Does your R4 fart?

[Pieter]

I couldn't resist the title, sorry Clementine, I've dragged the tone of the site irrevocably down.

However, if you were a humble french car and pushing forty (or just pushing forty) wouldn't you have occasional problems too? ops:
My '68 model (R1123 dogleg 4 speed made late '67) has an embarrassing problem in that on hot days in traffic it will get to a point when stopping at the lights it will, errm, "blow off" a large gout of blue grey smoke on takeoff. Initially thought "valve guides" but it doesn't happen every time, only every fourth or fifth time I stop at the lights, and for the other times no smoke at all. Likewise at speed it doessn't blow any at gearchanges like my old alfa did, and the oil consumption is nothing terrible, about 1- 1 and a half pints every 3000 miles (or maybe that is terrible). It seems to happen more if the oil is at the high level mark on the dipstick, particularly when slightly overfilled (to the "running in" mark, but almost never happens once the level is about halway between the high and low marks.

I'm wondering if it is the (so-called) emission control- could oil vapour be collecting in a low point in the tube from the rocker cover breather to the carby, and occasionally getting sucked into the carby when I take off? I notice the later cars have a T piece in this tube going down to a small orifice in the inlet manifold below the carb, which would potentially drain any such puddles. Maybe this is worth trying.

Interested in any ideas or comments but I'm going to experiment by temporarily replacing the tube with a clear one this weekend and seeing what I can see.

 

[malcolm]

I've never experienced farting problems in my Renaults - or at least never from the car. I do get the occasional troublesome passenger.

My first thought would have been valve guide stem seals (assuming these cars have them), although it does seem odd that the problem isn't consistent. You could experiment with letting the rocker cover breathe to air and blocking the holes in the carburettor. That would rule out the breathing. Otherwise it could only really be the valve guides.

It's funny - my Renault has developed a problem. I have a long wait at a junction about 2 miles from my house. The car starts to idle badly and gets to the stage where it will only pull away on 2 cylinders. It sorts itself out after another mile. I'm baffled.

Maybe these cars just don't like sitting still.

 

[RichardIRL]

VW Beetles and Citroen 2CVs never stop farting

 

[Pieter]

An update on the fart story: I replaced the hose from the rocker cover to the carby with a clear one. For two or three days, nothing. Got bored and stopped looking. Then after about five days, a very embarrassing fart episode and afterwards I looked at the hose and very clear traces of oil collecting at a low point. I suspect it kept collecting until it covered the end or there was sufficient vacuum to suck it out.

Subsequent to that added a bypass to the inlet manifold, with orifices per the 70's R4 installation. It seems to have improve things, i.e. much rarer, and for less duration, less likely to happen in traffic. It still happens occasionally but not as bad as before. n.b. I suspect my valve guides aren't the greatest anyway.

I'm still fiddling with it. It seems a fair amount of oil gets in and will get sucked into the engine this way although its happening slowly all the time and not in occasional farty bursts. Some form of physical oil trap would be good, so any oil that gathers can run back into the rocker box. I'll try that next.

I think the waters are also a bit muddied by what petrols are used. ULP and LRP of various sorts seem to have various upper clyinder lubricants in them which presumably burn off in a catalytic converter but just come out the pipe in an old car. Have tried Shell Optimax, the BP one and plain LRPs with different results. Also in Australia our clever and deliciously laisses-faire government decided you didn't need to regulate petrol production standards because private industry would always do the right thing by the consumer, wouldn't they???!!!!! So you can have up to 10% ethanol any any amount of white spirit in petrol now.

 

[malcolm]

Petrol is a funny subject. In the UK some retailers are selling expensive petrol claiming it will make your car go faster. Actually with the modern knock sensors this could well be true as engines will advance their ignition timing up to just before the point of knock. It's mad, BMW apparently forced a change in US fuel regulations because high sulphur fuels were corroding their cylinder liners. In an unregulated fuel market you must be glad you are running a Renault 4 (which was designed to run on whatever fuel small French garages could brew up at the time).

Sounds like you have cracked the farting problem. I had a look the breather on my GTL. A very quick look as it's cold and dark out there. The breather pipe looks like it goes downhill from the carb to the engine so there's not much chance of oil puddling in there. I take it there is no way to arrange the pipe on your car so it does the same thing?