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 and I could smell a bit of burnt clutch or brake pad material. 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.
Yesterday on a short drive it lost power and locked up. Same smell. A few hours later it was good to move. No overheating and full transmission fluid.
Let’s assume brake pad material, so, next trip go equipped with enough jacks to get both rear wheels off the ground, this due to the rear axle LSD. If the rear wheels but not the front are seized then the solenoid actuated valve that applies the rear brakes when the throttle is closed is no doubt the problem, IF one is fitted. !!
And if both front and rear wheels are locked or dragging (determined by heat or smoke) there might be an issue with a sticking master cylinder or slave cylinder in the booster. Sometimes these self correct when left to sit for a period. If just rear brakes it also could be a bad brake flex hose between the body and the rear subframe. This also can temporarily self correct when left to sit for a while.
Yes, everything you mention is a possible cause, but if all 4 wheels are locking the reaction valve in the servo would be my first check.
Lyonsfin,
When the wheels lock , do the brake lights light up? ign on of course !
Much simpler than jacking up the car and playing around hoping the fault appears (and this would only work if it’s the rear at fault anyway), carefully (because it can hurt!) touch the wheels when you have the fault. If a wheel is hot the brakes are dragging. If no wheels are hot it’s not the brakes.
Robert , I stated to WAIT till the fault appears , then jack the rear wheels, as for heat transfer I suggest the rear inboard discs / calipers will be glowing red before any heat transference to the rear wheels. !!
Sorry. I hadn’t realised we were dealing with IRS. And same goes for LSD.
But my comment still holds; rather than going to the trouble of jacking up all four corners, feel the brakes for heat and eliminate something.
IR gun costs about $30, an excellent tool for auto diagnosis, check yr visitors for covid while ur at it
Thanks everyone! The grand kids are visiting so I won’t get a chance to continue diagnosing til later. Front wheels seem ok. Both rear wheels drag as indicated by the gravel in the driveway. I can move gear selector and it will rev in neutral, but can’t push it by hand. My Mk 2 is a manual, so I’m not familiar with the Auto Box. IR gun is a great idea and I’ve been thinking about one, now I can justify!
you may have a minor handbrake (parking brake) problem . they suffer from the location and stick. pad delamination leading to a wedging effect. your grandkids should be able to wriggle in there and take lots of digital pictures?
Update: I was able to recreate the issue and get it up on the lift…All 4 wheels were locked! An hour later, all turned freely! Thinking that it is the brake booster servo or check valve, OR is it possible that if the car does have vapor lock (issue appears when engine temp is (90C), could it be causing the vacuum of the booster to keep the brakes engaged until it cools down?