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1976 Mark IV New Owner Questions

Bill -

I have come into a low mile (36K actual) 1976 Mark IV, a very nice ride out on the road! I have gone through purging systems and changing fluids, etc. and added new tires and shocks. Would like to add a stronger set of sway bars to bring handling closer to current standards and was considering the Addco units. Any thoughts or recommendations on sway bars? Car seems to want to vapor lock after stopping motor for a few minutes. Has new fuel pump, filter and carb kit. The only thing I have found that stops this is running recreational fuel (no ethanol). Other thoughts? Finally, the air conditioning refrigerant system has been purged and tested good with R134 conversion. I only get about a 12 degree drop on recirc. There is no apparent heater control valve on this car and I am guessing the blend door is not closing off heat fully. Should I place a manual or vacuum shut-off valve on the heater core (inlet or outlet)?? This is a fair weather only driven car and have never called upon the heat functions. Low and medium speeds just failed on the Autotemp/blower while driving last Summer. High works fine but is a bit noisy. Fuse, relay and resister all seem to check good. I'm suspicious it is not the switch since both speeds failed while driving and switch hard to change out. What am I missing??

Many thanks for sharing your wisdom!



Hi Greg -

The 76 Marks are getting more popular over the years and are beautiful cars. It sounds like you are going to be busy with this one for a while.

We can't recommend replacement or upgrades for the sway bars as the originals are known to be quite adequate amongst our customers.

If using "no ethanol" fuel corrects your vapor lock issue and your carburetor floats were checked and adjusted correctly you could try other brands of fuel or continue to use no ethanol fuel.

Your refrigeration problem could be:

* Over charged system
* Undercharged system
* Faulty exp. valve
* Faulty POA valve
* Faulty compressor
* Faulty ATC Controls
* Faulty or incorrect cooling fan or clutch
* Faulty or restricted condenser

The 76 Marks do have a water valve that is vacuum controlled by the ATC system.

Your loss of lower blower speeds could be:

* High Blower relay defective
* Blower resistor or its contacts defective

Noisy blower motor on Hi speed could be:

* Worn motor or seizing armature due to dry bushings that need oiling
* High resistance in the blower wiring or the ATC blower speed contact

The above are only some suggestions based on common faults that we see and repair at Lincoln Land very often. Accurate diagnosis is required in order to avoid replacing parts that are not defective. Your last question "what am I missing? " indicates that you or your technician is missing the necessary correct service manuals to diagnose, service and correct these issues on your new Mark IV. We wish you the best of luck in the diagnosis.