2004 WRX - strange engine rattling when revving up

[njoubert]

Hi guys!

I went driving yesterday night and drove the car pretty hard on gravel roads (fun!), and when I got home I noticed an ugly rattling as I rev the engine. I took a youtube clip of the noise which I'm posting here in the hopes of someone having an idea of what it might be: http://www.youtube.com/watch?v=92xVttGnA8U

The engine sounds the same when idling, but as I rev up you can hear the rattle. I've looked around, and some people have suggested that this might be a timing belt, ac compressor or rod bearing (this video suggested that: http://www.youtube.com/watch?v=psQosyVc7z0 and it does sound kinda similar).

Can anyone help me out?

[zax]

it sounds unmistakably like a spun rod bearing.

But, "rod knock" is the amateur (like me) diagnosis for just about EVERY sound these days, so grab a mechanics stethoscope off of e-bay and try to pinpoint the sound. Also don't drive it around lest you'd like to throw a rod through your block!

Guess it's time for a rebuild!

[njoubert]

Thank you! I ordered one of those stethoscopes, and I'm going to jack up the car and check my exhaust mods to make sure it's not a leak on that.

[yvfcfire58]

i have the exact same noise in my 2004 wrx with 94k did you ever find a solution? my guess is piston slap but i don't know?

[nunez07c]

ooo. ... if you or any one comes up with a solution to this please tell me. I have this same noise, but just not as loud.

[wrx wagone]

spun rod bearing.

[SonicWagon]

Ouch, lots of spun rod bearings in here. That noise cost me allot of money... I could have had a 6 speed....

[timb]

Make sure your license plate isn't rattling.

[njoubert]

hi guys!

So, I've pulled my engine, opened her up through the oil pan, took off the bottom of the pistons and found that my nr.4 piston bearing is shredded all to hell. The oil filter is also full of little metal particles.

I've been looking into ways to fix this, and it comes down to four things:

1) just replace the bearing (~$100)
2) remachine my block (~$1000+)
3) buy a new EJ205 block ($17xx from subaru)
4) hybrid build with an EJ255 block ($18xx from subaru)

Clearly option 1 is looking for serious trouble down the line so I'm not considering that. Remachining is a possibility which I actually havent explored that much, but the prices vary wildly. The performance shops mostly don't even want to do this since they only remachine new blocks to give you a larger bore and stroke etc. etc. but some machine shops in the bay area were saying that they could do it. The prices have been as high as $3k which made that seem unattractive.

The price difference between an EJ255 and EJ205 is almost negligible, so if I do end up buying a new shortblock I'm planning to go with a hybrid build. First I'll just replace the block without tuning or anything, so all I will get out of this is a more durable engine. (I do plan to upgrade the thermostat as well since this appears to be a necessity on a hybrid, I will be using a different head gasket to ensure that the compression stays the same as the stock block, and I'll throw in gauges for oil temp, oil pressure and water temp so that I can keep an eye on what the car is doing.). Next year if I have some extra money I can upgrade the fuel pump and injectors, upgrade the cooling system, and do a tune. Then I should be able to walk away from this whole experience with a 300hp car which would make me feel better about destroying the current block!

Since I'm doing all the labor myself (my dad has a well equipped garage) the cost is not too ridiculous.

[SonicWagon]

While I chose to replace have the 2.0 replaced, I thought you needed to have the heads machined to reliably do the hybrid swap.

[njoubert]

I asked about remachining the heads, and was quoted $600 per head (so $1200 for both sides). People are saying that you don't need to do it if you spend some quality time with your current heads: http://forums.nasioc.com/forums/show....php?t=1085359

So I was planning to clean it up myself and making sure the valves are still good.

[zax]

I asked about remachining the heads, and was quoted $600 per head (so $1200 for both sides).

yai. I feel like you could pick up new heads for that price. But you'll have to add head spacers. The reason that the heads require re-machining when going hybrid is because the compression ratio with EJ25 block + EJ20 heads is right around 9.0:1 -- too high. Even then you're not optimizing the quench area for the increased displacement. I would just have them re-machined.

[06scoobyrex]

I asked about remachining the heads, and was quoted $600 per head (so $1200 for both sides). People are saying that you don't need to do it if you spend some quality time with your current heads: http://forums.nasioc.com/forums/show....php?t=1085359

So I was planning to clean it up myself and making sure the valves are still good.

Out of curiosity, did you get a quoat for a full rebuild? If so how much was it?

[SonicWagon]

Out of curiosity, did you get a quoat for a full rebuild? If so how much was it?

I think he is doing it himself.

he diagnosed it like a pro.

[njoubert]

Out of curiosity, did you get a quoat for a full rebuild? If so how much was it?

I did look into LIC Motorsports, Garage Tuning, Raw 1 Performance and a couple of local shops, but the concensus was that the price would be higher than getting a new shortblock, since a rebuild's labor is really high, and since my block has 82k miles on it most shops want to just replace it anyway.