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chasing a strange knock, advice requested

 
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Old 06 Jan 2013, 07:26 pm
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Default chasing a strange knock, advice requested

Finally got ma Cruiser after years of lust! Bought this Plum base model sort of low dollar ($1500 for a '03 with 79k mi) from a guy worried & not wanting to get involved in a knock that apparently just arose and needing exactly 1500 to pay off his house. Deal done. Pretty little car, good cosmetics, perfect for new driver daughter (CLEAR THE ROAD !!!)

Long time motorhead; 40+ years in Toyotas, Stangs, GMs, a 944 or two, BMW, jeebuz 100 cars and euro bikes and never been to a repair shop for more than tires & alignment. I have done almost everything from bumper to bumper, rag top replace to suspension bush, mostly by need, luck and feel (and reading) except a full paint job. Sick huh ? How you all doing ?


Trying to pin down a nasty little noise in the PT 2.4 engine. The knock sounds a little "throaty-er" than a small part ( valve train ) rattle, but not deep and solid enough to be a main bearing. A clatter if there ever was one. Often but variable.

I have not been able to pin point the location yet with a stethoscope. The knock can be quieted under modest throttles, sounds louder under high load, full open throttles, etc. Variable volume, you can hear it cold, but louder warm. Main observation is it relates to throttle; can be quieted under easy cruise, may or may not be there at idle. Its is kind of variable so far. Frustrating.

The car seems to run fine. Cranking compression (warm) is 175-180psi on all four after a dozen or so strokes. Vacuum through the manifold while running was steady, (30 ?) , showing no perceptible ticks or misses or flutter when running. Old plugs were garbage ( see below) very worn but dry and colored OK. I put new plugs in, drove a couple dozen miles, and inspected; they really look good for color, no oil sign. I have not checked to oil pressure but I do not get an idiot light.

I dismantled engine down only as far as into the valve cover, and did not see obvious problems, a tiny bit of gunk and decent looking roller tracks on the cams. I was expecting too see a failed rocker, etc, but did not find an obviously failed / soft lifter. I should have checked them more carefully but got to hoping I lucked out when noting the plugs (probably original) were worn open to 50, 75, 70, 50 gaps. Replaced plugs and the character of the knock changed but not eliminated. Reassembled after finding plugs so wide open, I was hoping I found a wide gap / miss. Not so lucky, still noisy.

No evidence of coolant in the oil, nor oil in the radiator ( some gunk apparently from mixing coolant types). Coolant was abysmally low [added about 3qts h2o upon first pass ] and yucky like a coolant-type mix occurrence, although overflow tank had level in it at the change.

Drained the not-too-old looking oil, running drainage through a fine screen, and I did note one tiny shiny 1mm x 1/2 mm aluminum flake. Holding the oil for possible analysis, and kept the filter for dissection to look for debris.

The knock is definitely irritating and obvious, but with very decent compression & vacuum, I hate to think about an engine pull. I dont have the ear to discern a piston slap from other possibilites.

Currently going to run car a while, hoping for warmer weather to get serious on it, and study results of another soon oil change, looking for debris. If it were not for the obvious and loud knock, I would call this a good engine based on all other evidence. Sigh.

If I have a request from this post, it would be to anyone who shot down a failed lifter or encountered piston slap or loose wrist pin., and could describe things. Any other strange things to check out on the 2.4 non turbo ? Does a piston slap respond to various throttle settings ?

Thanks and be assured I contribute to the forum whatever useful tips hints and conclusion that I encounter so , thanks for your useful reply.


PS the Felpro blue silicon gaskets for intake and valve cover are the way to go, good looking parts.

Last edited by gtgt_bangbang; 06 Jan 2013 at 07:34 pm.
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Old 06 Jan 2013, 09:10 pm
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Default Re: chasing a strange knock, advice requested

These engines do have balance shafts. I belive they are chain driven. Have no clue if that could factor in. Good buy anyway.
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Old 06 Jan 2013, 11:13 pm
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Default Re: chasing a strange knock, advice requested

appreciate the reply Budd.

Clatter is definitely engine-load affected and somewhat possibly eng temperature related affair. Noise is variable, which bothers me.

Not sure where the balancer shaft would factor in, hate to start grabbing straws already. At least I don't hear a sloppy chain, and with no unusual vibes, I dont really have reason to suspect that assembly.

I am thinking worse case is a piston slapping but the formidable compression numbers don't automatically cause me worry (yet).

Best case is a soggy / soft lifter; I suppose with dual valves intake and out take it would run pretty well even with one bad lifter, but it seems I would see some flutter effect on the vacuum , ey ?

I fear a wrist pin but it really seems that would be a profound knock.

I will wait for more aluminum flakes to show up in a quick oil change.

PS I really enjoyed any trip thru WV and did some really out back spooky ones, in addition to paddling the New (during very flooded) and the Gaully (sp?). Yall come see the NW Rockies someday, nice country and hardly ever any rust in the rockers.
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Old 31 May 2015, 11:48 am
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Default Re: chasing a strange knock, advice requested

I just recently bought a 04 pt cruiser, and it has the same problems you describe.
So, I was wondering if you still have your 03 and if you ever found out what was causing the noise? (the noise is driving me crazy, because I can't pinpoint where it is coming from)

Thanks.
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Old 31 May 2015, 11:57 am
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Default Re: chasing a strange knock, advice requested

Quote:
Originally Posted by rbrtsmith01 View Post
I just recently bought a 04 pt cruiser, and it has the same problems you describe.
So, I was wondering if you still have your 03 and if you ever found out what was causing the noise? (the noise is driving me crazy, because I can't pinpoint where it is coming from)

Thanks.
They haven't been on here since Aug 2013. Might want to give more info on your PT and describe just what you here and when you seem ti hear changes in the noise.
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Old 31 May 2015, 12:40 pm
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Default Re: chasing a strange knock, advice requested

[QUOTE=gtgt_bangbang;461600]

"Trying to pin down a nasty little noise in the PT 2.4 engine. The knock sounds a little "throaty-er" than a small part ( valve train ) rattle, but not deep and solid enough to be a main bearing. A clatter if there ever was one. Often but variable.

I have not been able to pin point the location yet with a stethoscope. The knock can be quieted under modest throttles, sounds louder under high load, full open throttles, etc. Variable volume, you can hear it cold, but louder warm. Main observation is it relates to throttle; can be quieted under easy cruise, may or may not be there at idle. Its is kind of variable so far. Frustrating.

The car seems to run fine. "


I have tried many of the same things that bang-bang mentioned in trying to track down the problem t no avail.

I don't think it's a valve problem, but it doesn't sound like a rod or mains problem.
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Old 31 May 2015, 01:06 pm
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Default Re: chasing a strange knock, advice requested

Rod knock in these sounds like it's coming more from the top than the oil pan.
Piston slap gets better as engine warms; no one has ever reported a failed wrist pin.

Valvetrains are foolproof or nearly foolproof.

Buy new rod bearings and install them. Inexpensive and relatively easy.
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