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  • Valve Clatter / dedicated CNG F150

    Just picked up a 2004 F150, dedicated CNG, 49,000 miles. Overall an awesome truck. I'm finally part of the CNG community!

    One thing I've noticed with the vehicle is a fairly quiet (but still perceptible) valve clatter. The noise is very much like what the valve clatter from a diesel engine sounds like, EXCEPT this is much much quieter.

    Noise is much more obvious when the engine is first started and cold. Seems to go away when the engine is warm.

    At first I thought I was hearing the pulsing of the injectors, but it's definitely a clatter and not a "ticking".

    Is this sound particular to my vehicle, or is this a normal thing for a dedicated CNG engine? (Wondering if it has something to do with compressions ratio and flame front of CNG, much like why you hear this sound in a diesel).

    This is my first CNG vehicle, so I'm interested in the experience of the more experienced people here.

  • #2
    Re: Valve Clatter / dedicated CNG F150

    I had an 66 Olds that had valve noise, a can of STP always helped keep it quiet.
    BLUE 09 GX

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    • #3
      Re: Valve Clatter / dedicated CNG F150

      The 5.4L engines are known for ejecting spark plugs. That ticking may be exhaust leaking past the threads.

      Even if it is not that, but if you do your own wrenching, it would be in your best interest to give the plugs a once over ASAP for correct torque.


      ?Innovation is driven by having access to things.? -- Gleb Budman, CEO of backblaze.com

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      • #4
        Re: Valve Clatter / dedicated CNG F150

        Getting to the plugs is no easy matter on these engines... Id change the oil as a first attempt to quiet noisy lifters.

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        • #5
          Re: Valve Clatter / dedicated CNG F150

          dont use cheap oil I have fixed quite a few valve noises just changing oil as most of your jiffy lube places use a low grade of oil what is your oil pressure at a hot idle as low oil pressure can cause lifters to collapse than you have to much valve lash

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          • #6
            Re: Valve Clatter / dedicated CNG F150

            Originally posted by cowboy View Post
            dont use cheap oil I have fixed quite a few valve noises just changing oil as most of your jiffy lube places use a low grade of oil what is your oil pressure at a hot idle as low oil pressure can cause lifters to collapse than you have to much valve lash
            I agree, I use Valvoline and Mobile One. I believe dirt is the more common cause of noisy lifters though. Just do NOT use junk Fram filters!

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            • #7
              Re: Valve Clatter / dedicated CNG F150

              Thanks guys.

              I will check the spark plugs first, then try the motor oil second. We'll see if either of those has an effect.

              Haven't noticed yet what the oil pressure is at hot idle. Will take a look.
              Last edited by Black Mariah; 06-09-2009, 07:39 PM.

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              • #8
                Re: Valve Clatter / dedicated CNG F150

                I've owned three CNG powered Crown Vics. My current car is a 2000 CNG Crown Vic. All three have been equipped the 4.6L engine. The first time I looked at one I thought something was wrong with the engine, because the engine was louder that a gas powered 4.6L. It sounded kind of like a mni diesel engine.

                I found out they all have that sound that way.

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                • #9
                  Re: Valve Clatter / dedicated CNG F150

                  Originally posted by detsgtjr View Post
                  I've owned three CNG powered Crown Vics. My current car is a 2000 CNG Crown Vic. All three have been equipped the 4.6L engine. The first time I looked at one I thought something was wrong with the engine, because the engine was louder that a gas powered 4.6L. It sounded kind of like a mni diesel engine.

                  I found out they all have that sound that way.
                  I would not say that my dodge van is any louder than a gasoline one or my pick up and is home made convert all I hear is the k+n filter sucking air

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                  • #10
                    Re: Valve Clatter / dedicated CNG F150

                    My 01 does it as well. I was told it was the injectors. But whatever it is, it is common.

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                    • #11
                      Re: Valve Clatter / dedicated CNG F150

                      I have a '98 dedicated with a 5.4 and at 90k miles it still is very quiet,on the other hand both my dedicated '00s with less than 30k miles have very noisy injectors. I've met a few other people with the same situation, I think you have nothing to worry about. Joe

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                      • #12
                        Re: Valve Clatter / dedicated CNG F150

                        Again, thanks for all the responses.

                        This weekend I'm going to get under the hood to: check the torque on the spark plugs (yeah, I know, don't over-tigthen), change the oil, and listen with my "mechanics stethoscope" (aka long screwdriver) to figure out exactly where the noise is coming from.

                        BTW, did look at the oil pressure at hot idle. Seems OK to me. Slightly above the half-way point on the gauge, tending towards 2/3, but not quite.

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                        • #13
                          Re: Valve Clatter / dedicated CNG F150

                          your oil pressure sounds good sometimes a peaceof garden hose works better than a long screw driver I checked a friends ford pu and if you listen close you can hear the injectors click so it might be normal

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                          • #14
                            Re: Valve Clatter / dedicated CNG F150

                            I have a 2002 F150 dedicated CNG 104k miles and it has the same distinct clatter. It's normal. I have been to Vegas and back several times from California without incident. I use Royal Purple synthetic oil and it is quieter than when I first got it. The drive costs me 15 bucks round trip. I love this truck

                            My 2002 CVPI CNG also has a very minor clicking too and I put 400 miles a week on it without incident as well

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                            • #15
                              Re: Valve Clatter / dedicated CNG F150

                              Don't be alarmed at the sound. It's the injectors snapping open and closed. I understand the injectors were originally developed by Bosch for alcohol, and were adopted and qualified by Ford for CNG. Liquids have a way of damping valves and not transmitting noise, where gases don't.

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