knocking sound 04 WRX - Subaru WRX Forum
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post #1 of 6 Old 03-11-2017, 10:00 PM Thread Starter
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knocking sound 04 WRX

Hey guys, I'm just looking for a list off all possible knocking sounds you have come across on your cars. I recently bought an 04 WRX which has been nothing but trouble. So when I bought this car I fixed multiple boost leaks and down pipe rattles which lead me to a knocking turbo. After pulling the turbo I ended up getting another used stock turbo with only 20k of low boosting. Once the turbo was installed I primed it, Checked all lines then started the car. While listening to the car while it was running it sounded great. Let the car idle for around 5 minutes then took it on a slow drive which only turned into 1/4 mile before the knocking came back worst than the first time. After looking at it, I figured out that it was starved of oil. I checked all lines which seemed to be clear Thinking I bought a bad turbo from craigslist, I quickly bought a Tdo4l rebuilt turbo to check off the turbo as the issue. After having a shop install turbo number 3 the knock remains. As soon as the car starts to get temp it starts a light random knock when idling. When feathering the gas as lightly as possible I can start to hear a constant knock. When listening around I do not hear any sounds coming from the heads other than valves and the knock from a distance. Transmission sounds good, Block sounds good but can hear a loud knock either right at the turbo or its echoing into it. Any ideas would be great I'm going to pull valve covers tomorrow and start the dig.
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post #2 of 6 Old 03-13-2017, 08:15 AM
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Hmm, check for metal particles in oil. If turbo is starving for oil, metal contamination could certainly do that. I don't see how a knocking sound is coming from different turbos.

It would be helpful if you could grab a video of this happening.

One other thing that pops to mind is that if you have a catted up pipe and the cat has failed, the loose metal could potentially rattle inside and pieces of that going into the turbo could damage... But that is a total blind guess.
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post #3 of 6 Old 03-13-2017, 08:43 AM
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When you check your engine oil, use a bright flashlight and twist the dipstick so the light hits it at different angles, this should allow you to see tiny metal specks in the oil, regardless if it was the engine or turbo causing this. You can also take a magnet and run it near the dipstick to pick up any metal that may be in the oil, just don't get too close or you may attract the dipstick first and need to start over. One last test would be to get an oil sample to BlackStone Labs, their test kit is free to ship to you, and once you fill the container and send it out you should get a response within a week or so. The cost for the actual sample testing is less than $30 so it could save you $$$ before you buy more parts, only downside is that you might not want to keep driving the car in its current condition as depending on what is actually could be causing more damage as you go. I did their sample testing after my turbo went bad to get a baseline of the oil before I changed it out to know what the contaminant levels shouldn't be and to see what changes after I run it again with new oil and a replacement turbo.

Also if you pull the turbo off again (I know I know) you can grab the shaft from both ends and push/pull in/out and towards the housings, you should have just the slightest jiggle but barely any due to not having oil pressure..but if it moves in/out, towards the housings more than 1 or 2mm the turbo may be shot (test your old one like this too).

Also can you post more info on your 04 wrx? Things like mileage, mods, services done, etc can help tremendously with diagnosing issues. Ex, a high mileage oil pump/pickup from 3 prior abusive owners could have seen blockage at least once due to improper maintenance and using dirty oil for extended periods of time, causing the bearings to not receive efficient flow and slowly overtime spinning the bearing. <- This is a more extreme example but still very possible.
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post #4 of 6 Old 03-14-2017, 09:49 AM
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Any luck? What oil are you using? Just curious. I would personally check the oil for shavings as already stated. If there is no metal in the oil I would invest in some high quality synthetic oil then seafoam it.....put some miles on it....Change oil. If knocking is still there, but better, Seafoam it again....put miles on it....and change oil. I would try that before you start tearing it down....I bet its a stuck valve. It can sound like its coming from the turbo, depending on which valve it is..

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post #5 of 6 Old 03-15-2017, 01:13 PM
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When using Seafoam, never hit boost. The high octane levels can ignite and cause detonation, seen it happen on a Mini Cooper S turbo...hit boost too much and smoke and knock
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post #6 of 6 Old 03-15-2017, 01:30 PM
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i have never heard of a turbo knocking. a video would really help.

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