rings... won't know till you get it apart or do a compression test.

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    BRUCE ROE is offline Cadillac Owners Fanatic
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    Re: Scary loud noises! Help!

    It might be something belt driven, like the air cond compressor. Unplug its clutch, or take its belt off if it doesn't run anything else critical. Bruce Roe

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    deVille33 is offline Cadillac Owners Connoisseur
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    Re: Scary loud noises! Help!

    The fan is attached to the water pump and when the pump bearings start to go, the fan may lock up temporarily. White smoke when you first start the engine is usually condensation exiting the exhaust pipes, mufflers, and cat - ylitic converter. If the white smoke dosen't stop after the engine is at operating temperature, there is a problem, most likely leaky head gaskets. This can also be caused by a malfunctioning water pump, which overheats the combustion chambers and allows water to get past the gasket seal. Usually the pump bearings failure will result in a small dripping leak at the pump weep hole, but not always.
    Your description doesn't say, the smoke white / blue is coming from the tailpipe? The front of the car? Dark smoke can be caused by your fan belts slipping on the pulleys.

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    79Devil'Girl's Avatar
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    Re: Scary loud noises! Help!

    Okay.. lol, it was the alternator, it had froze up and the belt was roasting. $150 later, car's back to normal.
    I'm such a retard
    ..However, while I have this thread - was gunna ask about the Q-jet.. I heard that you can't adjust them? Because they're computer controlled or something?
    Because the car bogs down and hesitates (usually when I most need it to go, i.e; stop sign, pulling out into traffic..etc) .. I had the carb rebuilt.. Idk if it's the carb or if it's the exhaust? I heard the cat can get plugged and make the car lose power?

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    BRUCE ROE is offline Cadillac Owners Fanatic
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    Re: Scary loud noises! Help!

    On any car of that vintage, I'd replace the original cat with a newer monolithic design. Smaller, less back pressure, legal even. You might want to get a new timing chain if it has the original. The plastic teeth on the cam sprocket can get brittle & fall off at any time. Check the advance on your HEI ignition too. Bruce Roe CLC # 14630

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    deVille33 is offline Cadillac Owners Connoisseur
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    Re: Scary loud noises! Help!

    ..However, while I have this thread - was gunna ask about the Q-jet.. I heard that you can't adjust them? Because they're computer controlled or something?
    Because the car bogs down and hesitates (usually when I most need it to go, i.e; stop sign, pulling out into traffic..etc) .. I had the carb rebuilt.. Idk if it's the carb or if it's the exhaust? I heard the cat can get plugged and make the car lose power?[/quote]


    1979? Computer? See Bruce if you have EFI, but with the Q-Jet, no computer.
    Bogging of Q-Jets are generally caused by poor vacuum signal. Please check other threads here, as this subject is covered several times.

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    Re: Scary loud noises! Help!

    Okie dokie. And I have a Q-jet. I shall search.. my mechanic said something about it needing what he thinks is an electrontic kickdown solenoid ..switch.. thing.. that plugs onto the carb.. as the original was not working when they rebuilt the carb.
    I didn't even know it had that, so, yeah. alien to me. We cut the cat off today (it was filled with nasty black carbon stuff) and putting a pipe in replacement tomorrow and gonna see if that helps, but we still don't know what that weird plug thing was. It seemed to not make a difference when they unplugged it, so, idk. It had two or three prongs and I thought it was part of emissions or something like that.

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    deVille33 is offline Cadillac Owners Connoisseur
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    Re: Scary loud noises! Help!

    The only electronic controls on you carb or near your carb would be a kick down solenoid for the transmission. It doesn't plug into the carb, but locates off the throttle linkage and has nothing to do with carb operation. The other solenoid is a idle reponse control which picks up your idle when the AC is in operation. This is also locates off the throttle linkage.
    All the other controlling motors on your carb are vacuum operated.

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    Re: Scary loud noises! Help!

    Okay so it must be one of those solenoids. Can I get either one of those at a parts store or are they hard to find?
    If its the kickdown for the tranny what would the symptoms be? Would it make the car stall under load? 'cause that's what it does most of the time unless you take your time easing up to speed, but quickly getting up to passing speed without bogging down and/or stalling? forget it!

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    deVille33 is offline Cadillac Owners Connoisseur
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    Re: Scary loud noises! Help!

    Quote Originally Posted by 79Devil'Girl View Post
    Okay so it must be one of those solenoids. Can I get either one of those at a parts store or are they hard to find?
    If its the kickdown for the tranny what would the symptoms be? Would it make the car stall under load? 'cause that's what it does most of the time unless you take your time easing up to speed, but quickly getting up to passing speed without bogging down and/or stalling? forget it!
    If it is the trans kickdown he is speaking of, it could be it is not adjusted properly. It is supposed to send a signal to an electromagnet in the trans, causes the trans to downshift. I think these are Cadillac only. I'm not sure the other divisions shared this part.

    Bog is caused by either vacuum signal loss or it could be caused by a sticky centrifical advance. Make sure these aren't your problem before getting into the carb. It wouldn't hurt to go through the full tune-up proceedure to ensure your engine is properly tuned. Check the resistance of your plug wires. Any leaks in the wires can result in crossfire, especially in #5 & #7.

    If you don't have either of those two problems, your fuel float may be sinking, which is a problem with phenolic floats and newer fuel, or your accelerator pump / passages may be faulty.

    Do not go into the carb until you are certain the other possibilities are eliminated. To go into the carb prematurely can be a waste of time and money and cause disappointment. If your mechanic isn't experienced with the Quadrajet, it may come back worse than before.

    A fellow mechanic brought me a car he had worked on for two days and couldn't get it to accelerate off idle. He was beating himself up on it. I replaced his vacuum advance canister, problem solved. It's the simple things you overlook that sometimes cause major problems. Remember KISS. That poor guy was still talking to himself when he left.

    As you describe it, having to feather the pedal to get it off the line, suggests a vacuum advance problem. If your spark can't keep up with your fuel demands, you can't support combustion.

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    Re: Scary loud noises! Help!

    Okay, got the cat cut, has much more power now however that 3 prong plug thing which I'm guessing is the transmission kickdown solenoid - it's missing. He took it off when he sent the carb away to get rebuilt. Now, it's gone. We were looking all over the shop for it, must have thrown it out.
    The car doesn't stall or bog when it's in Park revving, only when it's in drive and moving. IDK if the kickdown would make the car die.
    I'll suggest the vacuum advance idea..

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    cadillac_al is offline Cadillac Owners Connoisseur
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    Re: Scary loud noises! Help!

    It sounds like it's just out of adjustment. An old time mechanic should be able to adjust the carb and distributer in about 15 minutes. I hope your mechanic is over 45. I say 45 because I know of a few 40 year old Quadrajet hacks lol. I guess they moved on to fuel injection before they got carbs mastered. These things are pretty easy to work on though.

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