GMC 12514334 Thermostat,Engine Coolant

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Remove any gasket or sealer with the thermostat from the cylinder head. Unbolt the water neck by draining the coolant system below the thermostat level when trying to replace it. The next step is to remove the water neck and thereby expose the thermostat. Thereafter, clean off all traces of remnants from both manifold and residual gasket material or sealer on water necks that mate. Installing it with its wax pellet downwards is a good idea. Besides, apply some sealant on both sides of the gasket then put it on block. Finally, hold it down using retainer bolts.

To test the thermostat's operation, it should be removed from the engine. If one doubts about the thermostat, then it is most likely that it is cheaper to purchase a new one since they are not expensive. Before you can start testing, remove the thermostat. Examine if there is excessive corrosion or damage on the thermostat. Replace with a new thermostat if either of these conditions exists. Place in hot water 25 degrees above the temperature stamped on the thermostat. For example, since almost all Chevrolet V8 and V6 engines use 195-degree thermostats, the water temperature will be around 220. The valve must be completely open when submerged in this hot water which has been stirred vigorously. After that, unbend a piece of wire and draw out its thermostat before immersing it into water that is 10 degrees below what appears on its body. In most cases this cooler water temperature should be 185 degrees. This means that at this particular temperature, the valve should close fully. Reinstall if OK or purchase a new thermo-stat of equal rating to install your thermo-stat in case it checks out OK.

To check a thermostat, submerge the thermostat in water 25 degrees above its stamped temperature, usually 220 degrees for most GM engines. The valve should be fully open, then place it in water 10 degrees below the stamped temperature, typically 185 degrees, where the valve should close. If the thermostat functions correctly, reinstall it.

To replace the thermostat, undo the water outlet housing as well as the thermostat, and clean the gasket sealing surfaces. Reconnect the radiator hose, and refill the cooling system with an antifreeze/water mix. Finally, reattach the battery cable, start the engine, and add coolant until the radiator is filled, then seal with the cap.

The gasket should be secured in place using the retainer bolts.

After removing the thermostat, inspect it for excessive corrosion or damage.

Before installation, use a gasket scraper or putty knife to carefully remove all traces of the old gasket on the thermostat housing and the water outlet cover. Make sure not to allow any gasket particles to drop down into the water passage.

After installing the new thermostat, reattach the radiator hose to the cover fitting and tighten the hose clamp.

To reassemble the thermostat housing, you need to reconnect the radiator hose and refill the coolant. Then, start the engine and add more coolant if needed. Finally, install the radiator cap.

If the thermostat checks out OK, it should be reinstalled.

Begin by draining about three quarts of coolant from the radiator until the level is below the thermostat housing.

Before installing the thermostat back into its recess, you should apply RTV or equivalent sealer to the gasket surfaces.

Check the coolant level in the system. Verify the drivebelt tension is correct. Observe the temperature gauge or light operation. If the engine takes a long time to warm up, it may indicate a thermostat stuck open and needs replacement. If the engine runs hot, and the upper radiator hose isn't hot, it suggests a thermostat stuck shut and should be replaced. If the upper radiator hose is hot, it indicates that the coolant is circulating and the thermostat is open.

Remove the air cleaner and label all hoses for ease of reinstallation.

The thermostat is designed to open and close at predetermined temperatures to allow coolant to warm up or cool the engine.

For 1982 and later L4 models, the thermostat and housing have been redesigned for simpler servicing. To replace the thermostat, first remove the thermostat housing cap. Then, grasp the thermostat handle and pull it out. Replacement is completed by pushing the thermostat into the housing, making sure it is seated, and installing the cap.

When placed in water at a lower temperature, the thermostat valve should close fully.

After lifting the thermostat housing from the engine, the thermostat will be visible and can be removed from the engine.

If the thermostat does not check out OK, purchase a new thermostat of the same temperature rating.