Peugeot 308 CC - Falling apart now?

[RichardW]

Sounds like a GRQ (get rid quick!) car....

I suspect that you need to run it on the best petrol you can, possibly use an additive in the tank, oh, and drive it like you stole it! Quite possible that these sorts of problems are caused by pootling about in them - I remember hearing about some Jag engines which suffered with coking up (60's? maybe). Turned out they had been thrashed mercilessly during development and were OK, but then when put in Jags, which are often driven wafto style, and never worked hard, they quickly gummed up.

[CitroJim]

XUD diesels hate being pootled about so I reckon you may be on to something there Richard

[bobins]

I've come to the conclusion that the best way to get my auto-adjusting clutch on my X7 to auto-adjust, is to occasionally thrash the nuts off of it. Seems to have worked so far

[DHallworth]

The problem with the THP engine is that it's direct injection. That's really the route cause of the problem as there's no petrol coming in from behind the valve to keep it clean.

There's a specialist in the UK that has a theory that because the oil used in them is so thin it leaks past the valve stem seals and solidifies on the back of the valves.

If you Google it there's some pretty horrific before and after pictures.

Jamie @ SP Tuning in Hinckley reckons that in the UK they need doing every 30k miles.

David.

[CitroJim]

That's utter madness Peugeot should immediately withdraw this engine and compensate all unfortunate owners forthwith...

How could such a maker as PSA make such a fundamental error? Did they never learn from their (and others) earlier attempts at a direct injection petrol engine?

As George Santayana said "Those who cannot remember the past are condemned to repeat it.”

[xantia_v6]

It is puzzling that no-one seems to have (or release) any meaningful statistics about the issues with these engines. There has been a lot written on forums, particularly regarding the Mini in the USA, but very little credible information.

I am inclined to believe that in most cases, the carbon build-up is caused by PCV fumes (rather than oil from the valve stems, or combustion gasses escaping during valve overlap). The Peugeot dealer told me that late-spec engines have far fewer warranty claims than early engines did, and later engines did have a revised PCV system (the parts to upgrade this are outrageously expensive). I have also read reports that the PCV non return valves can fail, if the one at the turbo outlet failed, it would pressurise the crankcase and blow copious oil vapour into the turbo intake, causing rapid carbon build up.

Most folklore says that fitting an oil vapour catch tank eliminates the problem, but who to believe? I am tempted to fit an oil vapour catch tank, but that is made complicated by the design of the PCV system which has 2 different routes for on and off boost, and credible reports that some vapour separators ore only 25% effective, so a waste of money.

I will do some more reading.

[CitroJim]

PCV fumes make a lot of sense Mike... You only have to look at any XU or XUD/HDi engine to see just how much oil they pass into the inlet tract via PCV...

Hopefully a catch-tank and a bit of effective filtering on the PCV line will help a lot...

I will be interested to hear the results of your further research

[wurlycorner]

That's awful reliability... What on earth is it that's causing such problems on these particular engines?
Presumably consumable things like brake disc/pad renewal etc don't count towards fdsh, just the core service items (e.g. planned servicing of engine related stuff)? If so, sounds like it's worth sticking with dealer servicing on this car, for the extended warranty on something that will clearly need doing again while you still have the car!

[demag]

I'm a bit confused by this. So is this walnut blasting done with the head on, and if so how?

Sent from my Wileyfox Swift using Tapatalk

[wurlycorner]

Not the best of videos (typical modern video shot by someone that thinks filming everything as a pan shot and then editing with fast swaps between one view and another will make it look 'professional', when actually what it means is that you never actually get to see what's going on) but...
Tim will show you how:

[xantia_v6]

It seems that for this application a coalescing vapour separator is best, eg a http://www.westernfilters.net.au/proven ... 931070793/ or a http://www.rxperformanceproducts.com/pr ... h_can_kit/ Some catch cans don't have any separating element other than air and gravity, some just have baffles, some have a filter element that soon gets saturated and ceases to function.

The 2007 - 2011 THP engine has 2 PCV circuits which (broadly speaking) operate independently on boost and off boost. From 2012, the off boost PCV was deleted, apparently reducing the carbon build-up on the valves, but meaning that all PCV vapours go through the turbocharger.

Deleting the off-boost PCV seems to be a common modification on the earlier engines, but it is not clear what the side effects are. If fitting an external vapour separator, it is not clear whether the dual circuit is necessary at all (it complicates the plumbing), I suspect not.

I am still confused.

[xantia_v6]

After spending a few weeks gathering the required parts, I have now modified the crankcase ventilation system on this car. I will do a better write-up of the procedure with pictures later.

I fitted a vapour separator in the the PCV line from the engine top cover to the turbo inlet, running the condensate into a sealed container. With just this modification (and the other PCV line unmodified), running the car for about 200 km produced not a drop of oil in the catch tank, so it is pretty clear where the oil fumes don't go.

On receiving some blanking caps for the other PCV line, I have now blanked it off, so that all crankcase fumes must now go through the vapour separator. The first run we did was a 160 km round trip to Akaroa, which includes some significant hill climbing in each direction. On this trip, the new oil catch tank collected about 0.5 cc of clean engine oil. If you extrapolate that out for the period of an engine oil change, then that is quite a bit of oil that is no longer going to be hitting the inlet valves.

The really interesting thing however, is that the engine now behaves quite differently. The engine previously had a characteristic like turbo lag, if you accelerated briskly from rest, there would be a half a second or so of disappointing acceleration before a sudden surge of acceleration, that has now gone and the car accelerates smoothly. There was also a random surging sensation when driving uphill, as if the ECU was hunting to find the right parameters for the engine. That has also gone. The cruising fuel economy seems to have improved by about 15%.

The explanation I have for all of this is that there has been an air leak into the crankcase (probably through the check valve in the PCV path to the turbo intake), and this has caused air to be drawn though the crankcase and PCV system into the inlet manifold. The extra air flow through the crankcase would have been picking up oil vapour, probably causing the excessive carbon build-up in this engine. Additionally, as the manifold PCV path exits into the manifold runner for cylinder 4, this cylinder would have been getting extra air and running lean. The exhaust oxygen sensor effectively measures the mixture in the leanest cylinder, so the ECU will have been increasing the fuelling to all 4 cylinders to get the mixture correct in cylinder 4. Generally the ECU has struggled to keep the engine parameters under control.

So, it seems that blanking off a PCV path is the best modification that could be done to this car.

[CitroJim]

Mike, excellent This is looking very promising....

[xantia_v6]

The 308 CC is in the naughty corner again...

This morning after driving about 50 metres it threw a Battery Charging / Electrical System fault, followed by an Engine Fault / Repair Needed.

A voltmeter check showed that the battery voltage was OK stopped and running. I connected Diagbox and found a number of fault codes, some related to me inadvertently filling up with 91 RON fuel, triggering every engine knock code that exists, for every cylinder.

There were also a few other intermittent/phantom faults that I will ignore for now.

More interesting were BSI faults:
F55A "Supplies Protection and Management Fault : central power switch positive supply relay detected open while the main relay is active" and
F56B " Fault Supply Protection and Management Unit : lack of coherence between the status of the key and the status of the main supply relay following the switching off of ignition"

Not sure if these are real or not.

The Engine Management ECU had permanent fault codes P0693 and P0691 (both "Fan Unit"), which gave the first real clues to diagnose. After locating the fan controller fuse (F21, 5A), I found that it was blown, and fitting another, it blew immediately on starting the engine.

The fuse location guide indicated that this fuse also supplies the "turbo cooling", which a bit of googling informed me is an electric water pump for cooling the turbocharger (including?) after engine switch off. Disconnecting this pump stopped the fuse b;owing and eliminated the permanent fault codes (although the engine ECU notices that it is missing).

I have a new pump on order from a local Mini parts specialist, it should be here in a day or two.

Interestingly, there was a recall of all Minis and BMWs with turbocharged prince engines to replace this pump, as it was possible for them to catch fire when they (regularly) failed. PSA fitted a 5A fuse so they didn't catch fire, so no recall, and owners have to pay for the replacements..

[elma]

Wow, Louises car definitely likes to keep you busy. Lets hope the new pump cheers it up somewhat.