Embarking on an engine rebuild journey - some advice needed

[siLc]

My trusty 2011 Passat B7 EcoFuel has served me well for close to 9 years, from 76000km to 247000km before all of a sudden developing a voracious appetite for motor oil - almost 1l per 1000km. Also puffing white-grayish oily-smelling smoke intermittently, mostly when warmed up. The engine is a EA111 series 1.4 TSI Twincharger with engine code CDGA. It's just like the infamous CAVA/CAVB/CAVC/CAVD/CAVE and CTHD/CTHE engines, but meant to run on compressed natural gas in addition to gasoline. Every single oil change done at a VW dealer with an interval of 15000km with their Castrol 5W30 but last two changes were done with 0W30 because VW moved away from 5W oils. Before the oil consumption skyrocketed, it consumed a very manageable one liter per 15000km. The engine runs fine otherwise.

I had it diagnosed at a reputable local shop, who borescoped it and found that the cylinder wall and exhaust valves of cylinder 2 were oily, and also the spark plug being blackened. This is also the case for cylinder 3 but not as severe. Cylinders 1 and 4 were OK. So their assessment was that the valve stem seals need to be replaced. The quote for that was close to 1700€ most of which are the shop hours. Involves taking the intake and exhaust manifolds off, camshaft module off, chain cover and also surprisingly taking the oil pan off, replacing all appropriate seals and so on, and finishing it off with an oil change. Since I want to keep the vehicle for a few years more and I've already done things here and there, I want to do the rebuild myself, at least most of it. It would be a project car, essentially

I'll lay out some of my work steps which I'm not that sure about - please feel free to let me know if anything needs to be done differently.

Since the CDGA engine isn't all that common, then for familiarity's sake, you can assume this is a CAVA engine - engine mechanicals are pretty much the same.

• Since such aforementioned oil consumption probably can't solely come from valve stem seals, I can assume that I will have to take the pistons out and have a look at them?
  
  
• Take the cylinder head off. Send if off to get new valve guides, valve stem seals and possibly new valves, also a general cleanup. VW has TPI 2029499/10, which applies to my vehicle, and pretty much tells to install a new cylinder head with optimized valve guides. Freccia valves and valve guides are OK? Elring seals generally are OK?
  
  
• If pistons are all intact, clean them up and change rings OR get complete new pistons? The oil passages in the pistons might be gummed up - soaking in brake cleaner will solve it or not? CDGA engine has different pistons to the gasolene-only engines and those only seem available as factory spare parts. Which manufacturer rings to get? Mahle or something else?
  
  
• If pistons are removed, without a doubt install new connecting rod crank bearings? From which company? Mahle, Kolbenschmidt, something else? Youtubers measure the bearing clearance with plastigauge - is that actually needed for a non-performance engine?
  
  
• Obviously inspect the timing chain as mine's still factory original. It didn't have any chain rattle on startup. Probably a good idea to change it (while in there), though putting in the full chain kit is quite expensive. Chain kits from reputable manufacturers with the intake cam variator are ~500€. Something probably can be had at 300€. The variator itself is probably fine but the sprocket teeth wear will need to be evaluated?
  
  
• Oil pump chain, sprocket and tensioner also to be renewed (while in there)?
  
  
• Anything else I'm not mentioning?

If I have the head rebuilt and do everything else myself, I think I can have the cost down to approx. 800 to 1200€ and I will have a rebuilt engine, not just new valve stem seals.

It will definetly be interesting. Fortunately I will have something else to drive around in. Also, thank you if you read till the end.

 

[Uwe]

Also, thank you if you read till the end.

I don't have any advice for you, but do thank you for posting this in the correct section of the forum.

-Uwe-

 

[SaVAGeSoot]

I'm not trying to discourage you, but based on everything you've said, I'd say run thicker oil and just deal with some additional consumption.... doing a rebuild never works out as cheaply as you expect it to, and lots of times you'll break additional things while taking everything apart.... and you'll often times run into needing specialty tools, etc. Once you factor all those in, you're better off just buying another used engine, or dumping money into increase fuel\oil\plug consumption, etc for a few more years..... or... if you have my luck, some dummy will crash into you and write off the vehicle anyways!

If you just want to play, and have time to kill, that's a whole other story!

 

[Eric]

Maybe give this a try first, assuming the valve stem seal(s) on #2 isn't/aren't completely torn up?

Motor Oil Saver

Regenerates engine seals made of rubber and plastic such as shaft sealing rings, valve stem seals and prevents oil patches under the vehicle. Counteracts oil dilution. Reduces engine noise and oil consumption via piston rings and valve guides.

www.liqui-moly.com

 

[stefdds]

Every single oil change done at a VW dealer with an interval of 15000km with their Castrol 5W30 but last two changes were done with 0W30 because VW moved away from 5W oils.

I would think twice before following the dealers/manufacturers lead! Remember, "lifetime" to them is the warranty period, nothing more.


I would change back to 5W-30 and change every 4000miles.(IMO, 10K changes was only to lower maintenance costs). And in the summer months, substitute a quart of 40 weight.

 

[Eric]

I would think twice before following the dealers/manufacturers lead! Remember, "lifetime" to them is the warranty period, nothing more.

Yeah, my first thought was, the castrol got duly cooked&oxidized on those last 5000km, and hardened/attacked the seals as a reward.

 

[siLc]

Almost forgot. When the oil consumption and smoke first hit, I was far from home and with no auto parts store in reach. Someone got me a random 1l jug of gas station 5W40. Since I was down to minimum oil level, I poured it all in, drove home 250km on the highway during the evening when there was almost no traffic and reached home with zero oil consumption. It only started to smoke and consume oil when I was driving slower and in traffic in the city. So oil weight probably didn't make all that difference. This engine has 3,6l in total at full level.

As long as it's smoking, I won't pass the annual vehicle inspection here. That's coming up in October.

Used engine is an option with many of these CDGA engines available in local junkyards, but CNG Passats are generally used to rack up large mileages here and all of them have larger mileages than mine. I'd consider it if there could be a sub-200000km engine found, which is an unicorn!

I'll reiterate one point - if it's taking 1l per 1000km, then this magnitude of consumption can't possibly come from one or two cylinder's oil stem seals? There must be a piston oil ring stuck at least in one oily-walled cylinder?

 

[RGH0]

Stem seal wear normally results in smoking after the car sits idling for a period typically in city stop / go traffic., the smoking and oil consumption reduces when driving at higher speed with a more open throttle and lower cylinder intake vacuum. Piston ring failure normally results in more oil consumption and smoking when driving at high speed. Putting in a 40 or 50 weight oil will help in both cases. A seal swelling additive may help if its the stem seals.

A litre per 1000kms sound high for just a couple of worn stem seals alone.

 

[NZDubNurd]

Have you checked the PCV system?

My Mrs 2.0 FSI (Non-turbo) had been consuming piles of oil, just because I was too lazy to look at it. The breather pipe on top of the filter housing was broken and it was sucking in piles of air - I think the extra flow was carrying oil up into the intake, rather than it being separated and returned to the sump.. She drives really slow... I took it to "blow out the cobwebs" and I honestly couldn't see out the back I did a U-turn and came back a few minutes later and a cyclist had hopped off his bike, to walk through the remaining cloud I replaced the pipe, and it's much better... though it still needs a new filter housing as it's still leaking.

The petrol versions of the twincharger are known for breaking the ring lands on the pistons, giving low compression or destroying the block... oil consumption seems secondary... Perhaps the CNG makes a difference, as I'd assume it behaves quite differently to petrol, with the stupid low RPM the DSG aims for, with massive boost and petrol pre-ignition from "enthusiastic" spark timing... If only factory pistons are available, they may have been updated, but may also not be needed.

You could get away with just sending the head for checking (A decent shop can check for wear, and just so stem seals, if that's all it needs), put rings on the existing pistons (or fit new pistons and rings) and put it back together. If you have taken the rods out to do pistons and rings, you could fit big ends, but again - they may be fine! You can see the wear on them, generally. The chain will already be off, so may as well fit the updated parts... plus they're cheap - especially over your way! Spareto in your location are cheap, even with the shipping to NZ!

@Crasher has some "less than ideal" experiences with rebuilding these engines though...

 

[siLc]

The place where I intended the car to sit to carry out the repairs was just vacated, so next week I'll be driving the patient there. I've gotten advice to check the PCV - I'll do that then. The PCV was already replaced once at a dealer...in 2017, I believe. Come to think about it, I remember seeing some oil deposits on top of the engine near the PCV pipes, where there was no oil some time before. Mentioned that at the reputable shop but that was dismissed.

Since CNG is "dry" and rougher on the engine, it has different pistons, valves and stem seals on the exhaust side. SSP 425 is a great source of info on the CDGA engine.

 

[SaVAGeSoot]

I've only had a quick look at the FSM, and there's a lot of mention about replacing the head... I assume you've gone through all this, and are aware of the limitations as far as replacing the guides or reworking the seats, etc?

 

[siLc]

Yes, both the TPI and factory repair manual prescribe the wholesale change of the head - 03C103264H costs about 1900€ new. That's nowhere near reasonable unfortunately. Finding a proper used one isn't easy as that part number is not what's cast into the head.

I've read that the valve guides can be replaced and there are spare parts available for that. But I will keep this in mind when decisions need to be made.

 

[Dr Sheldon]

If I have the head rebuilt and do everything else myself

I moved from doing mechanical to a more specialised field decades ago.

Decades ago we could rebuild an engine and it worked EVERY time !!


Today I would say that these engines are too "Highly Strung" to be rebuilt and to KNOW when you refit that all will be fine.


Non Dealer parts.

From which company? Mahle, Kolbenschmidt, something else?

Risk factor ??

@Crasher has some "less than ideal" experiences with rebuilding these engines though...

Just that alone ^^^ would be enough for me to scrap that car / abandon that idea and crawl on my belly through a sewer the 11 miles to work and back.

 

[Crasher]

You cannot use a resurfaced head unless the gasket surface is re-heat treated using a Nitrogen based system called Hot Isostatic Pressing so it is easier to buy a new head from AMC.

 

[RGH0]

You cannot use a resurfaced head unless the gasket surface is re-heat treated using a Nitrogen based system called Hot Isostatic Pressing so it is easier to buy a new head from AMC.

Can you explain the hardness changes involved in this. In particular what is the HB value for the core of the head after machining versus the surface with this "Nitrogen based system"

 

[Crasher]

I am no metallurgical engineer, just a grease monkey. VW say it is “Not permissible to rework” these heads and from what I know it is for eliminating porosity.

 

[siLc]

OK, what if the head gasket surface of the head isn't reworked? Just cleaned up. Because I had no issues with oil nor coolant being in places they were not meant to be (in terms of the head gasket).

 

[Crasher]

Then you have to check it for flatness with an engineers straight edge and feeler gauge. BUT I have just realised this isn’t a Diesel so resurfacing is OK.

 

[siLc]

So, an update...

The patient sat for three weeks. Today I went to drive it to it's repair place. It was mostly highway, so not much visible smoke to be seen while driving. It did leave blueish puffs behind when taking off from intersections but otherwise ran well. I started by checking the PCV on top of the engine. I took it off and blew air in from the chain cover end - it came out the other side. When applying vacuum from that side, a rubber flap inside the PCV closed audibly. I didn't see any cracks in the PCV hose system - manufacture date is start of 2018, so not that old. By this diag, it should be fine?

The PCV part number's 03C103474AB.

 

[RGH0]

I am no metallurgical engineer, just a grease monkey. VW say it is “Not permissible to rework” these heads and from what I know it is for eliminating porosity.

Sounds like VW want to sell cylinder heads rather than you have a machine shop rework yours. Yes the hot isostatic pressing is to compact the casting and close up porosity, it does not impact surface hardness. I personally see little risk in skimming the head a few thousandth of an inch if it needs it.