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MGB MGB oil consumption

Carlbanan56

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Guys, I have posted quite a few times here about my problems with my granddad's 1975 MGB. I acquired the car 2 years ago, and it had been stationary since 1995. Over these two years, I have checked and replaced various parts to get the car ready for what is known as "Besiktning" in Swedish—a mandatory car inspection every 2 years. Once a car turns 50 years old and has passed inspection in the last two years, it's exempt from further inspections. Three days ago, the MG passed the inspection and became road-legal. As you can imagine, I've been enjoying driving the car that I've been working on for 2 years over the past few days. It's been super enjoyable!


As with every previous post I've made, there's always a problem, and this one might not be a simple fix... Yesterday, I took the car for its longest ride yet, about 25 km. Before setting off, I checked the oil, which was right above the minimum mark. This should have raised an alarm because the last time I checked, it was right under the maximum mark. This morning, as I was planning to take the car for another drive, I wanted to ensure the engine had enough oil... but it didn't. Check the picture; the oil level is significantly below the minimum mark.


I could think of three causes for this. The first one is oil leaking out of the oil plug. I checked the plug, and it was dry. The second and third causes both involve the engine consuming oil, which would make sense given how poorly the engine would run. It would start and idle great, but driving was fine only as long as you didn't press the accelerator past a certain point. Initially, I thought this sounded like the engine was getting too much gas, but now I suspect it might be getting too much oil... I'm guessing either the rings or the head gasket are faulty.


If the head gasket is faulty, it should be a relatively simple fix—installing a new one, right? Of course, it will be a significant job, but still relatively straightforward. I'm much more concerned if one or more of the rings are faulty. Then I'll be forced to dismantle the whole engine. Hoping you guys have some insight.
Young and inexperienced
 

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BobHaskell

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On a drive do you notice any smoke out the exhaust, on start up, during acceleration or decels? Any large oil spots on the driveway/garage floor? A compression test will give you a idea if the issue is with the head gasket or the rings. Another issue may be the valve stem seals have failed allowing oil to get sucked into the cylinders.

A leakdown test would be another option, but that requires the leakdown gages and a source of compressed air.
 
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Carlbanan56

Carlbanan56

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No smoke when warm. But I have noticed some oil coming out of the exhaust and some oil on the spark plugs. I did not know about the valve seals, may as well be the issu. I will check the compression to narrow down the faults.
Tank you😄
 

JPSmit

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I would also not rush to take things apart. If the car has been sitting for over 25 years there is a good chance things just need to run in a bit to seal better. I might keep an eye on the oil and run it for a few hundred miles before you do anything too drastic. I would also change the oil before too long.
 
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Carlbanan56

Carlbanan56

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I did a compresion test to day and 3 of my cylinders hade around 150 psi of pressure while one was a bit lower at around 135 psi.
 

Mickey Richaud

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Those are good numbers. If accurate, sounds like the rings are good. Valve stem seals would be suspect...
 
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