EJ207 Cold knock or piston slap?

[AspirinWhite]

I recently completed my version 7 EJ207 swap into my 03 WRX and it fired up with a noise that was similar to a engine knocking noise. However when the engine was warmed to temperature, the noise disappeared.

I've been looking up through a lot of threads and most of the answers leaned toward piston slap while a handful claimed it was rod knock.

I'm quite stumped about this problem and really paranoid if the engine I've purchased was bad from the start. I tuned the engine immediately via open source to eliminate the possibility of pinging/detonation due to crappy California 91 gas. The engine runs very strong but the cold knock doesn't seem to go away.

Any help would be great.

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[danger1138]

You just said the noise goes away after it warms up. So essentially you have no issue.

[AspirinWhite]

Originally Posted by danger1138

You just said the noise goes away after it warms up. So essentially you have no issue.

So is it pretty normal make that noise when cold? I will post a vid of the sound once the car gets cold again

[danger1138]

Well,
For the most part yea; it is normal. Ive had a built motor that was pretty noisy, particularly when cold. But remember it was a built motor.

My stock ej251 on my 04 legacy wagon is also loud and has piston slap when cold. My oil levels are above the "F" mark btw too. So not a low oil scenario in my case.

[AspirinWhite]

Originally Posted by danger1138

Well,
For the most part yea; it is normal. Ive had a built motor that was pretty noisy, particularly when cold. But remember it was a built motor.

My stock ej251 on my 04 legacy wagon is also loud and has piston slap when cold. My oil levels are above the "F" mark btw too. So not a low oil scenario in my case.

I'm running with valvoline synthetic 10w30 and I religiously check for oil levels to make sure it's in the right level as well.

[Cobrakai]

I'm in the same boat, my V7 swap is noticeably loud during cold starts but it quiets down at operating temperature.

It's a slapping/knocking sound only audible on reversing and taking off in first during cold engine conditions.

The car has been looked at by numerous Ej207 guru's and Subaru Mechanics, they've said everything is A-OK, which puts me at peace.

[AspirinWhite]

Originally Posted by Cobrakai

I'm in the same boat, my V7 swap is noticeably loud during cold starts but it quiets down at operating temperature.

It's a slapping/knocking sound only audible on reversing and taking off in first during cold engine conditions.

The car has been looked at by numerous Ej207 guru's and Subaru Mechanics, they've said everything is A-OK, which puts me at peace.

That does put me in the ease a bit. How many miles have you put on your engine so far?

[Cobrakai]

Originally Posted by AspirinWhite

That does put me in the ease a bit. How many miles have you put on your engine so far?

~2800.

Few late night canyon carving sessions and daily WOT pulls on the freeway onramps, hasn't gone boom yet.

If the noise is present at operating temperatures I'll start worrying haha.

[AspirinWhite]

Originally Posted by Cobrakai

~2800.

Few late night canyon carving sessions and daily WOT pulls on the freeway onramps, hasn't gone boom yet.

If the noise is present at operating temperatures I'll start worrying haha.

Yours is still relatively new then. I officially went through one full tank so far. Lots of power for sure but that cold slap/knock really is annoying.

Did you get yours tuned at Churchs?

[2slofouru]

Forged piston cold slap, normal. Even my 97 ej20k with cast pistons did it, worse in cold weather, but ran silky smooth and never skipped a beat. I believe the flat engine design makes it easier to hear as well.

It could also be the timing belt tensioner, did you replace it with new?

[2slofouru]

Tensioner noise. Imagine how many subaru owners have gotten screwed out of money or even sold their cars because they were told it was a "spun bearing".

How to tell if your Subaru engine knock is from the timing belt tensioner. - YouTube

How to tell if your Subaru engine knock is from the timing belt tensioner. - YouTube

Defective timing belt tensioner on a Subaru - YouTube

Defective timing belt tensioner on a Subaru - YouTube

[AspirinWhite]

video uploaded

[Cobrakai]

Originally Posted by AspirinWhite

Yours is still relatively new then. I officially went through one full tank so far. Lots of power for sure but that cold slap/knock really is annoying.

Did you get yours tuned at Churchs?

No but I wish I had.

I went with another big name shop in socal, good tuner - terrible customer service.


From what everyone tells me Church is fantastic with a 207, if I had the choice to do it over again I'd go with him.

Originally Posted by AspirinWhite

video uploaded

That's exactly how my car sounds.

[AspirinWhite]

Originally Posted by 2slofouru

Forged piston cold slap, normal. Even my 97 ej20k with cast pistons did it, worse in cold weather, but ran silky smooth and never skipped a beat. I believe the flat engine design makes it easier to hear as well.

It could also be the timing belt tensioner, did you replace it with new?

I haven't yet but it won't be a bad idea replacing all the idlers and belts

[CarmelValleyWRX]

my car does that too (exactly the same sound when blip the throttle) but its an EJ205 stock motor. it did not always do it. it slowly got louder. i replaced all my pulleys because i thought it was timing belt related. it still runs ok but it makes noise when hot too now. i dont trust my det cans now because the mechanical noise is so loud i cant hear anything.

[Samurai Jack]

Originally Posted by 2slofouru

Tensioner noise. Imagine how many subaru owners have gotten screwed out of money or even sold their cars because they were told it was a "spun bearing".

I'd lean toward this ^^^ before cold piston slap.
There have been a number of posts re: people having what they thought was rod knock only to discover later that it was a bad tensioner.

... and no, I'd say it is not normal. I don't have cold piston slap on mine.
I think many people just call it piston slap because the v7s have forged pistons so they call it normal, because they are comparing it to a built motor w/aftermarket forged pistons.
Easy answer so they don't have t look into it.

You should check the tensioner to be sure before it's too late.

[AspirinWhite]

Originally Posted by Samurai Jack

I'd lean toward this ^^^ before cold piston slap.
There have been a number of posts re: people having what they thought was rod knock only to discover later that it was a bad tensioner.

... and no, I'd say it is not normal. I don't have cold piston slap on mine.
I think many people just call it piston slap because the v7s have forged pistons so they call it normal, because they are comparing it to a built motor w/aftermarket forged pistons.
Easy answer so they don't have t look into it.

You should check the tensioner to be sure before it's too late.

Is the bad tensioner noise temperature dependant though? The noise I'm hearing disappears once it's warm and appears only when lower rpm from cold start.

The tensioner noise sounds like it's constant

[silvercookie]

My IAG stage 1+ block does the same thing on cold start especially in the winter.

Just piston slap from having forged pistons until they expand when they warm up.

[Samurai Jack]

Originally Posted by silvercookie

My IAG stage 1+ block does the same thing on cold start especially in the winter.

Just piston slap from having forged pistons until they expand when they warm up.

You can't compare a "built" motor to an OEM motor. "Built" motors do normally have some piston slap. How much is dependent on which brand pistons you use and the piston material and how the builder set the PTW clearances.

[Samurai Jack]

Originally Posted by AspirinWhite

Is the bad tensioner noise temperature dependant though? The noise I'm hearing disappears once it's warm and appears only when lower rpm from cold start.

The tensioner noise sounds like it's constant

It may only be the tensioner. It may be showing up when it's cold, but could continue to deteriorate. Worth checking the tensioner than just ignoring it and wish you did. All I am saying is it is worth checking now just to rule it our, or in

[AspirinWhite]

Originally Posted by Samurai Jack

It may only be the tensioner. It may be showing up when it's cold, but could continue to deteriorate. Worth checking the tensioner than just ignoring it and wish you did. All I am saying is it is worth checking now just to rule it our, or in

Well, I ordered the Gates blue kit and gonna change everything when it comes in. It may or may not fix the issue but I think it's a good idea to change it.

[AspirinWhite]

Originally Posted by Cobrakai

No but I wish I had.

I went with another big name shop in socal, good tuner - terrible customer service.


From what everyone tells me Church is fantastic with a 207, if I had the choice to do it over again I'd go with him.




That's exactly how my car sounds.

Have you replaced your belts/tensioner yet?

[Cobrakai]

Originally Posted by AspirinWhite

Have you replaced your belts/tensioner yet?

No, the timing components are brand new. Tensioner was bled properly, I’m swaying towards piston slap.

My friends gf has a V7 swapped bugeye and it makes the same sound as well.

I’m going to drive it until something breaks

[AspirinWhite]

Originally Posted by Cobrakai

No, the timing components are brand new. Tensioner was bled properly, I’m swaying towards piston slap.

My friends gf has a V7 swapped bugeye and it makes the same sound as well.

I’m going to drive it until something breaks [IMG]

https://media1.tenor.com/images/b8a3131f330d1dd7d73c64a37f5fd132/tenor.gif?itemid=10570702[/IMG]

Sounds good. If you're in oc, let's do some ej207 meet haha

[D-Rodman]

My v7 ej207 piston slaps at cold start but quiets down fairly quick, under a minute. Keep in mind when buying a used motor you are trusting the vendor is representing the mileage accurately. A higher miles motor will have more wear and looser tolerances.