1986F150Six

https://www.ebay.com/itm/NOS-1985-89-Ford-F250-4WD-Front-Locking-Diff-E5TZ-4026/153033586314?hash=item23a183368a:g:73oAAOSwc~5bBXZW

Thank you for your kindness!

https://www.ebay.com/itm/1981-1995-FORD-PERFORMANCE-MUSTANG-5-0L-302-CRANKSHAFT-DAMPER-M-6316-M50/114286442126?hash=item1a9c00b68e:g:~HUAAOSwuEhe~ao4

https://www.ebay.com/itm/NEW-OEM-Ford-E3TZ-9G459-C-Exhaust-Air-Supply-Control-Valve-Hose-1983-4-9L-L6/184347760451?hash=item2aebfb9743:g:3B8AAOSwsPRe-7aU

https://www.ebay.com/itm/OEM-1980-81-82-83-84-85-86-F-Ser-Truck-Bronco-Front-Grill-Chrome-NEW-TAKE-OUT/124243901709?hash=item1ced837d0d:g:XzgAAOSwkCRe~RV7

Look carefully due to missing data. https://www.ebay.com/itm/NOS-1983-Ford-F100-F250-Heat-Cable-HVAC-Heater-Air-Conditioner-Vent-P-M/233636309841?hash=item3665cf2b51:g:DDQAAOSw3hZe~E08

Sounds quite reasonable!

Plus, "free shipping".

And, their shipping costs are more than reasonable!

Didn't you tell us, long ago, that your Dad would drill a small hole and lubricate blower motor bearings? Everything looks good!

Sometimes one has to cut one's losses and let go.

https://www.msn.com/en-us/autos/enthusiasts/how-to-repair-your-dash-and-flock-the-top/ar-BB16araC?ocid=spartan-dhp-feeds

You do not see these very often. https://governmenttransitsurplus.com/products/ford-e0tz-7a110-b-indicator-assembly-nos?variant=7886450065461

I like it!

Perhaps a retest is in order?

Some [Gary and Matthew] have inside information!

Since there has now been several caps [3?], and the likelihood that all the caps were defective is low [I would think; especially since some were from one source and one was OEM], what if there is a crack or defect in the radiator mouth, where the cap rubber seal mates? Could the pressure in the radiator push the coolant to the expansion bottle, and as the radiator/coolant cooled down, if the rubber seal could not properly seal due to the radiator neck defect, maybe air would be sucked in rather than coolant from the reservoir?

Jim - I'm in total agreement. It defies something. The implication is that it isn't getting cool enough with the cool down. But we didn't use to have this problem, even in the summer. David - Interesting idea. So I just pulled a cleaning brush through the hose and only got a few fibers that were probably from the string I used to pull the brush. And, I ran a q-tip through the port in the radiator's neck, but there wasn't much in it either. Thanks, guys. But I'm David - Interesting idea. So I just pulled a cleaning brush through the hose and only got a few fibers that were probably from the string I used to pull the brush. And, I ran a q-tip through the port in the radiator's neck, but there wasn't much in it either. Thanks, guys. But I'm Okay... now, how about the reservoir, itself. Could there be junk in the bottom, where the hose connects?

You are a teaser!

Interesting... front bumper with guards and no rubber strips on the bumper.

I don't know about it being a better idea, but here goes. If you did not find any leaks in the hose going to the expansion tank [I assume not as you did not report doing so], then maybe there is a blockage inside the tube? Perhaps under higher pressures [16+ psi], hot coolant can get by the blockage, but at lower pressures, the blockage is such that what is in the reservoir cannot be drawn back and a few psi is maintained above the cap, preventing the cap from being able to operate as designed?

Welcome!

Well, Jim, in that picture, the truck is certainly not idling!

https://www.ebay.com/itm/NEW-1978-1989-FORD-F-100-350-TRUCK-BUMPER-GUARD-PADS-PAIR-ORIGINAL-TOOLING/303606866804?fits=Year%3A1986%7CModel%3AF-150%7CMake%3AFord&hash=item46b0612374:g:e~IAAOSwnQFcz3Xq

https://www.ebay.com/itm/NOS-Ford-1970s-1980s-Air-Cleaner-Hose-Mustang-Thunderbird-Truck-Torino-17/254636080856?hash=item3b497e3ed8:g:OZ4AAOSwv-Ze9keL