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Unhappy Engine Ticking/knocking

I know there are a lot of threads posted on this subject, but believe you me I have spent countless hours/days reading practically all of them, and none seem to fully answer my concern!
For the last month or so my engine has started making a pretty loud ticking which after a period manifests itself into a loud ticking plus slight knocking sound.
At cold startup it makes the classic oil drain tick, but dissappear's within a couple of seconds, when all is normal and quiet. But after continuous driving, when i come back to a standstill at idle the ticking starts. It seems to get especially bad after stop/start driving. If I rev beyond 1500rpm it goes away, but reoccurs when the revs drop. The longer I leave the car idling, the more prominent the noise seems, and then the intermittent slight knocking sound occurs. The intermittency of the knocking made me think injectors, but I'm not so sure. I'll try and describe the sound at idle; continuous tick, tick, tick, tick fairly rapidly plus; knock, knock, knock, knock.........few seconds pause.......knock, knock, knock,knock.........more pause.......knock, knock, knock, knock etc. Is it the timing chain tensioner? Injectors? Tappets? Lifters? The sound seems to be coming from the front and slightly to the left of the engine block if you're looking at the car head on.
The general noise level under the bonnet seems to increase a fair bit after a lot of stop/start driving as well. When in a traffic jam for example. Another sound which only seems to occur after a lot of hot stop/start clutchy driving is a very faint squeel when pulling away at low revs. It's not a loud squeel like when someone's cambelt is on it's last legs, more of a little squeek. This is with the aircon off.

A few points;
-I've recently had an oil change, and my oil level is fine (oil & filter changed for the very reason of solving ticking/ knocking sound but no luck!)
-engine runs smooth, plenty of power/pull.
-Ticking noise when engine is at operating temperature, not when cold.
-Ticking/ knocking, squeek; all noises occur regardless whether aircon is on or off.
-I only use 98 octane fuel.

If anyone could please help I would most appreciate it! It's starting to worry me! I have been to a few mechanics. One said it was noisy injectors, but I'm not so sure. The other suggested the oil change. But that didn't help.
ANY ADVICE PLEASE!!
Old 08-15-2005, 05:15 PM
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Alright, you've got a few things you can do right off hand. First off, you can add some Rislone or Motor Honey to your oil to thicken it up and help quell the tick and the knock. That's short term.

For the tick, that usually stems from tappets/lifters. They are hydraulic and need to 'pump up' to work properly. You get a touch of valve train clatter on higher mileage vehicles because it takes a moment to get the oil pressure up and everything running like it should. If you get a crushed/collapsed tappet, then you start to get slap on your cam, and it results in a 'ticking' sound. If it gets bad, you get a clack, clack, clack or a knocking sound out. Knocking can also be from a spun bearing on the rod or a 'wallering' out of the wrist pin connection at the piston... also known as 'rod knock', but my understanding of these engines is that the lower ends are pretty bulletproof (as long as you don't loose oil pressure or ignore regular changes). I have a friend who is a European engine mechanic up in Seattle... he said he's never had to dig into the lower end of a Beemer in years of working there.

If you are talking about the M50 I-6 engine, then it is a dual over head cam (DOHC) layout. Not sure how the I-4 is all laid out, but I'm sure it's similar. Anyhow, your clammer could be from the VANOS system, or it could be from the chain tensioner, but I think that usually comes across with the sound of 'pinging' or detonation... that kind of clammer, not an actual knock. The ticking sound really sounds like a tappet issue, but can't be sure. It makes sense that when you run up in RPM, they pump up with oil pressure, and when you run at lower RPM, there is a time lag that they can tend to slightly collapse. The scenario fits. Motor Honey helps the tappets to stay a bit pumped up, Rislone is an overall engine treatment like Slick50, without the outrageous price tag.

The slight squeal you hear on take off is probably a belt slipping on the crank. Either your main accessory belt or A/C belt. It could be from a little oil sloshed on the belt during the oil change. It should either just wear off or you can spray some cleaner in there (or they have special stuff to make the belts a little tacky so they don't slip... I think it's just in a can called 'anti-belt slip' or something self explanitory).

So far, it doesn't sound like your problem is critical, but you may want to thicken up that oil a bit, give it a viscous advantage, keep an eye on it, and see if the problem progresses. If you can hear the tick or knock at idle, you can use a tube or stick and press it against different spots of the engine and listen for where the sound is most prominent.

Good luck and any other input you can give always help in diagnosis.

Old 08-15-2005, 11:51 PM
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tappets = lifters (same thing).

When I rebuilt the head on my 325is, it had a sticky lifter that just did not go away. I changed the oil a couple of times, and varied the viscosity. Finally, adding some Mobil-1 very thin viscosity oil did the trick. There's probably just an air bubble or something caught in the lifter that is causing it to not accuate. Worst case scenario is to remove the lifter and replace is (not an easy job). Try varying the thickness of the oil first, and try some Mobil-1 - it worked for me!

-Wayne
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Old 08-16-2005, 12:18 AM
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Ooh, that'd be nice if it were just a sticky lifter/tappet, and not a crushed one. Let's hope Wayne's method of varying oil viscocity works... it'll be a lot cheaper than chasing and replacing a crushed/failed tappet.
Old 08-16-2005, 05:54 AM
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It sure would! My Engine by the way is the 2.0 liter M52 VANOS 6 cylinder. All the mechanics around here are unsurprisingly suggesting replacing the tappets. If it did come to that, what would you expect to pay in your region?
Old 08-16-2005, 11:05 AM
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Oh man, to find that out, you'd need to find the time required for the job, then just multiply that by the mechanic's rate. If I were you, and it did come to that, I'd get the parts in advance if you can. Sometimes (depending on the shop), that can save you money.

The guy who would probably know better than anyone what something like tappet repair/replacement would cost would be BMWCowboy on here. Either him, or Wayne should have a good estimate of the time required, then you just need to find the shop you want to use.

You know, I haven't really heard of any tappet failure from these cars/engines. Has anyone else known of anyone having problems?
Old 08-16-2005, 11:46 AM
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Here's a link that may be of assistance... http://www.automotiveforums.com/vbulletin/t247387.html

another note I saw on a buyer's guide: Engines Pretty strong but cars with over 80,000 miles can have slight tappet rattle when cold.

Here's another info link... http://www.***************/html/oil_pressure.html
Old 08-16-2005, 12:06 PM
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what about this new method "engine flush", just heard about it. don't know much about it apart from that it's supposed to clean the engine out including the tappets
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Old 08-16-2005, 12:28 PM
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I haven't heard about 'engine flush'... is it a product?
Old 08-16-2005, 01:01 PM
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sort of.. they hook up a large thingie to the engine and flush it:-)

check this http://www.redwoodgeneral.com/flush.htm
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Old 08-16-2005, 01:16 PM
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Nice!!! Disolves varnish and removes particulates down to 3 micron... man, sign me up and flush my engine out!! AdamB, that's definitely something you should look into... it would clean and loosen any sticking tappets that you might have.
Old 08-16-2005, 01:20 PM
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just do a google on "engine flush"
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Old 08-16-2005, 01:24 PM
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Looks like potential snake oil to me.

There's a BMW factory procedure for bleeding sticky tappets. I tried this on my BMW 325is, but it didn't work. I'll see if I can find the document...

As for a crushed tappet? I don't know what that means, and I dont' think that's technically possible?

-Wayne
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Old 08-16-2005, 10:38 PM
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I think it's a quite common procedure here in Sweden, if it's b*ll or not I can't say;-) I have not tried it on my car/engine
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Old 08-16-2005, 11:21 PM
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A more definitive characterization of a 'crushed tappet' is more of a 'collapsed' tappet. Below is the basic configuration of a hydraulic lifter tappet. You'll see a spring, a plunger, a plunger cylinder, ball, ball seat, etc. When a tappet crushes or collapses, it can be from the retaining spring breaking, collapsing/crushing, or the failure in the ball and ball seat interface that won't allow the hydraulic tappet to pump up.

Hydraulic tappets are great in that they pump up with hydraulic fluid and maintain a set displacement of the valve due to cam location. The hydraulic buffer takes up any slop or misadjustment in the cam/tappet/valve interface (which is why hydraulic lifters are considered maintenance-free, while solid lifters have to be adjusted all the time and tend to drift out of adjustment... they are solid and don't compensate). If the hydraulic system in a tappet fails, it crushes/collapses and therefore the hydraulic buffer is no longer there and the tappet collapses against its internal parts... this creates slop between the cam and the valve, which makes the 'tick' sound... or clammer if it truly crushes down to where it won't pump up at all.

Old 08-17-2005, 01:17 AM
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Thanks for your input everyone. I'll have an expert look at it in a few days. I'm getting my clutch replaced soon, so I'll do it at the same time
Old 08-17-2005, 08:33 AM
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I believe a clog in the oil passages will result in similar problems...

Please let us know what you find out!

-Wayne
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Old 08-18-2005, 10:26 PM
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Yep, very true... a clog in the oil passages could starve a tappet or two and yield the same effect.

As far as the pressurized 'engine flush', we do that at work with some of our industrial equipment (pressure flush the crankcases to clear out debris, sediment, and varnish). It's like a little mini hot-tank dip for your engine without having to disassemble it. I can't see anything wrong with it... hey, they do it for cooling systems in cars, why not the oil/lubrication system?

Last edited by blkongry; 08-19-2005 at 09:39 AM..
Old 08-19-2005, 09:35 AM
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