I can hear a tapping noise from my engine, and cannot get a straight answer from my mechanic except that if it "bothers " me, he can do a valve adjustment for $200. The only thing that bothers me is if it is a warning that my engine is in trouble. Yes, it has been using more oil, but I check it regularly and it has never been really low; just an occasional half pint is needed. Can anyone explain whether this noise is a harbinger of doom or not?

First go and buy a bottle of Sea Foam and use the recommended amount in you Crankcase oil. My 1987 was doing the same tapping noise until I added Sea Foam. . I still want to do the Valves Shim adjustment on mine. So try the Sea Foam first because after so many heat soaks that our engines have done with the high mileage,varnish build up from the oil makes for noisy lifter hydraulics. Your Valve Train will love it.

Side benefit: when you're slurping the other third into the intake and the engine stumbles, you'll see if come out your leaky exhaust manifold gaskets. Good times.

The CHECK ENGINE indicator is illuminated on the dash? Or is it the SERVICE light (oil change reminder)?

How many miles?

Is the tapping noise new?

Adjust the valve clearances? Seriously? The repair technician or shop as access to valve adjusting shims? The same shop you are having troubles with?

A high note tickety-tickety that persists as the engine warms is very likely valve train noise. From the factory there were rubber engine hushers that embrittle and at essence get ground away.

Select and copy URL and past into new browser tab or window:

https://www.volvoclub.org.uk/faq/ValveTrainMainenance/ValveTrainMaintenance.html

Or here on the brickboard FAQ:

https://www.brickboard.com/FAQ/700-900/EngineMechanical.htm#ValveStemTipRubberSeals

Using a section of dowel or mechanic stethoscope, locate the sound at the top of the engine.

Piston slap is already treated for you here. Your low-friction engine may have piston slap, where the piston skirt contacts the cylinder wall. As the engine heats, the sound should abate. More of a slappy tockity sound that is louder in a cold engine where you accelerate harder.

There may be wear yet unlikely at the top of the connecting rod / piston inbterface. The other issue in oil loss is wear at the crankshaft. That is a lower tone knocking sound that changes little between cold and warmed engine. The tone of the knock can change as you accelerate or coast.

It may help if you could record video, and that the microphone / audio pickup & processing allows a quality sound recording. Upload and link or share the link to some sort of site that allows video to be posted so you can set a link for us to hear.

Questions?

Hope that helps.
--
Jonathan Harshman Winters III: The Mightiest, Greatest, & Most Powerful North American Comedian & Comedic Actor in Perpetuity

So the "tapping" noise I was hearing has been diagnosed by a real Volvo mechanic (150 miles away; I used to go to him) as exhaust manifold gaskets needing replacement. It'll cost upwards of $800. so I'd love to learn more about how serious this issue is... Been told "annoying but not serious" to "could lose your engine". Any education on this would help. And yes it's a turbo. (250k miles 740 sw 1988)

If exhaust is leaking at one or more of the exhaust manifold to cylinder head there is a tut-tut-tut sound. There may be a streak of exhaust stuff.

When the engine is cold, you can use a dish detergent mix and spray the gaskets. An assistant can start the engine and where you see bubbles is where the leak is.

However, I'm unsure, without hearing your engine using a recording device, like a mobile phone, with good sound transduction, to record and provide link here, whether the exhaust leak is the "tapping" noise.

Else, you can try to locate the an internal tapping sound using methods I described in my prior response to you.

96$ hourly. I guess that is compensation for rapid and forced US dollar devaluation by the oligarchs that rule the good ol' Yoo Ess Aaaaaaayyyyy, Fonzie. Ha!

Questions?

Hope that helps.
--
Jonathan Harshman Winters III: The Mightiest, Greatest, & Most Powerful North American Comedian & Comedic Actor in Perpetuity

Adjusting the valve clearance in a b230f is more involved than simply checking to see if the clearance is within specs.

You can carefully remove the cam cover and check the clearance with a feelers gauge. You might find that one (or more) are enough out of adjustment to produce that noise you hear. If they are close there would be no need to move ahead with an adjustment, and it would remove one possible source of the noise.

Piston slap is another source of the type of noise you could be hearing. Less critical than rods knocking at the crankshaft but annoying for sure. It is produced by wear at the wrist pin.

Many of us have experienced piston slap in these engines, but for the most part we live with it. Diving in deep enough to address piston slap can be very expensive and they can run a long time by simply living with it.

Randy

--
Any twenty minute job is just a broken bolt away from a three day ordeal

+1
On piston slap. A common source of noise with these engines as they age. Often quiets down once the engine is fully warm. How many miles on your engine?
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Will I buy another Volvo??? We'll see....

"Can anyone explain...."

No, not with certainty. At least not with the information you've provided thus far. And even with more info from you, diagnosing something like this successfully via the internet is a shot in the dark. We're all guessing.

Does the 'tapping' vary with engine speed? Does the sound change when the engine is cold started vs. running fully warmed up? Does the sound change when you're accelerating vs. decelerating? Does the sound change when the engine is under load vs. not under load?
"Change" could mean the volume of the noise, the tone/quality of the noise, etc. "Tapping" could describe the marbles-rattling-around-in-a-can sound of detonation. It could be the deeper, more ominous sound of rod knock due to a rod bearing having spun (or being worn out). It could be the lighter 'ticking' of the valve lash being too big. It could be the slightly more ominous sound of a cam lobe/lifter being worn beyond proper tolerances. Some of those are repairable pretty easily; others, more troublesome/terminal/expensive. My dad hit a piece of debris in the road once, and afterwards the engine was making a "tapping" noise. It varied with engine speed. Turned out that a small inspection plate on the bottom of the bell housing had been bent so that the flywheel/starter teeth were lightly hitting it when the engine was running. He loosed the one bolt that held the plate in, bent the plate back to "straight" eliminating the contact with the flywheel, and the noise stopped. No harm, no foul. 10 minutes of repair time. It could be something like that. My daughter's 760 wagon had a "tapping" noise. Turned out that the motor mounts had worn out allowing the engine to sag so that the fan was hitting the shroud, cracking it. New motor/tranny mounts and a minor repair to the plastic shroud. No more tapping. It could be something like that. Or, you could have a rod/crank bearing that has let go. Or valves that need adjusting.

Your best bet is -- a mechanic you trust. If your mechanic has heard the noise and thinks the valves need to be adjusted, I can only think you're asking us here because you don't trust the mechanic. My counsel is find a competent mechanic you trust and follow his/her lead. Good luck - hoping for an inexpensive fix.