[freekmccoy]

I have a 99 GC Ltd 4.7L that needs the thermostat replaced...any help on where it goes would be appreciated

[Texas ZJ1]

Your best bet is to get a Haynes or Chiltons repair manual for the location and then you'd have pics and instructions that would be better than us just saying right above the waterpump or whatever.

Hunter

[Myrtle Beach]

The thermostat is located in the lower part of the motor, where the lower radiator hose connects to the block. I would also recommend a cooling flush while you are at it. How do you know you need a new thermostat? are you having cooling problems?

Follow these instructions--

4.7L engine - Thermostat removal


WARNING: DO NOT LOOSEN RADIATOR DRAINCOCK WITH SYSTEM HOT AND PRESSURIZED. SERIOUS BURNS FROM COOLANT CAN OCCUR.

1. Disconnect negative battery cable at battery.

2. Drain cooling system. 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.

3. Remove splash shield.

4. Remove lower radiator hose clamp and lower radiator hose at thermostat housing. See cautions above for removing radiator hose clamps.

5. Remove thermostat housing mounting bolts, thermostat housing and thermostat.



4.7L engine - Thermostat installation


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 in. lbs. (13 N·m) torque.

CAUTION: Housing must be tightened evenly and thermostat must be centered into recessed groove in timimg 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. Be sure that the radiator draincock is tightly closed. Fill cooling system. See refill directions above.

8. Connect negative battery cable to battery.

9. Start and warm the engine. Check for leaks.

[freekmccoy]

thank you!
I'm actually hoping that the thermostat is all I need,coolant levels are ok but it seems to run alittle cool and blows no heat.

[Myrtle Beach]

By the way, the thermostat for the V-8 costs about $25. You will want to stick with the 195* thermostat. It's pretty hard to find an aftermarket one for the vehichle anyway.

[Myrtle Beach]

here is a pic from WJJEEPS.COM

[Meerkat]

You go Myrtle!

[freekmccoy]

found and changed thermostat (thanks for the help BTW)
but still blowing cold air after warming to around 195

so,would heater core be next option to try?

[Meerkat]

That seems a bit extreme....
Are you sure your blend doors are working properly?
If you get to the point you really think it is the core, I suggest merely disconnecting the hoses and blowing air through to make sure there is a clear path for flow.
Normally heater core failure is in the form of a leak, vice blockage.

HTH

BTW you should still invest in that Haynes manual. It is well worth the $15.00 (less on eBay).

[treats]

Yes both of my blend door servos were bad (dam plastic gears) dual zone temp.

[freekmccoy]

I did a CC code check on it and came up with (2) seperate numbers -54&56 any ideas on what these codes are??

I felt both lines going into heater core and they seem to be equally hot

[Meerkat]

I have posted all the codes in the FAQ.....

[JoeyJoJo]

freekmccoy, thank you for posting this as my 99 GC with the auto climate is having the same problem. I was about to change my thermostat as well. I just checked for error codes on my climate system and the following came up:
49...........................Mode door travel range too small
54...........................Left temperature door travel too large
55...........................Right temperature door travel too small
From reading other posts (wvd and treats), it sounds like my blend door servos are bad. Does anyone have experience replacing these? Does the entire dash need to be removed?

[JoeyJoJo]

Hey freakmcoy, did you get your Jeep to blow hot air again?

[JoeyJoJo]

Thanks for the no help - but here, for the next guy that has this same problem, is the procedures for replacing the blend door actuators (referred to as servos in this thread). I'm buying and installing them this afternoon.

BLEND DOOR ACTUATOR
DESCRIPTION
The blend door for all models is actuated by an electric actuator, while the AZC system uses 2 separate actuators to allow the driver and passenger to select individual comfort levels. In the following procedures,
service for both types of actuators is covered. The blend door actuator is used on all models, whether equipped with manual or Automatic Zone Control (AZC). This actuator is located on the front of the HVAC housing to the right of the floor panel transmission tunnel, and can be removed from the passenger compartment without instrument panel or HVAC housing removal.
(1) Disconnect and isolate the battery negative cable.
(2) Remove the glove box door. Refer to Instrument Panel System for the procedures.
(3) Remove the lower I/P glove box door surround panel. Refer to Instrument Panel System for the procedures.
(4) Unplug the wire harness connector from the blend door actuator (Fig. 17).
(5) Remove the 2 screws that secure the blend door actuator to the HVAC housing.
(6) Remove the blend door actuator from the HVAC housing.
INSTALLATION
(1) Install the blend door actuator on the HVAC housing and tighten the two mounting screws to 2.2
N·m (20 in. lbs.).
(2) Plug in the wire harness connector to the blend door actuator.
(3) Install the glove box door. Refer to Instrument Panel System for the procedures.
(4) Install the lower I/P glove box door surround panel. Refer to Instrument Panel System for the procedures.
(5) Connect and the battery negative cable.