Mk5 GTI smoking on Decel

[Kenner]

Hey guys,
My mk5 has been having an issue lately of smoking terribly on deceleration in a low gear, and now even when coasting down a hill in gear. I’m wondering if this is a valve issue, or what. I did my research and found that valve stem seals could be the issue, but wouldn’t it be a valve not seating correctly? I’m very lost and need some help.
The turbo was also replaced less than a year ago, and as all mk5’s do mine burns oil.
thank you!

 

[Kenner]

Have the BPY engine code, and FSI

 

[ROH ECHT]

They don't burn through much oil when all is well. Is the crankcase ventilation working properly? Or did you remove the vacuum for it by adding a PCV delete or Catch-can? If you did remove the PCV, you may try just reverting back to it and see if vacuum restored helps.

Mine never went through more than 0.5L/5k miles...until it had issues at 120k miles. Then it got to a 1L/800 mile ratio due to hardened valve stem seals, worn valve guides, and a piston ring stuck in its groove in the #4 piston.

Some find just the valve stem seals need replacing, but it is wise to have other things checked while doing the seals. Valve stem to valve guide clearance is one. You may want to have compression checked before removing the head for the valve seal work. If the combustion chambers are oily when the head is removed, it may be in need of rings as well. This was mine when the head was removed...oily in the #3 and #4 combustion chambers. So I also replaced the rings and rod bearings.

 

[GTI's]

Do a leak down test.

 

[ROH ECHT]

↑ I agree with that ↑

 

[Kenner]

They don't burn through much oil when all is well. Is the crankcase ventilation working properly? Or did you remove the vacuum for it by adding a PCV delete or Catch-can? If you did remove the PCV, you may try just reverting back to it and see if vacuum restored helps.

Mine never went through more than 0.5L/5k miles...until it had issues at 120k miles. Then it got to a 1L/800 mile ratio due to hardened valve stem seals, worn valve guides, and a piston ring stuck in its groove in the #4 piston.

Some find just the valve stem seals need replacing, but it is wise to have other things checked while doing the seals. Valve stem to valve guide clearance is one. You may want to have compression checked before removing the head for the valve seal work. If the combustion chambers are oily when the head is removed, it may be in need of rings as well. This was mine when the head was removed...oily in the #3 and #4 combustion chambers. So I also replaced the rings and rod bearings.

View attachment 217823

I still have the PCV system and I haven’t checked it. I’m just trying to track down the reason for the smoke. I’m not exactly sure how to check my PCV system, but I did the dipstick trick pulling it out while running and my motor did bog down per normal.

My first assumption is valve issues. I could be wrong. But I’m gonna do a leak down test soon and see what’s going on. My car has burnt oil since I got it at 162k miles (now at 183k).

 

[ROH ECHT]

It may just be worn valve seals, but still do the leak-down to see if any leaks into the crankcase through the rings. If no air leaks through the piston rings....then the smoke may be coming from oil through the valve guides and seals. While doing the leak-down test, pull the dipstick to see if pressure is lost through the rings. Anyone correct me if this is incorrect info.

 

[Kenner]

It may just be worn valve seals, but still do the leak-down to see if any leaks into the crankcase. If no air leaks through the intake or exhaust valves, then it leaks through the valve guides and seals...or the piston rings. While doing the test, and it shows air leaking (again, not to the intake or exhaust), disconnect the tube from the PCV going to the oil filter housing to both isolate the upper from the lower and to determine which the air leaks through. Anyone correct me if this is incorrect info.

I’ll do the test and see what comes of it. I’ll let you all know. Thanks for the help!! I really hope it fixes it.

 

[GTI's]

I do not see how a leak down test can check your V seals, I can see it checking the Intake & exhaust valve sealing to the cylinder head seats and the condition of piston rings to cylinder bores, also for any detecting leaks in the gaskets, head.

 

[ROH ECHT]

Oops. I wrote it in a confusing way. I didn't mean to place it where I did. I meant to say "If the leak-down doesn't show anything...then the smoke may be coming from the valve stems and seals." I will correct it. Thank you.