Advice!

Guys... Girls... My first post here so I’m not sure how this goes. I needed some advice from the community. About 2 weeks ago I noticed a small, subtle knock coming from the engine compartment on my 138k mike 2009 GT. At this point, and 2 dealerships opinions, they say I have piston slap! I don’t like it!! Is this something I trade the car in for, keep it and fix it later, or just keep driving it until the problem tops out. If anyone has advice or ideas please get back to me. My options are open.

If it's piston slap, just keep driving it. Every Subaru I've ever owned has had it to some degree. However, piston slap typically goes away when warm. Does yours?

So upon start up it’s at its worst, which is still quite minimal. I can only hear it while inside the car though. Coasting at a low MPH I can still slightly hear it with RPM fluctuation but it’s definitely worse when I first fire it up. I’m not very mechanically inclined but my wife is pressuring me to just get a new car and keep the Subaru in the garage to work on and play with. I’m afraid I’ll be in over my head

Is the car in nice shape? Do you have room to store it and gather parts for a build? There must be a shop or two in the area that could handle the work if you think it's too much for you? This of course would require opening the wallet and shelling out the dollars. I say drive it until you are forced to answer these questions and have a back up plan (be ready to buy new wheels at any time). For what it's worth my 2009 GT w/ 63k miles makes some knocking noise too but runs great.

 

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If you can keep it and want to learn how to replace the short block in th efuture, this is the place to give you help.

 

These cars offer great bang for the buck. Most of us love our cars, that's why we're here.

 

I'll warn you then can become expensive, but if you enjoy driving the car, it can be worth it.

 

My click here link in my sig has become a "how to do it right" the first time, lesson.

I think my non-turbo always has piston slap when the engine is stone cold during the cold weather months. Not something I'm worried about at all, but I'd be curious to hear your noise.

A bad timing belt tensioner will create a noise like a rod knock when it’s bouncing on the belt. I would imagine that one that’s not fully gone could sound like piston slap. Search YouTube for that and you can hear what it sounds like for comparison.

 

 

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Thank you for all the help guys. The car is in amazing shape besides that noise. I paint cars for a living so I have always kept it “looking” as clean as possible. Wishing I were a mechanic about now though! I have a garage to store it if it ever goes under the weather and money won’t be too stressful. I’ll most likely go grab me a new reliable base model from someone and keep my Subaru like my first love. There’s a few shops around here that revolve around Subaru’s so I’ll reach out if I ever need. Thanks again

A bad timing belt tensioner will create a noise like a rod knock when it’s bouncing on the belt. I would imagine that one that’s not fully gone could sound like piston slap. Search YouTube for that and you can hear what it sounds like for comparison.

 

 

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What he said. Granted, it doesn't fall under the worse when cold issue but still something to look into. When was the last timing belt installed and was the tensioner replaced?

any video with audio? piston slap on oem block... piston slap on oem isn't normal. That to me sounds like incoming s***'s about to go south. piston slap is usually from aftermarket pistons made from metals that expand, so it will happen when cold , but when they warm up they expand and the noise goes away. Oem pistons shouldn't have the issue.

any video with audio? piston slap on oem block... piston slap on oem isn't normal. That to me sounds like incoming s***'s about to go south. piston slap is usually from aftermarket pistons made from metals that expand, so it will happen when cold , but when they warm up they expand and the noise goes away. Oem pistons shouldn't have the issue.

 

You'd be surprised. I've had piston slap on cold starts, to some degree, in every OEM motor I've had (3 turbo, 1 non) except my YNANSB. None of the motors blew up after tens of thousands of miles (YNANSB was a nip-it-in-the-bud when original motor popped a head gasket). I drove my 2.5i Impreza with cold start piston slap that sounded dead nuts like rod knock for 60k before I sold it at 110k. I still get random service emails from Carfax about it, so I assume it's still happily chugging away for the new owner. The explanation I got for the slap at the dealership when I asked is that the OE piston design is a little short in terms of skirt length, which allows the piston to rock back and forth in the cylinder a little bit until it comes up to temp.

piston slap on a oem 2008 lgt motor?

Why not? For me it's 2x 2005 LGT, 1x 2013 WRX, 1x 2008 Impreza 2.5i.

 

Worst on the Impreza, but there to some degree on cold start with all the rest. The Type RA block is the only one that doesn't make a sound. Or, maybe I can't hear it over the racket the ID1000s make ha

The explanation I got for the slap at the dealership when I asked is that the OE piston design is a little short in terms of skirt length, which allows the piston to rock back and forth in the cylinder a little bit until it comes up to temp.

 

Interesting, that's what he says here too, I didn't know that.

so worn piston rings are the real cause. I would do a compression test just to be sure.