This is an interesting and weird one. I need your feedback because I am out of ideas.
 
A local Skoda Felicia owner came to me asking for help because the engine oil level got higher. He changed the oil and the oil filter some 15 months ago then he drove around 1,500 miles. The oil level was half between MIN and MAX on dipstick. He checked the oil level a month ago and it was at the MAX sign!
 
Not knowing what to do, he took out some oil (~0.5 l) to restore the initial level. Yesterday he came to me because the oil level got higher again...
 
He used to fill with 10W40 mineral oil. But then he was ill advised and he used a German brand of oil at last oil exchange (MANNOL EXTREME 5W40 fully synthetic). This is all info he got for me. The oil looks and smells normal, maybe it is a little more thinner, less viscous.

 

Here is what I thought.

The only 2 fluids that could get into engine oil are: fuel and coolant. Being a 1.3 l carburetor engine with a mechanical fuel pump, I suspected the fuel pump rubber diaphragm might have suffered a small rupture. I took the pump out and did a pressure test. It hold brilliantly.

 

Then I did a pressure test on the cooling system hoping to find an internal leak. But again, no pressure drop. Furthermore, the oil cap is totally clean, the coolant has no oil traces. I even let a sample of oil (100 ml) overnight in a clear bottle to see if something separates. But nothing showed. The used oil doesn't burn and doesn't sizzle on a hot plate, just smokes...

 

I have checked the compression thinking that maybe the rings are worn or the gaps got aligned. The compression is excellent (13 bar at 75,000 miles) and uniform. Needless to say, there is no blue smoke or any smoke on the exhaust pipe. The car is well maintained and carefully driven.

 

That is the strangest case experienced by me. What is your take, please?

If he does lots of short trips & the engine doesn't get hot it might just be blow-by of the bi-products of combustion.

 

It's a bit like folks that do short trips around suburbia all the time &  claim they never use oil - then they go on the annual motoring holiday and have a heart attack because the oil level drops dramatically.  It's just that the engine heated up properly and burned off the moisture & light hydrocarbons.

 

About the only mechanical thing you haven't checked is the carburettor - the little valve in the float bowl that closes when the float comes up.  If that's worn then when the engine is turned off, the residual pressure in the fuel lines will overcome the seal of the valve and the fuel will dribble into the inlet and into the combustion chambers & past the rings diluting the oil.

Thank you very much for your reply.

 

I will start with the carburetor part of your suggestion. I guess you're talking about the float needle valve not sealing properly thus flooding the intake manifold. Right now the only sure thing is that during normal operation the carburetor is not flooded. That would result in rough idle, black smoke on tail pipe, higher consumption, and gasoline smell in the cabin. Where you might be right is what happens when the engine is stopped. Although pressure can't build up because there is a fuel vapors separator before carburetor fuel input. But I will check further on that path.

 

About the short trips part. Yes, he does short trips (we all do, we live on a small island), but not so short that the engine doesn't get hot. It's quite hot in here all the time. Yet only his car developed this weird higher oil level symptom.

 

About the blow-by part, let me see if I understood correctly your description. You say that an engine not hot enough allows some of the combustion gases to pass the rings, right? OK, but we're talking about an engine that has very good compression, no worn rings, no oil consumption. Even so, how could gases build extra liquid(?) in the oil pan? I don't understand also the "moisture & light hydrocarbons" part. Could you be more specific please? and take me chronologically into your reasoning? I might be thick momentarily

 

Off topic or maybe not, one other paradox, but this applies to all Felicias on carburetor, is about the blow-by pressure build up. There is quite a lot of pressure pulsing out if we take off the oil cap. I've seen cars with the oil cap 'dancing' (the oil cap is not the screw-and-lock type, it has only a thick o-ring). Theory says that if such 'breathing' blows then piston rings are gone. But that is not the case because the compression is very good (13-14 bar). There is no PCV valve from factory.

 

How is that heavy 'breathing' building??

as you initially postulated, surely its could only be fuel or coolant getting in?

 

my guess would be fuel.... as you seemed to rule out coolant well... anywhere else fuel can get in besides the fuel pump ?

Other than petrol leaking (you've eliminated the fuel pump so it would have to be carburetor but that would give him a high fuel consumption, I can only think it would be condensation.

 

So, on the condensation theory, is there any sign of mayonnaise inside the valve gear cover?

 

On the oil viscosity, I've not used that brand, but it's entirely normal for a 5W oil to "look thin", in fact to flow almost like water, when the engine is cold.

Steam (H₂O in gas form) is one of the blow-by gases, since most of the H's in the HydroCarbon fuel get turned/burned into H₂O, just as the C's become CO_2.  Blow-by happens even in a healthy engine with no compression problems, but is worse in older, more worn engines. For the first few miles of running, the engine is cold enough that steam in these gases will condense to liquid water. Later it re-evaporates once the engine/oil is hotter.  That's what Brad and Ken are suggesting, I think, but it is a bit doubtful due to your observation that the oil cap is totally clean (not covered in 'Mayo' which is a white/yellow emulsion/mix of oil and water, often associated with short-journeys where the oil doesn't get hot enough for long enough), and also because any water in the sump would tend to sink to the bottom, and your sampling should have found that (if you sampled via the drain plug?). 

 

To rule out condensation, an experiment could be done where the car is fully warmed up, the oil level measured, then the car taken for a long drive (round and round as necessary!) to try to evaporate any water out of the sump, then re-measure the oil level and see if has gone down?

 

What about if the excess volume is gas, not liquid? If the owner is measuring with the dipstick just after shutdown, might it be that there are a lot of bubbles in the oil, which are increasing the volume metered by the dipstick?

I don't really have an idea about why the oil would be getting a lot of bubbles in it though. Might well be visible on the dipstick if it is happening?

Thank you guys for further clearing things for me.

 

The more I am reading the more makes sense the crankcase not being vented properly scenario. Blow-by gases (steam and unburnt fuel) condense inside crankcase thus raising the oil level.

 

So the question is this: why the crankcase of this car is not vented properly? Is something blocked?

 

One other thing: Felicia engine with carburetor is very similar to Favorit engine. Does anyone have clear photos that show:

1. Which way crankcase gases get up into the valve cover?
2. Which way the oil from valve cover gets back into the crankcase?

Better yet, I took a photo of the upper part of the engine head of the said car. Please draw on it.

 

Edited 15 July, 201510 yr by RicardoM

Well, condensation should evaporate from the sump with oil at running temperatures, but reaching those takes about 10 miles.

 

I'm now wondering if the car might benefit from a catch can modification to the rocker cover breathers?

Ricardo, we just crossed, and are thinking similarly. the idea of a catch can mod is that the rocker cover will be at atmospheric pressure, and the (usually external) line from it to the crankcase will achieve the same thing down there.

 

As to your questions, on any engine I've seen (including Skoda Estelle, so same block and head castings) the main oil return from the head is internal to the block.

My questions still stand. Please help.

1. Through which holes crankcase gases get up into the valve cover?
2. Through which holes the oil from valve cover gets back into the crankcase?

 

Sandwich view

• head top side
• head gasket
• head bottom side
• block with head gasket seated
• block

I think oil drain and air vent are the same holes that the pushrods come up through.

 

I've edited your headgasket picture a bit to add 4 more coolant pathways (light blue scribbles to match the original blue coding for coolant (green is bolts), a red one for high pressure oil upwards into head and then pink scribbles in all the pushrod/oil-drain/air vent holes.  I'm assuming there isn't a rubber (air) hose external to the engine between block and head.  There's nowhere else left really, all the holes in the gasket are accounted for, so I think in your first image of the side view of the engine, you should move the blue arrow on top of the pink one.

 

Just a tought: have you checked the hose connections form rocker cover to air filter and intake manifold? If they are leaking vacuum there would be no crankcase ventilation.

Just a tought: have you checked the hose connections form rocker cover to air filter and intake manifold? If they are leaking vacuum there would be no crankcase ventilation.

Both hoses are intact.

 

@Wino

You are spot on! I took the time to redraw on my initial photos to match your reply.

In case somebody needs them, they are below fully annotated.

 

I'm guessing there is no way the crankcase vents inside Felicia's engine head and block could get clogged... Or am I wrong? Because if I am wrong the only valid theory for higher oil level falls short. If the crankcase ventilation is good and the engine got warmed up on each daily routes (it's HOT in here) then I'm clueless again. What am I missing? I can't change parts blindly unless I find proof of something faulty...

 

 

 

 

 

I agree, there's no way the sump/crankcase and head/rocker cover can be at different pressures with all those big holes linking the two areas.

 

The hoses coming from rocker cover towards the inlet need to be more than just intact though; they also need to be not blocked up with anything.  SaltySkoda's reply indicates that there are two? One above the carb and one below? The one below will be important for good crankcase ventilation at idle, and has to be narrow-bore and going through a narrow jet at the point it meets the inlet manifold (or maybe where it leaves the rocker cover) to avoid 'spoiling' the manifold vacuum too much, so check that this hose/jet isn't blocked. Also make sure the one to the airbox is clear, including any flame-trap or one-way valve that may be there.

OK, I will check the hoses for any restriction.

There are no 1-way valves that I know of in any hose.

Here is a photo from the actual car (after I drained the oil) that shows how PCV hoses look like.

 

Have you thought of going back to basics (more basic than you already have)?

 

If the oil level behaved normally before he started using Mannol then why not go back to the old oil & see what happens?

 

Also, do you have any way of doing a used oil analysis to determine what is increasing the level?

The engine head vents could only get that much blocked if there's a serious sludge buildup. I assume this is not the case here. But the narrow jet on inlet manifold could easily get clogged, try to clean it with compressed air or WD-40 and a needle/thin wire.

Also, have you investigated the obvious possibility of someone topping up the oil without the owner knowing? Many years ago I loved to fiddle with our car while daddy was taking an afternoon nap. :zzz:

 

By the way, the manual highly recommends against using 5W grade oil. Me too. Especially if you live in a hot climate, and I see you're in Dominican Republic.

The 135/136 engine is ancient by design and doesn't like modern, thin oils. The clearances are too large for 5W grade oils. Lack of lubrication leads to bearing failure, and we all know what that means.

I would suggest using thicker oil, at least 15W40. Consult the owner's manual about recommended oil grades, you'll see an outside temperature vs. oil grade graph.

Edited 17 July, 201510 yr by SaltySkoda

Thank you, guys for bearing with me.

I have checked both PCV hoses and also the small hole to intake manifold. They were all clean. Also there is no PCV valve because that is Skoda factory design. So I have to conclude there was good crankcase ventilation all the time.

So far I can say I ruled out the following possible causes:

- fuel contamination

- coolant contamination

- short trips with cold engine

- bad crankcase ventilation

I hate to go forward without finding any evidence for that extra 0.5 liter of engine oil. I asked the owner about the possibility of somebody else filling with oil. He laughed out loud. He's single, no zealous kids , nobody used his car, never went to a garage. I did my homework too on used engine oil analysis possibility. Again, no luck. It's hard to find a spectro-photometric analyzer when you need one...

Unless you have other ideas, I will have to put the same 10W40 semi-synthetic oil I have been using for the last 7-8 years (no multigrade mineral oil in here) and hope for the best. If the oil level gets h8gher again, I'll shoot myself

I think reverting to 10w-40 semi-synth is a good idea

Since (I think) I ruled out all usual suspects for a higher oil level, the logic should tell me that by elimination the culprit should be the oil itself.
 
BUT...
something is bugging me. That 0.5 liters of 'extra' oil had to come from somewhere. And I remember the OIL FILTER has that capacity / volume of oil in it at any time. What if... somehow the oil filter started to fail mechanically(?) up to the point of being bypassed? What if instead of sitting inside oil filter, the oil gradually had been drained into oil pan then the filter got totally bypassed?
 
I don't know the guts of an oil filter. What do you think?
 
The car had a MANN filter installed.

If the oil filter is on the same angle as in post 10 then I can't see it making a huge difference.  Mann are good filters so I can't imagine it collapsing.

 

As you are doing an oil change, you'll be doing a filter as well so you can dismantle the old filter & have a look

I did the autopsy of oil filter. There was no restriction in it :( My last theory didn't apply in this case.

 

The owner of the car refuses to replace blindly the oil and the filter hoping the situation will improve with God's will. I am on his side on this one. Yeah, it is frustrating, but something happened. It must be the oil itself. But why??

...

 

What about if the excess volume is gas, not liquid? If the owner is measuring with the dipstick just after shutdown, might it be that there are a lot of bubbles in the oil, which are increasing the volume metered by the dipstick?

I don't really have an idea about why the oil would be getting a lot of bubbles in it though. Might well be visible on the dipstick if it is happening?

 

Did you have a look for bubbles in the oil? Maybe this particular oil is vulnerable to foaming in this particular engine design? 

I admit, this seems improbable as an explanation, but it's my last idea.

Well, if it's not oil, coolant or water then it must be the fuel. Unless the engine is somehow creating something out of nothing. In that case, kudos to Skoda engineers.

I would check the carburetor. It may be boiling fuel under the heat, which then spills over into the intake manifold.

Is the car difficult to start when hot? Is it running rich on a hot start, but then gets better? Also, check the idle cutoff solenoid. Has the carb mounting plate been tampered with? Is the hot air pickup (on exhaust manifold) still in place?

@Wino

The oil is not prone to bubbling and foaming from my knowledge. I have shaken an oil sample in a glass bottle just to be sure. No foaming. Furthermore, the oil level was checked in the morning after staying a night still.

 

@SallySkoda

The fuel system is working well, no faulty fuel shutoff valve. But there is a strong possibility of fuel to boil in his carburetor because he decided to get rid of ducts that suck colder air  from behind the front bumper. Now the air is sucked right from the engine bay. If only I could analyze the oil in a more empirical way for gasoline in small amounts...