Not an easy job.You need to remove the intake manifold plenum to do it.
99 Honda passport has a timing belt.
WE DON'T KNOW!
The thermostat is located in the housing on the engine side of the upper radiator hose on a Honda Passport 3.2 engine. You will have to take the air filter tubing off to get to it.
Replace Thermostat
Thermostat is in the housing under the left coil in the housing connected to the radiator hose. Takes about 30 minutes, if that long, to change.
Honda Passport was created in 1994.
I have a 99 that did the same thing try the fuel regulator?maybe
No
On 99 Passport it probably has a yellow handle end that you grab to pull the dip stick out it is located on the lefthand side of the engine.
top front of engine follow top radiator hose to where it clamps its in that housing should be two bolts
location of the heating thermostat for the 99 Buick lasabre
top front of engine follow the top radiator hose to where it goes to engine it will be a rounded top housing the hose clamps directly to it take off housing thermostat inside