smoking exhaust

[mojobaby]

my car is running pretty well! Good acceleration, good idling, good cruising. I do however have a smoking exhaust problem, but it only happens when I go up a hill. The smoke is a light blue/grey colour and it billows out! If the car is idling there is no smoke or even when I rev the engine.
I've had a compression test done and it was fine. From what I've read up, I'm thinking rings or valve guides. How do I tell the difference, cos if I do the job myself I don't want to fix the wrong thing

 

[Steve Hennessey]

Welcome to the forum. I have just moved your post as it's a technical issue. It's always a good idea to state the model, year and engine capacity when asking questions as it helps forum members to help you more readily.

The first question I would ask is how much oil does it use? The smoke is definitely indicative of oil burning. Do you also get the same problem when accelerating on a flat road?

 

[mojobaby]

Thanks! It's a Renault 4L 1980 and 1100 motor. If it does smoke on acceleration on the flat, it's not at all noticeable, so I would say it doesn't. The perfect scenario would be that I'm in 4th gear going up a long hill, the speed drops, revs drop but I don't change into a lower gear, and then the smoke starts.
There is a rubber tube from the carb and also one from the breather pipe on the tappet cover. They both lead into a cone shape plastic container. If I disconnect them, the smoking stops but I get a lot of oil pushing from the bottom of the plastic cone thing and then running down onto the engine. I could take a photo of that if you wish.
I just have the impression that the oil pressure somewhere is too high, if that can happen. And yes, I do top up the oil quite often

 

[politeperson]

I assume the oil level is not over full.

 

[alewis]

Not heard of a cone thing. The cone thing isnt some kind of filter thats blocked is it forcing there to be excess pressure in the engine ?

+Does sounds like there is alot of crankcase pressure

 

[barnfind]

Sounds like under certain throttle conditions, the breather system is sucking oil splashed around in the rocker cover, back through the breather into the carburettor, and back into the engine whence it burns off and smokes through the exhaust. Have you a photo of the cone shaped thing?

In terms of valve guide wear, this used to be reckoned to show up as a puff of smoke when the throttle was opened again after the engine had idled or coasted for a while with an otherwise clear exhaust. A puff of smoke on startup is also common.
Bad rings tend to cause smoke on idle and on overrun, eg: when coasting down a hill using the engine as a brake, when the vacuum in the manifold acts to draw the oil up past the worn rings.

 

[mojobaby]

going to take that plastic cone thing out tomorrow and take a photo with all the pipes connected to it. I think you're definitely correct-it's part of the breather system although why it sucks up oil is beyond me. Somehow it is indeed getting to the carb because the rubber hose that connects the two is also slightly oily
So, thank you, til tomorrow!

 

[mojobaby]

the plastic cone thing is just a junction box. The pipe to the left goes to the rocker arm cover breather pipe. The one on the top goes to the carb. The bottom pipe goes to the shaft of the oil level dipstick.
Today I went to town and disconnected the pipe on the left which goes to the rocker arm cover breather pipe to see what would happen.
No problem going to town but on the way back, up "killer hill", half way up the car started spluttering and smoke gushed out the exhaust.
When I stopped the pipe from the cover breatherpipe had spat out a lot of oil all over the engine.Really a lot!! Must have been a lot of pressure in the cover

Because it was disconnected, the oil must have come from the dipstick, through the plastic cone and straight to the carb. The little flat plate in the carb was also oily.

Put my finger into the rocker cover and it felt pretty dry, and the inside of the cover is caked with dry oil. Felt like the inside of a chimney stack. Could some of this gunk be blocking a hole somewhere, or the oil filter, causing pressure build up

 

[Steve Hennessey]

Never seen one of those before. Most bizarre. Just wondered if the oil level is too high and it's being sucked into the carb.
Can you feel any crankcase pressure comping from the rocker cover breather outlet? If not then that could be blocked.

 

[mojobaby]

this is what I said in my previous thread:

"When I stopped the car, the pipe from the cover breatherpipe had spat out a lot of oil all over the engine.Really a lot!! Must have been a lot of pressure in the cover."

That's not true!!

The oil didn't come from this pipe, and therefore not out of the rockercover breather tube; it came from the plastic cone thing where I disconnected the pipe.

So therefore all the pressure is from the bottom pushing upwards towards the carb.Just taken the cover off and cleaned it; it was caked! Whats the best way to clean the rocker arms?

The oil is definitely not over full.

I blew into the rocker cover breather. Air went through but not so freely. Just tasted like shit! I'll check it out. Thanks

 

[mojobaby]

I blew into the rocker cover outlet through the pipe. Air did go through but not that freely. I'll check it out

 

[Steve Hennessey]

I wouldn't worry about the carbon on the rockers for now. It sounds as if the engine isn't breathing freely from the top end. In the rocker cover is a plate that is spot welded to the top and this stops the oil from being splashed into the breather pipe. This gap between the plate and the rocker box gets bunged up with carbon. Best way to clean is to soak the rocker box in something that will dissolve the carbon. If you stop up the breather outlet and pour old fashioned paint stripper inside the box to a level that covers the plate, it should help dissolve it.

 

[barnfind]

Nice looking car, incidentally.

 

[mojobaby]

Thanks Barnfind and Steve, I love her.
Next week I'm going to drain the oil, change oil filter, and try aand clean off the old carbon gunk etc. Is there any way to check that the oil from the oil pump is reaching the tappets at the top?
I've checked in the Haynes manual and its a bit difficult to follow the diagram. The rockers looked a little dry and I think the oil pressure is so great in the sump that its pushing up past the dipstick and then into the plastic cone thing and then to the carb.
Perhaps the passage to the top is blocked and the oil can't find its way to the top through the normal channel

 

[barnfind]

If you run the engine with the oil filler removed, you should be able to see oil on the rockers and indeed there should be a fair amount of it flying about out of the filler itself. The inside of the cover itself should be wet with oil if the engine has just run.

If you aren't certain after doing this, take the rocker cover off, remove the sparking plugs and spin the engine on the starter. You should see oil arriving quite quickly through the feed holes in the rockers and the shaft. Don't overdo it on the starter motor however. By the time the oil light has gone out, oil should be starting to appear.

 

[barnfind]

If you run the engine with the oil filler removed, you should be able to see oil on the rockers and indeed there should be a fair amount of it flying about out of the filler itself. The inside of the cover itself should be wet with oil if the engine has just run.

That's oil filler cap incidentally.

 

[mojobaby]

Thanks for clearing that up. for a moment I thought you meant running with the oil filter off, which would have been a bit messy!
Drained the oil today, cleaned the rocker cover thoroughly and was just about to put in a new filter when I discovered it was the wrong size. There are two different sizes and of course I had to get the wrong one. I need the one with the bigger hole for a "82 model.
So I'll get it tomorrow, fill up with oil and see if she still smokes uphill.

 

[mojobaby]

Still smoking up "killer hill" People were flashing their lights at me!

If the compression test results were above average, is it safe to say that the rings are OK?

 

[barnfind]

It still sounds like excess crankcase pressure to me, you must have something blocked somewhere. A Hillman Hunter owned by my father many years ago, generated enough sludge to block the breathers and actually blew out the dipstick!

Poorly sealing rings can create excess crankcase pressure, but in that case, you would get smoke at other times, particularly when idling. Your problem seems to occur when your engine is labouring under a wide throttle opening....does it stop smoking if you change down a gear and use less throttle?

According to the Workshop Manual, Some models had a restrictor valve in the breather pipes that restricted airflow through in order to avoid introducing too much air into the carburettor and messing up the mixture. These were like a plug in the pipe, with a small drilling through it. It wouldn't take much to block one of those up if your car has it fitted.

What is happening at the bottom of the cone. Where exactly does that pipe go to? Where does the dipstick fit in relation to it?

 

[angel]

This plastic part is a cyclone oil separator, it collects oil from crankcase vapours and returns it back in the sump.
I found such a thing on my Jogging engine, it must had been fitted on early 1108s. Do you have a photo of it with its hoses on their places, or do you remember how was it connected? Mine had all the hoses removed, and I can't find how they were connected.