Cold weather engine "knock"... HELP!
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This is a discussion on Cold weather engine "knock"... HELP! within the General Maintenance, Troubleshooting & Accidents. forums, part of the Tech & Modifying & General Repairs category; So I just bought a 2005 WRX with right at 70,000 miles on it and after sitting through a colder ...

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    Cold weather engine "knock"... HELP!

    So I just bought a 2005 WRX with right at 70,000 miles on it and after sitting through a colder night, the engine has a slight knock in it when the engine is under load. The knock occurs for roughly five minutes until the car "warms up" and then it purrs like an angry kitten.

    The knock sounds like someone lightly knocking on a door and gets faster as the engine gets faster. Is this a typical scooby occurrence as they just don't like cold weather or am I slowly looking forward to a new engine.

    Very paranoid about this.

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    Registered User EvoEatr's Avatar
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    Does it do it at idle when the engine is cold as well as under load when cold? I'm thinking from what your describing is a slight piston slap...Is it a deep hollow knocking sound? or like a slightly deep kind of tapping sound? I'm assuming it increases in rhythm in relation to RPM's? This was more common on the earlier model Subarus in general..Do you have any history on the vehicle? Is the oil level sufficient?

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    Probably piston slap... OK, don't worry about it. If it goes away it's normal. My '02 WRX did that and it's still running, 311,500KMs/194,500miles.
    '02 WRX 4EAT, 311,000KMs/194,500Miles, Sold. Best car I ever had. '09 STi stage 1, hope this one will be good too...

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    Admiral Ackbar the 1st mycologist's Avatar
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    Sounds like this?

    Engine problem?

    It is very common at least with bugeyes. Mine's done that basically since new, 6 years & 65K ago. No oil use etc. My car has run synthetic and I always changed before 3750 miles. I was just thinking today how nice it has been running lately. Basically if it goes away when it warms up ignore it. If that doesn't do it for you you can try a heavier oil (I switched to 10w-30 and it is somewhat less). Some people even get a little at really low load when it is warm.
    "From a little spark may burst a mighty flame." - Dante
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    Well... Turns out I was a quart low on oil. Here is why I didn't think of oil at first.

    According to the guy I bought it from, it had been 2500 miles since the last oil change. Since he was running full synthetic i was going to let it go to 5000 and then have it changed. I have never seen any oil spots under the car nor have i smelled oil dripping onto the exhaust manifold or anything and haven't noticed blue smoke from the exhaust. So I'm thinking that whoever changed the oil last just didn't put enough in the car or gremlins.

    Thanks for your responses and hopefully nothing is bad wrong with the car

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    Admiral Ackbar the 1st mycologist's Avatar
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    Quote Originally Posted by ljmcscoob View Post
    Well... Turns out I was a quart low on oil. Here is why I didn't think of oil at first.

    According to the guy I bought it from, it had been 2500 miles since the last oil change. Since he was running full synthetic i was going to let it go to 5000 and then have it changed. I have never seen any oil spots under the car nor have i smelled oil dripping onto the exhaust manifold or anything and haven't noticed blue smoke from the exhaust. So I'm thinking that whoever changed the oil last just didn't put enough in the car or gremlins.

    Thanks for your responses and hopefully nothing is bad wrong with the car
    That is a very dangerous assumption. Turbo boxers are not like Hondas in terms of oil consumption. Check your oil at least once a month or every 1000 miles if not sooner.
    "From a little spark may burst a mighty flame." - Dante
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    Quote Originally Posted by mycologist View Post
    That is a very dangerous assumption. Turbo boxers are not like Hondas in terms of oil consumption. Check your oil at least once a month or every 1000 miles if not sooner.
    So turbo boxers use oil and don't expell blue smoke out the tail pipe or any other symptoms like that? If you can't tell i am a NOOB on the turbo scene so any info like that is greatly appreciated

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    Admiral Ackbar the 1st mycologist's Avatar
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    Quote Originally Posted by ljmcscoob View Post
    So turbo boxers use oil and don't expell blue smoke out the tail pipe or any other symptoms like that? If you can't tell i am a NOOB on the turbo scene so any info like that is greatly appreciated
    They are known to randomly run low on people with no notice given. Lots of extra places for oil to get out with the turbo seals etc. There are many stories of spun rod bearings and people waking up to realize they are two quarts low or something. Some people think it is correlated with M1 but there is no proof. My car never needed to be topped up between changes. Except the one time when it was on low all of a sudden for no reason (i.e. checked at 2000 miles and it was gone at 3000). That was at like 12K and now it is at 65K. Car has not ever dripped or leaked and no smoke of any color including blue has ever been seen.
    "From a little spark may burst a mighty flame." - Dante
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    I will definitely keep my eyes open because a spun rod bearing doesn't sound very fun. Thanks for the info.

    Any personal input on motor oil i.e. is one "better" than mobile 1?

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    Quote Originally Posted by ljmcscoob View Post
    I will definitely keep my eyes open because a spun rod bearing doesn't sound very fun. Thanks for the info.

    Any personal input on motor oil i.e. is one "better" than mobile 1?
    I don't really buy that M1 is a problem (at least if you check on it). I used it for most of my car's life.

    As far as longevity goes unless you are going for long intervals I don't think it matters according to blackstone even if you don't use synthetic. If you are going long, then whatever you use get it analyzed. Even with moderately extended intervals these considerations are orders of magnitude less than letting it run really out.
    "From a little spark may burst a mighty flame." - Dante
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    Quote Originally Posted by EvoEatr View Post
    Is the oil level sufficient?
    Yeah man I hope it isn't anything serious..If its still noisy after you topped it off..Ive heard some good things about Lucas oil stabilizer...

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    So first oil change happened this morning at 10:00. I drive my car a mile back home go to school to work on a project and come back hours later. For kicks and giggles i check the oil to find that there is nothing showing on the dip stick

    I take the car back to the place and they acknowledge the mistake that they evidently just didn't put enough in the first time. Mobil 1 5W 30 is what was used this morning and this afternoon all they had was Mobil 1 DW 40 and topped it off with that.

    Is it alright to mix oils like that? Since the weight of the second oil is lighter should I get the oil changed sooner? If by chance he put too much oil in it, is there anything I can do about that or will it just burn off in the engine?

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    Quote Originally Posted by ljmcscoob View Post
    So first oil change happened this morning at 10:00. I drive my car a mile back home go to school to work on a project and come back hours later. For kicks and giggles i check the oil to find that there is nothing showing on the dip stick

    I take the car back to the place and they acknowledge the mistake that they evidently just didn't put enough in the first time. Mobil 1 5W 30 is what was used this morning and this afternoon all they had was Mobil 1 DW 40 and topped it off with that.

    Is it alright to mix oils like that? Since the weight of the second oil is lighter should I get the oil changed sooner? If by chance he put too much oil in it, is there anything I can do about that or will it just burn off in the engine?

    I assume you mean 0W-40? Most people say that mixing different weights is fine.

    You probably figured this out now but it is best to change your own oil and if not always check the level before driving off.
    "From a little spark may burst a mighty flame." - Dante
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    Never again will I get my oil changed at a service station...

    So the oil is now way over the full line. I've heard that if it is too high the crank shaft will froth up the oil and it won't lubricate the engine causing bearing failure and fun stuff like that. Any thoughts on how to get excess oil out of the car?

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    How far over the full line is the oil level...A little bit shouldnt hurt anything. However, if it is excessive you can pull the drain plug for a second and quickly reinstall...Than check your level again....Whenever I do an oil change on a Subaru 4cyl turbo motor I usually give it about 4.8-5.0 qts..Although that is slightly over spec..

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