Series 3 Poor pick up, rear wheel spins and locks

Colthebrummie said:

I think the pressure caused by the pedal being jammed down for hours causes small air bubbles to find their way into the master cylinder reservoir.

Col

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With the pedal down the recuperating valve in master cylinder will be closed how do the bubbles get past.

Blackburn said:

With the pedal down the recuperating valve in master cylinder will be closed how do the bubbles get past.

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The brake system may contain a number of small bubbles that move up and down the pipework causing that spongy affect. Forcing the brake pedal down for a long period causes the small bubbles to rise to the highest point, e.g. The master cylinder. It's true, the closed valve will prevent the bubbles getting back to the reservoir but when the hammer is released the valve opens and the air bubbles get into the reservoir. This is my understanding and I have used the technique with success on several occasions. It helps if the front of the car is facing uphill. I would only try this after conventional bleeding fails to get all of the air out and of course all of the brake components need to be in good condition.

Col

When I had a 109 I also found that parking it nose uphill made a better job of bleeding brakes, the steeper the better.

Thanks for the jam down the brake pedal trick - it worked. But the misfiring is more serious. We took off the air filter trunking and started the engine. As before it seemed to be firing on 3 cylinders. Air gasped out of the carburettor barrel accompanied by a spray of fuel. Verdict: an inlet valve is sticking. So i took off the rocker cover to investigate. Turned the engine over with the starting handle. All the valve gear seemed to work normally and the valves went up and down as i would have expected. Is there any easy way to work out what isn’t seating properly?

While there you should set the tappet gaps using rule of 9

Have you got a starting handle if so try turning the engine over slowly with ignition off.
As you turn it feel for the compression you should have four even pulses over two revolutions if not you have a valve failing to close.
Best do it with the rocker cover off and the distributor cap ie when rotor arm pointing to no1 spark plug both valves for no1 cylinder should be closed.
Firing order from memory is 1342.
Long time since I worked on a petrol think I got that right if a inlet valve is not closing the compression will feel different.

You might hear some hissing in the in,et manifold when on the compression stroke if leaking

I am now suspicious that the misfiring is caused by the distributor. The reason is: the tappets all have the right clearance (0.010”). All the valves seem to be operating as designed. The engine slows slightly when i remove plug lead 3 or 4. When i remove lead 1 or 2 it stops. When touching the plug leads 1&2 give a much stronger shock than 3&4.

I bought a new distributor cap from Bearmach suitable for a Series 3 2.25 litre. It doesn’t fit. There are insufficient lugs on the cap, including a thumbnail sized cut-out to accommodate a wire connection. Any idea which one i should get? See photo of old distributor cap.

Re the pinking.
This is generally caused by one of three things.
a/ Ignition too far advanced
b/ Carbon build up in the combustion chamber, it gets red hot and causes the fuel mixture to light
c/ wrong type of fuel, i.e. unleaded when it should be leaded although this can be eliminated by retarding the ignition beyond the setting suggested in the manual.
(You will need to either stick an additive in the fuel or get around to getting the ehad off, decoking it and then getting the exhaust seats at least replaced with hardened ones.

A good test of timing is to accelerate from a low speed like 20 mph in top gear, listening for pinking. Keep backing the timing off/retarding it until the pinking just about stops, lock up the dizzy then reset the tickover.
Did you replace all the ignition leads, the king lead, the rotor arm, the points and the condenser? If so and you are still getting uneven power at the plugs your distributor spindle may be worn, thus opening the contact gap unevenly. You can get electronic ignition to fit in your distributor which is not expensive and fit and forget.
Best of luck.

This guy has good reputation for ignition parts
http://www.distributordoctor.com/

Hah. The cylinder compression test shows: 1: 130, 2: 120, 3: 20 and 4: 20. Looks like there is a head gasket failure between numbers 3&4. Head off! Any tips as to which gasket set to buy, and what else i should do with the head off?

Good you have found problem, I used Elring from Turners , I would also clean up valves, do valve lapping and oil stem oil seals at same time and check for wear in valve stem diameter with a mic

Thanks. What’s valve lapping?

It’s basically using carborundum paste on the valve seats and spinning the valves to get a good seal so you know the valves close perfectly all around the circumference with out leaks / loss of compression
This is one video there is prob loads more

Lapping the valves and valve seats will remove any leaded petrol memory which may still exist. So if you are not already using lead additive in your petrol, you will need to after. Personally, I'm not much of a believer in lead petrol memory.

Col

Ok. So this is the culprit for the misfiring. New gasket in place. Running sweetly.

But...the brakes are still awful. Despite all the air having been purged from the brake lines the pedal bvwhen first depressed is still spongy. And the rear wheels lock up under medium braking (the offside one is particularly bad). I have tried to adjust the rears so they bite later than the front but it doesn’t seem to work. I have replaced all the wheel cylinders. The shoes and drums are in good order. Any ideas?

good outcome on the head gasket,
Assume to you have chamfered all shoe leading edges as in earlier post
If both rear wheels locking they are working really well so to balance them maybe tinker the adjustment cams
Have you the twin leading shoes on 11 inch drums on front or other type
Springs correctly on front ?
Shoes set square using the adjustment screw?
Brakes shoes adjusted ?
Definitely no air ?..... can clamp the both the front flexis and then see if pedal good
Then release one side and see how that feels then reverse
If you have t(e front drums off perhaps post a pic of each side

Also, have a good look at the flexible hoses whilst someone applies the brake, if they are perishing inside, they swell up and give a spongy pedal.

Col

Thanks Steve and Col very helpful will try both. Could brake fluid be getting past the master cylinder piston?

It sounds like you have good pressure as backs work nicely, if master cylinder leaking levels would drop