Mechanical Tips for MGB Members
Brake Bleeding (Bergerac Trip 2002)
We had quite an eventful holiday in France this year, with the car, I will no bore you with another holiday story. Needless to say 100 miles into France we had a fuel pump failure, I have written this up in another story so will also leave that alone.
What are the chances of a seat belt return spring failure, pretty slim I am sure you would agree, about ten days into the holiday a whirring sound came from Doreen belt she had yards of webbing, when we stopped I jammed up the mechanisms so as to have a static belt, would you believe two days later the same thing happened to mine what the chances of this happening?
The other problem that I have had for some time, I believe is trouble with the brake servo, I spoke to a guy from High Wycombe who repairs them, about the problem he seemed to confirm my thoughts, having struggled with the problem for some time, I needed to do some thing as after baking the bakes were coming half back on and screaming like hell, the guy at Wycombe wanted 4 weeks to repair the unit but we our commitment to the Register I could not really be without the car that long, so had to buy a new unit, for what they cost you would think they were gold plated.
As the Gaydon event was due I decided to leave the fitting till after this, the event over I fitted the unit, refilled the master cylinder bled the brake system with an Easi-Bleed unit, it did not matter what I did the pedal went to the floor, I got Doreen to pedal pump instead for me, same result, I remember the last time I fitted a servo to the car some 12 years ago a mate and I had the same trouble, he gave up and left me to it.
I then remembered what I had done before so thought it worth a try, again I fitted the Easi-Bleed to the system, pressurising it, then getting into the car Stamped on the brake pedal two or three times, then bled the fluid at the nearside rear cylinder, then felt the bake pedal, it had come up a bit, so done the same again giving the pedal three very hard stamps, then bled the same cylinder again, on getting to the pedal I was winning so went through the process again, bleeding, then locking off the nipple, I now have an almost perfect pedal, may be worth a try if you are struggling, maybe the air get trapped in the servo, I really don’t know but this seems to work.
If you have found that your Handbrake has become stiff in operation and down on efficiency no matter how you tug on the lever, it could be due to one or all the following.
a) Lack of lubrication of the flexible cable despite grease having been pumped into the nipple provided on the outer cable close to the rear axle. Often the grease only oozes a few inches from the nipple leaving the majority of the cable with no grease resulting with the inner binding in the outer.
If the cable has not yet got to the state of complete seizure but is merely oozing grease under grease gun pressure clean the outer cable with e.g.. Thinners, allow it to dry off then bind the outer with for as far as necessary with a good PVC tape making sure there is plenty of tape overlap. Then try again with the grease gun.
If the cable is seized there is no alternative than to take the cable off the car and indulge in some patient freeing off on the bench using plenty of penetrating oil. Having got the inner cable moving freely go back to the clean and bind routine and then pump in a reasonable amount of grease before sliding the inner back and forth a few times to distribute the grease.
b) The rocking lever mounted on the rear axle on earlier cars may have become seized on its spindle. The cure is to dismantle the lever from the axle case, clean and lubricate the spindle and the bush in the lever. Reassemble using a new Nyloc nut and check that the lever is free to rock from side to side.
c) The rubber boots on the rear brake back plates (at the point where the handbrake cable ends are attached to the brake shoe actuating lever) are perished and/or split, thus allowing water to get into the drums and seize up the in-drum mechanism. The clevis pins which attach the cable ends to the actuating lever may also be worn, giving rise to lost motion.
d) Remove the wheels (always use axle stands), brake drums, the aforementioned clevis pins, the brake shoes and the handbrake actuating levers. Clean and lubricate sparingly all the bits. When reassembling fit new rubber boots and worn clevis pins and the brake shoes if they are well worn. Refit the drums, adjust the brake shoes and, if necessary the cable, beneath the handbrake lever underneath the car.
Do all that and you should have a smooth moving, free acting and efficient handbrake and lever.
Thought the following may save some one some grief. I ordered a new fan belt from Moss. They sent me a Unipart GCB 10900. When I went to fit it, it was too small! I rang them only to be told this was correct for the MGB-GT. The comment was someone must have changed the pulleys! I found a fan belt in the boot that I had bought at an auto-jumble.
It was an AC Delco 925 which fitted. I was told by Moss that the last three numbers are the length of the belt i.e. 10900 is 900mm long. I checked to see if I had a spare in case this one broke. As I had, I did not bother any further. Yesterday I needed a fan belt for the roadster that I am building. Again the Unipart belt is too short, so are both my cars WRONG!?? I tried the 925 AC belt and it fitted. Now not having a spare, I went to Halfords, had a look on their racks and found a 925 belt.
I asked what they had listed for the MGBs. When he looked it up it was HB900. We went to the Halfords range and he gave me the 900. When I told him it would be too short he told me – sorry that’s what we have listed. I asked him to confirm the last three numbers were the length. He said he did not know.
I picked two HB925a belts from the rack, a little while later he came and found me in the store to tell me that the last three numbers are in fact the length. So check and make sure your spare belt is correct for your car. You have been warned!
Curing a Misfire by Nicholas Stoyle
I don’t think we have published this tip before. I came across it amongst all the material I have received from Don Bishop over the years and thought it was rather pertinent as I have just experienced a similar problem which actually turned out to be a faulty HT lead. I sued the same check procedure to locate it as described in this tip.
Don attributed Nicholas Stoyle as the author and running a query in the new Access database (show off!) I have found Nicholas to be the owner of a ’78 pageant blue GT and living in Chester-le-Street. The tip is dated 2001 – so a belated thanks!
Intermittent misfire developed whilst on a rally/fun-run much to the amusement of friends who were following (August 2000).
Logical sequencing lead to the following checks:
- Check points gap and apparent condition of the condenser. Re-check strobe timing. All seemed satisfactory –misfire still there
- Check condition of plug leads – could be better so replaced – misfire still there
- Check plugs – Bosch fitted but Champion recommended – replaced with Champion RN9YCC – misfire still there
- Check rotor arm and distributor cap condition – could be better so replaced – misfire still there
- Tappet clearance checked and adjusted – misfire still there
- Coil suspected so replaced – misfire still there
- .Idea – could there be a manifold problem? Ran the engine up to working temperature and extremely carefully (fire extinguisher to hand) (dodgy! –ed) poured a little white spirit substitute over the inlet and exhaust manifolds to check for an air leak – none detected and no fire either – however misfire still present
- Distributor removed again – points and condenser replaced – starting problem
- Lead/plug to rear of alternator found to be loose – reconnected into position. Trial run over 6 miles – no misfire
- Engine kept running during lights and indicator checks – no misfire
- Is the misfire cured? Only time and distance will tell but a logical approach was followed – so far so good!
Comment from another classic car enthusiast after the condenser had been replaced – if the alternator connection had bee vibrating intermittent output would occur and this could cause premature failure of the condenser. In future the pre-run check will include the alternator lead connection too. Happy motoring and carry a spare condenser
A Tale of “Ragged Running” by Don Bishop
It’s a matter of pride to me that my GT engine runs a smooth as a nut; or as near an approximation to “s.a.a.n.” as you are likely to get with a good old “b” – series which hasn’t had the benefit of balancing etc.. What I really mean is that it pulls like a train with equal compressions and no misfiring. Normally, that is – it normally runs etc. etc.. Until a couple of weeks ago when I happened to be on a trip across to Weston -on – the – sea (aka Weston super mare) and having my son as a passenger – of itself a rare occurrence as 1) he lives in the USA and 2) he’s more of a Triumph man anyway (says a lot for my parental influence, dunnit?) when IT happened.
We’d just climbed a short sharp hill near Yeadon and come over the top to be greeted by a T-junction and a marked loss of power, in that order. Took the corner and bowled way downhill with a return of said power, no apparent further problem. Spent the day with friends, motored back with n.a.f.p. until we reached the M27 near home when I started pressing a bit harder to keep fairly well up with all the traffic doing 80+. Alls well for about ½ mile when came a vibration which felt for all the world as though a back wheel had gone badly out of balance. There was bags of noise anyway, what with the open sun-roof and windows, cassette player and so on. I eased off the loud pedal a bit and everything returned to normal with a reduction of only about 3 mph. I thought about it and resolved to sort it out soonest, Expatriate son was offering all sorts of suggestions, of course – the sorts of things that might well happen on a Triumph, most totally ignorable of course. Dreadful thing pride y’know.
Anyway, what could it be? I looked at my service records and noticed that the spark plugs had done nearly 20,000 miles so a new set wouldn’t come amiss. The leads all looked quite good with no bad miss-routing to cause possible arcing. Out with the distributor, may as well do the job properly. The points looked quite badly pitted so in went the spare ( new) set. Could it be the condenser? No real way of telling although in my experience condensers don’t usually cause intermittent problems: they either work or they are dud. Change it for a new one just in case. Cap and rotor arm looked fine – no signs of arcing anywhere, inside or out. I would stress that changing the plugs didn’t cure it, having road tested it at each step. Neither did the points-and-condenser change (OK so that’s two steps but it was easier to do both together while the distributor was on the bench.) How about the coil – could it be breaking down under the heat and stress (don’t we all dear?) I will say at this point and in my own defence that the car did seem to be running a bit better than before, so the ignitions renewals might have been overdue; but again, when pushed, the misfire came in and it felt as though one carburettor was giving up it’s share of the work but returning to the fray when the throttle was eased back.
Wait a minute, there’s a clue. When under hard acceleration the power was on tap for a few seconds but fell away with the onset of misfiring. Could it be fuel starvation? New pump last year should be up to the job. Come to think of it, on early morning start-up I had the vaguest impression that the pump had taken to ticking very slowly instead of setting to with a will. So – disconnect the fuel pipe from the rear carb., put a tray underneath it and switch on: result – a dribble. Then (but not before) I remembered that little extra I’d fitted quite some time ago, in the form of a small in-line filter, hidden out of sight (and mind) round behind the washer bottle on the near-side scuttle. Sure enough, it was chokka-blooming-block with rust and sediment, wasn’t it? No wonder that not much juice was getting through when heavy demands were made; but just enough when cruising on a light throttle (here be nasty thoughts about the state of the bottom of the tank.)
So it was back on the road, reassured that all should now be well. And it came to pass for about five miles, when we suddenly went onto single-carb. Mode again; but this felt different because the misfire came at tick over particularly, accompanied by a strong smell of petrol and much ticking of the pump – obviously one carb. Was now flooding due to an over abundance of go-juice. So it was a quick peep underneath to see which overflow pipe was dripping (after switching off course;) and remove the float-chamber lid of the offender, in this case the front one. The out with the spindle about which the float pivots and catch the needle valve before it hit’s the deck. Blow through the pipe feeding the valve, where it just had to be a chunk of rubbish, disturbed by the previous work, holding the valve open instead of it being closed by the pressure of the float upwards. Reassemble and drive back home with no further problem, then take the float-chamber lid off again and put a new gasket on (you’ve got spares in the shed/garage of course, haven’t you?)
Now that’s a whole lot of words to cure a simple problem or two. “A bad case of fuel starvation caused by a blocked filter, followed by a flooding carburettor caused by some of the same dirt that gave rise to the original starvation.”
There – not half so much fun, though, is it? And the ignition system’s had a birthday to boot. Now the car “standeth not upon the order of its going.” Runs well, too. (Retires, humming “If I can help somebody as I move along……….”)
Oil Cooler Radiator
The fitting of V8 type metalastic bushes to the wishbone arms improves the front end stability of the MGB. This modification has been found to give a firmer ride but also overcome the comments of the dreaded MOT tester who often considers the original split rubber bushes to be in a rapid state of decline due to the visible flange distortion that takes place over the years.
However there is a further modification that any owner fitting V8 type bushes should consider if their B is fitted with a oil cooler and that is to provide a flexible mounting for the oil cooler radiator as the firmer front end can cause the oil cooler radiator to leak. To provide a flexible mounting insert Dexine tap washers between the oil cooler and the body on the 4 oil cooler radiator fixing bolts.
When fixing the rubber Diaphragm or Webbing onto the seat base frame a good tool to buy is a “Peg Puller” which can be purchased from a camping shop. It allows the steel clips to be clipped onto the frame easier whilst you stretch the diaphragm/webbing.
The “Peg Puller” will cost about £3.00.
Tip received from John Inness.
Re-Covering MGB Seats
Download the PDF file here – Recovering MGB Seats (1.2 mb)