2001 Infiniti QX4 4WD
3.5L V6 (VQ35DE) 190k miles
Things which have been replaced:
Thermostat, Water Control Valve (second thermostat), Water Pump, Radiator Cap
Chemical Block, Cooling System Pressure, Compression, Leak-Down
I bought the vehicle after inspecting it personally and finding no major issues outside of a coil pack issue. A couple days later the vehicle overheats after being on the interstate for 2 miles. Vehicle will idle without overheating, and can be driven less than 35 mph without overheating. I replaced the main thermostat, did not resolve the problem. I was afraid I did not bleed the system correctly, took it to a local mechanic. No change after bleeding cooling system, so he did a block test which “failed” but he was perplexed due to no coolant leaking and no mixture of oil/coolant. Suggested I take it to a Nissan specialty shop. The specialty shop ran chemical block test and vehicle passed. The specialty shop stated that after bleeding cooling system using Varajet system, the vehicle would get approximately 5 miles interstate and overheat. They manually bled the system and found major air pockets. They then ran coolant system pressure test and compression test, both passing with flying colors. We replaced the water pump, did not fix the issue. Decided to replace the water control valve (second thermostat for the block). The water control valve sits underneath the intake manifold. They found dog food underneath the upper and lower intake manifolds. It was then obvious the vehicle had been sitting for a while. They also found a leak at the block water outlet (see attached picture). They cleaned that mess up and replaced the block water outlet gasket, water control valve, and bypass pipe gaskets. Still overheating. The specialty shop is perplexed.
EDIT: Also adding pictures of the cooling circuit for reference since it’s an odd system.
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