MFG Metal on metal noise

I think we need more detail Chris! The motor of my '97 MGF VVC has always produced an unhealthy sounding vibration upon first start up, it clears its throat soon enough, but I suspect your problem is on the over-run. I have not has this problem, but my Cortina Mk2 ( some 30+years ago) had 4 point welded exhaust heat shields. One weld fracture gave me circular saw noises on the over-run. Any analogy? P '67B & '97F

Not sure what more detail to add really!

It started today and never makes a noise when it is stopped, only when moving, can last for 2/3 mins at a time and then goes away a while - sometimes several miles. Have no idea where to start!

Circular saw is a good analogy.......

Chris

Most, but not all, serious engine difficulties go clunklunklunk or bangbangbangbangbang, sometimes really fast. Things that would make a whirry sort of grinding noise are likely to be things that are hooked onto the outside of the engine. I would first check the alternator to see if the pulley-end bearings are shot, possibly because the belt has been adjusted way too tight. If you're comfortable releasing the belt tensioner and temporarily taking the belt off, a very brief startup of the engine should tell you whether it something driven by the belt or not. That shouldn't heat up the engine, as long as it's short. If it keeps doing it after the belt is off, I would guess something cam-related, maybe the cam timing chain pulley rubbing on the timing cover. Normally long before a water-pump begins to make a noise, it has started to leak really badly, so I tend to doubt that's it.

If your car is typical, the alternator mounting is just a bit flimsy to act as the alternator bracket AND the belt-tensioning mount, so one way to quickly and easily see if it's the alternator bearing, and that's to lean on the alternator a little bit, while the engine's running, to see if the sound changes at all. Don't break anything, it doesn't take much; if it's the alto bearings, they will change their song with even a small change in belt tension.

Standard caveat: Any time you get near a running engine, treat it with great respect, like a loaded pistol with no safety. Always expect the worst case, so as to be prepared for it. A fan belt can remove a finger quicker than a knife. If you use a strobe-light, never move instinctively, since your reflexes will make you reach through the fan for something, with disastrous results.

-Rock

"Chris Brown" wrote in news: snipped-for-privacy@sabbath.news.uk.clara.net:

Lots of good,friendly advice available from

Good luck

Seconding the rotating noise comments, I use a mechanics stethoscope to find these problems. Just touching the metal probe to the alternator, water pump or other rotating bolt-ons around the engine bay will quickly isolate the particular problem. Even if a bearing only screams when it's hot and at high rpm, tell-tale complaints can usually be heard whenever it is turning by using the stethoscope.

On the other hand, I almost replaced my mini-van because of really scary noises that seemed to be coming from the engine bay. Saved a few thousand of whatever currency you may use when my garageman found a loose heat shield on the muffler, located right under the driver seat.

Tommy T.