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MG MGA - Crank shaft disaster!!

Hi chaps, last week, whilst on my way to the Silverstone Classic, my oil pressure started to drop from the usual 60, down to 40 - for no reason. I stopped at the next services after a couple of miles, and as I was parking, the guage registered zero - so I quickly switched off, at which point the temperature guage went from 190 to it's max of 240f. I was trailored to Silverstone, (enjoyed a great weekend) and then trailored home again (thanks RAC!!) My mechanic has now taken the engine out and I need a new crank. My problem is wondering what caused it in the first place - especially the rise in temperature.

When the engine was cold during the Silverstone weekend, I checked oil and water levels and they were both ok. I also started the engine, and at cold tickover got 50 pounds pressure. I drove it for a couple of miles, and then heard knocking from the engine. The car had an oil and filter change a month ago - and until last week was running as sweet as a nut.

I'm reluctant to have a new chank, oil pump, drain on my bank balance etc - until I know what the likely cause was, in case it happens again - anybody got any ideas??
D J Hill

Sorry to hear about this but one thing you don't mention is what type of engine it is?

Paul Dean

I had a customers MGA in for new bushings in front suspension. On the road test I watched the oil pressure go from 60 to zero in less than 1/2 mile. Car had been driven from Texas to Sebring for a GOF without any problems. I had to replace crankshaft as it had spun two rod brgs and was seriously blue from overheating.
ss sanders

Why do you need a new crankshaft, is it broken in half or has a bearing run scoring the journal below that that can be corrected by grinding?
You don't have much choice in spending the money if the crank is cactus. A rebuilt engine by a reputable engine builder will get you back on the road for another few years/100,000 kms. They will insure lubrication, alignment and clearances are correct. These type of failures do happen to 60 year old cars/engines.
Mike Ellsmore

The temperature rise after switching off is totally normal. Usually people don't notice because the rarely sit in the car looking at the gauge after a hard or long drive.

Sounds like the big end(s) went fairly quickly and I don't know how common that is, but an examination of the engine parts normally tells all.

A couple of years ago there was a case in the US where one of the (other MGA) forum guys had a felt oil filter disintegrate, trashing his engine. Again pictures of the stripped engine or a better explanation from the mechanic are required.

These engines are as bulletproof as any engine, more so. A properly rebuilt engine is good for 10s if not 100s of thousands of trouble free miles.
Neil MG

Sounds like a spun rod bearing....Hey at least you don't need a new engine block!
Steven Devine

As Neil has indicated the engine temp goes up because the water pump is no longer circulating cooled water.

John Bray

This thread was discussed between 02/08/2014 and 03/08/2014

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