Are you sure its abnormal?

I've never had that engine, so I wouldn't know, but it doesn't sound obviously broken to me.

I suppose if there is an abnormal "popping noise" it could be valve clearance, wear or sticking perhaps allowing some compression/combustion to escape into the intake.

Compression test might be informative, but not generally a DIY proposition on a diesel.

If I'm reading this right these do not have hydraulic tappets but use bucket and shim, but allegedly they are not a huge PITA to do.

www.matthewsvolvosite.com/forums/viewtopic.php?t=4...4

If I'm reading it wrong and they do use hydraulic tappets, could be one or more of yours is clogged and you need an oil change

Alternatively, if its a turbo, which I suppose recentish diesels usually are, perhaps a boost leak?

I dunno if there is enough boost at idle to leak, but if it was that it should get worse at higher power.

Edited by edlithgow on 28/11/2021 at 17:05

"Can we confirm its leaking compression? How could I check which cylinder it is from"

You cannot confirm leaking compression without doing a compression test.

Compression tester sets for diesels are not expensive.

www.amazon.co.uk/DHA-Diesel-Engine-Compression-100...=

Try to get a set that can use glow plug adaptors to avoid the pain of removing injectors.

Make sure the battery is fully charged,

Run the engine so it is at working temperature,

Disable the injectors by removing the electrical connections to stop the engine starting while you are doing the compression test.

Crank the engine until the highest pressure is shown on the gauge for each cylinder.

Don't expect to achieve the compression test figures quoted in a workshop manual, in my experience it's unlikely, even with a brand new engine straight out of the crate.

Remember - you are doing a comparative test to find if one cylinder has a low reading.

Best of luck!

It took a long while for me to work back on the intake removal.

I've got a serious problem. On the exhaust side, one in the pair of 5th cylinder lifters is broken and it has sheared off the lifter hole - yellow arrow in the pic. Red arrow one is the good one in that pair. So that exhaust valve is closed permanently

I searched for the broken pieces in the entire area, including intake side but no single piece was found! I have to replace the cylinder head.

I've got a pic but can't see an option to upload

Some further concerns/questions

(a) Whence cometh your popping noise?

IF there are 2 exhaust valves/cylinder (?) it might just be more violent exhausting via half the usual port area. and not of concern

OTOH, if there is only 1 exhaust valve/cylinder (I don't know this engine) if the exhaust is permanently closed and not leaking, the noise might be "backfiring" of the un-exhausted gases into the intake tract. Seems likely that you wont get a very good "burn" after the first bang. since the cylinder will probably have more residual exhaust gases so wont get as much of a charge. This might limit the potential for damage, but I'd still want to check the turbo impeller blades and such.

A third (though I think less likely) popping possibility is that something had to give. This wont matter if you've got a cracked head or gasket since you'll be replacing those, but you'd be annoyed if it turned out your block was damaged.

(b) Why did this happen?

Casting defects aside, the obvious cause for this kind of damage ((if this is an interference engine(?)) is valve timing error causing the piston top to clout the valve head, though it might be expected to affect more than one valve.

You will be able to check for valve and piston top damage (better check the lot, and also the cams if not replacing) when you take off the head. You should also check the valve timing, though I suppose you'll be doing that anyway.

I don’t know if this is a VVT engine or if VVT is capable of generating this sort of error transiently, but that might be worth looking in to

Morning all. Car still not working. I've been checking one by one everyday and Today's update....

https://youtu.be/aFz4gaPUuvk

In this video I'm checking the SCV connected to the pump. SCV gets closed when ignition ON and very small amount of air getting to plunger side. Is this how SCV should work?

I'd highly appreciate if you could advise me on this

Thanks

Edited by zakmuh on 02/01/2022 at 10:33