I have a 67 3.8S automatic. When I test drove, owner said it suffered from vapor lock and it, of course, choked off and we pushed it of the road. When I purchased it a few months later it was colder weather and I found that the banjo bolts to the carbs were leaking. Solved that issue. I drove the car in the Spring and it did eventually choke off after several errands. This time it couldn’t be moved even in neutral. When it cooled down it moved. I noticed the transmission fluid was almost empty and the engine was running hot. Replaced transmission pan gasket and thermostat…no issues and temperature is correct.
The other day on a short drive it lost power and locked up. A few hours later it was good to move. No overheating and full transmission fluid.

 

Check fuel flow to the carbs.
When it locks up, can you hear the fuel pump, do the float bowls have fuel in them ?

How old is the coil, old coils intermittently fail when they get too hot.
When was the last time the points and condenser was replaced ?

Is the breather line that vents the fuel tank clear ?
Some tanks breath right through the fuel cap, others, like mine have a separate line on the side of the filler tube.

Other things to check is the glass sediment bowl on the inner fender well, many are missing the fuel filter, some have a fine screen in them that can get blocked up.
Filters where the banjo bolts are that feed fuel into the float bowl.
There is an internal filter inside the pump, that can get clogged too as well as the one right in the fuel tank, but all other causes have to be eliminated before assuming that those others are the problem.

Sticky needle valves in the float bowls and or failing floats.

Also, when it stops, is there a strong smell of fuel in the engine bay, does it appear to be flooding ?

There are so many things that can cause your symptoms, start checking and going through things eliminating the simplest things first.

Personally I would start with the ignition to eliminate that and take it off the table, especially if it still has the old Lucus coil in it, 98% of fuel problems are faulty ignition.
Bosch makes a blue resin 3 ohm coil that works very well and very reliable, just make sure you get the genuine article, there are a number of fakes out there.

Wires, plugs ???
You can't run resister plugs and wires, 5000 ohm resistor caps with non-resistor plugs work well with solid copper core wire.

Old schools cars like this are very simple, it's just a matter of eliminating things to find the problem.

EDIT:
The other thing to do if it quits again, is to take the fuel cap off, turn the key on and listen for the tick of the fuel pump, wait for it to stop, and try to start the car.

 

Thanks. I have gone through most of fuel system and starting the ignition checks. Could these issues cause the car's rear end to lock up? Rear wheels will not move, even when in neutral or accelerator applied in D, L, or R until car cools down.

 

Could be a brake problem, sometimes related to the servo.
Brakes won't release, but then the front may be effected as well.
Check the flexible line to the axle as well, they collapse and wrought internally and cause your problem.

If it's the transmision, then that's out of my scope of being able to help you.

"Car won't move when in D, L or R" Does it load the transmision up and pull the engine down as if the rear brakes are locked, or does the engine rev freely as if the transmision is not getting power to the rear wheels ?

 

It loads up and pulls engine down. WHen in neutral won't move. An hour later, it is driveable again... I think the brakes are working OK I do not seem to have the LSD as when in the lift, the rear wheels move together.

 

If it's neutral and won't move, then I would suspect the brakes are locking up, it's either that, or the transmission, start with the least expensive.

Check that flexible line that I mentioned earlier that connects the rear axle to the hard brake line.

Just doing a visual check on that line will tell you if it's been in there for many years.

If this was my car, I would start with the brakes, the external vacuum servo can cause the same problem as well if it's not been rebuilt at some point.
Start with that brake line, and I would also check on the front flexible lines on the calipers as well.

In most cases, faulty automatic transmissions don't usually behave intermittently like that, they will either work, or they won't.
When the car is driving properly, and the reverse works, then at this point I doubt it's the tranny.
Reverse takes the most oil pressure inside, so if that works, then I would suspect the brakes _ or at least until someone else comes along and suggests otherwise.

Auto transmissions don't usually lock up, they slip, and the car won't move very well.

Checking an intermittent problem on the lift is not reliable.

EDIT:
What you can do is have your jack and jack stands handy, when it does it again, jack both rear wheels off the ground.
If it's the tranny that's locking things up, there will be some natural rear end play in the axle alone when the wheels are moved by hand.
If it's the rear brakes, there will be no play at all.

 

You might have a duff inline anti creep brake solenoid or circuit that is fitted to all automatic S Types (DG, 35 etc.). At idle in drive the car applies the rear brakes until you push the throttle. You will find a throttle switch on the carbs, The solenoid is supposed to release the rear brakes as you pull away. Also acts as a hill holder. They don't hold full pressure forever which might be why the rear brakes finally release. I would check out the entire circuit & the solenoid/valve.


Anti Creep Solenoid on rear brake line.

 

Glyn my September 1967 built S Type with a BW35 Auto box does not have the anti creep. Not sure when it was deleted possibly with the fitting of the BW35 box. As Lyonsfin's car is stated as a 1967 S Type so it might be an early 67 or a 66 built car with the DG250 box which was fitted with the Anti creep so you could have hit the nail on the head. Good shout.

 

I'm sure I've seen a car with a 35 with the anti creep. But the transmission could have been a later fitment by the owner. Also strange things happened with late cars as they did with 420s/Sovereigns. It's all I could think of with an auto that would display those symptoms. I'm used to Manual OD's

I've also seen a US JCNA Concours winner Manual OD with an anti creep valve fitted. Go figure.

 

You might have seen a BW35 with anti creep and no doubt you have a photo of it in your collection Glyn.lol.
They might have had some spare anti creeps in a box and just fitted them to whatever was on the production line in front of them. No rhyme or reason in the bad days of Jaguar and cross over to British Leyland.

 

As mentioned above check the brake, it might be that a brake hose had collapsed and is holding pressure, I would check the rear first as if it was a front brake holding I would expect that either the engine would overcome this and move the car a bit or that the rear wheels would start to slip/spin depending on what surface you are on.

If you can jack it up when the problem occurs that would be helpful but of course if you have the limted slip diff in the car both rear wheels need to be off the ground otherwise it could still move and pull itself off the jack.

Let us know how you get on.

 

Thanks All. My 61 Mk2 is a 4speed and I don't think I have ever owned a classic with an automatic except for a few early 70's Mercedes so I'm in new territory. With the storm approaching, I may have some time this afternoon or this evening to get the car up on the lift and poke around. The rear wheels definitely drag as evidenced by the tracks in my gravel driveway.

 

If the rear wheels are dragging on the brakes then it wouldn't produce tracks in the driveway as the input from the engine to the diff will be fighting against the brakes (also on the diff), none of the opposing forces would be at the wheels which would either turn or stay still depending on whether the engine was stronger than the brakes.

If the front brakes were sticking however it might do this but on a gravel drive I would expect that you would just get massive wheelspin and gravel thrown everywhere. It may therefore be something wrong in the gearbox where two brake bands are engaging at the same time, what colour is the transmission fluid? If it looks or smells burnt that might give you a clue.

 

Solenoid is present but the wires are NOT connected. Does this mean it is "bypassed" or might the issue be with the valve itself? I did not check for switch, but my guess is that the switch wasn't working properly and that is why it was disconnected.

 

If the valve is electrically disconnected then it shouldn't be doing anything but its possible that its faulty internally and jamming the brakes up.

The first thing is when the car has the problem to investigate where the problem lies, the issue is that if you just start altering things then you won't know if the problem was actually fixed or whether it just went away to come back at a more awkward time.

 

If you have no intention of restoring the anti creep system to good health I would remove the solenoid valve from the circuit & replace it with a solid pipe. We have no idea how it is reacting to fluid movement/pressure at this time. While about it I would also replace the flexible jumper hose from the car body to the rear axle assembly. As I understand it in it's present state the solenoid valve should not operate & impede the brakes but we don't know what is happening if the valve is faulty internally. I can find no diagram of the valve internally.

Download & blow up if necessary. All can be found in Section FF of the workshop manual under Automatic Transmission ~ NOT Brakes.














Another thing that comes to mind is that the auto adjusters in the rear caliper pistons might be damaged. But if so I don't know why the rear brakes would ever release.

Good luck!

 

I haven't had much time to check everything out, but here is a brief update. 1) The banjo bolts are leaking a bit at the carbs and I will install new washers as tightening them only lasts for a short time. 2) The parking brake setup is not the culprit as when parked on a 45 degree incline the parking doesn't hold the car (yes, I need to adjust). 3) The car did hold on the same incline in "Park" the first time I set it, but the next few times it rolled with a clicking sound. I am leaning toward some type of transmission issue.?

 

It sounds like your parking pawl in not engaging the detents that lock the transmission internally. Not uncommon on Jags of the era.

 

UPDATE
Finally got a chance to recreate the problem. I drove locally and then in my yard. Temp got up to 90-95C. It began to act up and got it into the lift bay. Placed it in neutral. Rear brakes were not particularly hot. Both rear AND front wheels locked in place. I couldn't budge them. An hour later NO issue, they all turned by hand!

 

Well, at least you have a place to start.