Strange noise from me old Fiesta.

Oil pump pressure relief valve?

That's a ball bearing with a spring.

Yes, I can imagine that. Good idea.

I believe there can be an issue with sticking valves on fiesta engines, that could cause a clack till it warms up a little and unsticks itself. Probable cause is lack of correct oil changes and supermarket petrol.

Supermarket petrol is no different from that bought at petrol company owned filling stations - just cheaper.

Hydraulic tappet being a bit slow to ?pump up?? That would vary with engine speed though...

Tim

IIRC they are shimmed in solid buckets.

The base probably is, but the additives are what makes the difference.

The oil is old in age (a few years), but not in mileage (the thing only does a couple of miles a week). I'll change it soon, though. I run it on Shell V-Power (like I say, it's low mileage so it's a luxury I can afford), because I think it reduces the pinking that it tends to do under high-ish load.

Yes, I wish to God it had hydraulic tappets, but no. Flipping shims.

Oil has to be changed at age as well as miles. The only oil that isn't true for are preservative oils as used by the military to store vehicles. That has limited running time / mileage (~ 50 miles IIRC) after which it's just a normal oil.

Low miles and failing to fully warm up the engine means the oil accumulates much more water than a car that's run. Most blow-by is during start up before the pistons warm and expand.

When it's not running it's still absorbing water as condensation forms on the block wall and runs down in to oil. Lots of unused classic cars have had the bottom drop off the sump when it's rotted off from the water at the bottom of the sump that the oil is floating on.