I have a 2001 jeep grand cherokee with a 4.7 and I just changed the thermostat in it because the housing was cracked now the engine will heat up to around 200 deg or so then the fan will kick on and the temp drops to the normal op temp but only does this while idle runs at 195 while driving not sure why it no longer holds a steady temp

Follow the top radiator hose to where it attaches to the engine, that's the thermostat housing, remove it to expose the thermostat.

Hi there:

It is located at top front center of engine:

Remove radiator upper hose and heater hose at thermostat housing.

Disconnect wiring connector at engine coolant temperature sensor.

Remove thermostat housing mounting bolts, thermostat housing, gasket and thermostat. Discard old gasket.

Clean the gasket mating surfaces.

To install:

1. Install the replacement thermostat so that the pellet, which is encircled by a coil spring, faces the engine. All thermostats are marked on the outer flange to indicate the proper installed position.
2. 
   
3. Observe the recess groove in the engine cylinder head.
4. Position thermostat into this groove with arrow and air bleed hole on outer flange pointing up.
5. 
   
6. Install replacement gasket and thermostat housing.

Hope this helps; also keep in mind that your feedback is important and I`ll appreciate your time and consideration if you leave some testimonial comment about this answer.

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Do not loosen radiator drain **** with system hot and pressurized. Serious burns from coolant can occur.

NOTE Do not waste reusable coolant. If solution is clean, drain coolant into a clean container for reuse. If thermostat is being replaced, be sure that replacement is specified thermostat for vehicle model and engine type.
Instructions

1. Locate the Cherokee's thermostat intake housing by following the top radiator hose to the engine. The hose connects to the thermostat intake. A second, smaller hose connects to the left side of the radiator hose. This is a bypass hose for the heater.
   
2. Remove the two bolts that secure the Cherokee's thermostat intake housing to the engine with a socket and ratchet and lift the intake upward to drain the coolant in the hose back into the radiator.
   
3. Remove the gasket and the thermostat from the engine and discard them. Wipe the mating surfaces of the thermostat intake housing and the engine off with a clean towel.
   
4. Place the new thermostat, spring down, into the engine and place the thermostat gasket over the thermostat.
   
5. Place the thermostat intake housing onto the thermostat gasket. Thread the bolts into the thermostat intake by hand to avoid cross-threading the bolts and then tighten them using a socket and ratchet.
   

Additional information:

1. Clean mating areas of timing chain cover and thermostat housing.
2. Install thermostat (spring side down) into recessed machined groove on timing chain cover.
3. Position thermostat housing on timing chain cover.
4. Install two housing-to-timing chain cover bolts. Tighten bolts to 115 inch lbs. (13 Nm).
   CAUTION Housing must be tightened evenly and thermostat must be centered into recessed groove in timing chain cover. If not, it may result in a cracked housing, damaged timing chain cover threads or coolant leaks.
   
5. Install lower radiator hose on thermostat housing.
6. Install splash shield.
7. Lower vehicle.
8. Fill cooling system.
9. Connect negative battery cable to battery.
10. Start and warm the engine. Check for leaks.

Good Luck and if this helps don't forget to vote.

Hello,

To install a thermostat on Your 1999 grand cherokee jeep. You will be needing these instruments, Container, Clamp tool or vise-grip pliers, Thermostat and gasket, 10mm socket or wrench, Razor blade, Flathead screwdriver (if necessary). Then You carefully follow the steps below:

1. Open drain **** on the radiator to drain the coolant from your Jeep Grand Cherokee. This drain **** is located on the lower right side facing the rear of your Cherokee. Use a seal able container and reuse the coolant if it is relatively new and clean.
2. Follow the upper radiator hose to the point where it meets the thermostat housing. The thermostat is located inside the housing. Use a clamp tool or vise-grip pliers to loosen the clamp holding the hose to the housing. Work the end of the radiator hose free of the thermostat housing.
3. Remove two bolts holding on the thermostat housing cover. Pull off the cover. Take note of the position of the old thermostat. Remove and install the new thermostat in exactly the same position.
4. Scrape off residue of the old thermostat gasket from the inside of the thermostat housing cover using a razor blade. Avoid getting any debris inside the thermostat housing.
5. Install the new gasket. Reattach the thermostat housing cover and radiator hose. Start your Jeep Cherokee and run the heater on high. Allow the engine to warm up. Check for leaks.

Those are the steps to follow to install your thermostat.
Hope this was helpful. Thank You for using fixya!!!

1. On 2000 Jeep Grand Cherokee 4.7L V8
2. Remove lower radiator hose clamp and lower radiator hose at thermostat housing.
3. Remove thermostat housing mounting bolts, thermostat housing and thermostat.

2000 Jeep Grand Cherokee 4.0l v6Note:on the In-line 6 4.0L model the thermostat housing is mounted at the top of the engine block next to the water pump.

If it is the 4.0 engine there have always been bad to have a cracked head,right between the valves in one of the cylinders.

1. Disconnect negative battery cable at battery.
   
2. Drain cooling system.
   
3. Raise vehicle on hoist.
   
4. Remove splash shield.
   
5. Remove lower radiator hose clamp and lower radiator hose at thermostat housing.
   
6. Remove thermostat housing mounting bolts, thermostat housing and thermostat.
   

To install:

1. Clean mating areas of timing chain cover and thermostat housing.
   
2. Install thermostat (spring side down) into recessed machined groove on timing chain cover.
   
3. Position thermostat housing on timing chain cover.
   
4. Install two housing-to-timing chain cover bolts. Tighten bolts to 115 inch lbs. (13 Nm).
   

follow top radiator hose from radiator to engine wear hose ends, it will be clamped to whats called the gooseneck, thermostat is under that. you will have to drain coolant, not all, maybe 1 half gal. before you remove it. 2 bolts new gasget new thermostat, just remember spring on new thermostat goes in engine.

sounds like an air lock joe

It is near the thermostat housing.