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Old 12-04-2001, 07:30 AM   #1
Dons Soobie Doo
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Default "knocking" noise when engine is cold

I own a 2002 WRX Sportwagon with just 1400 miles. Over the past week when the engine is first started, I've noticed a knocking sound coming from the engine. First, is the valvetrain adjustable? It doesn't seem feasible that the noise is coming from there....I don't know. Secondly, are the pistons castings or forgings? To me, the noise sounds like piston slap...because after about 5-10 minutes the noise is almost gone. Anyone having these noises? For the record, I use Mobil 1 synthetic, 5W-30.

Another problem is a whooshing sound above 2500 rpm. It almost sounds like a huge vacuum leak...but if it was the car probably wouldn't run. Might it be a intercooler hose or something like that has come off? Any ideas on where to look would be appreciated.

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Old 12-05-2001, 11:14 AM   #2
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I had a knocking noise that took me forever to locate. Believe it or not I pinned it down to a loose Turbo heatshield. Some metal couplings from the AC lines I think would rattle against the turbo heat shield producing a very annoying rattle/knock.

With only 1400 miles on the car, I think you're just getting used to the "sounds" of the car. Believe me, when I got my WRX, I thought I was always low on oil. I was assured from other subie owners that it's characteristic of the cars. As far as that whooshing sound...that's gotta be your turbo working. I love that sound!
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Old 12-06-2001, 03:40 AM   #3
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Agree with WRX4me on both accounts... could easily be piston slap, and the first time I got a ride in a friends turbo Merkur I finally new what all those guys had been saying about "noisy" turbos!

Ben
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Old 12-06-2001, 01:46 PM   #4
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I have the EXACT same problem (since <1000miles). EVERY time I start the car after it has been sitting for awhile, I'll get this faint knocking noise that increases with revs. As the engine begins to come up to normal operating temp, the noise goes away. As WRX4me suggested, I checked the turbo heatshield and also checked the timing belt (and surrounding areas), didn't find a single thing wrong. I posted something about this awhile back and apparently it seems to be a normal thing. It's just very very annoying though and I'd like to find a solution. If ANYONE can maybe give some hint as to what it maybe, I'd very much appreciate it. Thanks.

-James-
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Old 12-06-2001, 07:11 PM   #5
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I have the same problem with mine, just when it's cold and then operating temp's it's fine. I've heard RS people have had the same problem, thought it was piston slap but in fact it was a falty timing belt tensioner..? IIRC
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Old 12-06-2001, 07:27 PM   #6
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I had that too and it turned out to be a cam belt tensioner. Do a search on cam tensioner, there are more details to be found on the subject.
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Old 12-06-2001, 11:33 PM   #7
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is it a knock or a tick?
Whenever I hear people talk about this I think of the loud valve tick that subarus have. A heat shield noice wouldn't (in my opinion) change with acceleration, or go away when the engine get's up to temp.
Mike
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Old 12-07-2001, 08:56 AM   #8
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In my case, I was describing a "knock" as opposed to a "tick". The weird thing is, when you first cold start the car, you would hear the knock at idle. Press the accelerator and the sound goes away. Once you get warmed up, the sound is not as evident, I guess because when the car is warmed up it does idle lower. (Still took me forever to find it, sounded like something was rattling in my glovebox).
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Old 12-07-2001, 09:21 AM   #9
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WRX4me, does your knocking sound appear to be coming from behind the firewall? Is it very prominent at a certain rpm, say 1100 rpm? Try listening to your engine with the hood opened to see if the sound is coming from the front or the rear.

--
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Old 12-07-2001, 04:07 PM   #10
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Richard-
It was hard to hear it with the hood open, you could only hear it at idle from inside the car. I held the metal coupler near the bottom heatshield (I think from one of th AC lines), and that was causing the knock. The dealer replaced both the upper and lower turbo heatshields a while back and I haven't heard the rattle since
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Old 12-13-2001, 09:28 AM   #11
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After listening very carefully this is what I think....after starting the engine cold, the car will "idle" at around 1200 r.p.m. for about 2 minutes then drop down to around 750 r.p.m. What I hear is a metallic "tap" (I referred to the noise as a "knock" or a loud "tick") but am not sure of the origin. When I've got my head under the hood, I can barely here it but inside the car you hear it distinctly. From about 750 r.p.m. to about 1200 r.p.m....the frequency of the tapping increases with r.p.m. Above 1200 r.p.m. I don't notice it as much....not sure if the noise is gone or other mechanical noise drowns the tapping noise out. Once the engine is completely warm, the noise is virtually gone. I've put a long screwdriver on the valve covers, fuel injectors, front timing belt cover and other things to see if I can isolate the noise. It doesn't seem to be coming from those areas. Someone mentioned it could be AC lines hitting somewhere near the firewall...I've checked underneath the vehicle and can't see anything hitting. Is this noise normal? Does anyone else have any ideas of where this tapping noise eminates from? Thanks.
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Old 12-14-2001, 04:25 PM   #12
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I too had a knocking noise on my wagon when starting from cold. It did not sound like tapping or ticking at all...just loud knock. This noise only occurred if the engine is cold and the ambient temperature is cold. The noise would disappear after the engine is warmed up. Dealer replace my Cam Belt tensioner and the noise is gone.
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Old 12-15-2001, 12:19 AM   #13
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I have a knock when my engine is cold that can only be heard from inside tha car. How do u prove that u have a knock when by the time i get to the dealer my engine is all warmed up and the knock is gone????
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Old 12-21-2001, 08:34 AM   #14
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answer to shaggee, arrange to leave it at the dealership but outside in their lot so that either the mechanic or the manager can experience the same thing in the morning.

If they don't hear it or SAY they don't hear it, you may need to arrange to do it again, then get there first thing and start it with someone in the car with you.

I've got a tap at cold weather start up too but it just seems to me that the oil has got to get on all the parts. I use synthetic oil too, maybe it's something to do with Mobil 1??

Ron
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Old 12-22-2001, 09:29 AM   #15
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Quote:
Originally posted by whitewag
I have the same problem with mine, just when it's cold and then operating temp's it's fine. I've heard RS people have had the same problem, thought it was piston slap but in fact it was a falty timing belt tensioner..? IIRC
I had that problem and your are right for me it was a the cam belt tensioner. The noise started happening when the weather turned cold like 35F or less and the car sat for more than around 3 hrs after being warmed up. The noise sounded hellatious like a bad rod or something. It would go away after driving for a few blocks or 5-7 min. The tensioner goes bad and the belt apparently contacts the plastic cover making the noise.

Peaty
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Old 12-30-2001, 04:48 PM   #16
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I've also got a little bit of a knocking sound that dissappears at running temp now that it's cold out, BUT during the summer I switched to Mobil 1 10W30 and experienced a louder engine with knocking really bad...I'm not saying Mobil sucks, just stating that's the only change I made. After a few hundred miles it didn't get better and my CEL came on. I immediately drained the oil and used the same brand of filter going back to Castrol GTX 10W30 and it was MUCH quieter, then after 2 days the CEL went off. Fine ever since!
Maybe the MOBIL 1 is too thin!??

-JR
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Old 12-30-2001, 05:08 PM   #17
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Quote:
I had that problem and your are right for me it was a the cam belt tensioner. The noise started happening when the weather turned cold like 35F or less and the car sat for more than around 3 hrs after being warmed up. The noise sounded hellatious like a bad rod or something. It would go away after driving for a few blocks or 5-7 min. The tensioner goes bad and the belt apparently contacts the plastic cover making the noise.
I had the same problem on my '99 Rs, and it was the Timing Belt tensioner and idler pulley. The belt was smacking the timing belt cover.

A freind of mine with a WRX had the same problem. The dealer I had my RS fixed at picked up the noise on his car while doing the 1000 mile service, and repaired it under warranty.

My new WRX does not have the problem.

Paul G.
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Old 12-30-2001, 09:58 PM   #18
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With so many cases of failing timing belt tensioner, I hope Subaru has learned about the problem. One would think that Subaru would fix it or redesign it.
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Old 12-31-2001, 01:04 PM   #19
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I don't think it was a bad design issue, but more like a bad batch produced. I don't know for sure though.

Paul G.
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Old 12-31-2001, 02:13 PM   #20
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Exeter Subaru just fixed the timing belt tensioner on my WRX. I had the exact symptoms you describe. It's always made a bit of a "flutter" sound or something like that (not sure how else to describe it) and has gotten worse over the past month since it's been colder in NH. From what I understand this is one of the more common problems with Subarus. Definitely take it to the dealer; if it's bad enough you could possibly have your timing belt skip teeth under load. Valves open+piston up=bad news.

--Greg--
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Old 01-01-2002, 04:56 PM   #21
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Don,

Have you had any luck fixing the Knock? Mine has just started since it got cold (down to 30 or below at night). I still have the factory oil in at 2500 miles. The knock goes away only when it gets really warm, have to run at least 10 miles. On a really cold morning, it doesn't quite get warm enough on the trip to work to eliminate the noise.

Just wondered if you have gone back to your dealer and gotten any help.

Thanks,
Dave
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Old 01-02-2002, 01:36 PM   #22
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Dave,

No I havn't brought the car back to the dealer. I was going to wait until 3000 miles. Anyone know why you can only hear the noise inside the vehicle and not under the hood? As annoying a noise as it is, you'd think you would hear it plain and clear.

Anybody that has had the cam belt tensioner replaced on a WRX, can you post your service order on the site. Please let me know the mileage, comments by the service manager, willingness of the dealer to fix the problem, etc.

Thanks,
Don
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Old 01-02-2002, 10:26 PM   #23
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Funny, I had my car fixed at Exeter Subaru, and my friends WRX I also spoke about above was fixed there.

I love going to a good dealer.

Paul G.
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Old 01-04-2002, 11:11 PM   #24
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Quote:
Originally posted by Bimmer
Agree with WRX4me on both accounts... could easily be piston slap, and the first time I got a ride in a friends turbo Merkur I finally new what all those guys had been saying about "noisy" turbos!

Ben
Hey do you know where I can find a sound download a piston slap? I never heard the sound before..
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Old 01-04-2002, 11:50 PM   #25
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Quote:
It's always made a bit of a "flutter" sound
When are you getting this "flutter" sound? I have a flutter like sound between about 2500-3500rpm on my car. Happens either hot or cold, and only when the motor is under low load, and accelerating.....
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