Tapping noise

[Chrisrich]

My '70 S4 has started making a new sound: a ticking that sounds like a traditional valve tap, from the rear of the motor, on the exhaust side. When I pull the 4th plug, it goes away. I've pulled the cam cover and checked clearances, and I'm around 9 thousands on that valve, which is right around where all the exhaust side valves are. I don't see anything unusual -- the lobes look fine all around. There IS a pool of oil over the most rear-ward intake and exhaust valve (pict). Any reason to be suspicious? I would think not. I've retorqued the head and cam bearing caps (they only get 9lbs?).

The plugs don't reveal much, although the inner plugs seems leaner than the outer plugs, but all within reason.
I don't THINK I've got excessive smoking, at least nothing that brings attention to itself.
When driving, you hear the ticking under load. It can easily be heard at idle with the bonnet up.
Does not seem to change when it's warmed up. Stays consistent.
Oil pressure seems fine, around 30 at idle, around 40-50 at around 2500. No temp issues.
I don't notice any performance issues, either.
I'm sure it's not a detonation noise.

Anything I could be missing? This noise just arrived a few weeks ago, and I've driven the car 5 or 10 miles since, somewhat gingerly. I can't think of anything that was changed to prompt it.

Any help appreciated-

Chris

[Elanintheforest]

Check out the exhaust header gasket, Chris. When this is leaking, it can sound like a very mechanical ticking sound.

Mark

[Chrisrich]

Good call.
Let me look at that.

[neilsjuke]

Has it been pinking this can do the little end bearings do the plugs look the same ?
Neil

[collins_dan]

I've got the same noise and gone through the same checking process. I concluded that it was a leak at one of the rear exhaust gaskets, so put a new set on. Its still there, so my new conclusion is that my header has a leak in one of the rear welds. This winter I will pull it off and either send it off to be repaired and ceramic coated (to reduce engine compartment temp) or replace, depending on what's involved in fixing. When I pulled the header off to put the new gaskets on, I changed from studs to bolts and it has made removal and replacement of the header much easier.

Dan '70 S4

[Chrisrich]

No, it has definately not been pinking, and the advance is pretty conservative.
Plugs all look similar, with the middle plugs slightly leaner.

[prezoom]

Like Dan, I am using bolt in lieu of studs for the exhaust manifold. I chose 12 point, reduced head bolts. The use a 5/16" socket, and when used with a short handle 1/4" ratchet, over torqued bolts are not a problem. Used the same style for the starter and engine mounts. Much easier to work on.

Rob Walker
26-4889

[collins_dan]

What torque setting did you use? Thanks. Dan

[Chrisrich]

Thanks folks.
Dan, couple of questions for you, as I've got a brand new jet-hot coated header sitting here that I've never put on the car.
Do you think you can extract the original cast iron manifold and replace with the new piece without removing the motor or lifting the body? Can the stock manifold be backed off to have gaskets replaced without moving anything?
I'm assuming if there's an exhaust leak, I'm going to see that, no? I mean, there should be no mystery to it, should there?

grazie, Dan.

Chris

[dusty]

Thanks folks.

I'm assuming if there's an exhaust leak, I'm going to see that, no? I mean, there should be no mystery to it, should there?

grazie, Dan.

Chris

You might not see it but you can feel it. Put on a heat proof glove such as a welding gauntlet then have a grope around the suspect area of the manifold, if you hve a leak then when your fingers cover it the noise will change / quieten.

obviously exercise caution and common sense, we don't want reports of burnt hand or forearms!!!

[m750rider]

Dan

I replaced the original cast iron manifold with stainless headers many years ago so I don't remember exactly how difficult it was, but I know I did not pull the engine to do it.

Bob

69 S4

[billwill]

Because the cast iron header has a joint only about 5 inches down I'm pretty sure that in the past when I still had the original manifold, I took it off on several occasions without any trouble. In fact that was usually a prelude to taking the engine out or head off.

On putting it back I seem to remember putting gun gum paste at the lower joint with the exhaust pipe.

===============

On the other hand if you have now bought a double-Y tree-style new headers, I am not at all sure that you can thread those in with the engine already in place.


==============

For those who now use bolts.. The Original system uses brass nuts on steel studs to ensure that they do not seize in place. Are the bolts likely to seize in the ally head?

[collins_dan]

Bill, I used anti-seize (copperslip) in hopes of preventing seizing and the bolts I purchased were intended for use on an exhaust. Fingers crossed, I guess.

Chris, I have a header, which I would like to have jet-coated. I do not have an original exhaust manifold, so can not speak to getting that off without removing or at least loosening the engine. What I can say is that in order to get the gaskets on without removing or loosening the engine, I removed the studs, slipped in the gaskets and bolted it back on. I have not been able to see any signs of the leak, I'm sort of guessing where it is based on the sound. I'll try the glove grope and report back results. As to fully removing the header without pulling the engine, I haven't done that yet, so can't say for sure, but it looks like it should drop down enough to twist out, but others may know better.

Good Luck. I'll be curious to hear if you can find it and what signs or sounds helped you to track it down. This one has been bugging me for a couple of years now.

Dan

[Chrisrich]

I wonder why it was beyond me to put a (gloved) hand on the exhaust manifold to see if the sound would change?
This working on old cars is humbling.
Yes, there is a manifold leak, at the top of the fourth cylinder.
This is going to be a tricky fix, as I cannot even seem to get a wrench (or socket) on those nuts.
Ok, but at least we isolated the problem.
Thanks boys.

chris

[billwill]

I wonder why it was beyond me to put a (gloved) hand on the exhaust manifold to see if the sound would change?
This working on old cars is humbling.
Yes, there is a manifold leak, at the top of the fourth cylinder.
This is going to be a tricky fix, as I cannot even seem to get a wrench (or socket) on those nuts.
Ok, but at least we isolated the problem.
Thanks boys.

chris

Slim socket wrench with a short extension bar is what you need.