Has the time finally come for a DS3 Racing engine rebuild??

[notrix]

Hi guys!

I have a MY2012 Citroen DS3 Racing which has done 50k km. or about 30k miles. For years I have been living in fear of the inevitable THP engine "blow-up" and it now seems like the time has finally come

Lately I've been experiencing rough idle and occasional blue smoke from the tailpipe during hard acceleration. The oil comsumption has also suddenly increased by quite a bit. Yesterday I was doing an oil change when I immediately noticed a strong smell of petrol as I was draining the oil. The viscosity of the oil also seemed lower than usual. After a search on Google on how petrol could possibly have gotten into the oil I quickly realised it could be a sign of a very serious problem with the engine. My initial thoughs are worn piston rings, cracked ring lands or broken pistons. However the car runs fine except for rough idle and maybe a little down on power. The EML is not lit and have never been. Also there are no faults stored in the ECU (checked with DiagBox). So.. what should I do next to diagnose this further? Could it be something less serious or am I possibly looking at a full engine rebuild?

The symptoms I've noticed are;
- Occasional blue smoke from the exhaust while accelerating.
- Rough idle - "popping sound" from the exhaust like a misfire.
- Petrol smell from the oil and dipstick.
- Unusally high oil comsumption.

What I've checked so far;
- ECU faults - none detected.
- Twisting off the oil filler cap checking for vacuum - vacuum seems fine sucking the filler cap against the rocker cover.

Appreciate any tips or hints on what to do next.. cheers guys

[myglaren]

This may be too simplistic and vague as it isn't something I have ever confronted, having diesels for so long, but at least some cars had a petrol vapour purge cannister that accumulated petrol vapour and discharged it - presumably into the inlet manifold, at some predetermined time.
I wonder if something has gone horribly wrong with yours, if it actually has one or something similar and fuel is somehow getting into the oil.

Welcome to the FCF

[xantia_v6]

I presume that you have not modified the crankcase breather system, so still have the rear breather pipe from the top cover into the manifold. This pipe can carry a lot of oil vapour, and could be the primary cause of your blue smoke, and even the rough idle, especially if the PCV valve in the engine top cover has failed. Try running the engine with the rear breather pipe blocked off and see if the symptoms change.

I don't think that this would explain (apparently) petrol getting into the oil, but I would suggest that you need a compression or leak-down test to check the condition of the cylinder and rings.

[notrix]

This may be too simplistic and vague as it isn't something I have ever confronted, having diesels for so long, but at least some cars had a petrol vapour purge cannister that accumulated petrol vapour and discharged it - presumably into the inlet manifold, at some predetermined time.
I wonder if something has gone horribly wrong with yours, if it actually has one or something similar and fuel is somehow getting into the oil.

Welcome to the FCF

There is indeed a charcoal cannister and a purge pipe connected to the air intake before the turbo. I have inspected the pipe and there is no visible fuel in it, neither any obvious fumes from it. However.. I should probably check to see if the purge valve could be faulty. Could it be that if the cannister is full and the purge valve not functioning fuel could get back into the intake manifold?

[xantia_v6]

There should never be any liquid fuel in the purge canister, it receives vapour from the tank which is stored in charcoal granules in the canister and then released as vapour into the the manifold when the engine is running, but at a rate (governed by the size of the valves and hoses) that prevents any change to normal engine operation.

[notrix]

I presume that you have not modified the crankcase breather system, so still have the rear breather pipe from the top cover into the manifold. This pipe can carry a lot of oil vapour, and could be the primary cause of your blue smoke, and even the rough idle, especially if the PCV valve in the engine top cover has failed. Try running the engine with the rear breather pipe blocked off and see if the symptoms change.

I don't think that this would explain (apparently) petrol getting into the oil, but I would suggest that you need a compression or leak-down test to check the condition of the cylinder and rings.

I bought a dual catch can system but unfortunately it's still lying on the shelf.. I was thinking maybe the PCV system could be at fault but as you say I wouldn't suspect it beeing the reason for petrol getting into the oil.

[notrix]

There should never be any liquid fuel in the purge canister, it receives vapour from the tank which is stored in charcoal granules in the canister and then released as vapour into the the manifold when the engine is running, but at a rate (governed by the size of the valves and hoses) that prevents any change to normal engine operation.

Right.. so I got it all backwards then.. the pipe connected to the air intake is used for drawing air through the cannister to purge the fumes into the intake manifold?

[notrix]

I took a cheap borescope down the plug hole to inspect the top of the pistons. The picture quality was pretty bad so it was kinda difficult to see but it seems like there is a lot of carbon build up. Really no surprise there given how bad these engines are in that regard hence why I wanted to install a catch can system. But it got me thinking maybe the piston rings are not worn merely stuck or not sealing properly due to carbon build up. Next up I'm gonna do a compression test to see if there are any obvious pressure leaks in any of the cylinders. Is there any way to clean the pistons and piston rings without dismantling the whole engine?

[notrix]

So I did a compression test today.. I got about 185psi or just shy of 13bar across all the cylinders.. seems a bit high heh??

[mickthemaverick]

Hi, I have just read your thread for the first time and can offer the following. Excluding an incorrect engine build which would have given high compression from the beginning, there are three elements to compression.1) The volume of the combustion chamber, 2) the travel of the piston, 3) the seal of the valves and rings. Assuming the piston travel is as built or you would have knocking from the con rods then the most likely cause is a reduction in chamber volume caused either by carbon build up or head skimming. Again assuming the head is original then the first thing I would try is to use an appropriate fuel additive to try to clear the carbon. If you get a noticeable reduction in compression then I would have the head off and give it a good going over. As to the petrol in the oil, apart from the suggestions already mentioned, there may be an over fuelling combined with high compression causing mixture to leak past the rings during the compression stroke. I have never come across that myself but it was an issue in some of the early cooper racing engines in the 1950s so worth a mention! good luck and keep us posted.

[notrix]

Hi. Thank you for your thoughts and suggestions. They are pretty much in line with what I'm thinking now.. gonna try and find some good cleaners/additives to see if that helps with either of the issues. I'm also tempted to go ahead and change the spark plugs and coils to see if the misfires go away.

[mickthemaverick]

That would make sense but I'd run the additive first to start from the cheapest and work upwards. If the carbon is the source of the problem cleaning the plugs will almost certainly suffice and new coilpacks will be an unnecessary expense at this stage.

[Hell Razor5543]

Something that can also help (I do not have personal experience of it, but I know another forum member did this and got a noticeable improvement in performance) is getting the engine "shelled". This is using walnut shell fragments to, in effect, sandblast the engine but (because the shells are softer than sand) it takes of any buildup of dirt without also damaging the metal. You can do a Google search about it, and here is one article;

https://www.azom.com/article.aspx?ArticleID=10431

Here is the link to the forum member who had it done;

https://www.frenchcarforum.co.uk/forum/ ... 7&start=45

[notrix]

Something that can also help (I do not have personal experience of it, but I know another forum member did this and got a noticeable improvement in performance) is getting the engine "shelled". This is using walnut shell fragments to, in effect, sandblast the engine but (because the shells are softer than sand) it takes of any buildup of dirt without also damaging the metal. You can do a Google search about it, and here is one article;

https://www.azom.com/article.aspx?ArticleID=10431

Yes, I've wanted to get a walnut blast done for some time now as it is strongly recommended every 50-60k km. to keep these engines problem free. It's just that I haven't found any shops offering these services here in Norway yet. Also I think the walnut blasting just cleans up the back of the intake valves and not the combustion chamber and piston tops.. but I could be wrong

[Hell Razor5543]

Well, when David had it done (I added a link to his thread) it added 21BHP onto the 207 GTi with the THP engine, because it was now a lot cleaner.