willrobinson

Hi guys

This noise just came in to my engine. Happens under acceleration from low revs, more so from sharp stabs of the throttle than smooth increases. Happens under similar conditions to rod knock I've had before, but seems higher pitched, so was thinking small end knock?
Have a listen and tell me what you think.
Early 85 944 157911miles, big end bearings replaced by previous owner. 15w40 oil

willrobinson

Anyone any ideas?

joes

In my experience when a rod starts to bad you don't really hear the "rod" knocking as much as the piston hitting the head. there is almost no clearence between the piston and the head except for the head gasket thickness. The "knocking sounds end up being up in the head instead of the crankcase.

shakazulu720

I had a similar sounding issue with my 84' but I just switched to 93 octane and re-timed the belt (just tensioned it ) that removed all the clicking/ knocking in the front end I don't know what type of fuel you are running and I know its not a definite fix but try filling half your tank with the good stuff and see how she runs then, just what worked for me..
- shaka

StoogeMoe

Hey WillRobinson, where's Doctor Smith?

Hard to tell from the audio, but it sounds more like an exhaust leak to me.

Does it do it when the car is standing with the hood open? Could probably tell better.

BTW, you should be using 50 wt oil.

konakat

Could also be belt slap. Take off the timing cover and make sure the tension is right on timing and balance belts.

willrobinson

Thanks guys
Joes, that's interesting, it is a peculiar sounding knock, and sounds like what this could possibly be. I will pick up a stethoscope today and have a closer listen. Also cut open the oil filter and look for metal.
Shakazulu, thanks for your suggestions, I am running 95 octane shell fuel as is the premium here in Australia. I also have the timing belt cover off and the sound appears to be coming from inside the engine, belt tension is good, I have the porsche tensioner, and timing is perfect.
Doctor smith is in the 911 turbo forum
I can hear it with the hood open, and there is an exhausty tone, I must have a small leak perhaps, but there is a definite knock noise too. As for the oil the 40weight fits comfortably inside the operating range as in the manual as does the 50w I just stuck with what I was using in my last car.
Will let you know what I find in the oil filter and with a stethoscope

willrobinson

So I cut open the oil filter, and found metallic particles. There seems to be quite a few even for 5k miles on the filter. Anyone experienced know if this is an acceptable amount or a strong sign of trouble ahead?

kens_74911s

You can take a 3 ft screwdriver or broom stick touch it to spots on the block while someone revs it, you may be able to sound most it at specific a RPM. Then move from the oil pan to side of the block and down 1-2-3-4 cylinders the head as well as around the timing area. We just did this on my wife's 03 V8 explorer and pinpointed the dreaded Ford Ft timing timing guide/tensioner failure. Opened it up and sure enough the location of issue was right where it sounded off the screwdriver.



The large end rod noise will have a frequency based on RPM and depth to it resonating off the crank. May be a good idea to start thinking about pulling the oil pan. If its a rod bearing the large end bearing shell metal may be in the bottom of the pan magnetic drain plug or have exited on oil change. Small end is a bronze bushing and not normally prone to betting beaten oversize compared to large end.