Whole story goes,
Car is new to us, customers just purchased it without a pre purchase inspection as a toy for summer. Car had been sitting for approx a year. It was booked in for a misfire and coolant leak. Customer was concerned if we knew how to work on opti spark. My senior tech found a shoddy minor tune up with the wrong plugs and ignition wires poorly routed and one fell off. Plugs and wires later ran fine. Pressure test showed a cracked plastic tank on rad. RE&RE rad and upper lower hoses, filled with air-lift vacuum to and ran. Cooling fans cycled, both stages work with A/C on and temp never went past 1/4. We never road tested car as there was a very dangerous tire. Released car and though it was a good fix. Oh, BTW after rad went in pressure tested again and found another split in the small plastic joiner/restrictor in the heater hose. Replaced it with a brass joiner. Customer phoned two days later saying it got hot while driving it home.
Car came back and we've:
Checked cooling fan both stages with tech 2
Replaced t-stat, found it was new.
Checked condenser for debris blocking air flow.
Found original cap faulty not holding 5 psi but coolant never blew over.
Car will only heat when driven, when pull over it will cool down.
Pressure test pinned to 30 psi. HC test 1400 hc.
Pulled heads and warped .008" Surface and P/T and OK. Assemble same problem. Removed cover on water pump
and checked impeller and OK. Just today checked deck and .003". Getting pissed at this thing. Ideas?