C8 2.2HDi really hates hills - turbo or DPF issue perhaps?

[MattBLancs]

Bad news for me, unfortunately, I think. The garage has discovered that smoke pumped into the inlet, with the engine off, comes out of the dip stick. I guess the piston rings don't seal especially well at low pressure, but I'd not expect a particularly quick leak that way.

That's an interesting test, I've not heard of that being done before! What are they generating the smoke with?

I'm surprised any meaningful amount of smoke pushed into the inlet could appear at dipstick without massive internal engine problem (like a piston with a hole in it!!)

Actually! Brain has clunked into action now:

PCV positive crankcase ventilation = that is a route between inlet manifold pipework (normally pre turbo inlet, low pressure side of inlet) and the crankcase, via the (large unrestricted oil drain routes through the head)

I'd be pretty confident you/they were detecting a failed PCV valve (normally a diaphragm on the connection on cylinder head) providing a route to the dipstick.

Blank that off (normally 19 to 25mm rubber hose between inlet and cylinder head cover) and see if smoke disappears would be my suggestion.

Especially ahead of:

It sounds like a reconditioned engine - which is almost certainly too expensive. Anyone able to offer me any hope that we're missing something?

EDIT: There is a doubt in my mind - if you pump smoke into the inlet, it's got to come out somewhere... And if the only path is past the one (probably) open inlet valve into an otherwise-sealed cylinder - that's pretty much got to be past the piston rings. Presumably the piston rings naturally seal better when the cylinder is in motion.

As above, leaky rings would still be a very small route for this smoke to travel through

[darbuck]

The only way to test bad piston rings is a compression test a smoke test is for vacuum leaks. As Matt eluded to earlier pcv valve will allow smoke out of the dip stick. I would be going elsewhere for testing.

[darbuck]

Just because it doesn't have a sensor for the fuel cap doesn't mean a bad one won't affect running.it could be causing a vacuums leak which the car is detecting with a different sensor such as on the low pressure fuel pump differential pressure or something along them lines. It can cause an issue on any car. Have you checked your fuel filter for water a lot of these types of problems can be from unexpected sources. It sounds more like a fueling issue to me. I would change fuel filter, throw a fiver of kerosene or a double dose of dipethane in the tank and change the fuel cap. All of these will fix a lot of problems. How many miles have you put on the car ? when were the glow plugs changed if ever?If more than 100,000? I would be looking at changing them, warm the engine up first and spray with penetrating fluid of some description leave them sit and then carefully extract them. You need to start methodically eliminating systems before spending money on bigger jobs.

[tearing hair out]

I've never noticed any suggestion of vacuum in the tank when removing the fuel cap and it's had a replacement fuel filter (which wasn't very old anyway, but it's cheap). Glow plugs - as far as I know they are original and almost 150,000 miles old. I suspect they are almost impossible to access - like pretty much everything else on the top of a C8 engine.

[darbuck]

Well if they are in there that long chances are they need changing, it might not be noticeable to you but it could upset the ecu its part of the emissions system in the car. As I said earlier elimination.

[Rp0thejester]

I remember taking out glow plugs from diesels at the garage and putting them in a 'sonic bath' never understood why. It was basically water, brake cleaner and washing up liquid vibrating with the glow plugs dangled into it. Only way to clean them I suppose

[MH123456]

I've had similar experience of DPF related problems in a Ford Focus 1.6 TDCi. It was the PSA engine and the DPF faults came up early on after buying, so I would force regens using Forscan. The tank empty fault also came up, so refilled to overflowing with around 200 ml Eyolys fluid and reset the counters which solved that problem - looks like the previous owner had refilled without resetting. The problem was it was failing regens, luckily this was traced to one glow plug. As mentioned previously only one needs to be bad to make them all look bad. Test each one for continuity with a multi meter without taking them out. Replacing one is better than all, you can replace the others later after eliminating all the other culprits. The DPF finally wouldn't do a forced regen, so I took it off and like others, back-flushed it with the hose for several hours, refitted (without too much drying in my case, since this just came out as steam in normal operation) which solved the problem temporarily. Remember the soot and other deposits when mixed with water can turn into a cement like compound, so make sure you keep shaking it throughout the process and reverse flush first. The main culprit for eventual engine failure was the fuel cap sensor - the magnet was there but I suspect the sensor was bad. After several forced regens and some attempted auto regens without notification from the filler sensor that the tank had been filled, the extra diesel used had washed the small end bearings causing the tappets to eventually fail.

I'm sure you can get after-market replacements for the fuel filler sensor to retrofit to the loom for the DPF fluid tank. The filler cap always showed the same state regardless of position but it doesn't throw an error, so no DPF fluid was being added to the fuel and normal regens were unsuccessful regardless of being completed, resulting in engine damage. Forced regens would be more successful as they're more aggressive but again with the same final outcome.

[darbuck]

Why would you only replace one glow plug if one is bad the rest will go out in sympathy if you change one the ECU will see the difference and throw a fault, apart from anything else you are already in there finish the job. I treat them like spark plugs you wouldn't just change one. If the control unit is faulty go new second hand could be worse than the one you take out . The glow plugs should be replaced every 100k minimum anyway.
"The filler cap always showed the same state regardless of position but it doesn't throw an error, so no DPF fluid was being added to the fuel and normal regens were unsuccessful regardless of being completed, resulting in engine damage".

Did you ever try changing the fuel cap because they can cause issues if they are faulty.

[Rp0thejester]

As long as glow plugs are cleaned why replace every 100k minimum? If it ain't broke, don't fix it

[darbuck]

Because the internals fail and lead to the problems the OP is having and no start in cold weather.no amount of cleaning can fix a broken resistor which is essentially what they are.

[Rp0thejester]

Can you quote who is having cold start problems please? I must have missed something

[darbuck]

I am just saying bad glow plugs can lead to cold start.my point was preventative maintenance reduces break downs.

[Rp0thejester]

Okay, I got you. Yes prevention is better than cure (2 kids later). Unfortunately I don't think DPF or Turbo issues can be prevented, unless driving an electric vehicle

[darbuck]

Poor maintenance, constant low speed driving ,city driving, will kill a dpf faster but the glow plugs as previously stated by someone else if they fail can reduce the efficacy of the regen so can bad injectors ,wrong oil to name a few.How many people do you know ignore an EML for months and then complain when the car packs up. I am not saying this is what happened here some times you can be unlucky I can attest to that myself as you Know from my own threads you have posted on.

[tearing hair out]

I'll have a chat with the garage on Monday about compression testing and glow plugs. I suspect the glow plugs are pretty inaccessible - I think they are on the exhaust side of the cylinder head which has a metal bodywork panel on top of it - which is possibly why no-one with a C8 would voluntarily replace their glowplugs. Or, for that matter, the EGR valve.

I'm not even sure that it has wiring for a fuel cap sensor, if that model isn't suppose to have a sensor. But then, I don't understand why its complaining about a missing one in that case either. And I guess potentially running it with the fuel cap off (assuming the fuel isn't full) might be a way to eliminate the cap ventilation not working.

I did find a post saying that they were having performance issue on their C8 and it turned out to be a badly adjusted accelerator cable. I'm crossing my fingers for that one!

(And no EML at all, at any point, for me to ignore. Not even now when it's clearly sick.)