If you aren’t planning to drive it in cooler weather, you could consider knocking the riser flap out and reinstall the shaft to keep exhaust fumes from accumulating under the hood. I agree with earlier assessments. You may need to flush the cooling system.
With all due respect, that seems like a horrible idea. Wouldn't that allow exhaust heat to blast the intake full time?
Now if you had suggested to leave the flap in place as long as it is stuck in the fully warmed up position, I could understand your point.
I still wouldn't do that unless ambient temperatures where I lived were around 160 degrees most of the time.
That flapper valve heats up the intake rapidly upon startup to prevent the air/fuel mixture from becoming liquid gas upon contacting an intake runner which is many degrees cooler than a fully warmed up engine would have. This leads to raw fuel falling on the top of the piston then leaking past the rings to contaminate the oil. This will happen to some degree regardless of local temperatures.
