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Thread: '78 280Z making ticking noise when engine warms up

  1. #1
    Orange '78 dankfrye@charter.net's Avatar
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    Default '78 280Z making ticking noise when engine warms up

    I've been working on a problem for several of months that I can't figure out. When my engine warms up all the way, it starts making a ticking noise. It is worse under load. I first thought of an exhaust leak but they usually happen cold and go away when things warm up. By pulling off one plug wire at a time and one injector plug at a time, I have narrowed it to #6 cylinder. I swapped #5 and #6 plugs, then #5 and #6 plug wires and the noise was still in #6 cylinder. I took #6 injector out and tested the spray. It looked good, but I cleaned it several times any way. I then switched #5 and #6 fuel injectors but the ticking still came from #6 position. I have replaced all my hoses, have a new distributer (my vac advance wasn't working. I have removed all of my EGR stuff and have a non EGR manifold. I have also disconnected my BCDD valve. I have all new fluids. I noticed the ticking right after adjusting the timing and the valves. After buying my new distributer, I reset my timing to 10deg TDC with the vacuum advance capped off. I thought that I might have got the valves a little tight so I re-adjusted them again. The problem has not changed. I'm running 93 Octane, non ethanol gas. The car runs good and idles steady but the noise gets really annoying when the engine warms up. Sorry this is so long but I didn't want to leave anything out. I would really appreciate any input that anyone has on this problem.
    Thanks,
    Dan Frye

  2. #2
    Registered User cozye's Avatar
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    It doesn't tick when the plug wire is off number 6?
    1978 280z 4sp

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    Orange '78 dankfrye@charter.net's Avatar
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    No! When I take either the plug wire or the FI connector off the ticking goes away. Some how it's related to #6 cylinder.

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    Registered User CW240Z's Avatar
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    Could be a sticky rocker arm. Mine on cylinder 5 ticks when the car starts up, but quiets down a bit after it has warmed up and oil has been pumped through the system.
    1972 240z 51K original miles
    1976 Datsun 620 pickup
    1991 BMW 3 series - Daily Driver
    1974 Porsche 914 1.8

  5. #5
    Registered User cozye's Avatar
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    Definite exhaust manifold leak. It's common. If it where a valve train related tick it would do it whether you had combustion or not since the cam is still spinning and opening th valves
    1978 280z 4sp

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    Orange '78 dankfrye@charter.net's Avatar
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    Thanks! I suspected that but I thought that most exhaust manifolds mostly leaked when everything was cold then went away when things warmed up Gaskets expanding and such). I'm still kinda of new to this.

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    Registered User cozye's Avatar
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    Quote Originally Posted by dankfrye@charter.net View Post
    Thanks! I suspected that but I thought that most exhaust manifolds mostly leaked when everything was cold then went away when things warmed up Gaskets expanding and such). I'm still kinda of new to this.
    I suppose the going away when hot thing is possible, but that's not the norm. On these cars the end bolts like to snap off due to rust, heat, and warpage. Especially on 1 or 6 at the end. It's not too bad a job if you take your time, use lots of heat and pb blaster. Don't get impatient and work the bolts slowly back and forth very gently. Nissan still makes the gasket, which is higher quality than the replacements
    1978 280z 4sp

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    Orange '78 dankfrye@charter.net's Avatar
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    I have already replaced the gasket. It don't go away when it's hot though. It starts ticking when it gets hot; just the opposite.
    Thanks

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    I would normally agree with Cozye -- probably an exhaust leak at the manifold/head junction. However, if you're SURE you don't have a leak there, it might be a sticking valve or rocker that gets popped shut when there's detonation in the cylinder. You can try using a motor flush like Gunk. Only do this if there aren't heavy crusty deposits in your engine. Gunk is a great way to flush away the varnish and get your valves moving freely. You might also need to SeaFoam your intake.
    My last three sports cars while I still owned all three:

    2001 BMW Z3 Roadster 3.0i soft/hard top (sold)
    1966 Ford Mustang Coupe (sold)
    1978 Datsun 280Z (enjoying very much )

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    Registered User cozye's Avatar
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    Didn't you check the manifold for warpage or cracks? Some owners have to get the manifold milled down to straighten the maiting surface.
    1978 280z 4sp

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    Registered User cozye's Avatar
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    Poor some seafoam in while running and see if it blows smoke out the suspect area
    1978 280z 4sp

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    Orange '78 dankfrye@charter.net's Avatar
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    Thanks for your suggestions. I was contiplating using Gunk valve medic or something similar but I was afraid that I might break some deposts loose and clog up my oil pump. My valve train does look prettty clean though so I might try it. I have cleaned my intake and throttle body both off and on the car so I think it's pretty clean. I have also taken my injectors out, cleaned them and tested the spray pattern. I guess the exhaust manifold could possibly have a leak. I have some sea foam and might give that a try.

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    Registered User robftw's Avatar
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    I put seafoam in my crank case and ran it for 500 miles, my car used to tick like yours.

    After that + adjusting the valves the problem went away.

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    Orange '78 dankfrye@charter.net's Avatar
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    Thanks! I'll try that.

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    Registered User cozye's Avatar
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    Quote Originally Posted by robftw View Post
    I put seafoam in my crank case and ran it for 500 miles, my car used to tick like yours.

    After that + adjusting the valves the problem went away.
    Did it stop ticking when you removed the plug wire to #6 ? I think that's the key here.
    1978 280z 4sp

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    Orange '78 dankfrye@charter.net's Avatar
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    Yes. It stopped ticking when I removed the plug wire to #6. When I swapped #5 and #6 plug wires, though, it started ticking again. I pretty much ruled out the plug wires, plugs and injectors by swapping them out. I also have brand new NKG plugs and plug wires.

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    Orange '78 dankfrye@charter.net's Avatar
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    Did the Sea Foam treatment through the brake booster hose. Besides smoking up my garage and half the neighborhood, I did find an exhaust leak at the bottom of #6 exhaust bolt on the manifold. I tightened it up along with all the others and readjusted my valves the right way. The car seems to run quieter and stronger. I still have a light tick when engine is warmed up but it's not near as bad. My valves were all tight because the guy that showed me how to do a valve adjustment said to put the feeler gage under the tappets on the drivers side instead of directly under the cam lobes. This apparantly makes a pretty big difference.
    Thanks for all you guys help!

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    Default Great find!

    So glad I found this thread. I've been having a similar problem (ticking after warmup) with my '78 280. I've had suspicions about my exhaust, and now when I get back to where the car is this summer, I'll know what to look for! What a helpful thread and awesome example of the community here. Registered just to say that

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    Z geek at large FastWoman's Avatar
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    Welcome, Orange, from another '78 owner! :-)
    My last three sports cars while I still owned all three:

    2001 BMW Z3 Roadster 3.0i soft/hard top (sold)
    1966 Ford Mustang Coupe (sold)
    1978 Datsun 280Z (enjoying very much )

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    Registered User cozye's Avatar
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    Quote Originally Posted by dankfrye@charter.net View Post
    Did the Sea Foam treatment through the brake booster hose. Besides smoking up my garage and half the neighborhood, I did find an exhaust leak at the bottom of #6 exhaust bolt on the manifold. I tightened it up along with all the others and readjusted my valves the right way. The car seems to run quieter and stronger. I still have a light tick when engine is warmed up but it's not near as bad. My valves were all tight because the guy that showed me how to do a valve adjustment said to put the feeler gage under the tappets on the drivers side instead of directly under the cam lobes. This apparantly makes a pretty big difference.
    Thanks for all you guys help!
    Is the bolt stripped? I'm not sure how it would have loosened up enough to leak if you had just replaced the gasket. If its leaking at all it will only continue to get worse as the host exhaust gas burns what's left of the gasket out. I'm afraid you will still have to pull it all off, install a new gasket, and install helicoils in any stud that has weak threads. While its off, check the manifold for cracks and for warpage on the mating surface
    1978 280z 4sp

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    Z geek at large FastWoman's Avatar
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    Yeah, it might be warped or corroded. That old '77 Chrysler Marine 318 I have in my boat is giving me this headache. Unfortunately the problem is on the mating surface of the head, not the manifold, or else I'd just have it milled.
    My last three sports cars while I still owned all three:

    2001 BMW Z3 Roadster 3.0i soft/hard top (sold)
    1966 Ford Mustang Coupe (sold)
    1978 Datsun 280Z (enjoying very much )

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    Orange '78 dankfrye@charter.net's Avatar
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    The exhaust manifold might have a slight warp but now it is very small and the noise is barely audible. I never remove the exhaust manifold because the 3 bolts on the flange were very rusted and would not budge, even with much PB blaster. I did wire brush qand clean the are good and put some high temp exhaust/muffler sealer on it. I'll see if that helps. If it don't then I'll tear it all down later. I would rather get my new rear bushings on now.

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