Engine not coming up to temp. Looks like a simple job to replace the thermostat. Is it as easy as it looks

have a compression check if you haven't already as this is indicative of a head gasket or cracked head.

if your motor is the 3.4 then you dont have to worry bout the exst pipe since the thermostat housing has a slotted hole were the pipe is, but beware that those two 10mm bolts are somtimz very tight so youll probly need little extra leverage, otherwise its simple

if you have the 3.5 v6 izuzu engine the thermostat is a major job, requires removing upper intake ,because it is under not in front of like most thermostats.
about 3-4 hour job depending what kind of problems you run into.

COULD BE THERMOSTAT IF TOP RADIATOR HOSE IS NOT HOT AND BOTTOM RADIATOR HOSE GOING TO WATER PUMP IS HOT THE THERMOSTAT STICKING PARTIALLY CLOSE.IF TOP HOSE IS HOT THE RADIATOR,ENGINE BLOCK HEATER CORE NEED FLUSHING OUT.IF WATER PUMP WEEP HOLE LEAKING REPLACE WATER PUMP, FAULTY WATER PUMP WILL CAUSE ENGINE TO OVER HEAT.REPLACE RADIATOR CAP MAKE SURE YOU HAVE 50 / 50 MIX SOLUTION ANTIFREEZE AND WATER IN COOLANT SYSTEM. IF ALL LOOKS GOOD CHECK ENGINE OIL ON DIP STICK, IF OIL IN DIP STICK LOOK LIKE MILKSHAKE YOU HAVE BLOWED HEAD GASKET THAT WILL CAUSE ENGINE OVERHEATING WHILE DRIVING CAR IN SHORT DISTANCE AND ENGINE OVERHEATING.

Hello kingsgo,

The P0128 is a code for the thermostat, it is common.

The ECM will set this code when the time it takes the engine to reach 176 degrees is out of the range that the ECM expects.

The fix is to replace the thermostat. Follow the steps below for removal and replacement.

1. Drain the necessary coolant from the radiator to be below the the thermostat housing.

2. Remove the alternator.

3. Loosen the hose clamp at the thermostat housing see 1 in figure below then remove the hose.


4. remove the thermostat housing bolts. See image below.



5. Remove thermostat housing from engine block.

6. Clean the engine block sealing surface.

The new thermostat will come with the complete housing assembly.

To install reverse above procedure, torque the thermostat housing bolts to 89 inch lbs.and fill coolant to the proper level and check for leeks.

I hope this helps.

Regards,

netvan

its not easy. so make sure its bad. Have a shop scan the engine computer while you think the engine is at normal engine temp. it should be 190-195f if its lower than that, yes the thermostat may be bad. but its a job to replace.

THE 4.9L ENGINES COOLANT TEMPERATURE SENSOR IS ON THE THERMOSTAT HOUSING. WHICH IS LOCATED BEHIND THE DISTRIBUTOR. THE 4.6L ENGINES COOLANT TEMPERATURE SENSOR IS LOCATED ON THE BACK SIDE ENGINE THE SIDE FACING TOWARD THE FIREWALL BELOW THE EGR VALVE.

turn AC on. If fan still does not come on then the fan may be bad. Note! fan only comes on when the temp reaches around 220 to 225 degrees. If the sensor is lieing to the computer the fan will not come on so a scanner could come in handy to see what the PCM is seeing. Doing the AC trick only confirmd the fan is ok and the PCM has the capability to turn the fan on. This car may also have a fan relay. Swap it with the horn. It should be in the engine fuse block.

partially clogged radiator

Try replacing your thermostat. I haven't had to replace one in years, but I remember it being a cheap and easy job. It should be located where your upper radiator hose meets the engine. You should only need a screwdriver to loosen the hose clamp and the same screwdriver to pry the old thermostat out. Be sure to let the engine cool off first!!!
This link explains how they work.
http://auto.howstuffworks.com/question248.htm