Leaking coolant from a small hole located in the block right under the thermostat housing coolant inlet. we removed housing and gasket replaced gasket and installed, leaks from small hole?

drain coolant system half way until coolant below thermostat.to locate thermostat follow upper radiator hose to engine.just remove both thermostat housing two bolts then clean all traces of old gasket material. be sure to have new thermostat gasket and gasket sealer on hand.make sure both thermostat housing and engine block clean dont have any traces of old gasket material if so you will have coolant leak.but besure to put gasket sealer both sides thermostat gasket just need thin layer RTV silicone.you can buy can of gasket remove to help remove old gasket material. try not to damage thermostat housing surface or engine surface with scraper deep scratches cuts in either surfaces will cause coolant leak be careful.

Please see my tip at http://www.fixya.com/cars/r5929960-s_thermostat .

Specific instructions for your car are as follows. Let me know if you get stuck or have more questions.

Removal & Installation

4.2L Engine

1. Remove the necessary coolant from the radiator.
2. Remove the alternator, as outlined in the Engine Electrical Section.
3. Loosen the outlet hose clamp at the thermostat housing. Remove the outlet hose from the thermostat housing.
4. Remove the thermostat housing bolts.
5. Remove the thermostat housing from the engine block.
6. Clean all of the surfaces of the thermostat housing.
7. Clean the sealing surface of the engine block.
   

To install:

1. Install the thermostat housing to the engine block.
2. Install the thermostat housing bolts and tighten to 89 inch lbs. (10 Nm).
3. Lubricate the inner diameter of the radiator hose with engine coolant.
4. Install the outlet hose to the thermostat housing. Secure the hose with the clamp.
5. Install the alternator.
6. Fill the cooling system with specified coolant and concentration.
7. Inspect all sealing surfaces for leaks after starting the engine.

5.3L Engine
NOTE The thermostat is not serviceable separately. The water pump inlet and thermostat must be replaced as an assembly.

1. Drain the cooling system to a level below the thermostat.
2. Remove the radiator outlet hose.
3. Remove the water pump inlet bolts.
4. Remove the water pump inlet and thermostat from the water pump.

To install:

1. Install the thermostat and thermostat housing to the water pump.
2. Install the thermostat housing bolts. Tighten the bolts to 11 ft. lbs. (15 Nm).
3. Install the radiator outlet hose.
4. Properly fill the engine cooling system and check for leaks.

JUST DRAIN COOLANT LEVEL BELOW THE THERMOSTAT. CATCH COOLANT IN A DRAIN PAN UNDER RADIATOR.THEN REMOVE RADIATOR HOSE FROM THERMOSTAT HOUSING ON THE CYLINDER BLOCK.THEN REMOVE THERMOSTAT HOUSING AND THERMOSTAT.CLEAN THERMOSTAT HOUSING SURFACE AND THERMOSTAT HOUSING SEALING SURFACE ON CYLINDER HEAD.INSTALL NEW THERMOSTAT IN PLACE,MAKE SURE THERMOSTAT AIR BLEED HOLE FACING LEFT SIDE UPWARD ON THE ENGINE.SOME THERMOSTAT HAS TOP STAMPED ON IT.MEANING MUST BE FACING UP.WHEN THERMOSTAT IN PLACE.TAKE NEW THERMOSTAT GASKET.PUT SEALER ON BOTH SIDES OF GASKET.THEN.PUT GASKET ON THERMOSTAT HOUSING.THEN PUT HOUSING IN PLACE TORQUE HOUSING BOLTS 16 - 20 FT LBS.WAIT 1 HOUR UNTIL GASKET SEALER CURE.THEN FILL UP COOLANT SYSTEM.BLEED COOLANT SYSTEM AND CHECK FOR LEAKS.

Follow the large hose coming out of the top of the radiator. That should take you to the thermostat housing. You need to place a container under the drain spigot on the radiator and drain a gallon or so of coolant from the radiator so that coolant doesn't run out when you remove the housing. Remove the housing (usually don't need to remove hose) and scrap clean both surfaces of the housing and the block. Take not of the position of the gasket and thermostat you are removing. Replace thermostat, put a small amount of gasket sealing material on both surfaces, put new gasket on and tighten the housing back down. Some engines have a small plug in the housing. You have to remove the plug as you replace coolant back into the motor until you see coolant running out of the hole and then put the plug back in.

Here is a video that show the gist of changing one.
http://www.youtube.com/watch?v=RIC6Z4D6Q3E

Follow the large hose coming out of the top of the radiator. That should take you to the thermostat housing. You need to place a container under the drain spigot on the radiator and drain a gallon or so of coolant from the radiator so that coolant doesn't run out when you remove the housing. Remove the housing (usually don't need to remove hose) and scrap clean both surfaces of the housing and the block. Take not of the position of the gasket and thermostat you are removing. Replace thermostat, put a small amount of gasket sealing material on both surfaces, put new gasket on and tighten the housing back down. Some engines have a small plug in the housing. You have to remove the plug as you replace coolant back into the motor until you see coolant running out of the hole and then put the plug back in.

Here is a video that show the gist of changing one.
http://www.youtube.com/watch?v=RIC6Z4D6Q3E

Follow the large hose coming out of the top of the radiator. That should take you to the thermostat housing. You need to place a container under the drain spigot on the radiator and drain a gallon or so of coolant from the radiator so that coolant doesn't run out when you remove the housing. Remove the housing (usually don't need to remove hose) and scrap clean both surfaces of the housing and the block. Take not of the position of the gasket and thermostat you are removing. Replace thermostat, put a small amount of gasket sealing material on both surfaces, put new gasket on and tighten the housing back down. Some engines have a small plug in the housing. You have to remove the plug as you replace coolant back into the motor until you see coolant running out of the hole and then put the plug back in.
Here is a video that show the gist of changing one.
http://www.youtube.com/watch?v=RIC6Z4D6Q3E

Follow the large hose coming out of the top of the radiator. That should take you to the thermostat housing. You need to place a container under the drain spigot on the radiator and drain a gallon or so of coolant from the radiator so that coolant doesn't run out when you remove the housing. Remove the housing (usually don't need to remove hose) and scrap clean both surfaces of the housing and the block. Take not of the position of the gasket and thermostat you are removing. Replace thermostat, put a small amount of gasket sealing material on both surfaces, put new gasket on and tighten the housing back down. Some engines have a small plug in the housing. You have to remove the plug as you replace coolant back into the motor until you see coolant running out of the hole and then put the plug back in.

here is a video. probably not your car type but you'll get the gist of it

http://www.youtube.com/watch?v=RIC6Z4D6Q3E

Toyota Celica, Corolla, ECHO & MR2 1999-05Toyota Celica, Corolla, ECHO & MR2 1999-05

2002 Toyota Celica 1.8L MFI DOHC 4cyl

The thermostat is located in the water inlet housing that is connected to the lower radiator hose.
The thermostat is equipped with a by-pass valve. If the engine tends to overheat, removal of the thermostat would cause a decrease in cooling system efficiency.

CAUTION NEVER drain coolant directly onto the ground! NEVER open, service or drain the radiator or cooling system when hot; serious burns can occur from the steam and hot coolant. Also, when draining engine coolant, keep in mind that cats and dogs are attracted to ethylene glycol antifreeze and could drink any that is left in an uncovered container or in puddles on the ground. This will prove fatal in sufficient quantities. Always drain coolant into a sealable container. Coolant should be reused unless it is contaminated or is several years old.


Fig. The oil filter must be removed to access the thermostat on the 5S-FE engine

1. Position a suitable drain pan under the radiator drain **** and drain the cooling system.
2. On the 7A-FE engine disconnect the engine coolant temperature switch harness from the water inlet housing.

Fig. Disconnect the engine coolant temperature switch wiring located on the side of the thermostat housing

1. Remove the oil filter on 5S-FE engines.
2. Loosen the hose clamp and disconnect the lower radiator hose from the water inlet housing.

Fig. Loosen the radiator hose clamp ...



Fig. ... then slide the hose off the thermostat housing

1. Remove the two nuts from the water inlet housing and remove the housing from the water pump studs.

Fig. Only two nuts hold the housing to the cylinder head



Fig. Pull the housing straight out to remove

1. Remove the thermostat and rubber O-ring gasket from the water inlet housing.

Fig. Then pull the thermostat and gasket out



Fig. Sometimes the gasket is stuck and has to be pried out of the head
To install:

1. Make sure all the gasket surfaces are clean. Clean the inside of the inlet housing and the radiator hose connection with a rag.
2. Install the new rubber O-ring gasket onto the thermostat. On 5S-FE engines, align the jiggle valve with the upper side of the stud bolt. Insert the thermostat into the housing.

Fig. Only use the correct temperature range thermostat when for replacement



Fig. Align the jiggle valve within a 10°gap of the stud bolt-7A-FE engine



Fig. Align the jiggle valve within a 5°gap of the stud bolt-5S-FE engine

1. Position the water inlet housing with the thermostat over the studs on the water pump and install the two nuts. Tighten the two nuts to 78-82 inch lbs. (9-10 Nm).

Don't forget to install a new O-ring onto the water inlet pipe. Apply soapy water to the O-ring prior to installation.

1. Connect the lower radiator hose to the inlet housing and install the hose clamp.
2. Attach the water temperature switch connector.
3. Install the oil filter and check the oil level if removed.
4. Fill the cooling system with a good brand of ethylene glycol based coolant.
5. Start the engine and inspect for leaks.

1. Remove the right hand cover under the engine.
2. Drain the engine coolant.
3. Remove the fan and generator V belt.
4. Remove the generator assembly
5. Remove the water inlet via the two nuts.
6. Remove the thermostat.

To install:

1. Install a new gasket onto the thermostat.
2. Install the thermostat with the jiggle valve upward. It can be set within 10 degrees on either side of the prescribed position.
3. Install the water inlet via the two nuts. Torque to 8 ft. lbs. (11 Nm).
4. Install the generator assembly.
5. Add engine coolant.
6. Inspect for leaks.
7. Replace the cover under the engine.

I hope help you with this (remember rated this help) Good luck.

Most thermostats are located in the upper radiator hose housing mounted to engine block. Make sure engine is cold put a catch pan under your car to catch any antifreeze that comes out. Remove the two bolts holding the housing on the engine and remove thermostat and gasket. Clean engine block where gasket goes very good and also the housing, have to remove all gasket material so when installing new one it will seal and wont cause a leak. Make sure when you put the thermostat back in it goes in spring side down towards engine. Replace housing and bolts. replace lost coolant with a 50/50 mixture in your recovery tank. Start engine let heat to temp and check for leaks.

DRAIN COOLANT

1. REMOVE WATER INLET

1. Remove 2 nuts, and disconnect the water inlet from the cylinder block.

1. REMOVE THERMOSTAT
   1. INSTALL THERMOSTAT
   1. Install a new gasket to the thermostat.
   2. Install the thermostat with the jiggle valve upward. HINT: The jiggle valve may be set within 10° on either side of the prescribed position.
   1. INSTALL WATER INLET
   1. Install the water inlet with 2 nuts. Torque: 9 Nm (92 kgf-cm, 80 inch lbs.)
   1. ADD COOLANT
   2. INSPECT CHECK ENGINE COOLANT LEAK Follow your rad hose and you will see the thermo housing the thermostat is under that should be upper hose