Blue Smoke - what to check in what order?

Hey all

Been driving my MK1 a bit more than normal and noticed its using quite a bit of oil with no external leaks.

Then today when overtaking i noticed a big plume of blue smoke come out of the back, from reading on here it looks like what someone else described as worn valve stem, someone else said piston rings, someone else says gaskets etc so it looks like i have a few things to check!

its a 1.8 GTI with the DX engine, millage reads as 33,000 and online MOT records match up but previous owner says its incorrect as it was rebuilt and had new cluster and he estimated it to be approx 120,000 and i am currently using 10W40 oil.

I am planning to do a compression test etc, but in order of easiest first what would you check?  - want to leave taking the head off as a last resort although i expect its going to have to come off…..Thanks  

Check the breather, depending on the age of the car/engine this will be mesh inside the cam cover rhd side as looking at the engine with a rubber hose connected to the inlet fanimold plumping to burn off any fumes. Or if later, a cylinderical plastic wotsit on top of the cam cover.

What happens is that over time these get blocked with years of oil gunk up causing internal back pressure inside the engine that then forces oil out of various seals. In the past I have removed the cam cover and tried to wash out with petrol or burn out the congealed oil but that just leaves debris that will fall back into the engine.

The best way I found was to chisel off the internal cover plate spot welds. Drill out the spot welds holding the mesh together, clean the mesh segments and re-weld everything back together. Sounds complicated but if you remove the camcover it will be self explanatory.

Loads of big block engines have been pulled apart, rebuilt or scrapped because people thought that the blue smoke was from worn values or piston/bore wear when it was bunged up breathers…… if the breather is clear you probably will have those problems though….

  

Valve cover mesh.


Valve cover heated a tad, and sprayed with Oven/Grill Cleaner and allowed to sit over night.






Sprayed with water and then Brake Cleaner and left out to air.  (you can use a hair dryer to help).  




Just my way of cleaning the crud out of it.

Excellent - thanks for the advice and for the photos as well!!!

Forgot to add (if this changes anyone's opinions or advice) it's only smoking when I let it engine brake at high revs then hit the accelorator again in 2nd or 3rd - so I am thinking the engine braking is building the vacuum higher than "normal" and that's causing a seal to give way and leak somewhere?

There is no smoke on startup, when revving, or on normal driving - only if I let it engine brake then hit the floor with the accelorator.

Thanks for the advice, I will see what the weather is like next week and get the cover off to take a look!