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Help - Loud Clicking Noise


Bruggles

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Okay, I have searched and tested and am not quite sure what is going on. The engine has a few thousand miles on it and has been running great. I was testing AFRs in it at different constant RPMs in 2nd gear and noticed that the temp started rising (3/4) and the oil pressure was pretty low (less than1/4) so I drove faster at a lower rpm to get the temps down. As the temp normalized and oil pressure started rising a clicking sound started. I was a couple of miles from home so drove back home to do a little diagnosis. 

 

When I got back let it run with the hood open to see if I could find the issue, it sounded like it was coming from the middle to rear of the engine from the top end and was louder on the exhaust side. I also noticed oil leaking from the head gasket - The head gasket is a felpro which have had oil leak problems with the rubber ring instead of the copper ring - so I am not sure that the oil leaking is indicative of a blown head gasket, but I am getting tempted to remove the head and check for issues. I let it cool down and started it again - The clicking sound was now intermittent, it would click maybe 3 times then not click for 6, then click... once warmed up the click is constant. I adjusted the valve clearances - none were more than .002" off, re-torqued the head, re-torqued the header and intake and restarted but the sound came back just like before. With the oil issues I was worried that it might be a rod bearing that slipped but I can't find any evidence of that - pulled the dipstick and listened with a hose and no clicking coming from down there, also pulled all plugs one at a time and it didn't change the clicking sound. I also pulled two at a time (always next to each other so 6&5 then 5&4 and so on) with no change in clicking. When I put a long extension to various parts of the motor, none are that loud - the loudest spots are the intake manifold on cylinders 3 and 4. I pulled the spark plugs and all looked normal, I also looked in the spark plug holes with a boroscope and couldn't see anything out of the ordinary - I didn't rotate the engine and look extensively but no obvious damage. Also when visually inspecting and wiggling the rockers nothing seemed out of the ordinary.  I put a hose around the exhaust to see if I could hear anything and I couldn't hear anything obvious. I also checked my carb throttle plates to see if the screws were still in there and they were.

 

Any thoughts on what I should check next? Anything that I could check without major diss-assembly?

 

I am thinking of removing the head to check valve condition, replace the head gasket with a non-felpro gasket and replace the intake/exhaust gasket. If nothing looks obviously wrong I could drop the oil pan and look there or just drain the oil and put a boroscope in the hole while rotating the engine with the starter. 

 

 

 

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Exhaust leaks often make a mechanical sounding ticking noise.  Kind of sounds like the temperature rise has made you sensitive to all kinds of normal noises.  Oil pressure will drop as temperature rises.  Does coolant temperature still rise at higher RPM?

 

If you don't have an HG leak in to the cooling system, your cooling system should have been able to maintain temperature.  I'd fix your cooling system first.  Sounds like it might need work.

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Thanks for the response, I am out of town, but will check more thoroughly for exhaust leaks when I get back and digging around more with a stethoscope. The noise is certainly not normal, my daughter who was in the car with me was like "whoa what is that sound" about 15 seconds after I noticed it. Although I don't like the higher temps, they certainly seem reasonable and under any normal driving the temp stays around the middle of the gauge, when driving with sustained higher rpms in 90-100 degree temps it does get up to 3/4 but drops back down quickly if I shift to drop the rpm range. I am not a huge fan seeing the oil pressure gauge go below 1/4, but even more than that sound that the was recently developed worries me.

 

Maybe I should be more concerned about the coolant temp, and maybe it is the cause of all of this. Does anybody that races keep their temp at the same level as normal driving? This is the only car I have ever taken to the track, so I don't have anything to compare it to.

 

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Well, it looks like there is a bad bearing or 2. The oil looked clean from the pan, but this is what came from the filter so I will be pulling the engine to investigate and fix the problem. I will also be adding an oil scraper, an oil cooler (this will be cheap insurance to prevent this in the future) and looking to see if I can retard timing and keep performance to possibly have it run a little cooler in the future. I tried to get a scraper from Ishihara-Johnson scrapers to no avail (I talked to Kevin a few months ago to place the order and it still hasn't shipped) so I will measure it all and get them cut - would anybody else like one for a 280z crank?

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