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MG Midget and Sprite Technical - side cover drain tube

I have oil coming out of the side cover drain tube. What to do about that? Been trying to get the whole crankcase vent thing sorted and reduce oil droppings as much as I can.
J Van Dyke

sorry, 1098cg.
What is the purpose of this tube anyway?
I think I read somewhere it was too vent the engine, when moving down the road it'd have a venturi effect and draw a little vacuum on the crankcase? Not, presumably, intended as a constant loss oil system.
J Van Dyke

Yeah I think those where installed for the sole purpose of leaking oil in the event you have a rare non oil leak engine....god forbid.



sorry Im afraid I dont know the awnswer and wouldnt want to even try guessing. but I do kn ow what your saying.

prop
Prop

J. The tube should be attached to the frontside carb. So to create a negative crankcase pressure (or vacuum) Otherwise it could leak out of the main seal at the trannyside. Tuners want to take that tube off the carb because oil isnt a very good fuel but afterwards most Spridget owners complain about leaks. If its leaking now (the tube) it has positive crankcase pressure (as all Spridgets have)

Some take a piece of rubber tubing and mount the thing up with a breather attached to it but then you miss the suction from the carb. The canister attached to the plate attached to the casing is ment to separate oil from air but does the job poorly so oily damp will get into the carb. But thats the way it should be.

Bas
Bas Timmermans

I'm talking about the metal tube that comes straight off the side plate inspection cover right under the head, runs straight down towards the ground, on a 1098cg.
J Van Dyke

Very early cars (948) had the vent from the rockercover, later cars (1098) had ik from the front tappet chest cover. Early ones (1098 CG)have just a metal pipe but mine has that pipe with a canister attached to it (probably the later 1098 CC cover) to separate oil from air. If you have a copy of Horler at hand check page 81 (that one shows the later style canister attached to the emision control thingys).

The one with just a pipe, the pipe should point upwards and with or without a separator and connected to the front carb air filter. at page 81 in Horler it is already attached to the emision control valve unit.

At page 60 Horler sais: "The crankcase ventilationpipe was fitted to the front tappet chest cover was reshaped with an upward turn in a forward direction; this was as to act as a means of reducing the amount of oil likely to be directed into the lower ventpipe."

On page 61 he sais: "The front filter was fitted with a stub intake for the breather pipe from the .."

Hope this will answer your question.
Bas
Bas Timmermans

948 engines had both the front tappet chest breather and a rocker box breather. Rocker box to pancake air filter. Tappet chest to atmosphere.
Alan Anstead

Alan, I didnt know that but I guess that with the sucktion of the rocker cover breather it wont leak that much out of the tappet chest cover. Without any sucking device connected they are prone to leak and when I say leak its way more then the normal teritorial markings:-)
Bas Timmermans

The crankcase ventilation system on the 948 cc and early 1098 cc (type "CG")engines only works when the car is on the move.
What happens is that when the car is moving,a certain amount of vacuum is created at the end of the downwards pointing metal pipe which comes from the front tappet cover. (The length protruding from beneath the car and the angle at which it is cut-off is imperative for its good functioning)
Air is sucked into the engine from the front air cleaner (so it's clean) through an orifice in the rocker cover and into the tappet chest. Here it is mixed with the leak-gases coming from the crankcase. It is important that a non-venting oil filler cap is used otherwise there is too much airflow. There should be a baffle plate in the front tappet cover to avoid oil spray being taken with the ventilating air into the metal pipe. This system is not full-proof however and very often a small puddle of oil forms under the pipe when the car is stationary and the engine idling.
Later Spridgets ("10CC" onwards),have a positive crankcase venting system (PCV) which also operates when the car is on standstill.
Hope this helps.

Nick, '63midget.

Nick

Interesting.
I get a decent puddle under it after I stop and I only idle there long enough to shut the car down, couple seconds.
I have the original rocker cover (not on the car), which has a vented cap on it (doesn't mean it's the correct cap or rocker cover for a 1098cg either, just because it's in the parts box the PO gave me, 45 years later, who knows?). Engine now has a aluminum rocker cover which didn't have a vented cap. I just drilled a very small hole in it thinking that might make a difference, according to the above statement, that may have been a mistake. Have been told elsewhere that earlier engines all had vented caps. (BTW, it had no discernable effect)
I do have a hose from the rocker cover going into the Weber's air filter housing but there it would be under slight vacuum at speed, no? If the "drain" pipe from the tappet cover is also at a slight vacuum (at speed) who would win the suction battle? Maybe the baffle in there is gone. Weird.
I have since decided part of the problem is a leak from the distributor housing so I'll go after that too.
I'll get there. Not going for leak free, that's likely impossible but there's too much as is. Must reduce it more somehow.

J Van Dyke

For what its worth but I have exactly the same car and the same engine. For some reasons I have a vented side cover with the pipe pointed upwards and no pipe on the rocker cover. I connected the side cover vent pipe (which contains also the oil separation canister) with the HS6 carb house. (converted my car to a single carp spec and the HS6 has an outlet at the top of the body so its not at the filter.

So I only have one vent and its connected with the carb and I have absolutely no leaks whatsoever. Ok nowadays I have a 5 speed with improved rear main seal but before that it was 1 drop a week now its 1 drop of oil every 2 weeks.

In terms of Brittish cars its out of oil:-)
Bas Timmermans

Got any pictures of your set up? Yours is a cg version too? What's your engine number? Mine is 10cgDAH6925.
Suppose I could flip the cover upside down (though I'm pretty sure the pipe would hit the intake or exhaust before it got too far, not to mention the hood at some point!). I just ran 1 mile, ran an errand (voted!), 1 mile home and I have a 3" diameter spot and evidence of oil on the chassis in that area. Maybe there's something "wrong" in the engine. I have not touched it yet aside from pulling it out, putting it back and resetting the timing. It didn't used to leak from here (I only have 2 months and 700 miles to go by so far though). Not sure I changed anything dramatic. I did mess up one thing though, I suspected my dipstick was letting oil out. I got an expansion nut to put in the oil just to check but I pushed down a bit hard and, yep shoved it down into the tube. Now I get to try to extract it, yikes. I'm also pretty sure it's leaking out of the dizzy housing. I'm planning on pulling that and resealing tonight.
J Van Dyke

I tried to upload a photo of the original vent-pipe setup on my 10CG engine (sorry for the bad quality of the photo).
The original setup of vent-pipe and rocker cover/air filter hose, should leak only a minimal amount of oil (much less than you describe).
If not: something else is wrong. This cannot be rectified by "modifying" the crankcase ventilation.
By the way: they can leak from the cork gasket between side covers and block too....
Hope this may help,

Nick, '63Midget


D.G.J. Herwegh

Trying once more....


D.G.J. Herwegh

I certainly have different side covers. Probably from a later type. I do have the cover with the pipe bending upwards, not as long as shown above but with a canister at the top.

Bas
Bas Timmermans

Bas,
The whole side cover/vent-pipe issue is a complete minefield. According to parts manual AKD3566, there are at least five different front sidecovers. The model with the upwards bending pipe-stub and the ventpipe in front of the petrol pump, is usually associated with the 10CG engine (even Horler mentions this in his book). Though mine and a few other engines I've seen, have the downward pointing (or 9C/9CG)model with the vent-pipe behind the petrol pump.
The ventpipe itself has always the same parts number (2A118)indicating this part never changed (?)
The parts book never mentions a model change by engine and/or chassis number; establishing which is "correct" as nigh impossible.
However a cannister attached to a sidecover is absolutely not a 9C/9CG/10CG item. But who cares as long as it's working well...
Cheers,

Nick '63Midget


D.G.J. Herwegh

Mine is as pictured above. If originally intended to go down into the slip stream thus inducing a bit of vacuum, an up ward tube or canister or such would defeat that I'd think. I don't care much which is "correct" (no concourse for me) but what works sounds nice. Maybe I could just attach a U pipe and put a breather on it, see how long it takes for the U to fill with oil. Must be a reason for that oil though, unless the baffle that is supposed to be in the cover isn't there.....
J Van Dyke

I took a close look to my engine and what: its 10CG-DA-L-9623 and the upward bending pipe with canister is combined with the 10CC rocker cover. I know the PO did source some parts to complete the car but sourcing both of the later 10CC would be very unlikely.

But if I read Horler I do have the 10CG but the 10CC side cover and rocker cover. Sorry to cause any miscommunications but I do have to state that its without any serious leaks!

Bas
Bas Timmermans

Bas,
After re-reading your previous mails and watching the photo on page 81 of "Original Sprite and Midget", it indeed seems you have a 10CG engine with 10CC (GAN3/HAN8) crankcase ventilation parts on it. Do you have the membrane-valve on top of the inlet manifold ?
(Am I correct in thinking it needs a vented oil filler cap too ?)

Nick, '63Midget.
Nick

Nick,

No membrane valve overhere. But then again I have a Titan Fitted with single HS6 carb. Before that a combined inlet exhaust of a Mini was fitted.

The rocker cover cap could be vented. I'll check later on. But that would make sense. Sucktion from below and a little vent at the top could make it a well balanced oil retaining engine:-)

Bas

The car was bought as a boxed puzzle so some parts arent very original. The head is from a 998 Cooper but as the valves are big and the compression is superb its a good combination. The lump itself is a genuine 1098 CG.
Bas Timmermans

I think most of us know that the A series needs a small amount of negative pressure and reasonably good seals to remain oil tight. Pressurisation happens mainly due to a combination of the pumping affect from the pistons,and leakage past the rings and valves. With a standard engine - in good condition - the factory breather systems cope adequately, but even so there are very few engines out there that are fully oil tight.The balance in favour of the engine retaining negative pressure rests with the regulated manifold depression being greater the pressurisation produced within the engine. Changes to compression ratio,cam timing,overbores and carburation will all affect this balance,and a worn engine more so. Once negative pressure in the crankcase turns to positive, every orifice becomes a potential oil leak,and in extreme cases even the dipstick and distributor seals are compromised. Of course the race guys have known this for years and don't bother with sealed systems. Two or three large breathers into an open catch tank is standard procedure. For the rest of us who have modified cars with a few miles under their belt,open breathers will be familiar. But I'm looking at another possibility. A closed system into a sealed catchtank that runs on manifold depression. This - in theory at least should allow the oil mist and blowby to be collected, and a negative pressure system employed at the same time. It may require a blow off valve on the tank and an adjustable intake bleed but I think it will function OK. The oil leaks I currently have are not dramatic - a blob or two from the rear main bearing, but for well modified cars like mine this could be an option.
f pollock

This thread was discussed between 02/08/2008 and 09/08/2008

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