Clanking noise

[ScotStern]

When I first start my MGB(1975)I hear a "ringing" type of sound in the front of the car (might be water pump). After the car warms up, the sound is gone. The car seems to run fine after it is warm. I don't hear it again until it is a cold start. Any thoughts?

Thanks,

Scot

 

[JoshP]

Usually, the sound of a water pump going bad is a squealing sound. Your engine might have a minor ping which goes away after warmup. Try upgrading the octane rating of gas that you use and see if that takes care of it.

 

[Guinn]

Is the "ringing" noise at idle, easy load or heavy load or any load? Are you hearing it with the hood up or down, standing by the car or in the seat?

Pin it down and we may be able to help.

And welcome to the format.

Guinn

 

[ScotStern]

The "ringing noise" is heard at idle, from inside the car in the driver's seat. You can raise the hood and still hear it. It appears to be comming from the front of the engine.

By the time you drive it the noise is not noticable. It is a definate ringing noise and only at idle when you first start the car. It will last until it warms up.

Thanks,

Scot

 

[Guinn]

HI, Scot. That type of noise does not sound familiar to me. Perhaps someone else will chime in on this. In the mean time, if you have a mechanic's stethoscope, try touching it to different parts of the engine (carefully) and see if you can more accurately locate the noise source. A long screwdriver or a one inch dowel works, too, only not quite as good.

Check at the water pump, at the flange where the oil pan bolts to the block and at each accessory, like the alternator or anything else you may have running off the fan belt. Use care near moving parts - as if you haven't heard that all your life!

Personally with the little I know so far, I would suspect something worn and loose in the alternator. Wild guess!

Guinn

 

[Guinn]

Another wild possibility: You might have a restricted oil supply to one of the tappets and it could be noisy until the oil manages to get to it. Wild, but possible. Try removing the valve cover with the engine cold and see if the noise seems louder, then quiets some when you set the cover back. Oh, yeh. You press the end of the screwdriver to the flap of your ear, not in the ear. You know, that flap that almost covers the ear canal.

Guinn

 

[Deleted member 3577]

Try taking your belt off and running it for a few min. Might be a dynamo thing

 

[LLAngus]

Check the pullys to see if they are tight. A ringing noise sounds like thinish metal. Check when the engine is not running!!

 

[Guinn]

Scot, let us know what you come up with. It could help someone else in the future.

Guinn

 

[PAUL161]

I would check the oil supply to the rocker arms. How is your oil pressure? If the oil pressure is low or there is a restriction in the flow to the rockers you might be running slightly dry during startup. Are you using a thin oil? PJ

 

[ScotStern]

The oil pressure is fine and the oil is normal weight for California. This sound is not really internal. I am going to start detective work this weekend and I'll report back. If I had to guess, I would say smog pump and or related plumbing.

Scot

 

[rodesmg]

i don't own a B but my midget made a sound like that and it was the fan clutch.

 

[LarryP]

If it still has the stock ZS carb setup with the thing in the path to the air cleaner that directs warm air into the carb when it is cold, (air diverter valve? can't remember what it is called). Anyway, if the bi-metal holding the flapper in the housing is weak or broken, like mine was, it rings like a clapper in a bell at low RPM. Just a thought.

Larry

 

[Guinn]

As stated above, I would try a stethoscope (or dowel) to help locate the noise. It is not a good idea to start taking things apart or replacing "possibles" unless you can't locate a probable. FWIW,

Guinn.

 

[Bruce74B]

The first thing I would check would be the alternator pulley...remove the belt and torque the retaining nut to insure a snug fit. Start the engine with the belt still off and check it. Refit belt and check it again. That tin pulley and fan can make some strange noises when they are little loose. Also check the alignment of the alternator to the rest of the belt system. I suspect you may find your "ringing" there.

Good Luck!

Bruce /ubbthreads/images/graemlins/cheers.gif

 

[kennypinkerton]

I vote the hot air flapper. mine does the same thing. 1975 MGB's have ZS carbs right. It's the black part in the right side of this picture, with the hose attached to it...
https://www.mgcc.se/images/Motorrum_Amerika.jpg

 

[Nunyas]

my '76 makes a similar sound, and it too comes from the "flapper". Assuming your car has the stock ZS carb it could very well be this part. It's not really anything to worry about. I believe it's there for emissions to help the car warm up to full operating temps quicker by puling warm air in while the engine is still cold. Once the engine warms up the flapper (made of a bi-metallic material) will bend itself so that cool air is pulled in from the other side. I've wedged a small piece (i.e. scrap) of rubber fuel line in so that it always pulls from the cool side, and never clatters.

When you have a chance, look under the bonnet it'll be obvious if that's the item making the sound, because you'll see the "flapper" flapping and it'll stop making the sound if you put your finger on it.