325 knocking,.. please take a listen.

Mp3 here: http://www.rockisland.com/~zephyr/boat/325knock.mp3
I'm not that net savvy so I hope this works.
At 145k miles, my "previously owned" '88 325 makes this sound when I
first start it up. I've only owned it about 500 miles now and it's getting more noticeable the colder the weather gets. It's about 38F for this recording. It goes away after the car warms up to operating temp. It taps if it's been sitting for a few hours during the day til the temp comes up again but not this bad. It drives fine and doesn't smoke or use much oil. I had a little trouble with the recording so after the starter cranks that's me turning the sound up a bit. If anyone has any car mechanic type advice I'd be grateful. Thank you.
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Top end ish.
Does this car have hydraulic tappets?
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It sounds to me like hydraulic tappets - I had the same symptoms with my previous BMW - but nothing to worry about. On my car the noise went away after 10 or 20 seconds. Alternatively it could be injector noise?
Regards,
Laurence.
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An '88 325i would have an M20 engine, which does not have hydraulic valve lifters. Probably needs a valve lash adjustment.
FloydR
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Floyd Rogers wrote:

I have to agree. It either needs adjusting, or they are worn out. Take off the top cover and visually inspect the valve train.
It also sounds like the timing belt is too slack or worn, just as the engine starts.
It doesn't sound like injector noise, they are not that loud.
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Lighthouses are more helpful than churches. -- Benjamin Franklin

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I always try to look at the simpliest solution first. Since it is temperature sensative my first question is what type of oil are you using?
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wrote:

It had dirty oil in it when I bought it. It made the same sound, same symptoms then. I changed it using 10-30 chevron from costco at $20 a case. It didn't make any difference that I could tell. Thanks to everyone for their responses. It looks like the valves are adjustable so I will put my best man on this weekend.
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wrote:

10-30 chevron. I forgot to ask,.. can anyone tell me what size the crank pulley nut is so I can roll the engine over by hand to adjust the valves? The Bentley manual seems a bit vague in describing this setup. It just says, turn the engine until both cam lobes are generally pointing down for each cylinder, and gives the order.
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Maybe try 5W-40.
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32mm
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Jack wrote:

Isn't that engine supposed to use 20W-50? My 1989 325i does.
And by the way, I find it easier to put the car in 5th gear and push it a little to get to the correct valve timing position. YMMV.
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What year did BMW go to synthetic??
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wrote:

The 1988 owners handbook just gives a chart based on climate temperature, recommending different viscosities for different temps.

whoops, should have mentioned it's an auto. can't have everything. wish I had the heated seats!
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