MGExp

MGB & GT Forum

two annoances

Moss Motors
AutoShrine Sponsor
AutoShrine Sponsor
AutoShrine Sponsor
AutoShrine Sponsor

Tim NJ Avatar
Tim NJ Tim O
Cliffside Park, NJ, USA   USA
1978 MGB 41000 miles

I replaced the alternator with a rebuilt. seems to work fine until I put lights on. With lights I get a screech. turn lights off and it goes away. new belt and sprayed belt stuff but no success.

2nd problem is at 3500+rpm I get a loud vibrating sound from under the car. Sounds like it is near the muffler hanger (the one under the drivers seat). the exhaust system seems tight and hangs well, I can't get much movement at all/

. Hide banner ads & support this website by becoming a > Gold Supporting Member <
ClayJ Avatar
ClayJ Silver Member Clay Johnston
Mt. Olive, MS, USA   USA
1972 MG MGB
Alternator: A) belt not tensioned properly, B) belt not aligned properly, C) improper belt, D) new pulley improper for belt type.

Vibration: If not speed sensitive, the mid-exhaust pipe (or center muffler) between the down-pipe and the rear muffler comes very close to a notch in the fixed crossmember. You may need to pry exhaust away from that notch point or better center the pipe in the notch. If it's speed sensitive I would check the drive shaft phasing and u-joints.

Tim NJ Avatar
Tim NJ Tim O
Cliffside Park, NJ, USA   USA
Thanks clay,

The noise that the exhaust makes is hard to describe, it is not hitting the body. It is more like a loud buzz than a vibration, I don't feel anything just hear a racket.

. Hide banner ads & support this website by becoming a > Gold Supporting Member <
riley1489 Avatar
riley1489 Gold Member Bruce H
Great White North, QC, Canada   CAN
1953 Jaguar XK120
1959 Riley 1.5 "King George"
1973 MG MGB
In reply to # 3494550 by Tim NJ The noise that the exhaust makes is hard to describe, it is not hitting the body. It is more like a loud buzz than a vibration, I don't feel anything just hear a racket.

maybe loose baffles inside the muffler/resonator?

B



Check your ego Amigo!

RAY 67 TOURER Avatar
RAY 67 TOURER Ray Marloff
Fort Bragg, CA, USA   USA
1967 MG MGB "My Girl"
Make certain that the bracket, that goes around the downpipe and attaches to the transmission, is in place. The problem with alternator may be that the pulley wasn't tightened properly and is slipping under load. An impact wrench is needed to get it tight enough. RAY

ClayJ Avatar
ClayJ Silver Member Clay Johnston
Mt. Olive, MS, USA   USA
1972 MG MGB
Tim, hearing the vibration is a rattle smiling smiley I would look close at where it passes the crossmember and the support mentioned above that attaches to the downpipe.

Chalky Avatar
Chalky David White
Coventry, Warwickshire, UK   GBR
Have you taken the centre console / gear surround apart recently. The four screws that hold the metal gear surround down are different lengths. The one that faces the front of the car is shorter than the other three. If there's a long screw at the front you'll hear a loud buzz and a banging noise - sounds just like the exhaust. It's the gearbox touching / hitting the screw.

. Hide banner ads & support this website by becoming a > Gold Supporting Member <
BH Davis Avatar
Thompson, CT, USA   USA
1973 MG MGB
How old is the front muffler? When mine was ready to replace the internal baffles came loose and rattled at idle but not at higher rpm. While opposite of your rattle in terms of rpm my guess is that this is the problem. You can try tapping on the muffler with a rubber mallet to see if it creates a rattle.

BH

garyd Avatar
garyd Gold Member Gary Dabrowski
Naugatuck, western Connecticut, USA   USA
1957 MG MGA 1500 "Long Gone"
1974 MG MGB
1975 MG MGB
1976 MG MGB
Agree with the above. I had baffles come loose in a center muffler. Created a buzzing rattling annoying noise.


Member Services:
Maker of carb and choke brackets for MGB cars fitted with the SU HIF4 carb & later car HIF4 upgrades. Maker of the Air Filter Builder’s Kit, a compact and stylish alternative to Coopers Cans using economical, locally purchased air filter elements.
woodstock1 jim jensen
cleveland, USA   USA
....bad alternator from the rebuilder...have it checked..........

. Hide banner ads & support this website by becoming a > Gold Supporting Member <
Tim NJ Avatar
Tim NJ Tim O
Cliffside Park, NJ, USA   USA
Thanks guys!

I took off the front exhaust strap and it stopped. Put it back on in a different spot where the pipe was a little fatter and and the noise is still there but not as loud.

Is there a purpose for that front strap?

riley1489 Avatar
riley1489 Gold Member Bruce H
Great White North, QC, Canada   CAN
1953 Jaguar XK120
1959 Riley 1.5 "King George"
1973 MG MGB
In reply to # 3495835 by Tim NJ Is there a purpose for that front strap?

yes

this strap serves to secure the dual down pipe in line with the engine hence preserving the exhaust gasket/donut at the joint of cast iron header & down pipe. .

B



Check your ego Amigo!

spikemichael Avatar
spikemichael Platinum Member Michael Caputo
Ocean Shores, WA, USA   USA
1973 MG MGB "Freebie"
1973 MG MGB
1974 MG MGB "Spike"
1979 MG MGB "MegaBeanie"    & more
It should snugly clasp the exhaust pipe



Michael J. Caputo
'79 RBB and '73 CBB owner with extensive experience in 12v Audio System design and installation.
Vendor of Regalia and Promotional Products. Forum Member with a warped sense of humor.


Member Services:
Calendar Photo Submission Deadline: July 31! Email tips@MGBCalendar.com for FREE PHOTO TAKING TIPS! You can always call me at 978-249-5760 PST about Weber DGV Carbs, the calendar or just to talk MGB!
. Hide banner ads & support this website by becoming a > Gold Supporting Member <

To add your reply, or post your own questions

Members Sign In   or   Create an Account

Registration is FREE and takes less than a minute!


Having trouble posting or changing forum settings?
Read the Forum Help (FAQ) or contact the webmaster