Stock 01 Knocking Noise At 3k Rpm

Discussion in 'SN95 4.6L Mustang Tech' started by AP113, Nov 16, 2013.


  1. AP113

    AP113 New Member

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    I recently got my car checked out at a jiffy lube and got an oil change (full synth, overpriced do it myself next time) car ran much stronger after I got it done, but the guy said he saw some coolant in the sparkplug wells (I had also noticed this days prior) but he didn't do anything about it. A few days later I had some fun and did some burnouts, that night driving home I noticed a knocking noise from 2-3 rpm.

    1: It knocks only when I press the throttle in either neutral or when lightly pressing it cruising in gear
    2: Does not knock when I lay it down in gear (but it does when I lay it down in neutral)
    3: It only knocks when the car's hot and not when I initially turn it on when its cold

    Do I need to get myself a new intake or what?
    I have a video of the noise that I can post if it makes it easier, I just had trouble uploading.
    Thank you for any responses in advance!
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  2. 1987stangman

    1987stangman Member

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    Intake is likely cracked if you see coolant in the wells, or you have a heater hose leaking. These cars had issues with the intakes cracking particularly around the front coolant crossover and the rear heater hose nipple. Ford eventually redesigned the intake with an aluminum coolant crossover but the rear nipple is still an issue. As far as the noise goes I would get that intake off, pull the cop boots and get that coolant out because it's likely causing a misfire. Buy a new one from Dorman or Ford Racing, your choice. Hopefully this is all your looking at and probley is but a bit of advice here would be maybe not burn out and lay on it so much.

    If it makes you feel any better, I just had to replace the stock intake on my 2000 for the notorious coolant crossover leak at 114k.
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  3. AP113

    AP113 New Member

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    First of all, thank you for replying.
    My buddy helped me open up the intake aaaaand... it was cracked, IMG_20131123_142915_466.jpg so after a compression test (which came out fine) some coolant splashing and a stop to pep boys; we slapped on a fresh intake and fired her up. Good news is, it doesn't leak coolant anymore (also found it was coming from the heater hose). Bad news is that it still knocks in the manor that I described and it still chuggs along as before. We did identify that it was coming from the left back side of the block, so we're going to open up the valve cover and see if we can identify any problems in there. Any other advice?
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  4. bhuff30

    bhuff30 Founding Member

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    I didn't want to say it earlier, but a knock at light loads when hot can be a rod bearing. Is it getting worse as you drive the car more?
    You could try pulling spark plug wires (COPs?). That may help you narrow the issue to a specific cylinder and give you an idea what the issue is. If it goes away without spark, then it could be a rod bearing.
    Just curious, have you checked the oil level since the monkeys changed it? Hopefully they didn't put in 5 quarts and call it good. :rolleyes:
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  5. 1987stangman

    1987stangman Member

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    What intake did you use? Brand? Hope that it wasn't the Dorman. But unless Pep Boys started selling better parts I do beleive that's what you got.

    As far as the knocking is concerned, usually at hot idle a bearing will be slightly noticeable and increase with RPM but can't be ruled out. Could be a roller follower or lash adjuster too.. You have the right idea by opening up a valve cover and checking things out.
    #5

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