MG-Cars.net

Welcome to our resource for MG Car Information.

Recommendations

Parts

MG parts spares and accessories are available for MG T Series (TA, MG TB, MG TC, MG TD, MG TF), Magnette, MGA, Twin cam, MGB, MGBGT, MGC, MGC GT, MG Midget, Sprite and other MG models from British car spares company LBCarCo.

MG MGA - Rod Bearing Noise????

I have a stock 1500 which has always run very well, but a bit noisey, (vales are chatty, and various rattles under the hood). It holds almost 80lbs of oil pressure cold, and between 40 and 60 when hot & idling. It never runs hot, always staying under 200 degrees.

However, lately at shift point I "think" I am hearing a bearing rattle noise, which would usually be a rod bearing. But when I try to duplicate the sound with the car sitting still by reving up to the same RPM's, I can't hear the noise.

With this good of an oil presure, it shouldn't have a bearing problem, as low oil pressure usually goes hand in hand with worn bearings.

Since the oil pressure is good, and I can't get the engine to make the noise when sitting still, should I stop worring about it? Am I just being paranoid?
Robert

It sounds as though your car is "Pinking", check the points as the cam has probably worn, and they have closed up. This then has the effect of advancing your timing, which will cause early detonation under load (but not necessarily standing still revving the engine under no load).

But fix it soon, predetonation will destroy an engine VERY quickly.
dominic clancy

Robert,
I've had the metal fan give off a rattle between gear changes.
Try removing it all together and driving the car, but not in traffic and don't put it back on in reverse.

Check the tappets are all at 17 thou.

If you still think it's a big end, then take the sump off quick. I've done this several time with the engine still in the car, by just putting wedges under the engine mounts.

If a big or small end lets go it's very costly, as my brother found out.

hope this helps.
Cheers <MARK>
Mark Hester

The best indication of a loose rod bearing is to run along in top gear and apply light acceleration followed by a light lift off the gas. Rod rattle is most apparent under light loading. Normally they will not rattle under a heavey load unless they are in very poor shape.
John H

Hi Robert. A few years ago, I heard what i thought to be rod bearing noise. When I pulled the engine the noise ended up being a very worn clutch release bearing! THe carbon part of the release bearing was completely worn away, so the metal casting of the release bearing was hitting the clutch pressure plate. This created a loud rod bearing like knock that occurred at all RPM's from idle to redline. I am posting this so you dont jump to potentially incorrect conclusions about your rod bearing noise without doing some diagnostics first. Hope this helps. Glenn
Glenn

Have you checked the timing chain tensioner & also the cam nut. I know some one had the same noise in a 1800cc this was hes problem.
Jones

Robert.
Start by doing a coasting test to rule out other drivetrain parts. Get to the point where the noise starts and then put the car in neutral with the clutch released.
I had a UJ fail on the drive shaft and I also thought it was engine related.

Neil
Neil Purves

If it's bearings, they usually complain more when the oil is hot and thin. If you change to a heavy weight oil and it improves, you've probably got the diagnosis right.

My car's rod bearings are a bit clattery (is that a word?) if I'm using light oil in the summer heat. When I'm using 20W50, it takes quite a bit of heat to make them clatter. At least that's my theory. The heavier the load and the thinner the oil (lower pressure), the more they clatter.
Tom

This thread was discussed between 04/06/2006 and 07/06/2006

MG MGA index

This thread is from the archive. The Live MG MGA BBS is active now.