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MG MGB Technical - Oil/water mixing

Hi all

Currently rebuilding a 77BGT.
Had the head off last year and replaced gasket ( Mechspech, unbranded). After several short engine start-ups then long winter layoff I have noticed much of the dreaded "Mayonaise", in oil filter housing, oil cooler pipes, tappet chest and around mounting stud(RH side opposite nos 3/4 cyl) on now just removed head.

Is a "Payen" head gasket the best option ?.
How do I flush the oil system and what product is reccomended ?

Note. On start up and running the oil pressure showed a good 60 to 80 psi.

Any help and advice would be appreciated.
P Liles

Refer to thread below. (engine compression) for info how to deal with leaking head gasket. Yes, the Payen is the best. Whilst head is off , check carefully for cracks. Clean off as much of the emulsion as possible. Most motor factors sell a flushing oil which will help remove most of the remainder. Run the engine to full temperature, you can even use it gently on the road to thoroughly circulate the flush at full oil temperature,( not just water temperature) then drain whilst hot, change the filter and fill with a relatively cheap 20/50 and run that for a few hundred miles. drain again and fill with good quality oil of choice. Change the filter again. Any emulsion still left will be out of harms way and will probably steam off with further use. Alternatively you could strip and wash out the engine.

jim soutar

Not so quuick to drive the car!!! Water displaces oil. That means the water will displace the oil in the lubrication process.

Yes, flush the crankcase with as many "oil changes" as it takes to clean out the "mayonaise" and then AFTER the "mayo" is cleaned out, drive the car very easy and change the oil again after you are sure the engine is free of contamination

79 mgb
gary hansen

Make certain that your cylinder block and head are perfectly flat or your new head gasket will suffer the same fate as the old one. A simple straight edge will do the job. The heads, installed on U.K. cars, didn't have the four emission ports so are much less prone to cracking than those on U.S. cars. RAY
rjm RAY

Hi P
Have a good look at your cylinder head around the area from no's, 2&3 spark plugs up the sides of the centre headstud boss and accross the top of the head towards the valveguides of 2-3 exhaust valves in case you have won yourself -THE CRACK-
It is quite common for heads to crack here and if the crack is in fact inside the tappett cover the coolant goes directly into the oil
William Revit

Head gasket?
Dan Robinson

This thread was discussed between 18/07/2012 and 21/07/2012

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