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Clickety-Clack at idle


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Hi,

 

My engine started making a slight, intermittent, valve-like ticking/rattling noise at idle so the first thing I did was check the valve clearances.  They were a tad tight so I set everything to spec.  Noise is still there.

 

Next suspect would be the timing chain tensioner, correct?  I searched that topic and it looks like in some cases there was noise caused by the chain.  Are there other things I should also consider to be on the suspect list?  Given that the engine may be on its original tensioner, should I just replace it, regardless?

 

Thanks!

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Do you have a mechanical fuel pump?

 

Are you using an engine oil with ZDDP (zinc) additive?

 

Might be an exhaust leak at the manifold... these can sound very much like a clicking noise.

 

Use a mechanic's stethoscope to pin point the source of the clicking... they are cheap at most local auto parts stores and really do work.

 

Ed

Edited by zinz

'69 Granada... long, long ago  

'71 Manila..such a great car

'67 Granada 2000CS...way cool

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Cold, or hot?

 

What ZINZ said.

 

Tho I had a slightly loose pulley once make similar noises.

 

Try it with the clutch in, also.

 

Cheers,

Ray

Stop reading this! Don't you have anything better to do?? :P
Two running things. Two broken things.

 

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The chain tensioner is pretty robust.  My original tensioner was worn at 100K but still functional.  The timing chain itself can get sloppy and cause extra noise, but from my experience it's not usually the culprit.

 

Listen through the grill.  If the click/clack is prominent then I suspect it's your oil pump chain hitting the return oil line to the pump.  A new chain or even a shim will remove that sound.

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New chain added.  Chain slack should be approx 5mm.

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73 Inka Tii #2762958

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Welcome to my world. My car has been doing this since the engine rebuild last year. The sound is there ONLY at idle. I thought I had it nailed down as coming from the oil pump chain...but I changed it, got tension right, and it still makes the noise. I run Brad Penn 20-50.

I've been running with the theory that it is piston slap...however, it does not go away or change when the motor gets up to temp. It runs good and strong, blows no smoke, great even compression across all cylinders. I have made a number of trouble free road trips in the car...it just makes this noise at idle. I actually had someone next to me at a light ask me if it was a diesel!

Edited by arminyack
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If at very low RPM only and worse when cold, probably the fuel pump. They do that sometimes, usually not a problem unless they leak or stop working. My car does it if it has been sitting a couple weeks and only if I kick down the choke too soon and the RPM drops below about 900.

74 Golf

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Also... Pull the cap off the dizzy and see how much axial play you have in the dizzy' shaft (up and down). My old '75 made a noticeable rattle. 

 

Ed

'69 Granada... long, long ago  

'71 Manila..such a great car

'67 Granada 2000CS...way cool

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Yeah, it's usually the o- rings.  I shy away from diesels, same logic...

heh

 

The M20's do this, too- it's disconcerting to have it idling along,

start ticking, then shut up before you can pinpoint where it's coming from.

 

t

 

"I learn best through painful, expensive experience, so I feel like I've gotten my money's worth." MattL

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Stupid one to rule out: if you are standing with the hood open listening at idle, I had one where a bit of engine shake would get the hood wobbling and then 'knock' as it moved. One hand on the hood cured it. 

rtheriaque wrote:

Carbs: They're necessary and barely controlled fuel leaks that sometimes match the air passing through them.

My build blog:http://www.bmw2002faq.com/blog/163-simeons-blog/

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You might consider posting a video with decent audio.

 

Without hearing it, the sound could also be from the oil spray bar a.k.a. the tube that delivers oil to the cam and valve assembly.  I have seen them loose and in one case, cracked.  The rocker arm shafts and the springs between rockers can develop wear and this can also result in occult noises.  If the rocker shafts develop wear, or the corresponding rocker bushings are worn, noise can develop, although the sound tends to be fairly rhythmic.  However, different speeds produce different harmonics. This situation also makes accurate valve adjustment, questionable.

 

Separate from any issue with the hydraulic cam chain tensioner, there is a plastic guide and a hinged rubber coated steel "shoe" guide that work in conjunction with the tensioner.  Even if there is nothing wrong with the tensioner, If the plastic guide breaks, some noise can result.  If the rubber on the steel shoe is sufficiently abraded and/or degraded, some noise can result.  Although unlikely, the chain can stretch beyond the limits of the tensioner and associated hardware - and - you guessed it, noise.  Think about it.  A chain in continuous use for four + decades will at some point out live its usefulness.  The easiest means of determining stretch would be to compare it with a new one.

 

A slack oil pump chain can produce noise even without contacting the surrounding parts.  Changing to a new chain may seem logical and easy (with a master link) but it may introduce new wear patterns on corresponding teeth, including those found on the crankshaft.  One school of thought is to shim the oil pump rather than make piece meal replacements.  The best practice would be to replace all worn drive components as a set.

 

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Edited by avoirdupois
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