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NA HLA Tick

Original Author: Phil Barnett (prb) - 2013

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Q) My valves make a ticking sound, what should I do?

A)
  • The ticking comes from your valve slapping the valve seat due to the HLA (Hydraulic Lash Adjuster) not being fully pumped up. This can be caused by quite a few things but by far the most common is that your engine oil and filter need to be changed. Many of us hear the ticking get worse when the oil starts to wear out or as the filter starts to flow less due to trapped particles. We use that signal to change our motor oil and filter if it happens before our normal change interval.
  • Your HLA's can cause tick from using the wrong weight of oil. What's the right weight you ask? Well, you'll have to experiment to find that. Every engine can be different. Some are quieter on synthetic vs traditional oil. Some are better with thicker oil, some are better with thinner oil.
  • Your oil filter might be clogged and reducing the flow to the top end of your engine causing minor oil starvation. You can help mitigate this by changing your filter more often. You can extend this interval by using the extended size oil filters recommended in the tune up parts page. Higher cost filters usually equate to higher quality and longer lasting filters. Purolator and Wix are preferred by many. Wix manufactures many aftermarket filters but there's no chart that I've found that tells which ones. NAPA sells Wix in most areas. The Wix 51356 may be the best filter made for our engines.
  • Your oil galleries might be plugged up reducing flow to the top of your engine causing minor or major oil starvation. Some engine treatments such as (in no preference) the 2Twisty flush, Sea Foam, Marvel Mystery Oil and Rislone (and many others) added to the oil can start dissolving that gunk and getting it out of the engine with the next oil change. Be aware that once you add an engine cleaning treatment that you'll need to change the oil within a few hundred miles. The more aggressive cleaners get the gunk dissolved and into the oil fairly quickly. I've seen oil change from clear to black in a couple of days. It might take several cleanings to really remove a lot of what's built up over the years.
  • You might have a collapsed HLA because it's faulty or gummed up. Some people have had success taking them apart, cleaning them, filling them with new oil and reassembling them. Others have had some success with replacing them entirely. Early HLA's had a smaller oil feed hole in the side. Later ones had larger feed holes. Some say changing to the larger ones can make a difference. That's an expensive path.
You're probably going to have to try all of these things in stubborn cases. I use Mobil 1 10w/30 and an extended filter and my HLA's are quiet pretty much all the time. Once in a while one sticks for a few seconds, then goes months between the next time. I don't worry about that.

If your HLA's only tick occasionally, you can ignore it. There's no damage going on, it's just annoying.

How does an HLA work?

Every HLA is fed by pressurized oil. There is a one way valve that lets oil in, but won't let it back out. This pressurized oil causes the HLA to expand to take up any slack between the cam lobe when it's not pushing down and the valve that is closed and against it's seat.

So if it's working properly, the back side of the cam lobe touches one side of the HLA and the center of the HLA is just touching the top of the valve stem. The oil pressure make them just touch.

Now, when the cam lobe comes around to push the valve open, it starts pressing down on the oil inside the HLA. When the pressure starts to rise, the one way valve shuts and won't let the oil back out. At this point, the lifter is essentially solid. Oil won't compress and it can't get out. Well, actually it's not true that it can't get out. Since the inner plunger is just well machined and sitting in the bore of the upper part of the HLA, a little bit of oil is constantly leaking out and runs down the valve stem. This tiny leak is not enough to collapse the lifter so the valve stem goes down when the cam lobe pushes from above.

So what can fail here?

  • The inner plunger might get stuck in it's bore. This causes the HLA to become a solid lifter that no longer automatically adjusts to take the slack out. If it's just the right length when it sticks, you now have a properly adjusted solid lifter. But if it sticks when it's too long, the valve can't close and it burns up. Or if it's too short, your valve is constantly slapping it's seat as it closes.
  • The one way valve can stick open. When the cam lobe comes around to press on the HLA, instead of the oil being trapped and becoming hard, it leaks out all the time the cam lobe is pressing down. This causes the HLA to lose thickness. If the leak is bad, the HLA loses enough thickness that the valve slaps the valve seat when the valve closes instead of being let down softly. You hear this as a tick each time that HLA lets the valve slap against it's seat in the head.
  • You might have inadequate oil pressure for the HLA to pump full. This can happen due to a clogged oil filter, a bad or bypassing oil pump. And if you've just had the head off, you can block the flow of oil to the head by putting the head gasket on backwards. When you do this it blocks all oil flow to the head. Caught too late, this wrecks the head.

A good HLA is full of oil and pressing the two halves together causes the one way valve to close. It then feels like a solid chunk of steel. If you can compress a lifter, it has air in it or the one way valve isn't preventing back flow.