My darling 4.6 has started to tap quick loudly, it sounds top end and changes with engine speed. IT’s intermittent but more often than not now. It’s when the engine is at temperature and not cold. It goes away briefly with light throttle and heavy throttle, but not medium throttle and I can hear it until the wind noise overwhelms my hearing!

Is this the dreaded slipping liner??? And is that the end of the engine and heads if so?

I’ve replaced cam followers and cam within the last 3 years.

I use decent oil and change frequently….

Thoughts?

Well I would have gone with lifters until I read you replaced them...

Liners slipping can be more of a knock than a tap ... but that's not definitive.,,,
Lots of examples on YT for comparison, eg: https://www.youtube.com/watch?v=UOblANah7Vo

( Pretty sure it's not Greta Garbo though )

grab a long screw driver and have a prod around the engine ,just put it on the surfaces and on your ear , you will hear any noise that is in there. you may need someone to rev the engine for you .

Thanks.

I have a proper mechanics stethoscope somewhere…

Could be the oil pressure a bit low ? Just take the pressure switch out & use a gauge to check it.

Cam & followers should be ok, but some do fail early. Definitely use the stethoscope to see if the noise is top, middle or bottom. Maybe take the rocker covers off & measure rocker gaps ?

I’ve been pulling it apart looking for this noise. Cannot find anything that looks amiss. All lifters are firm, plenty of oil everywhere and stethoscope doesn’t reveal tapping in the block (or top really) just sounds like everywhere when it happens.

It’s more frequent now, every journey. Starts soft and gets louder the hotter the engine gets/longer it runs for.

What other symptoms would I have if a liner was slipping? Does it ultimately result in a breakdown?

If a liner was slipping you'd be pressurising the cooling system. Does it sound louder from underneath the car? I've had a tapping noise from mine since I bought it at 205k and decided it was probably a cam follower, changed them and it made no difference. At 287k I had the engine rebuilt and it was still there but while doing something else realised it was sounding louder under the car like it was coming from the bellhousing. Decided it must be the torque converter but that was replaced, along with the flex plate, when I changed my gearbox about a year ago at 454k and the tapping is still there. With the lower cover off the flywheel (separate on a GEMS but part of the sump on a Thor) and the engine running, it looks like the toothed ring for the crank position sensor is fractionally offset so it could be one tooth on that just touching the crank position sensor as it turns. I've had a good look at it and none of the teeth looked 'shiny' like they had touching anything, they are all dead straight and the gap is perfect on all and there are no witness marks on the crank position sensor either. It sounds louder when hot but has never got any worse or better, so I just ignore it. It would be nice if it wasn't there though.....

Maybe I should just ignore it and enjoy the radio???

Mine is only there at idle and sounds horrible when I pull up at passport control when I'm getting on a ferry as it reflects off the side of the booth and the engine is nice and hot then. Give it a bit of revs and it goes away. I can just hear it from outside the car when started from cold and louder when warm but, as I say, it has always been there, never got better or worse. If I get an excuse to separate the engine from the gearbox again, I'll probably replace the flywheel and if it is still there then I really have no idea where it is coming from.

The spare also does it but to a much lesser extent and I've heard a similar noise from others too.

j_rov: Then perhaps it is GG after all ? https://www.youtube.com/watch?v=ilmOHfnIpFI

Seriously I swear with these things that once we hear them we become convinced and focus on them ?
And after changing things we are quite convinced are causing the problem it makes them louder too (?!)

Once with such a ticking (although not a p38) using (slightly) thicker oil 'solved' the problem... temporarily:
Accordingly I then earned to live with it and nothing unpleasant happened (yet) !

It’s definitely louder at the bottom, but doesn’t sound like big ends to me…

Is it one tap per revolution? If it isn't peeing it down tomorrow, I'll get under mine and see if I can record the noise I have.

I reckon it's one tap per rev yes.