Turbo banjo bolt, restriction sensitivity

[Snagger]

Hi all.

I have periodically mentioned in various relevant threads that my 200Tdi has been burning a considerable amount of oil ever since it was installed.  It was rebuilt from scratch with a rebore, new pistons, head rebuild, followed by a second head rebuild and two turbo rebuilds (the second by Turbo Technics because the first was a rip off by someone else).  For all that, the oil consumption and blue smoke on the overrun and at idle has remained.  I was also a bit displeased with the oil pressure, which sits at around 15 psi at idle and 50 at high rpm once the oil is at full temperature.  The spec figures are 25 and 55 respectively, which is what my 12j gave with the same gauges and temperature sender.

The latest Binky video may have given a clue.  It seems the banjo bolt on the turbo oil feed line meters the oil flow, so too big a bore would cause problems.  
 

My question is could an incorrect banjo bolt allow enough oil flow to give those low pressure readings, and could it swamp the bearings enough to cause oil to leak through the turbine seals directly into the turbine and belt burnt off in the exhaust as visible smoke at idle?  It would seem to make sense, as when the engine is working harder and the exhaust pressure is higher, there isn’t visible smoke and perhaps the seal isn’t leaking.

I have a bit of oil contamination through the breather system into the air filter (set up like an earlier 12J, breather into filter intake), but the induction system between air filter and manifold remains clean and dry, so there is no oil loss at all through the turbo’s compressor seal.

Also related, do the banjo bolts to the piston jets in the block have valves or restrictions?  I reused the originals during the rebuild, but wonder if they may be contributing to the lacking pressure.

[Gazzar]

Does the 12j have the piston cooling oil jets?

 

[western]

The oil jets & banjo/relief valves under the pistons are fitted to all the 4 cylinder diesels, from 2.5n/a to 300tdi, 

The n/a, TD, 200tdi use the same oil piston cooling jet banjo/relief valve items ETC5592. 

I replaced them during my 200tdi rebuild, so I think the could contribute to low oil pressure if the relief valve springs inside are very weak. 

[Snagger]

So the jet banjo bolts have internal valves.  That’s one thing to replace.  Any ideas about the turbo oil feed banjo bolt?  That could explain both pressure and oil burn, if unrestricted flow could bypass the turbine seal.

[lo-fi]

The restrictor on Binky is because they're using a ball bearing turbo. These need a tiny amount of oil compared to their journal bearing cousins - hence the restrictor in this application. The cheap turbos on TDI engines are oil cooled too, so need even more flow than a journal turbo with proper water cooling.

Is the turbo oil return line definitely clear, and is the crank case breather working correctly? 

[Daan]

Did you try running it with the crank case breather disconnected?

[western]

2 hours ago, Snagger said:

So the jet banjo bolts have internal valves.  That’s one thing to replace.  Any ideas about the turbo oil feed banjo bolt?  That could explain both pressure and oil burn, if unrestricted flow could bypass the turbine seal.

Turbo oil feed is just a plain banjo & associated bolt, no restrict or or relief valve le in it. I can't see why that would cause excess oil usage. It drains back to the sump, turbo would only use oil if the seals were trashed. 

[lo-fi]

The seals in turbos are not oil seals. Their primary function is to prevent gas leakage. The return path relies on three things: gravity, a large, unrestricted path for oil to travel down to the sump and a pressure differential keeping that path flowing. Two of those factors can be quite variable. 

[Snagger]

Thanks for the replies.  I’m a little disappointed that it looks like a cheap and easy fix is off the cards - I’d hoped that the previous owner of the engine had used a wrong bolt!

The breather is clear.  It does produce a bit of oil vapour, enough to contaminate the side of the air filter (2.5 type) on the side nearest its intake, but not swimming in it.  I use a K&N for that reason, but it only needs washing every 15,000 miles or more and there is no more than a 1/4 teaspoon of oil in the filter housing at the 5,000 mile service intervals I use, if that - literally a couple of drops.

I think the return hose is ok, but replacing it may be worthwhile as it does look a bit degraded on the outside, so presumably the interior is worse.  But I think bore glazing must be back as the number one suspect - I may have been too gentle running in and adding Slick 50 to the oil changes at 5000 miles and the next few may have been too soon (I’ve read a few comments online that it can cause glazing in any age engine). I guess it’ll need honing and new rings, but will probably still elude me!  Damn!🙄
 

Best to try that return hose first, though, on the off chance.