Engine rattling noise at idle

[ryu_haneda]

Hey everyone,

Got my car back roughly 3 1/2 weeks ago, and most everything is running well. However, on the advice that my dad gave me, I wanted to post a question about engine rattle.

When I start my car up and it sits there idling, it sounds like a diesel engine (even though it's unleaded gasoline). I tried searching the forums, and I'm not sure if it's what you folks refer to as a "cowbell" noise or if it has anything to do with a heatshield problem.

My dad was disappointed, because he knew I just dumped about 4100 bones into replacing the longblock (and he thought that paying that much for a repair would remove a problem like that - I can't blame him).

I'm going to check into it with a mechanic on Monday. Thoughts?

-ryu_haneda
-AWD: already waiting for december -> I WANT SNOW

[GrassyKnoll]

what type of rattle is it? When you open the hood at idle, can you pin point where it is coming from?

[ryu_haneda]

hmmm, nope (not like the rattle that came from my timing belt tensioner which wrecked my other EJ25 longblock)... of course I have not opened the hood while it is rattling. It sounds like a general rattling noise, literally like I swapped a Cummins turbodiesel into the car.

I've listened to my wife drive away in the car to work on certain mornings, and the rattle goes away as she drives off (read: as she accelerates, the rattle goes away. It's usually only when we are idling - I don't know if it comes back when we are at stoplights).

[Huffer]

Does the rattling subside as the engine warms up? If it does, this could just be piston slap from the noisy DOHC...

[Plays_with_Toys]

I'd take it to the mechanic and explain that the car should be nice and buttoned up for $4100 and that they should locate the rattle and fix it because the rattle occured while under service at their shop.

Anyway to get a video? Is it a rattle or a ticking noise?

[Wiscon_Mark]

Is this a thin metal type rattle? My money is on heatshields.

[ryu_haneda]

Mark: I think I agree with you - the rattle is definitely like thin metal. I've seen other posts where people complained about heat shields, this might be the noise associated. (If that's the case, do I have to remove the heat shield to remedy? Hope not... at least not with my lack of knowledge.)

Huffer: I'm hoping it's not piston slap, although if something is going on, I will find out shortly why the recently replaced engine is not running up to spec.

I don't mind the noise in the morning, but I know that the previous engine went bad because of a noise I thought sounded like extra air going through the engine (when it was really a busted timing belt tensioner). Since these answers are going to be coming in handy, I will give the benefit of the doubt and keep an eagle eye on stats (overheating and other conditions), and come up with a plan Monday.

Thanks for the help all... this will be handy for figuring out what to do next.

God bless you all. Later!
-ryu_haneda

p.s. I might be able to get video of the rattle... depends on whether or not I can get my camera, and take video when I first start engine in the day.

[=STAT!XXX=]

I had a pretty bad rattle at idle too, my fix was to remove the really bad heat shields and clamp the decent ones so they wouldn't rattle anymore, and it's all good now :)

[LeeLee D]

My car rattles when its cold or idles too but its not my heat shields lol...one rattle is from my WR SW Short ram vibrating against my snorkus and the other is my rear bumper molding...it seems to have broken off of the screws that were holding it on by the muffler

[GrassyKnoll]

I agree with Marky Mark.

[Wiscon_Mark]

If it is heatshields, you can remove them pretty easily with a sawzall or something comparable, but I wouldn't suggest it, honestly. They're there for a reason: to keep engine temps down, and to keep the heat moving through the headers and not leaking out, which creates better exhaust flow.

I took some exhaust repair caulking type stuff ($3 at Advance) and stuffed all the cracks around the heatshields and that seems to have elminated the rattle (but for how long?).

Hope this helps.

Piston Slap would not sound like a little thin metallic rattle.

[Huffer]

Piston slap is common on the DOHC engine. If the engine was reman. to Subaru specs (for that year) it's likely that the engine will have piston slap as the pistons warm up (and thus expand) to fill the cylinder.

Hence why the noise goes away/subsides when the engine is warm.

[SHOfast]

If it is Piston Slap I would be questioning the rebuild. I should say that just about every Subaru has piston slap, some just worse than others. I notice it in mine from time to time and I have 113k miles with no problems.

Engine rebuilders have been using revised pistons with better skirts to reduce the piston slap, I know Jasper Engines lists this on their website. My point is that if the engine was rebuilt and it already has a noticable piston slap (less than 1ooo miles) I do not think they addressed the cylinders or short block, just inspected them. That is not a rebuilt motor to me.

[ryu_haneda]

Excellent, excellent... this is all good information.

I might just contact The Engine Shop (Upper Darby PA - where I got the engine) to discuss why piston slap could be occurring. It is worth noting that the stock engine that came with the car (when I got it anyway :| ) also had that similar "rattle" when starting up.

To be more specific, the rattle does not seem to be so present on some days when idling in park, but definitely when idling in gear (I listened to my wife drive away this morning... the car started to "rattle" when she shifted into drive, then it subsides as she gets on the gas).

The rattle is like a tin can, sort of... the fact that it was occurring on both engines that were in that car recently makes me think it could be more of a heatshield problem than anything (it'd be cool if I could make it go away by just tightening something, but I would :shock: ***DEFINITELY*** :shock: want to make sure I knew precisely what to tighten before doing anything like that).

Still too close to call for me.

-ryu_haneda
-enjoying my tin-can-sounding all-wheel-drive Subaru experience

[Wiscon_Mark]

it's heatshields. When you fire up the car, get underneath it, and put your hand on the heatshields to see if the rattle goes away. You should be able to tell pretty easily. They don't get hot instantly, but wear gloves if you feel like it.

[ryu_haneda]

Where is the heatshield? Closer to the front, or directly underneath the engine?

[Wiscon_Mark]

The heatshields are actually on the headers themselves. They're like armour around the piping.

[Huffer]

The rattle is like a tin can, sort of... the fact that it was occurring on both engines that were in that car recently makes me think it could be more of a heatshield problem than anything (it'd be cool if I could make it go away by just tightening something, but I would :shock: ***DEFINITELY*** :shock: want to make sure I knew precisely what to tighten before doing anything like that).


Heatshields. You could cut them off with a sawzall... or angle grinder.

[d1giPhux]

I had a metal rattling sound and stuff.. it was the heatshield.. as stated before.. thats pretty common on these cars it seems. I fixed mine by using some metal wire or something to keep them from moving around.. it was a ghetto fix, but it worked. This was on my last BD though, and now i need to do it on the new one too! hahah. :lol:

[ryu_haneda]

NOOB WARNING! NOOB WARNING! NOOB WARNING!

I've seen the EJ25 engine taken apart, and I'm not sure if the headers are the part of the engine that contain the valves, or if they are also the piping that is over or around the engine itself. (Hey, someone's gotta ask the question! :grin: )

-ryu_haneda
-did I say I was a level 0 Subaru wrench apprentice? :grin:

[d1giPhux]

Its the part(s) that connects from the engine to the exhaust. Or as google says :

'part of the exhaust system that routes exhaust from the engine'

Not a very good description, but hopefully helps you out a little. Here is some on ebay.. just so you get a closer look at it :

http://cgi.ebay.com/ebaymotors/Borla-He ... enameZWD1V (http://cgi.ebay.com/ebaymotors/Borla-Headers-Subaru-Forester-Impreza-Legacy-GT-97-04_W0QQcmdZViewItemQQcategoryZ33631QQihZ001QQitemZ110051597840QQrdZ1QQsspagenameZWD1V)

[Reason]

Is this a thin metal type rattle? My money is on heatshields.

[d1giPhux]

^ yeaaaa yeaaa. heatshields like a mofo. :grin:

[Superu264]

I took some exhaust repair caulking type stuff ($3 at Advance) and stuffed all the cracks around the heatshields and that seems to have elminated the rattle (but for how long?).

Did you do all the heatshields or just a certain spot? I'm pretty sure my rattle is coming from the rear I'm hoping I can get away with just "fixing" that one spot.

[Wiscon_Mark]

Pretty much every spot. When the exhaust system is cooled off, go around and wiggle the heatshields, it should give you a good idea of what's loose.

[ryu_haneda]

Got the heatshields removed this Monday. Ahhhhhh... no more rattle...