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Foamy, gunky residue on oil cap?

Posted by ShawnaNana 
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ShawnaNana Avatar
Shawna Nelson
Mound, MN, USA   usa
Hello! I just bought my 78 Midget this weekend and when I checked the oil, there was a kind of gunk on the oil cap. I'm not sure if it was condensation or what. It's been sitting for a couple of years, so I'm trying to figure out the best way to get it clean. My boyfriend suggests doing an oil change using 10/30 (since it's December in Minnesota) and run it for a while to clear things out, then doing ANOTHER with 20/50 to get it ready for summer driving. Does this sound like a good plan? Any advice from you seasoned MG professionals?


jamesm5858 Avatar
James Moore
Kent, Ohio, USA   usa
There is a good chance that coolant has leaked into the crankcase. If that is the case,blown head gasket is likely the cause. That is a fairly easy fix. The worse case of course would be a cracked block or cylinder head, and those are much more serious problems. Good luck . JM

Bill Masquelier
Santee, Ca, USA   usa
I would take the car on a fairly long drive (50 miles or so) to really get it warmed up and see if the goo is still there. If it is still there or worse then it is possible an engine problem but if it is gone then it was just condensation.
It is probably best to change the oil to the 10/30 before the drive if you can.

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Tire Guy Avatar
Jason Hoffman
BUFFALO, New York, USA   usa
1969 MG MGB "Argo"
1975 MG Midget 1500 "Mobile Gastronomy"
2004 Chevrolet SSX "Purple Flamer"
2004 Ford Mustang
Do you have any oily residue in with the coolant after you run it or it sits?

ShawnaNana Avatar
Shawna Nelson
Mound, MN, USA   usa
We haven't gotten it running yet, still needs a little work. There was no oil in the coolant, though. Also, the guy I bought it from rebuilt the engine within the last 5 or so years, so the head gasket should be good. Hopefully I'll be able to work on it a bit on Christmas and get more answers then.

Thanks again! smiling smiley

7mg2 Avatar
Andrew Hardie
Calgary, Alberta, Canada   can
1969 MG MGC GT "Mr "C""
1972 MG Midget MkIII
Get it running and up to operating temperature. Taking it on a short drive is best if you can to get it hot.
THEN do a complete oil and filter change. 10'30 is good for the winter, 20/50 for summer.

Condensation can form in the engine and form a sludge if the engine is repeatedly run for short periods. The motor doesn't ever warm enough to dissipate moisture. With no oil in the coolant you might be golden, but coolant in the oil can cause the gunk/sludge too, so after changing the oil, keep an eye on things. If the oil on the dipstick gets a milky color to it, coolant is likely getting into the oil. So long as the oil doesn't get milky, and the only "gunk" is on the oil cap you're likely ok. Clean it off and see if it comes back over time.
As long as the motor is getting up to temperature you should be ok. If it doesn't get warm, your thermostat may be stuck open and will need replacing.


NAMGBR# 20-7738
AMGCRA# 1678

jamesm5858 Avatar
James Moore
Kent, Ohio, USA   usa
You have introduce a new variable into the equation. I wonder why an engine that was rebuild in the last 5 years would not run. Many posters have weighted in on your problem, all with good possbilities. You need to get the engine running to really see what the problem. Sludge is caused by a break down of the oil due to high temps, and poor maint. A recent rebuild does not necessarly mean it was done right.

If the body is basicly rust free, you are way ahead of the game. Get the motor running and keep us informed. JM

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ShawnaNana Avatar
Shawna Nelson
Mound, MN, USA   usa
When we tried to start it up for the first time, we found it was leaking some gas from the carb (my boyfriend knows the specifics of it). Just ordered a carb kit to fix that. The body is basically rust free, too (lucky me!).

I don't have much experience with fixing cars at this point, though I expect this car will teach me a lot!

Perdido Avatar
Rut Rutledge
Tuscaloosa, Alabama, USA   usa
1960 Austin-Healey Bugeye Sprite "Scarlet"
1966 Triumph TR4A
1967 Triumph TR4A
1970 MG MGB "Sweet Annie"
Shawna N,
Welcome to the world of MGs and the forum! There is a ton of information in the tech library for just about everything. I will print out an article that discusses a certain aspect of my car and read it at my leisure...great way to learn. We absolutly LOVE pictures and would like to see what's going on with your car. Sometimes a picture will give someone a clue to a plumbing problem or possibly a PO modification gone wrong. Don't hesitate to ask questions, lots of people on here with a world of experience.

oldag98 Avatar
Jeff and Brittany Brackenridge
Choctaw, Choctaw, Oklahoma, USA   usa
1975 MG Midget Conversion
1976 MG Midget 1500 "Yellow One"
1977 MG Midget 1500 "Dunkirk"
1979 MG Midget 1500 "Parts Car"
Interesting color for a Minnesota car. I'd expect it more on a California car, don't ya know? Ya, you bet ya, it will be a good platform to be taught alot! It is a simple car to understand and to fix, but a pain to work on unless you are a midget yourself... Enjoy!

Steve J
The emulsion is caused by water condensing in the oil.
This could be a sign of head gasket failure but chances are its just short journeys causing this as already mentioned.

I would just clean it out and give a good run once engine is running.Just keep a check for oil showing in coolant or creamy coating on dip stick.
On UK cars there is a breather pipe from rocker cover to carbs and this can get blocked with this emulsion so it's worth checking if you have this and cleaning that out as well.

ShawnaNana Avatar
Shawna Nelson
Mound, MN, USA   usa
Thanks so much for your advice everyone! Unfortunately, it's stored a couple hours away so I have to wait til Christmas eve to get started. Can't wait!

66jalopy Avatar
Phillip Jolliffe
Lake City, FL, USA   usa
I would suggest that you catch the old oil in a clean oil pan and then what I do is funnel it into a large glass (1 gallon) bottle and wait for it to settle, time varies then you can see how much oil is on top, if any water it will be on the bottom, if it is coolant it will be green on the bottom, (if that is what is in radiator) very fine metal dust will settle to the bottom, (normal if not too much)

littlecars Avatar
David Bassett
Nashville, Tennessee, USA   usa
1965 Chevrolet Corvair "Ski Team Transport"
1970 Triumph Spitfire MkIII "Tamara's Turd... SOLD!!!"
1974 MG Midget MkIII "Lizzy...SOLD!!"
1974 MG Midget MkIII "Robinette"    & more
Welcome to the forum. smileys with beer Just be patient Shawna. These cars are cute but persnickety to say the least. Unlike a new MINI which is cute and has modern conveniences, you are dealing with a car that was cheap when it was manufactured--and that was 35 years ago! Storage, moisture and lack of use are a Midget's worst enemy. If you brace yourself for the inevitability that the car may not perform the same from one day to the next you will have learned a valuable lesson about LBCs!

Delbert Golightly
Spanaway Wash, USA   usa
Shawana.......the gray "gunk" (which is a good description) is "semi-normal". It is MOISTURE, which is a by-product of the combustion process in yer cylinders escaping by the piston rings. You MUST heat yer engine oil to "evaporate" the water that settles in yer engine oil. It is NOT an engine killer. (yet) It takes about 1/2-hr of engine running time to HEAT yer engine oil to operating temperature. (thats the same as 30-miles of driving) Unless you have a headgasket leak, (doubtful) the sludge is normal by-product of engine operation that you never notice until you drop yer oilpan for engine rebuild. A leaky headgasket will "steam-clean" one of yer sparkies, so un-screw yer sparkies fer a lookie-look. Me? as fer yer gunky oilcap, just putter in yer dishwasher for 1-cycle. Simple, eh? And keep yer itchy-twitchy fingers off'n them WEIRD dual SU carbs. ........HTH, Dell

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