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Old 12-17-2020, 10:23 PM   #1
hopperjon
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Join Date: Apr 2012
Chapter/Region: E. Canada
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2001 2.5RS
Red

Have a Nice Day? 2001 2.5RS Engine Noise Diagnosis

I've recently purchased a 2001 2.5RS with 112000km (69500 miles). Completely stock, untouched, other than a terrible paint job. Got it for a decent price, basically bought sight unseen. The future plans include an engine swap among other things. Considering the low mileage I would like to drive the car stock for awhile. I'm planning on putting it on the road in spring / early summer.


Anyways, through my poking around I've noticed the engine has a slight knocking noise. I'm coming from an '03 WRX so I know Subaru engines make a lot of noise.


The knock/noise happens regardless of engine temperature, although the engine is quieter once it's warm as all Subarus are. This is a more pronounced knocking noise than I've ever heard from a Subaru. My '03 WRX got scrapped due to rust (it was completely rusted out, had 300k miles, center diff went, etc) but never made a noise like this.


So I checked it out with a mechanic stethoscope. The weird part is, the knocking noise (which follows RPM) is loudest at the VALVE COVERS (both of them). Second loudest from the heads (both of them). At the block I can barely hear the noise through the stethoscope. I've also checked the power steering pump, alternator and AC compressor (I removed the AC belt almost immediately to remove it from the equation) to no avail.



I also tried disconnecting each spark plug wire one by one. The odd thing is, as soon as I pulled a spark plug wire (regardless of which plug) the noise went away. Maybe it has something to do with lower RPM associated with removing a cylinder.



After this, I did an oil change. 5W30 Castrol synthetic. No change in engine noise.



I inspected the oil that was removed, as well as cutting apart the oil filter that I removed (it was approx 1 year old) and the filter and oil was clean. No chunks, no metal pieces, nothing indicating a bearing issue.



The only other thing I can think of is excessive piston slap or timing belt tensioner issues (I haven't removed timing belt covers yet). Although I can't understand how this noise would be most prevelant at the valve covers.



Wondering if anybody has any ideas. I'd like to put this car on the road for a year or two before doing a swap, but don't want to waste the time and money if the engine is going to suicide itself shortly thereafter.



Thanks in advance.
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Old 12-17-2020, 10:51 PM   #2
hopperjon
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Member#: 316863
Join Date: Apr 2012
Chapter/Region: E. Canada
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2001 2.5RS
Red

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I should also mention, I did a cold compression test yesterday, and the results are as follows:


Cyl 1 - 190
Cyl 2 - 180
Cyl 3 - 185
Cyl 4 - 188


Give or take a few PSI each.
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Old 12-18-2020, 12:18 PM   #3
yarrgh
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2001 2.5RS
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You could try checking valve lash. Although when you state that ANY plug wire removed also removes the sound has me confused. Diagnosing sounds through text is damn near impossible, you might try a recording.

Even though the mileage is low, all the rubber bits are 20 years old, keep that in mind.
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Old 12-19-2020, 08:10 PM   #4
hopperjon
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Quote:
Originally Posted by yarrgh View Post
You could try checking valve lash. Although when you state that ANY plug wire removed also removes the sound has me confused. Diagnosing sounds through text is damn near impossible, you might try a recording.

Even though the mileage is low, all the rubber bits are 20 years old, keep that in mind.

It has me confused also. The fact the noise is loudest at either side of the motor and very quiet in the middle is also extremely confusing. FROM THE VALVE COVERS no less, which should only be receiving vibrations from the heads, but the noise is loudest from the valve covers. (????)



I'll post a video tomorrow evening, although phone recorded videos are notoriously terrible for noise diagnosis.. although I suppose it's better than no video at all.



Thanks for the valve lash recommendation, I've never had a 2.5L NA before and had no idea that was even adjustable. I need to replace the valve cover gaskets anyways so I'll be pulling those off and checking the lash tomorrow evening. Thanks for the suggestion.



My one good feeling here is the oil and filter was clean and clear so I doubt it's rod knock...

Last edited by hopperjon; 12-19-2020 at 08:24 PM.
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Old 12-21-2020, 09:43 PM   #5
hopperjon
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Link to video of noise. Not sure it'll be much help.

I haven't checked valve lash yet as I want to clean the dirt off the engine before doing so (and it happens to be four degrees outside so that's not happening right now). As you can see in the video she's a dirty girl at the moment.
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Old 12-27-2020, 06:04 PM   #6
hopperjon
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Much better video: (sound is most audible at around 15s)


QUICK RECAP:
Things I've checked:
- I have now checked / set valve lash on all valves (0.008" intake, 0.010" exhaust) and replaced valve covers (inside of engine was spotless)
- Compression checked, all good
- Bore scoped each cyl, nothing looks amiss
- Did the old push on the piston through the spark plug hole on the downstroke trick and found no piston movement
- Changed oil, cut apart old filter, inspected oil, stuck my finger into the drain plug hole to check bottom of oil pan for anything -- all was clean (oil was oldish so it definitely had some miles on that oil)
- Removed AC Belt for other reasons but it also is one more thing to eliminate
- Mechanic stethoscope tells me the noise is loudest from the valve covers, can't hear it very loud at all from the block
- Removing a spark plug wire one by one and revving the engine does not get rid of the noise
- Removed accessory belt (ps/alt), no change

Things I haven't checked:
- I have not fully removed the timing belt cover(s) to stethoscope the timing components
- I have not dropped the oil pan to inspect yet (ran finger on bottom thru drain plug when I did the oil change and it was clean)

I'm leaning toward excessive piston slap. Is there any way to check this manually with the oil pan dropped?

The only other things I can think of are bad / dirty injectors. Not sure if that would produce this sound or not.

Last edited by hopperjon; 12-27-2020 at 06:29 PM.
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Old 12-28-2020, 11:52 PM   #7
hopperjon
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Finally got the engine running with the timing belt cover off -- LOTS of noise coming from the tensioner through the stethoscope, so a timing belt kit has been ordered. Hopefully this will fix the noise issue. Frequency doesn't sound exactly right so I have my doubts.

Got the tires off this evening. Whoever did work on this car previously has no idea how brakes work... the discs are oily as hell. Ordered new brake pads as well as I'm sure they're contaminated.

On a secondary note, the car has recently started making noises from the throttle body area, but only for about ~3 or ~4 seconds after the engine is shut off. I've done some searching and can't find anything regarding this. Does anyone have any ideas?
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Old 01-01-2021, 12:44 PM   #8
mike_n
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Timing belt tensioner can definitely make a knocking noise when old if the fluid has leaked out.
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Old 01-01-2021, 01:13 PM   #9
thiessentr
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My timing belt tensioner sounded similar to your noise. When I pulled my cover I could see it moving around with the engine running. Hopefully the new timing kit fixes your issue. Goodluck
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Old 01-04-2021, 12:42 PM   #10
yarrgh
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Quote:
Originally Posted by hopperjon View Post

On a secondary note, the car has recently started making noises from the throttle body area, but only for about ~3 or ~4 seconds after the engine is shut off. I've done some searching and can't find anything regarding this. Does anyone have any ideas?
This is normal. I think it's the IACV resetting itself for the next startup.
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Old 01-09-2021, 09:45 PM   #11
hopperjon
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I've finally got the new gates timing belt kit and water pump...

Great news, I've stripped the tensioner bolt bracket hole.

I admit it's my fault, leaving the belt in the garage in almost freezing weather. New belts are already tight to begin with.

I remember the timing belt job on my old 03 WRX being easier than this.

At least it wasn't any of the other bolts (directly on the block). I finally found the part number (hopefully) for the tensioner bracket: 13156AA052

I'm trying to find a replacement online as the nearest Subaru dealership is 2 hours away unfortunately.

Thanks for the info on the idle control valve, I won't worry about it until the idle starts to be funky. Hopefully that won't happen at all as I'm planning on doing a swap in the next year or two or three. I'm in no rush and looking for parts as I find them. Either a 207 or 255/257 hopefully but I'll take whatever comes my way.

Last edited by hopperjon; 01-09-2021 at 10:19 PM.
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Old 03-21-2021, 09:40 PM   #12
Pix3L8
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Quote:
Originally Posted by hopperjon View Post
Much better video: (sound is most audible at around 15s)

https://youtu.be/rxyMqR6nG5U

QUICK RECAP:
Things I've checked:
- I have now checked / set valve lash on all valves (0.008" intake, 0.010" exhaust) and replaced valve covers (inside of engine was spotless)
- Compression checked, all good
- Bore scoped each cyl, nothing looks amiss
- Did the old push on the piston through the spark plug hole on the downstroke trick and found no piston movement
- Changed oil, cut apart old filter, inspected oil, stuck my finger into the drain plug hole to check bottom of oil pan for anything -- all was clean (oil was oldish so it definitely had some miles on that oil)
- Removed AC Belt for other reasons but it also is one more thing to eliminate
- Mechanic stethoscope tells me the noise is loudest from the valve covers, can't hear it very loud at all from the block
- Removing a spark plug wire one by one and revving the engine does not get rid of the noise
- Removed accessory belt (ps/alt), no change

Things I haven't checked:
- I have not fully removed the timing belt cover(s) to stethoscope the timing components
- I have not dropped the oil pan to inspect yet (ran finger on bottom thru drain plug when I did the oil change and it was clean)

I'm leaning toward excessive piston slap. Is there any way to check this manually with the oil pan dropped?

The only other things I can think of are bad / dirty injectors. Not sure if that would produce this sound or not.
very similar noise going on with my car, wonder if my tensioner is to blame...hmm
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Old 04-27-2021, 11:33 PM   #13
SubDubRX
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This sounds like almost exactly what I’m hearing on my 99 rs. Put in a rebuilt motor and heads, did the whole timing built kit, checked valve lash multiple times. I’m really at a loss. Hopefully you make some progress
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Old 06-01-2023, 01:59 AM   #14
03NA-TS
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Was this issue ever resolved? I recently rebuilt my moter and samish noise!
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