Crank knock at start up...Help?UPDATE W/ VID

[green97gt]

hey fellas. the wifes 97gt has developed, what sounds to me like crank knock.

i first noticed it after a trip to alabama and used some lucas oil stabalizer in an oil change while we were up there, the knock went away.(i know fluids aint gonna fix it..but they did shut it up..for a bit.)

1500 miles later

now when the car has sat for a while like overnight or something when you start it up the crank knock is back and badder then ever...for about 20 or 30 seconds, then it dramatically fades and is only BARELY audible right off idle

any recommendations on how to prolong the life of this car?

im already motor shopping, but dont have money at the moment to dump into a motor/rebuild and have thought about just laying this car up for a bit and rebuilding THIs motor, but would hate to pull it apart and find out the crank is scarred or something.

advice?

[Huffer]

Lucas oil stabilizer was the first problem. Never use an oil additive unless you are draining the oil ASAP.

Try draining the oil and replacing it with either 10w30 or 10w40.

[green97gt]

really? ive used lucas stabalixer in lots of noisey motors, shuts them right up...

and prevents dry starts..which is seeming like weve got going on here... i cant imagine the lucas would CAUSE/make the knock worse?

i spose the oil could be to thick at startup, but should be counter acted by the "stringy" nature of the lucas...

ill give it a shot, but the car seemed to make more noise before i put the lucas in it.

any way to take an educated guess on wether or not the crank/ cylinder walls would be scarred up?

im looking at rebuild kits also, any preferences?

[ouch1011]

If the noise is lasting 20-30 seconds, I'm kind of doubting its a bearing rattle. Mine occasionally rattles for about 1/2 second after starting, basically until it builds oil pressure. If yours had a bearing rattle for 20-30 seconds on every cold start, it would have probably spun a bearing and developed in to a constant rattle by now. You could try manually checking the oil pressure. The low pressure light comes on at like 2psi, WAY below the minimum safe oil pressure. You should also drain and check the oil. If the bearings are rattling that much, there will be metal in the oil.

Also, another possibility. I haven't seen an incident of this on a Subaru, but I've seen several engines with hydraulic timing belt tensioners have this issue. When the tensioner wears out, it allows slack in the timing belt, which allows the belt and the tensioner to rattle around, and it does sometimes sound like a bearing rattle. Especially since the tensioner sits towards the center of the engine.

[green97gt]

http://www.youtube.com/watch?v=rvW4xcgyjEI

^ link to video.

outside temp 75 +/-

car has been sitting for about 12hrs gold to about 60 tonight.

only does this on initial start up for about 30 or 40 seconds. wendy(the wife) will start it in the morning to go to work, sometimes it does this, on warmer days it does not.


then after the initial start up, it doesnt do this agian until the next day. she travels from office to office alot throughout the day and the car stays parked a max of 6 hours between driving.

no unusual vibrations during the knock.

no CEL

does this sound like crank or cam speed to you guys?

thanks.

EDIT:

Seems to ME to be coming from the drivers(left) side rear of engine, you can almost hear it get louder as i bring the camera down to towards the TB.

after the car warms up it runs like butter. no odd noises.

i have been running 10-40 w/ lucas oil stabalizer.

[Huffer]

That's just piston slap.

If you ran the wrong grade of oil (anything other than 5w30, 10w30, 10w40) before, then you may have done some damage but it's unlikely.

What causes piston slap in the EJ25 DOHC is simply that the factory pistons are not large enough when cold and rattle a bit in the cylinder. When the engine warms up, the pistons expand and they fill the cylinder better.

A thicker grade of oil (10w30, 10w40) will sometimes help quell this noise but at the expense of less cold weather protection on startups.

You have a couple of options - if she is start/stopping the engine a lot then you are going to experience a lot of engine wear. Change the oil more frequently, say every 3000 instead of 4000. Stick with a good oil maker, one that makes oil cling to surfaces is good (don't use Mobil1, it's too slippery).

2nd option, you can pull the engine and have the block "sleeved" which will reduce the gap in the cylinder. TWE makes products to help:

http://www.techworkseng.com/Products/Su ... istons.htm (http://www.techworkseng.com/Products/Subaru_Forged_Pistons.htm)

Impreza RS, Legacy, Forester, DOHC 2.5L

We offer your choice of forgings for the sometimes 'noisy' DOHC engine. Choose the long skirt design for reduced piston knock or the slipper skirt design for lower friction at high rpm.

* Long skirt forging for quieter running.
* Slipper skirt ultra light forging also available
* Quench pads for reduced detonation
* 9.0:1, 11.2:1 (91 octane) available off the shelf Turbo and N/A

[evolegacy]

yep, that sounds like mine, its just piston slap, dont worry bout it

[green97gt]

hey, thanks for the input guys.

thats a load off my mind.

ive already been changing the oil at 3k just cause im anal.

i dont remember it doing this when we bought it...maybe a tiny bit....

would the fact that it is finally cooling off in FL make it do this more?

ill look into changing it with some thinner oil like 5-30 next time i change it...

i usually run castrol GTX 10-40 or if i cant find that i buy valvoline max life 10-30...

EDIT: i just went out and looked, and it seems that last time i bought a case of oil my dumb ass bought valvoline max life 10-30 synthetic blend....oops. :smt018

[dodik]

when you intially bought you have no idea what previous owner put in it to remedy the sound. plus colder weather does bring out small things that are not noticed when warm.

[2.5GT]

You think that's bad. I've just switch over to Shell Rotella T 5W-40. It knocks like a freight train! I'm draining it out tomorrow with some Castrol Syntec 5W-30 that i have left in storage.

Remember, thinner oil in winter. Thicker oil in summer.

[anothernord]

Yeah, my car slaps like crazy for 30 seconds or so on a below freezing day, but it goes away soon enough. It did this even with a brand new short block, so its completely normal like Huffer mentioned.