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MG MGB Technical - Rattling on start up

On starting my 1978 mgb roadster tonight outside work there was a nasty loud rattling on start up for a few seconds which went away as soon as I accelerated. The journey home of 60+ plus miles was uneventful and the noise only returned for a few seconds (although a lot quieter) when I started the engine again to put the car in the garage. I subsequently restarted the engine a number of times and each time the noise returned for a few seconds after starting, getting less with each start. It sounds like its coming from the top/ front of the engine. Could it be water pump or alternator bearings or am I being to optimistic and something more drastic is amiss? Any suggestions would be appreciated and how can I check if its alternator or water pump?

Thanks.
D Callaghan

Remove the fan belt, if it is gone you know it is the water pump or alternator, also the air pump if it is still on the car. Watch your oil pressure gauge, if the noise exists only until the pressure comes up, it could be a bearing issue.
John H

Make sure that you have an oil filter with an anti-drainback valve, chack your oil level also.
I hope that it is nothing serious!
M. H. Dabney

It almost has to be bearings and lack of oil pressure, as anything else would exist at other times. Most oil filters have an anti-drainback valve, but they vary a lot in quality and effectiveness. What filter are you using? I have always had an acceptable delay between starting and oil pressure with Unipart, Champion and Halfords filters but someone else reported instant drain-back with new stock of the first two. I tried an MGOC Fram filter that reputedly had an improved valve but found that worse. Next was a Volvo/Mann filter and that was better than the MGOC, maybe about the same as Champion/Halfords, at about 50% dearer. I currently have a K&N Gold which is about double the price of the Champion/Halfords i.e. 50% dearer again than the Volvo, but worse than the Volvo. So next time it is back to Volvo.
Paul Hunt

I have an MGC with the original upside down filter that drains back into the crankcase overnight. When starting I can tell from the sound of the engine when the filter is refilled and oil pressure comes up. It comes no where near "a nasty loud rattling". Unless you are listining for it you don't even notice. If yours is that loud and is coming from the block, clearences are too loose somewhere in the oil system.
John H

This thread was discussed between 28/08/2008 and 29/08/2008

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