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MG MGB Technical - MGB loss of engine oil

My 1974 MGB GT was on it's first run out follwing being parked up for the winter.I had done about 3 miles when it looks like all of the engine oil has been forced out of the filler cap and covered the engine bay.I was only half a mile from home and managed to get the car back but don't know what has caused the problem, any thoughts from anyone please.
Ian

Ian. The only situation that could cause such a problem is if the oil could not drain out of the valve train area and back into the sump.

What did the dipstick read after the engine had cooled down? If there is no oil showing on the dipstick, I would suspect that major engine damage may have taken place.

At the very least, pull the rocker arm cover and look for some obstruction in the area of the pushrods which was not allowing the oil to drain out of the cover. Also, examine the valve train to seem of something was allowing excessive oil flow into the rocker arm cover. Oil should be draining out through the holes that the pushrods come up through, then down over the tappets and cam lobes and into the sump. Other systems have their own drain mechanisms, such as the front journal, rear journal, camshaft and connecting rods. But, if the oil is not draining out of the rocker arm area, you will eventually run out of oil in the sump and the oil pump will cavitate, cutting off the supply of oil to the system.

I would pull the sump and check the rod and main bearings for damage. Amazing what only a short period of operation without oil can do to bearings and the crankshaft.

Les
Les Bengtson

Ian,
Did you loose oil pressure?
If not then the lower end is probably OK.
After sitting up for months the rings may be stuck. If there is a lot of blow-by that cxould cause a lot of oil fumes to blow out of the filler and coat the engine compartment.
If there is oil pressure, run the engin until warmed up and take the filler cap of and rev the engine and see if there is a excess amount of oil fumes.

Steve
Steve

Thanks for your replies, unfortunately I did lose oil pressure although I don't know what the pressure gauge was reading just before the loss of oil. As I said previously I made my way home carefully as I was nearby. The car seemed to drive OK and hadn't appeared to have lost any engine power. Even though this was the car's first run out of the year it had been started several times over the winter months. There didn't seem to be any oil mixed with the exhaust fumes on tick over after the event. Any more comments would be appreciated.
Ian

As asked, what was on the dipstick immediately after the event? Did you refill? Did it run into the sump OK? What is the pressure now and does it vary from what it was before? The real arbiter is what noises you get when starting after having been left several days, i.e. is there any knocking/tapping that quietens as the oil pressure suddenly rises, and how long does that pressure rise take? Driving it with no oil pressure is asking for trouble.
Paul Hunt 2

Ian, I took the opportunity to examine a stripped 18V block yesterday, after I had read and responded to your question.

The main mechanism for draining the oil out of the cylinder head is through the pushrod holes. The oil can, in small amounts, drain down the sides of the tappets, lubricating the tappet and camshaft lobes. Between tappets two and three, and between tappets six and seven, there is a hole, of about 1/2" diameter, which serves as the primary means of training the tappet chests of oil.

I guess, in theory, it would be possible to pressurize the lower crankcase, due to stuck rings not making a good seal against the sides of the cylinder bores, and force some oil upwards into the tappet chest area. It might, then, be forced upwards into the rocker arm area through the pushrod holes in the cylinder head. But, this seems to be a rather difficult process to visualize since most of the oil is in the bottom of the sump and would have to be forced upwards, through several tight holes and two unrestricted holes, in the camshaft area. I suspect that such a pressure would also be blowing oil out of the rear main seal, the timing chain cover seal and the tappet covers.

Thus, the most logical way that oil could be forced, in excessive amounts, into the rocker arm cover would be some blocked oil passages, diverting most of the oil flow into the rocker arm cover. Certainly, the amount of oil necessary, and the pressures that would need to be generated, to lift off part of the oil filler cap tend to indicate that there is some serious form of problem here.

But, it is not possible to know exactly what that problem might be without an engine tear down.

Les
Les Bengtson

Thanks for all of your responses.
Unfortunately I have given you all some duff information, the fact that the filler cap was raised up at one side appears to have been a CRUEL coincidence, it was the first thing I spotted after lifting the bonnet and seeing hot oil dripping from the underside of the bonnet all over the engine bay.
I have found the source of the problem and it turned out to be a split hose to the oil cooler, I only found this after checking lots of things like the crankcase breather, the pressure regulator, checked the cylinder compression removed the rocker cover and poured oil down the pushrods to check the return path.
There was virtually no oil showing on the dipstick and after I had filled it back up to the min level and tried it again I noticed the leak from the hose. I have replaced the hose and the oil pressure is back up to over 60 psi, the engine is running mormally with luckily no knocking from the bottom end either.

Thanks for all your help again.

Regards Ian.
Ian

Oils well that ends well! ;)
Ross Kelly

Ian. This was the situation with my daughter's car--the oil line to the cooler split when she was driving along at highway speed. Chips of bearing metal in the sump and on the screen of the oil pick up. Rod bearings severely damaged with scoring of the crankshaft. Heat bluing of the lower portion of the connecting rods. Required a total tear down, cleaning, and rebuild--on a freshly rebuilt engine. The oil cooler hose was three years old. Great fun.

I am glad you found the problem. But, I would suggest that dropping the pan to see what damage may have been done, would be a very good idea. Ideally, your slower speed means that no damage was done and all you are out is your time and a sump gasket. But, if your engine sustained any damage in this incident, better to find it out know rather than when it self destructs along a motorway.

Les
Les Bengtson

I'd be thinking along the lines of steel braided oil cooler pipes. Im not going to get paranoid myself though. Ive enough to be worrying about. Im a motochondriac.
Ross Kelly

Just a thought.

You could eliminate the oil cooler. In Ireland it is probably not needed. The 18V replacement block in my 65 came with a steel line from the block to the filter head. No hose worries there. The filter is a hanging one that should work with the late model starter. Mine car retained the inertia starter. I don't think you can buy these parts but they may be available used.

Apparently a lot of the replacement cooler hoses don't have good end fittings. Check the archives.

Robert McCoy

This thread was discussed between 03/04/2008 and 08/04/2008

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