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Diagnosing 1.8T high oil consumption

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42K views 12 replies 8 participants last post by  Collectbrokencars  
#1 ·
So my relatively new to me 1.8T is using oil much faster than I would like. I have been doing some informal tracking (by memory rather than writing stuff down) and it looks like it would go through ~1qt of oil in ~1000 miles when I got it a couple of months ago. Not great, but from what I have read not bad enough that the dealer would have done anything about it were it still under warrantee (which it's not at 180K miles). BTW, this is an 2001 Audi A4 B5 platform, manual tranny. Very similar to my '01 Passat B5 4mo except for the manual tranny.

I have looked for the obvious things, oil wet areas, pools of oil under the car or on the plastic bottom plate, and have not seen any obvious signs. There is some oil wetness by the rear valve cover (opposite end from the timing belt), but not the sort of thing that looks like quarts of oil have been going out there. Turbo seals are another prime suspect I know, but I am a bit unsure how to check them on this engine. There does not appear to be an intercooler, and the turbo air output goes right into the intake manifold with the turbo bolted to the IM. So short of dropping the turbo, no way to check there, and the exhaust seem equally problematic to check. The car recently passed emissions with pretty good numbers. I have ocassionally noticed a puff of smoke when starting, but only a puff, it's not fogging the neighborhood. So perhaps the turbo seals are involved.

Just curious if folks have any suggestions of where to look. Any simple way to look at the turbo vanes and shaft or otherwise rule out oil there? Where are the other likely spots where oil could be escaping without leaving an obvious puddle or stain?

TIA
 
#3 ·
I'm just about at 180k miles on my B5 and it consumes oil at about the same rate as yours. There's no obvious leaks anywhere and there are no oil stains or puddles under the car. I just chalked it up to wear and oil blowing by seals in extremely small amounts. The car runs and rides great so I'm not complaining if I have to put a quart of oil in every 4-6 weeks. It's about what I'd expect for a 15-year old car.
 
#4 ·
The PVC system, if not in good condition, can cause raised pressure in the crankcase, which increases leaks and also more oil going up into the cylinder on the intake stroke, especially when idling. Another possiblilty is the intake valve seals, of which you have 12. Loose seals allow oil to pass from the camshaft area into the intake ports.
 
#5 ·
Opps, I must have been quite tired last nite when I was looking at this ;) Indeed what I was thinking was the IM was the exhaust manifold, opps (good thing I wasn't turning any wrenches)... Thanks for correcting me.

I will take a look at shaft play at the intake to the turbo, and look for oil at the pipe which feeds the IM after the intercooler. That should give a good idea of the state of the turbo bearings and seals.

yl, any way to diagnose leaky valve seals or PVC system?
 
#8 ·
Been pretty busy, so have not had time to jack the car up and pull the hose on the pump side of the turbo. But I did pull the hose from the intercooler to the intake manifold. At the IM end, that hose and IM were dry. Not sure on the 1.8T engines, but on all the 1.9TDI I've had, and I've had a few of them, when their turbo is leaking, the IM and intercooler hoses are wet with oil inside. So if the 1.8T is similar the turbo may not be the source of the oil leak.

I have been looking when I start the car lately and there definitely is some smoke at startup and for the first 30 sec or so. No huge clouds of it, but if its still out then you can see some smoke out back. So I think the valve stem test zmanico mentioned might be the next step. If nothing else will give me a look at the spark plugs.
 
#9 ·
If you cranked the engine with the spark plugs out, and oil shoots out, you'd have much bigger problems then valve stem seals. Valve stem seals usually leak more on decelleration, when the intake manifold vacuum is high. If the engine has proper compression (rings and valve seats in good shape), but it smokes when opening the throttle, after going down a hill with the throttle closed, the seals would be suspect.
 
#10 · (Edited)
Had some time to dig into this some more and I am back because I am still not sure where the problem is. So here goes...

Checked the intake manifold, no oil. Pulled the bottom hose on the intercooler and got 1-2 teaspoons out. Not what I would have expected if the turbo intake side was leaking (I think).

Pulled a spark plug, clean. No signs of burning oil.

But while pulling the coil pack of the plug, I noticed oil leaking from the VC to head gasket. Not a ton but enough to get things wet with oil. I also checked and there seems to be some oil leaking at the front and back of the VC, but nothing that big; doesn't seem wet enough to account for the oil loss I am seeing. But I obviously need a new VC gasket.

Had someone start the car while I stood at the tailpipe. A bit of white/grey smoke comes out on start and continues during idle. Not very much, not enough to see from the driver's seat but there.

Unfortunately I did not get to check the turbo shaft for play, because it started pouring.

So, what does this all say?

1. I am assuming that the missing oil is not going thru the cylinders. Otherwise the spark plug would have shown black soot.

2. I suppose that the oil could just be leaking from the VC gasket, but I would have thought there's be some really dripping wet spots under the car, no?

3. I suppose it may be leaking at turbo exhaust side. That would explain the exhaust smoke and clean plugs.

What do folks think? What are these symptoms pointing to? Just the VC? what about the tail smoke?

Could this be just a slow VC leak. Could that account for 1qt/1000mi and not have oil spots underneath or a really oil wet spots on the engine?

What else might I be overlooking? I will check the other plugs (in case it was just one cyl with leaky valve seals), but the engine is running smoothly enough that I think that unlikely.

I will check the turbo shaft play. Do these turbos fail by leaking on just one side?

These symptoms sound familiar to anyone? What is causing the loss of oil? Just one thing or several?

TIA
 
#11 ·
Regardless of what is causing the oil consumption, first fix the PCV system (check and clean all hoses and components and replace all broken ones), and then replace the vcg, tensioner gasket and half moon plug. If you are in the beginning stages of a vcg leak, might as well make plans to change it soon because its only going to get worse.

A blocked PCV system will not only push oil past the seals, but will deteriorate the oil by increasing its exposure to combustion byproducts. That sort of leak is incipient. It starts gradually and may go on for tens of thousands of miles if it's not caught early.

I don't know how much oil can leak through a bad vcg over 1000 miles. Taking care of that may be just enough to make your oil consumption a more tolerable 1qt every 2000 miles.

Beyond that, most people live with leaky stem seals and just add oil (and perhaps change their plugs a little more frequently) .
 
#12 ·
...there definitely is some smoke at startup and for the first 30 sec or so. No huge clouds of it, but if its still out then you can see some smoke out back.
From your posts, it seems your oil consumption is split between the ring packs (on pistons) being partially stuck due to carbon build-up and from the valve cover gasket.

If you wanted to get aggressive with those ring packs, set aside a few hours, pull the coils and plugs then pour 10-15 ml of Sea Foam into each cylinder through the plug hole and let it sit a few hours. Youi'll need to turn the crankshaft manually about one turn every hour or so during the soaking period. To remove the excess Sea Foam, place a few rags over the spark plug holes and crank the starter for a few seconds. This will make a small mess, but beats an engine tear down to unstick/replace the rings.

Reinstall the plugs and coils and be prepared for lots of smoke the next ~10 miles of driving as the Sea Foam burns off the ring packs. This is the burn off period. ;) The end result is greatly reduced tail-pipe smoke at start-up. You might also consider switching to a better fuel or more frequent use of Techron or other fuel additive to reduce carbon build-up. BTW, it's best to do all this right before an oil change.

Yes, I've actually done this to several cars.