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98 GF4
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Discussion Starter · #1 · (Edited)
Hello all! It's my first real post to the forum, after lurking for some time. Unfortunately, its due to a possible rod knock, failing timing belt tensioner, exhaust leak or all three, as stated in the title.

I've read many threads and watched countless youtube vids, but i would like to hear all of your opinions.

Peculiar thing about the ominous sound is that it only occurs after the engine has warmed/been driven. It is also most noticeable under light acceleration.

I took off the driver side timing belt cover and used a mirror and flashlight to check for my belt tensioner bouncing around, but didnt really see anything out of the ordinary. Thought it might be the tensioner, due to the belt being tight when cold, and gaining slack once driven/warm, causing the noise to only occur when warm.

No CELs, no overheating, and power doesn't seem to be lacking.
Here is a clip of the sound:



so what do you guys think?

and also, if it is a rod knock, how long do you predict she will last before totally failing?
 

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2001 2.5 RS BRP Coupe
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Sounds like a diesel.. Doesn't sounds severe enough for you to not be able to drive it, and if you don't feel a power loss i'd say drive it until it gets a little worst, then check what you have to see if anything got worse itself.. my friend has a legacy gt that sounds exactly like your motor and it drives just fine, so it could be something (hopefully) minor. good luck though.
 

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Green 97 OBS
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Usually if it's after warm, that tends to be rod knock. But I would get underneath and feel around the exhaust piping for pin holes if you think it's exhaust. If you want to dig into it to try and see where it is, I'd pull the timing belt cover and start the engine. If the timing belt tensioner is the culprit, you'd see it bouncing around. If you want to check rod knock, pull individual injectors or spark wires and see if the sound goes away on one of the cylinders. If it does, that would say that particular cylinder has rod knock.

Sounds mechanical to me, from the video I want to say the tensioner since it seems to be coming from the front of the block.
 

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98 GF4
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Discussion Starter · #4 ·
thanks for all replies so far.

I am definitely planning to pull all the timing belt covers as soon as I pick up the new tensioner next week. I just didn't want to pull everything apart, find that the tensioner is the cuplrit, put everything back together, buy the part, and then have to do the same work to install it. If its not the tensioner, I will just return the part, put in some heavier oil and hope that she'll see me through my last year of school. Once she fails, I plan to either swap in a ej25 or buy a new subaru, with the new income from my newly started career (hopefully).

I pulled the fuel injectors individually, and it didn't seem to make a difference.

However, with the driving side timing belt cover off, i pushed down on the timing belt towards the tensioner and felt a little slack, and heard what I thought was a little click, which I presume is my tensioner failing.

Upon further listening of the engine running, the sound definitely seems to be coming from the front of the block, i am beginning to think that the sound is not belt slack, but maybe the tensioner itself knocking on the block or belt cover.

Thanks again, and ill post back with the results when the tensioner gets here, for now she'll sit in the garage.
 

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Green 97 OBS
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That's good to hear. The belt should have NO slack whatsoever, so I'm gonna guess that's the case. Usually when a tensioner fails, you get the sound of the tensioner banging against the block, not the belt slap.

How long ago was the timing belt done? If you don't know, you might as well buy an entire t-belt kit and do it. You'll already be there and have to reset the timing belt anyway. At minimum take the belt all the way off and spin the idler bearings. If they make noise when they spin, you need new bearings too. Its also a good idea to replace the water pump with the t belt, less the bearing lock up and throw your belt. I wouldn't say this if I didn't have one go bad specifically because I didn't replace it when I did the t-belt. Lucky for me I saw it leaking out the weep hole so I was able to replace it before there was a problem.
 

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98 GF4
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Discussion Starter · #6 ·
The timing belt, water pump, and other pulleys were replaced last November. I can't remember if the shop I had brought it to replaced the tensioner, but if it is already failing i doubt that they did. Especially since my car sat in the garage from last February until about two weeks ago due to transmission failure.

The belt itself looks decent, but I will check all the pulleys and idlers. I should have just done the job myself back then, but I wast really confident in my skills. However, after swapping an RS tranny and rear differential into my wagon myself this last winter break, and with the timing belt DIY on sohc timing belt replacement here on the forums, the task does not seem so daunting.

Thanks again for all your help, your input is reassuring. I'll keep you updated on my progress.
 

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Green 97 OBS
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Yeah, in and of itself the T-Belt is not difficult. The toughest thing I found with the SOHC is to put the last idler bearings back on. The belt is quite tight and you have to push pretty hard on the belt to get the belt to stretch enough so you can put the bolt through. The one other thing I will say is make sure you use the timing dash, NOT the arrow for setting the marks. I did that the first time and could have easily screwed my valves up.
 

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98 GF4
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Discussion Starter · #8 ·
Diagnosis is rod knock unfortunately. Threw some 10w40 in her and hoping she'll fight on.

I guess it's time to start looking for swap options.

Thanks again for all your input man.
 

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opendeck251+stiInternals
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I agree, rod knock is your problem. If you want an easy fix, you can swap in any EJ22 block to get it running right again.

But if you want more power, now is the time to shop around for an EJ251 longblock. You could also put your EJ22 heads on an EJ251 block using your stock intake manifold. This makes a high compression motor that requires premium fuel.

Might also want to think about cams while you have everything torn apart, you have to tear down the heads, re-seal and re-torque the cam bridge, but it's worth it in my opinion.


~Josh~
 

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98 GF4
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Discussion Starter · #10 ·
Well for the time being, I'm pretty much going to just run her into the ground, unless an ej22 pops on here for cheap. Im in school full time and just don't have the funds. But once I finish school I was thinking the 25 swap as you mentioned, or buying a new STi or BRZ and using the my current gf as a beater/snowboarding car.

But lightest are all just dreams for now, until I finish school.
 
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