Clanking Noise - Chain tensioner defect?

[silver_911]

Hello,

Beginning of last year, I completely refurbished an SC engine. New pistons, valves, valve guides, timing chains, ramps, gaskets,...nearly everything.
I had a set of late style oil fed chain tensioners. They looked good, I primed them before installing, but I have no idea about their life.
After installing, the engine ran fine for 1 year and about 3000 mls.

Soon after an oil change (3rd time, I think), the engine was getting a bit loud. I have again adjusted all the valves which helped a lot. Checked the rockers and they seem OK. But there is still a "clanking" noise which seems to come from the left side valve train (used a stethoscope to locate it).
The car is going strong, no oil consumption, no smoke, nice oil pressure.
The noise appears ~30 to 60 seconds after cold start and will get worse if the car heats up.

Could it be a faulty chain tensioner?
Any other ideas or method to isolate the problem further?

Thanks and best regards from Germany,

Jens

[Flat6pac]

The dropped tensioner usually sounds like a marble in a can because the chain is slapping on the rails. Carrera tensioners are spring loaded besides the oil but the oil seals do fail and so the tensioners fail also.
Bruce

[silver_911]

Thanks Bruce, thats a pretty good description.
I will go for a replacement.
Would you (or anyone else) recommend to change both tensioners? They are same age, I guess...
Jens

[safe]

Aren't they rebuildable as the pre carrera tensioners are?

[Flat6pac]

If they are rebuildable why do it, the product is of a higher quality off the end of the production line than a novice trying to save money. There is a very expensive engine depending on quality parts, buy a good part or new part and go with it.
I would just do the one that failed.
Bruce

[silver_911]

Hello again,

Today I opened the left chain housing and checked the tensioner.
Everything looks OK! No slack in the chain, and the tensioner really needs high force (vise-grip) to compress. Chain, ramps, etc. look nice and clean (oily though), no signs of wear.
Once I am on there: any idea what else to look for?
And what next to check?

Thanks for any hint,

jens

[lucittm]

Silver,
Beautiful engine, I can appreciate the work that went into that rebuild.
Your description that the noise apprears ~30-60 seconds after a startup (when the oil is thickest) and then grows louder as the engine warms up (when the oil is thin) points to a leaking tensioner. The fact that it is hard to compress when cold does not say much in this case. I would replace the suspect tensioner and see if that makes a difference. If correct, the improvement should be dramatic and immediate. Well, at least after ~30-60 seconds.

Mark

[silver_911]

Hello Mark,
sounds like some sunshine at the horizon.
I am going to order the stuff and will put it together next weekend.
I'll keep you informed.
Jens
----
'76 2.7 CIS with '73 body conversion and 3.0 SC engine

[silver_911]

Hello Guys,
unfortunately, it was not the chain tensioner
After putting in a new one on the left side (primed with oil) and having assembled everything, the engine started up perfectly. And after ~40 sec., the noise was there again.
It is getting a little bit louder when the engine warms up.
I tried to check everything with a newly bought super-duper stethoscope.
The left side seems to be a bit noisier, but I can not hear any significant difference between the different rockers, inside and outside, left or right, nor between the cylinders.
I pulled the plug wires one by one-no change.
I ran the engine for a few seconds w/o the fan belt-no change.
Checked again the plugs: perfect brownish.
So what's next
Any ideas?
Thanks,
jens

[E Sully]

Does the noise change at different rpm? Any chance of posting a sound clip? Does the oil show any metallic debris or coppery color? Cut open up the oil filter to check to see what is in it.

[safe]

Is it like a out-of-adjustment-valve kind of sound?

A friend had sound/problem like that. It turned out to be the valve adjustment foot that was worn and dirty so it didn't operate very smoothly making it impossible to adjust.

[silver_911]

Hi,
I will try to record a proper sound clip again. The noise is there but not that much in the foreground to isolate.

Yes, the oil looks a little "dirty", but I more assume that this is due to remaining assembly lube as well as old gunk from the worn out 2.7 engine in the system.
It is not looking like copper, more than MoS2 & some aluminium.
There were some metallic parts in the oil tank magnetic plug, but none on the engine sump.
jens

[silver_911]

For the sound:
It is very similar to a loose rocker arm and changing with RPM accordingly.
In fact, I thought it's just a rocker out of adjustment first.
Adjusting all the valves (2nd time after rebuilt now) deleted a lot of the noise, but not that one. Its just easier to hear now.
During rebuilt, I cleaned and checked all rockers, and exchanged some of the adjustment screws if not moving easily. So I doubt this as the source, but a second look may not be false.
jens

[mca]

Did you use a new chain? Replace any intermediate shaft sprockets? What about possible chain alignment issue? Are you positive that it is an engine noise?

Just trying to think of some possibilities.

[Tall02]

Dear Silver 911

The noise you are encountering - you noted that it changes with the RPM. Does it get worst during acceleration or deceleration?

Have you posted a sample of the noise?

Best regards

[Walt Fricke]

Silber

I guess your stethoscope does not tell you if the noise is more toward the intake or toward the exhaust? Since now you are not sure you can even tell which side it is coming from?

I wonder about the rocker shafts - are they all tight? All lined up where they are supposed to be? I mention this because it is fairly easy to check when you have the valve covers off. Oil leaks are often the first indication of a shaft that has moved out of position.

You might also check rocker clearance with the engine at operating temperature. Jack it way up on one side so you don't lose oil, and pull the two covers on that side. Measure all the clearances. They should be larger than the specified cold clearance, but you are looking for one which is larger than the rest.

To rule out valves hitting pistons you might want to recheck the cam timing on each side. An unlikely issue, but easy to check.

I, too, wondered about chain gear parallelism - did you check that on reassembly, or at least make sure to put the same number of shims as before under each cam gear wheel assembly? But my understanding is that being out of parallel enough to make noise is going to make noise all the time, and even at hand cranking speeds.

With the valve covers off, you might retorque your head studs. They are probably fine, but who knows.

Although I have never done this, others have said that they were able to run their engine with the chain housing covers off without making a huge mess of oil. I don't know just what you might see which looks like it could cause a noise which happens every two crankshaft revolutions, but the likely suspects (those which don't involve taking the engine apart again) are dwindling.

I have often wondered if there was a way of getting an oscilloscope reading on things like this - one which would display the noise and also the spark, with the #1 cylinder indexed. Once per revolution? Twice? Random?

Walt Fricke

[Tall02]

Dear Silver 911

If you could upload a sound clip of the noise then there are some fellow mechanics or enthusiasts on this site that can anylize the sound and determine if it is in the crank or piston (every revolution) compared to a sound in the top end valve train (which would be a sound half the time). I have seen this done before.

Is your noise a ticking, rapping or knocking?

[lucittm]

There remains one more possibility that I did not see when reading through the thread. Both the cam chains and the sprockets wear down over time, but they wear together and this is a good thing because during engine break-in, they gradually wear down imperfections in the surface and the machined dimensions.

This is the reason that the chains and sprockets should be changed at the same time. Here are my questions for you:
1. You mentioned that the chains are new, are the sprockets new as well?
2. When you changed the chains, did you use endless chains or the type with a master link to connect the ends.

The sound you may be hearing is the sound of the worn sprockets on the partially worn chains. For the first 3000 miles, if the chains were new and the sprockets were old, the chains didn't fit. Now they are starting to fit and they are making some noise. It might get better or it might get worse before it gets better. It is of no concern and you should keep driving.

On the other hand, it is impossible to make a chain with a master link act exactly like an endless chain. If this is the case, just live with the sound and know it is a thing of beauty that your chain is doing it's job at 56,000 link engagements per minute (28 teeth x 4000 engine RPM /2).

Good Luck,
Mark

[silver_911]

Thanks for the hints!
During rebuilt, I exchanged the chains with endless ones and thoroughly checked the alignment. Ramps were also changed, of course.

The rocker arm bushings and shafts showed some wear. I showed them to my engine professional who also did the valve guides and upper rod bearings. Acc. to his measurements and judgments, they were good for another 100k miles, thus not to to be refurbished.
I have installed them acc. to spec. together with the RSR seals. Everything looks tight and no oil leaks detected.

The sprockets and their bushings have shown some wear as well, with the same judgment as above. Therefore, this theory would make a lot of sense-even if the sound seems not to match (but this is more a feeling from my side).

Sound clip is coming soon...

jens

[silver_911]

YouTube - P1020310.MOV