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MGB MGB Oil Consumption

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Dave, I don't blame you for your response.
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I'm going to drive it for another week before I do anything else. Sorry, I just didn't know that 1 full quart would stay up top when the engine was warm and gave me that much of a false reading. I almost didn't say anything today, but I can own up to my embarassing lack of technical knowlege.
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The fact still remains that my car was 2.5 quarts low since my recent oil change and that never happened before (I've owned this MGB for 20 years!) I still don't know where the oil went and am trying to figure out what might have caused it. I wanted to prevent any damage to my engine and catch the problem quickly.

If nothing else, maybe someone will read this and now know that a full quart stays up top when the engine is warm and won't jump to conclusions like I did.

Thanks again...
 
Hi Jonny,
It's just one of the hazzards of trying to diagnose a problem by mail. I'm glad that you don't have the original problem. It has been educational for both of us, made me think a lot. Thanks for the interesting experience & good luck. If you have other problems there will be help available.
D
 
Hey, thanks for understanding. I'll keep you posted if the oil consumption continues. The help and time you devoted to this issue has been stellar!

My next project is the bushing on the carbs (vacuum leak). Or the vibration in the shifter (noisey/buzzing shift knob), or the front end rebuild (king pins!), or.... You get the idea.
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So much to do! But she runs great, and always puts a smile on my face. That's what it's all about, right!

I'll be back ,and am extremely glad I found this site!
 
First off removing the air pollution system has absolutely nothing to do with oil cunsumption. Secondly the cap that comes with the valve cover is more than adequate. I have many customers who have the aluminum valve cover on everything from MG's to big Healeys and don't have oil comsumtion problems. Check the crank vent on the front tappet cover. Unhook the Y connection and blow through the 1/2" hose to see if it is open. If you still feel the consumption is because of your valve cover. Put the old one back on and drive it a week or so.
 
Hi Nial,
Good to have you in on this.

From reading my second reference above I am under the impression that the PCV was eliminated & replaced with the following setup. Jonny did say that he has a 1971 MGB.
https://www.mgbmga.com/tech/mgb9.htm
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"Carburetor Control System (1969 onwards)
With the introduction of this system, the front side plate cover outlet was now connected to the "Y" fitting from which hoses are routed to each individual carburetor. These carburetor connections are positioned between the piston and the throttle disc. Gases are drawn from the crankcase via the depression in this chamber. Increased throttle disc openings along with increased depression in the chamber allows a greater volume of gases to be drawn into the inlet manifold. The oil filter cap, as mentioned in the previous paragraph, is retained and works on the same principle. In 1970 a non- vented oil cap was introduced with breathing now taking place through a charcoal canister. This system stayed in effect until 1974, and was retained for the Zenith Stromberg carburetor equipped vehicles (1975 onwards). A redesigned front side plate cover was introduced on 18V engines to provide better oil separation and drain-back."
-----------------------------------------------------

The vent vacuum is taken from the carb at a point between slide & throttle blade & connected to a fitting on the front side cover. It also says that the previous model oil filler cap was retained. This cap is described below.

----------------------------------------------------
"PCV Valve System (1965 thru 1968)
As gases are withdrawn by inlet manifold pressure, a vented/filtered oil filler cap provides a supply of fresh air through a restricted orifice (9/64" dia.). "
----------------------------------------------------

I am guessing that the new filler cap on the custom valve cover is vented wide open (no restrictor.) If so, this would allow unlimited flow through the crankcase & to the carb vacuum ports. This could upset carb mixture & also prevent the slight crankcase vacuum which helps control oil leakage from the engine. Sort of counterintuitive. Eg. the cap restrictor takes the place of the previous PCV.

What do you think?
D

[ 08-10-2003: Message edited by: Dave Russell ]</p>
 
David, I have my GT set up with the aluminum valve cover, and an MG Magnett crank vent. It vents by way of a tube going straight to ground. I'm running a DCOE Weber that has no previsions for recycling the crank vent fumes. I still say ya'll are chasing your tails over this valve cover causing the problem.
 
Update: It is now about 200 miles since my last post, and I am down a quart of oil. So, my original observations were correct. I'm losing about a quart per 200 miles. This weekend I'm going to check the hoses for blockage, and I will be putting back on my original valve cover to see if it makes any difference.

A couple of questions:

If vacuum pressure is causing this oil loss, would I see smoke out of the exhaust? I don't see anything while reving up the engine. I've owned oil burners before, and could always see some smoke even though they lost a lot less oil than my B in it's current state.

I don't own a compression tester. Are they expensive, and are they hard to use? Will a cheap one do the trick?
 
Johnny,
Sorry to hear you are still having problems. I had a similar problem with misrouted hoses but I didn't lose that much oil. It did drag some oil up into the hoses, carbs, and the carbon canister. Plugged the cannister in fact. I found a picture of an engihne bay and confirmed my suspicions. I guess I would check the compression as a precaution. At least then you could eliminate that issue. They are not very hard to use at all. You will find a lot of information about the correct way to use a compression test in many manuals and likely thousands of entries on sites like this one. The tester itself will likely have instructions for proper usage. As for the specs, your manual should list the correct pressures.
Good luck. Just keep at it . Half the fun of owning a LBC is the challenge of working on them.
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MGFever,

Thanks for the advice. I'll look into a compression tester. Again, I assume a cheap one will do the trick? Or should I be concerned about false readings with a cheap one?

I've heard of canisters full of oil and blockage (read it on the web somewhere from another B owner). The thing is, my old valve cover vented to the canister. My new valve cover doesn't - it just has a vented cap. So no hoses going to the canister except one coming from the float chamber lids on the carb - and the other seems to go under the car somewhere (back to the gas tank?). So in my case, it can't be an oil filled canister.

Still have a few questions:

1) If an engine has excessive internal oil consumption caused from a plugged or inadaquate breather system - would it smoke??

2) Wouldn't any car noticably smoke if it acutally "burned" a quart every 200 miles? (example bad rings, valve seal, etc)

3) The PCV system: I don't see any PCV "valve" anywhere. Normally I've seen them on the valve cover of other cars (you know - shake it to see if it rattles). Does my 71' B have just a hose from the crank to the carbs via the "Y" connector? No valve? If it does have an actual valve, where would it be?

BTW: I'be pulled off the "Y" connector quickly to check it - it's extremely oily but not plugged. Is it normal for it to be lined with a lot of oil?

Sorry for all the questions!!
 
Johnny...back to the front tappet cover...is it stopped up?

An engine losing oil will not necessarily show smoke - especially if the oil is sneaking out of the engine somewhere because of a pressure blockage....same advice I gave Kim: power wash everything (especially under car & around transmission)...drive it & then relook the physical outsides of engine & tranny - &, no, there wouldn't necissarily be a big puddle under it either!

If your compression checks out & you're not dumping oil from some unusual place, its gotta be in the PCV/oil breather system..
 
One more place to check out...where I found alot of oil loss from my 74B was the on the anti-run on valve where the AIR hose used to be hooked u(the pump and lines were removed by PO)...and the drain pipe that goes out the bottom of the engine compartment from the anti-run on valve.

The old valve I have was taped before and I put new tape on it and noticed less oil consumption...which may have been a coincidence since I also changed oil, filter and drain plugs at about the same time.

But what have others done with the exposed hole in the anti-run on valve when removing the smog equipment???

Bruce
 
When desmogging an MG, there's no reason to remove the charcoal cannister or anti-run-on valve...neither effects engine power by an iota!...however, they both affect the fuel system as they're in-line with the pressurization & return system....put it back on & connect all the hoses back as they were originally!

Having said that, I've seen DPO's stick spark plugs w/hose clamps in the big hose & golf tees in the small hoses
 
Boy, this football has been kicked around so much the leather is worn out. The first thing you check is if the tappet breather is open. Just blow through the main hose to it and there should be no restriction. Second look at your plugs. If they are clean your not burning oil. If they are black and wet you need a ring job at the least. If you want to determan an exterior leak. Do what Tony said and gunk the engine off. Drive it for 30 min or so then dust the engine with baby powder to locate leak. Thirdly people keep talking about doing a compression check. Low Compression has absolutly nothing to do with bad oil rings. If anything worn oil rings will improve compression. Do those things and let us know what you find.
 
Hey guys,

Yes, this football has been kicked around a lot, but I'm learning quite a bit (just like football players learn a lot while wearing that leather down!)
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Tony, I'm not sure what you mean by "back to the front tappet cover...is it stopped up?"?. It's a new cover without a breather vent (the original had a breather vent), but has a breather cap instead. The cap is brand new - so it's clean.

"An engine losing oil will not necessarily show smoke - especially if the oil is sneaking out of the engine somewhere because of a pressure blockage"

That's a great point! I don't need to go through all the steps pointed out to find that I have a leak. I've had a small leak on my rear seal for as long as I've owned the car. But it still never lost this much oil until this year. Hmmm, excessive leaking through an existing small leak due to pressure is something I'm considering strongly at this point.

Bruce, thanks for the advice but I don't have a "run-on valve" on this year MGB (1971).

Tom, I'm not clear on what you wrote. "The first thing you check is if the tappet breather is open." The tappet cover (valve cover) doesn't have a breather anymore on the new valve cover except the new breather cap (Oil cap). It's new and clean. I checked my plugs tonight and all are white - no oil! So nice to see it's not burning the oil! Sounds like I'll pass on the compression test at this point per your post

Here's what I did tonight. I removed the crankcase hose, Y connector, and hoses to the carbs - all clear but very slimy with black oil. Cleaned them up and installed new clamps ( a few were a loose). Checked all plugs - white and clean. Reinstalled orginal valve cover along with breather line to the canister. Of course my original sealed oil filler cap too.

Finally my thoughts. I think the new breather cap isn't to specs and is causing too much crankcase pressure in the system. That would explain the crankase hose and Y connector being so oily. The increased crankcase pressure is probably causing a more severe leak out my rear seal (small leak turning into a big leak!). I'll drive it for a few hundred miles and report back. If this is indeed the cause, I'll simply drill out a breather vent in my new valve cover and route it to the canister like it was originally. And, if this is true, I hope others will learn from my experience.

Take care guys, I'll report back in a couple of weeks. But, if any of you think I'm wrong about my theory - let me know!!
 
jonnyc...maybe we're getting mixed up with terminology...by 'tappet cover' i mean the front cover on the side of the engine under the carbs & exhaust...it has a pipe pointing straight downward...inside is a wire mesh filter aka stel wool...if its clogged, pressure can't be vented from the engine...
 
John, just a tought, but have you checked to see if your breather cap really does breathe?? Just an idea, because it does match right in with changing the valve cover!! GOOD LUCK MAN!!!! I know what you are going thru, very well!!!
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Gary,I checked the cap to see if there are slits in the cap for breathing - and it does. Just wondering if they are truly in spec. the size of the holes sound important.

Tony, thanks for the clarification! I think I see what covers you are talking about.

see this link to moss

https://www.mossmotors.com/Shop/ViewProducts.aspx?PlateIndexID=28976

Number 6 and 7 appear to be the cover you are talking about. But if you notice the front cover, it has a tube coming out pointing up (which goes to the "Y" connector and the carbs). I don't see the tube pointing straight down or the wire mesh. I'll check it out if I can find it.
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I don't know what Tony's smoking, but MGB never had a breather that pointed down. When we refered to tappet cover #6 is the one. Unhook the hose at the Y and blow through it. There should be no restriction. What you have been talking about isn't the tappet cover it's the valve cover. I can tell you the hole in the cap is as big as the hole in the tube that the hose going to the cannester goes on. Now some thing the alloyed valve cover will do is leak at the gasket if you didn't glue it on with 3M weather strip ahessive. It will squeez out. I normally let it set over night so the glue has time to set up. You should see that leak on the ground. I don't believe the alloyed cover is your problem unless you didn't get the gasket on good. I have seen them leak at the rear, run down the backing plate and drip off the bell housing and appear to be a rear main leak.
 
Tom, thanks. I just took off the hoses to the carbs. Pluged one hose on the "Y" connector, and blew through the other. It's very clear, no restrictions to the crankcase. Of course the hose was very dirty (even after wiping it off), and I now have a black lip! Anyway, it's not a blocked breather from the "tappet cover".

As far as the seal around the new valve cover. Yes, it's not the same as the old one, is it. The new one doesn't have that "lip" going around it - it's very flat. I was concerned about this, but was told to put silicon gasket sealer between the gasket and the head and that should be enough. I did't use the sealant between the cover and the gasket - seemed pretty tight and no apparent leaks. Curious, if I sealed both the top and bottom of the gasket - how would you get it off without breaking it up? I figure a valve cover gasket should be good for at least one removal and replacement. Maybe I'm wrong, but this time saving the gasket came in handy.

[ 08-22-2003: Message edited by: Jonnyc ]</p>
 
I don't ever use silicone on a valve cover gasket. If you put too much it can break loose and get in a place you don't want it. I glue the gasket to the cover, the I put axel grease on the surface of the gasket that makes contact with the head. The grease helps to keep the gasket from sticking to the head so when you take the valve cover off to ajust valves it's not a problem. I have had the valve cover gasket on my engines for a couple of years now and they have been removed several times. Another trick is to put a little grease on the grometts and they will last longer as well.
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