Thread: hydraulic lifters always seem solid ???

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Hi MadMax,

I had my cylinder heads replaced on my '94 Ford Taurus V6, and afterwards the hobbyist mechanics couldn't get my car to start! They were desperate for two weeks. Today it turned out that the lifters were stuck in an extended position (i.e. hard with insufficient bleed-off), so that they kept all the new valves slightly open.

The solution was to remove the lifters, compress them carefully with a tool and make them "movable" again. I read a lot about this phenomenon today, and here is my understanding of why a lifter can eventually get stuck like that:

- Oil gunking up inside the lifter and limiting bleed-off
- High viscosity oil that bleeds slower

Interestingly, I also was running on a higher viscosity inexpensive oil, 10W-40 instead of 5W-40, because I thought it would protect the 130,000 mile engine better. I think that might have something to do with the fact that my lifters wouldn't bleed.

Another related phenomenon that I now understand is lifter "pump-up" at high rpm. It happened to me, too: When I tried to gun the engine, suddenly it would stall, falter, and recover over 5 seconds. That's because the lifters were starting to jump the camshaft, then they would expand to take up the slack, and keep the valves open. The engine stalls. 5 seconds of bleed-off were enough back then to collapse the lifters back down to operating size, but maybe only because the engine was warm, whereas my mechanics were trying to start a dead cold engine.

So my first suggestion is: Try and see if your engine stalls like that at high rpm, i.e. it needs several seconds to recover. This would indicate slow bleed-off! Then change the oil to a lower viscosity, higher quality oil. The lifters might then bleed faster, and the stalling will recover sooner. It's worth a try.


My second suggestion is to run synthetic oils or other cleaning agents (maybe Auto-RX, I'm gonna try it) to reduce oil gunking and remove, gradually, old gunk. If your oil has a tendency to gunk, and if it gunks inside your lifter, then they will definitely be stuck after 300 miles, leading to the exact described symptoms.

And finally, in my understanding the main advantage of hydraulic lifters is that they are self-adjusting. They can expand quickly, and bleed back down slowly. Until they gunk up - then they only expand and no longer auto-adjust in both directions. A really gunked up lifter might also not expand at all, and you'll end up with a rattling valve train.

So in conclusion, this is how a good hydraulic lifter should feel:

- Stiff, but with slow and noticeable bleed-off when it's filled with oil
- If you empty it, the now air-filled lifter should compress easily and freely against its internal spring and snap back immediately
- Once you reinstall the lifter, it will take a few seconds of cranking to fill it with new oil, but usually you don't need to do this manually beforehand - it seems these things fill themselves relatively quickly. Anyway, while the lifters expand and fill, the engine will stutter due to poorly operating valves, but after a minute or two it should run smooth and round. No clicking should be heard, and now the lifters should have eliminated all play and attained the proper length.

Sebastian