VW 3.0 TDI

[mikkhh]

(12-05-2025 )mikkhh Wrote:  Maybe problem arises on engines that have vacuum pump and that will pull air from crank case.

Simple test with engine running remove oil filler cap and see if there is vacuum inside or not. I have yet to see turbocharged diesel car engine that has vacuum inside crankcase with engine running.

Friday night and replacing aftermarket sensors to genuine ones on an Audi (engine runs properly after fitting genuine MAF sensor instead of new no name aftermarket junk), but vacuum pump will pull also AIR into crank case, so there is always positive pressure build up naturally happening.

Oh well that just checked a running example - 4.2 audi v8 Naturally Aspirated engine there is PCV coming directly into the intake manifold, not only just after air filter so that is why this crank case is pulling vacuum at idle and engine speed changes when remove oil filler crap. All of those crank seals etc engine leak point will cause running issues then. Looks even way more headachy system just to save some oil vapours, instead the modern stuff just leaks way more oil externally than there will ever come out of the PCV system on a healthy engine...

Long story short - PCV system on modern stuff is way more complex and creates myriad of issues to get rid of miniscule amount of oil vapours outside of engine.

(12-05-2025 )jmartin Wrote:  I think mikkhh asked for a pic of the damper

Those dampers usually rust away from center part and become loose. Try with your finger to see if it is already peeling loose. Also the rubber changes it's elasticity over time, reducing it's dampening effects.

Have you replaced the alternator freewheel clutch (if it is not freerunning in one way then you will damage belt and also crank dampener) and aux belt tensioner?

With engine running check the crank damper for excessive play and "jumping around"

There appears to be traces of big oil leak in the picture you sent or it is just dirty?

[mikkhh]

(12-05-2025 )jmartin Wrote:  I think mikkhh asked for a pic of the damper



(edited to fix image)

Those dampers usually rust away from center part and become loose. Try with your finger to see if it is already peeling loose. Also the rubber changes it's elasticity over time, reducing it's dampening effects.

Have you replaced the alternator freewheel clutch (if it is not freerunning in one way then you will damage belt and also crank dampener) and aux belt tensioner?

With engine running check the crank damper for excessive play and "jumping around"

There appears to be traces of big oil leak in the picture you sent or it is just dirty?

[jmartin]

Ha. I knew you were going to ask about that oil. It’s dirt oil mix from what appears to be an old leak that traces up to the valley. I assume maybe a valley leak was repaired in the past or somebody was really sloppy with oil filter changes. No fresh oil leaking out anywhere besides the pcv at the turbo inlet we discussed earlier. I do suspect there might be a very slow leak from seal at the fuel pump drive belt sprocket which is at front of driver side head, but it also is directly below oil filler cap so it could be sloppy oil change spills.

Did not know about alternator clutch. Will take a look at it. Sounds like it should be replaced preventively? I need to replace serpentine belt with its tensioner and idler and same service on fuel pump drive belt.

Slowly working through all this stuff. It’s well below freezing here and my shop is unheated so things don’t get done as fast.

Regarding sensors. I sprayed the MAF with maf cleaner. Will replace the charge air pressure sensor and delta P for the DPF. Is it OK to use Bosch sensors or must be from VW?

[mikkhh]

On cars that do not have alternator free wheel clutch the crankshaft dampener is more important and it does not last as long on those that do not use free wheel clutch. I would seriously consider fitting (INA brand is fine and originals are INA too cost is like 30-40) one onto my own cars.

Yours may or may not have it, just a thing to look out for. I have no idea why some modern cars do not alternator free wheel clutches. They have been very reliable and usually fail after very long time, but there is way less load on the belt, tensioner and crankshaft dampener.

On some cars that have alternator free wheel pulley from factory that is absolutely mandatory stuff since belt is routed in a way that if alternator free wheel clutch locks up solid then serpentine belt will break because tensioner will jump so much that belt is going to hit itself and that is going to happen in a few minutes of driving. Worst case scenario is when you have a car that has got timing belt and then serpentine belt shreds get caught between timing belt sprocket and then there will jump of timing and it is going to cost an engine in case of V0lvos (rockers snapped, tappet sockets broken off in head, timing belt tensioner or idler pulley stud holes snapped off in engine block). BUT if you use genuine serpentine belt from dealer then those belt just snap off clean and do not create shreds.


Maf on diesel cars is not a critical part unlike on naturally aspirated ones. Most diesel cars use MAF at low rpm and check if EGR is working properly. Maf cleaner has yet to work in my case. B0sch sensor may work, but in my case maybe there is problems with supplier, but the last five differential pressure sensor on 2.0tdi have all been faulty. After replacing you need to have ignition on, engine stopped and then learn the offset for diffrerential pressure sensor, the cheaper B0sch sensors I have tried lately every single one is not adapting since the sensor is reading way off for that adaption to allow it to be zeroed out. If you have to buy second one and deal with warranty that saga already costs more than original sensor from dealer. All the original ones have worked so far. If you want to save money you could use older part code original new old stock, at least on 2.0tdi case. On those commonrail 2.0tdi there are two options for buying diff pressure sensor, one option is just the sensor, second is sensor with bracket and pipes going to dpf, latter one costs like 300 from dealer, fist one is like 70-100. BUT the more expensive one has got old revision sensor on it that could be had separately for like 30-40, just a little bit more than B0sch. That newer sensor has B0sch codes on it too, BUT it is not sold as aftermarket part anywhere.

Same story with vitesco (owned by schaeffler, continental) sensors (MAF, nOx etc) they are only sold as genuine part from dealer with car manufacturer logos, they are not sold as aftermarket part. Maybe if revisions are updated old revision stuff will get passed on to some packagers that sell those things aftermarket, but you never know if the part is sold as no name due to it failing quality control or just being old revision.

[Rawze]

(12-05-2025 )Rawze Wrote:  

(12-04-2025 )mikkhh Wrote:  

(12-04-2025 )jmartin Wrote:  @rawze - yes it has the typical euro setup with crankcase vacuum pulled from turbo inlet thru an oil separator. I do not want the oil in there, but the problem with vent to atmosphere is when the hot engine cools down it will suck unfiltered air thru the breather tube and bring dust/dirt into the oil. Could put a breather filter on the end of the tube and that might be good enough. Also some factory separator designs require a little vacuum to open - if there is no vacuum they will build high crankcase pressure. Don't know if this one works like that. I may just go with a catch can setup and NOT set it up to drain into the sump.

All older engines do not have any crank case filtration, just a long pipe and usually steel mesh as a filter at cylinder head, the amount of dirt or unfiltered air coming down a like a meter long tube is neglible.

I agree with mikk on this one. - ALL older diesel engines vent to atmosphere. It was never an issue in the past.

In fact, that is the first thing I did to my Nissan pick up truck.. got rid of that garbage intake-gunking, turbo killing, cc fume building crap off it right away.

...

And here is exactly WHY I removed cc fumes from being shoved into the intake of my red engine ... I think that what is in the photos in this following link is a far worse problem to have, and I have seen it many times ...
info: https://rawze.com/forums/showthread.php?...9#pid85559

[jmartin]

I put a little pressure into the crankcase at the oil filler using shop vac exhaust side and it blows straight out the oil separator outlet. Appears to have no restriction or valve like some gas engines have. I will run a hose out of the separator to vent to atm.