Hi everybody!

Nissan Qashqai 2017 1,6 diesel, cvt.

About 86000 miles

So the car starts and runs fine, but I noticed a slight knocking upon coldstart. Almost as if the engine is having trouble building oil pressure. For about 4-5 seconds.

And I have crankcase pressure opening the oil fillercap + some smoke.

So a Pcv problem I thought. Changed the pcv and the knocking upon starting might have been slightly less. But still crankcase pressure.

If I disconnect the hose on the pcv and blow in it, there are not resistance. And I can’t find any defects on other hoses.

I notice a sound from the airfilter box, as if the engine is sucking air from a leak in the box. Dismantled everything but can’t find any leak.

Some oil in the hoses and around the filler cap, but nothing alarming.

Haven’t done a compression test as it’s not a high mileage car. Full service book.

Drives 40 + 40 miles everyday.

Can’t upload film as it’s to big..

Anyone who has experienced the same problem.

A couple of things come to mind - you could also try some additives to see if this improves things.
If it is breathing heavy then usually bores/rings, etc but if you have tested compression (wet and dry) then this may not be an issue.
Worth considering an additive such as StopSmoke or similar to see if any difference and also may change the engine oil for a heavier weight.
Finally, if the car has been driven in a high gear and just cruised along for most of its life then it probably isn't run in yet....diesels (as you may know) need to be run hard to bed everything in and to maintain and low carbon emission level (gummed up rings, etc)

12 hours ago, Trevor said:

A couple of things come to mind - you could also try some additives to see if this improves things.
If it is breathing heavy then usually bores/rings, etc but if you have tested compression (wet and dry) then this may not be an issue.
Worth considering an additive such as StopSmoke or similar to see if any difference and also may change the engine oil for a heavier weight.
Finally, if the car has been driven in a high gear and just cruised along for most of its life then it probably isn't run in yet....diesels (as you may know) need to be run hard to bed everything in and to maintain and low carbon emission level (gummed up rings, etc)

>Thank your for you´re input Trevor!

As the car don´t produce any blue smoke from the exhaust, has good power and starts easy, I´m having hard to belive that the compression is poor. But you never know.. And as the milage isn´t high.

But still I would say that it´s brooken in at 86000 miles.

I have tried a additive that should give less friction (can´t remember the name), bu no additive for less smoke.

I have one thing to try and that is if engine smokes from both dipstick and filler cap. I have understod that I can draw conclutions on the result of that test. Not sure what except that it´s worse if it smokes from both.

I would normally agree with you regarding the engine being run in but if a previous owner just took it to the shops once a week or crawled through traffic in urban areas the engine would not necessarily be run in correctly (many diesel engines with high mileage can be stripped down and still find the honing marks scored into the bores....suggesting that the engine has not been run in correctly).

I have torn down engines with just 21k miles and found the bores to be completely worn but equally I have found engines with over 100k miles to still be as fresh as the day it was built. It all depends on how it has been driven.

Another example is a BMW R1200GS motorbike I had for many years. When I bought it, it was consuming quite a lot of engine oil, I changed the grade but it didn't like it (just yet). The bike had only covered 24k miles but it was sluggish and didn't respond as it should. I rode the bike hard (as it should be ridden) with high revs in each gear and eventually it was a completely different bike. No longer did it consume oil but I could happily change the oil grade accordingly.
The long and short of it is that it was not run in correctly and I managed to change that by riding it hard for a period of time.

Most diesel engines are not revved hard enough to burn off carbon (which could be gumming up the rings into the piston and not sealing in the cylinder efficiently, blocked EGR, blocked DPF, etc.
All they usually need is an 'Italian Tune-up' to keep it all clean.

Moral of this lengthy reply is - if it is consuming oil between services then I would consider that my theory is correct. Also try a cylinder leak-down test which will show exactly which cylinder or valves have pressure leaking past them. Very easy test with visible and audible results

8 hours ago, Trevor said:

I would normally agree with you regarding the engine being run in but if a previous owner just took it to the shops once a week or crawled through traffic in urban areas the engine would not necessarily be run in correctly (many diesel engines with high mileage can be stripped down and still find the honing marks scored into the bores....suggesting that the engine has not been run in correctly).

I have torn down engines with just 21k miles and found the bores to be completely worn but equally I have found engines with over 100k miles to still be as fresh as the day it was built. It all depends on how it has been driven.

Another example is a BMW R1200GS motorbike I had for many years. When I bought it, it was consuming quite a lot of engine oil, I changed the grade but it didn't like it (just yet). The bike had only covered 24k miles but it was sluggish and didn't respond as it should. I rode the bike hard (as it should be ridden) with high revs in each gear and eventually it was a completely different bike. No longer did it consume oil but I could happily change the oil grade accordingly.
The long and short of it is that it was not run in correctly and I managed to change that by riding it hard for a period of time.

Most diesel engines are not revved hard enough to burn off carbon (which could be gumming up the rings into the piston and not sealing in the cylinder efficiently, blocked EGR, blocked DPF, etc.
All they usually need is an 'Italian Tune-up' to keep it all clean.

Moral of this lengthy reply is - if it is consuming oil between services then I would consider that my theory is correct. Also try a cylinder leak-down test which will show exactly which cylinder or valves have pressure leaking past them. Very easy test with visible and audible results

Thank you for your long reply :-)

Okey, I hear you!

I have been driven diesels for 35 years and a happy DIY mechanic, not afraid of projects.

My daily driver is a Subaru XV 2012 diesel. Seldom rev it above 3000 rpm, and no problem with smoke or performance. But I do some full pulls now and then, so that might support your theory. Also have an Oldmobile 1982 350 v8 diesel, but that one never get a full pull, and does not smoke..

Some more history on the Nissan.

It´s the wifes dailydriver, so it has not been driven hard. Normally cruises down the highway at 70 miles/h.

When we bought the car it had about 21000 miles on it and was 3 years old.

Does not touch the oil at all. I rarly fill in oil in between the services.

Smoke from both oilfillercap and dipstick. I´m absolutley certain that this hasen´t been like this for mstart of ownership..

If your theory is correct, would you say that it´s to late to try an Italian service? Or let me put it like this, would you do it?

I think I can organice a compression test, but the leakdown test will take some work as I don´t have the correct tools for the job.

What bothers me is that the car has good performace and runs just fine...

I appreciate your time!

All the best

Its never too late to 'break it in' by slowly and gradually increasing the revs over time to get it used to revving higher - easiest way I've found is drive it the same as normal but just use a lower gear for longer periods....just do it gradually and run on premium fuels