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MG MGB Technical - Dynamo/Alternator shot? Leaking BGT hatch? Small oil leak?

Here we go -
I have a '76 BGT. Over the last couple of days, I noticed that the starter motor worked slower and slower, windscreen wipers crept slower and slower across, indicator lights went on strike and OD did not engage. Now on Sunday, the starter did not engage, just made some whirring noises mixed with a loud clicking (and mixed with my wife cursing, she needed the car badly right then). We managed to push-start it, and it worked until yesterday afternoon, where it gave up the ghost altogether. Same pattern as on Sunday. When I took the battery out, it turned out to be completely flat.

I reckon the dynamo is shot, but before I fork out GBP 100 on a new one (+ the mechanic), I'd like to know if there could be anything else. What is a simple way to see if it is the dynamo? I am technically challenged, and no, no lights out of the ordinary warned me about what was about to happen.

Another thing: The rubber seal around the back hatch is badly rotten. How do I change it? The car seems to let water in there, and this being Norway, I need a reasonably watertight car. Any tips and hints would be appreciated....

One final thing, and then I'm done: There is a small hose, going from the engine block, visible on the left side, when peering down from the front. The hose goes from the block to a very small steel tube that disappears through a panel attached to the bulkhead. The hose is probably rubber, with a protective steel mesh on the outside. When you grab it with the motor running, you can feel the pulses of the oil within. I suspect it is for the oil gauge in the dashboard?

It has a small leak near the top. Can I change it myself without problems - and what is the part called if I need to order it?

Thanks a lot all you folks out there. Always great advise - educational and entertaining alike.
OYH

In regards to the battery, the dynamo as you call it or alternator as it should be called may not be bad. Batteries do not last forever and probably go out more often than alternators. From what I can tell, your symptoms seem to point to a bad battery(although I suppose it is possible for both to be bad.) Since your battery was shot you will need a new one anyway. If you have not replaced it do so now as it is the cheaper and easier of the two to replace. Then take your car to a competent mechanic or similar service station that is cabable of testing the alternator for proper output. I don't know what the specs are, but one of the electrical gurus on this site may be able to help you with that matter.

As for the small hose, if it comes out of the block in the rear of the motor in the vicinity of the distributor, then yes it is the line that goes to the oil pressure gauge in the dashboard. It is easy to replace. when the motor is off the line is not pressurized, a few drops may leak out when changing it, but it will not be very messy. I'm not sure what the proper name for this hose is, but any supplier that deals with MGBs should know what you're talking about. If not, try to find an illustated catalog from a supplier(do they have Moss in Norway? or maybe a UK supplier) and identify the part from it. Perhaps somebody from the other side of the pond could help with this area.

Now as far as the rear hatch seals go, I'm not sure what to do. In fact I'm interested in finding out the proper way to replace these as mine are going bad too.


Best of luck with your problems and I hope to have helped,
Jared
Jared Snider

Jared,
Thanks a lot for your feedback. The battery *should* be all right, it is only about a year old - a maintenance free, German make, relatively powerful with 62 aH capacity. I was able to charge it somewhat overnight. And this morning, the car worked as its maker intended it to. Until I get to the mechanic, I will have to charge it at night and go easy on the lights and fans, I suppose.
OYH

If you have or can get a small voltmeter (usally at an auto parts store) do some checks as you put in your new battery. Connect the positive side (or whichever is NOT the ground for your car) then connect the voltmeter between the ground cable and its battery post. With everythng off you should get no reading otherwise something is draining the battery. Next, connect the battery, start the car,and connect the voltmeter between the two terminals on the battery. You should get a reading between 14-15 volts if lower then your alternator isnt putting out as it should.
william fox

OYH,
Last season I replaced a very high quality battery in my B which was only 1 year old with an old battery taken from a different car the previous year because of age. I post this to show that a new battery, even from a reputable company, can go bad.
The old battery is from the same maker as the new battery, 12 years old and working well in the B. You never know how long a battery will last.

Try another battery (new) and have your Dynamo inspected at a reputable shop by somebody who knows their stuff - ie- if they ask what the dynamo is out of , try another shop.
Good luck
.

OYH:
It is likely that you have a spent battery, but don't discount the possibility of a bad alternator. You mention that you could get your car to run and then later it could not start at all (I am assuming that means that even by push starting, it did not respond and start). If my assumption is true, then I think it would be prudent to check out the alternator as well, just to be sure it is putting out voltage to run the car. Often, when we push start a car with a "dead" battery, the engine run solely on the output of the alternator or generator (dynamo) and if these are also "dead", then the car will not run at all no matter what we do. Good luck.
Bob Muenchausen

As for your other two problems, OYH,

1) I believe there is a good discussion on replacement of the rear hatch rubber in either the Lindsay Porter book on Restoration and Purchase of MGBs, or in a Brooklands/Osprey book I once had which also covered the restoration of MGBs. My suggestion would be, OYH, that you take a few fotos of what is there now, how it is mounted, and the relationship of the individual rubber pieces and the aluminum retainer strip (across the top) and then maybe take some notes on its removal with an eye to its reinstallation. To get excellent quality repro rubber pieces, I would try either the MG owner's club spares http://www.mgocspares.co.uk or MacGreggors in Canada http://www.macgregorukcarparts.com/ .

As for your second question, the flex hose for your oil pressure line is easily replaceable, but be sure that it really needs replacement. If the hose itself or the joint between hose and its fittings is leaking, then it needs replacement. However, it may simply be loose, and snugging up the pipe union nuts on both ends may fix your problem. If that does not work but your hose is not leaking, then check the intermediate fitting on the firewall and snug up the instrument pipe fitting. If it still leaks, check the soft metal sealing wad on the end of the instrument pipe AND the intermediate fitting for cracks or messed up sealing surfaces. Good luck!
Bob Muenchausen

Slow cranking could well be battery, but if the wipers are slow and the blinkers don't blink when the engine *is* runing then it is the alternator that is not charging. Could be a broken connection between the solenoid and the alternator plug, with a charged battery check for 12v on the brown at the alt plug. If you see it the alternator is probably bust, if not you have a broken connection.

Your ignition warning light should tell you if it the battery or the alternator. It should come on when you turn on the ignition and not go out until the engine has started and is revved to 900rpm or so. Thereafter it should remain out while the ignition is on, unless the revs drop below about 500rpm or so when it will probably come on again, not going out until revved to over 900rpm again. The only other time it will come on is briefly as you turn the ignition off. If comes on at any other time, even dimly, you have an electrical problem, probably poor charging. You can check the warning light by grounding the brown/yellow wire (NOT the brown!) at the alt plug with the ignition on, the light should glow. If it does, but doesn't when plugged into the alt, the alt is bad. If it doesn't glow then either the bulb is blown or you have a broken connection.
Paul Hunt

Thanks a lot for your input, gentlemen. I will see if I can get a voltmeter one of these days to check the alternator. I would have thought that as long I was cruising at motorway speed I would have no issue with slow / dead intruments if the alternator was working? The wipers, indicators and OD can't be supposed to run off the battery? Or does a shot battery suck up all the electricity an alternator generates?

As Paul noted, the wipers were terribly slow and the indicators were dead until I managed to charge the battery last night. However, the battery does not seem to have charged as well as expected (the charger has an indicator). The ignition warning light goes off in the proper manner when starting, as soon as I reach +/- 1000 RPM, and stays off until I switch the ignition off and the engine dies. That should then indicate that the alternator is OK, I guess?

Petrol stations are more like convenience stores in this country, but I will try and get someone there to check the battery tomorrow, if I can find someone at all among the Pepsi stacks, bake-off, videos and skin mags.

Thanks to you all, I have ordered the spare hose from Brown & Gammons, the old seems to be leaking where the hose meets the fitting. The rubber seal for the hatch is something I might ask the mechanic about, but if it were an easy fix, I'd rather spend the money on other stuff instead. (And some of the idea about having this car, was to get into some of the easier tasks as a hobby.)
Ø. Hellum

Under normal conditions it is the alternator that runs everything plus trickle charges the battery. Only if the electrical load increases beyond the alternators capacity to supply it (or the alternator output falls below what is required) does the system voltage start to drop (and hence dim lights and slow wipers and flashers), battery charging ceases, and eventually it is the battery that starts to run everything running it down. If the battery were so 'shot' that it sucked up all the power the alternator could generate you wouldn't be able to start the car even by towing it. You might *just* be able to start it by jumping it from another battery, but there would be a helluva spark when you connected and disconnected the jump leads!

"I will see if I can get a voltmeter one of these days to check the alternator"? Doesn't sound like you are planning to use the car any time soon, then ...
Paul Hunt

My rear hatch ('73 BGT)was leaking so I replaced the outer seal along the top. Was pretty straight forward and took about an hour and the problem has stopped. I removed the hatch from the hinges for better access.
william fox

This thread was discussed between 23/04/2002 and 27/04/2002

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