Helpful Tip Thread - New Thermostats DO Fail !!!
#1
08-16-2013, 03:48 PM
Helpful Tip Thread - New Thermostats DO Fail !!!
Last fall I did another plenum gasket on my 1998 Durango's 360. I ordered the Dorman kit from Rockauto and was very happy with it and the results of the swap. Obviously the kit came with a thermostat and gasket to be used when putting everything back together.
Last week I started noticing the temp gauge reading very high even on a short trip, so I started paying closer attention and keeping track of symptoms and constants like outside air temp, speed, RPM...things like that.
Normally I would suspect the temp sender first but I had replaced that a few weeks prior when the gauge went wonky and the warning light came on. Sender fixed the issue, and it was normal.
Since I new the sender was new I next suspected the thermostat. I would feel the upper hose when hot and it was limp and easy to compress. Not definitive, but a red flag. Fluid levels were fine in both the radiator and the overflow tank.
Thermostats are cheap so I grabbed one with a new gasket from a local shop, and set out to replace the thermostat this afternoon. It's a relatively easy process.
First, using the valve on the lower left corner of the radiator, drain the fluid out. Once it's drained for a few minutes you can undo the upper hose end at the radiator, then unbolt the water neck, and remove the upper hose all in one piece.
Then, remove the old thermostat and set it aside. Using a pot that the Wife won't mind you using, start some water on the stove and get it near a boil. Drop in the old thermostat and let it sit in the boiling water for 10 - 15 minutes. Inspect it, and as with mine, a bad thermostat will not open. It'll remain sealed.
That confirmed what I suspected, that my thermostat...my new Dorman thermostat from Rockauto, not even a year old...had failed.
Finally, clean the gasket surface with a long neck blade scraper, put the new thermostat on the intake, lay down the gasket, and drop the water neck...which is still attached to the bottom end of the upper hose...and install the bolts. Tighten them down good and snug to get a good seal of the gasket.
Add coolant and water, clean up your tools and such, all while letting the engine idle. I watched the temps climb up to normal, and hold at normal, for another 10 - 15 minutes. I spent that time checking all my other fluids and tire pressures.
I have had thermostats fail before, but usually it's immediately or many years after they are installed.
Top Tip: I always drill a 1/8" hole in the hat brim of the new thermostat to allow trapped air and steam to escape out of the system. If you have a pocket or air or steam under the thermostat, it'll never open, and you'll overheat. The tiny hole allows the air pocket to escape, and the hole is so small it won't affect the warmup cycle of the engine. Some new thermostats come with the hole already drilled, as was the case with the new thermostat I bought at O'reilly.
So if you start seeing a climbing temp gauge, first two suspects could be the sender and the thermostat...both cheap and very easy to replace.
Last week I started noticing the temp gauge reading very high even on a short trip, so I started paying closer attention and keeping track of symptoms and constants like outside air temp, speed, RPM...things like that.
Normally I would suspect the temp sender first but I had replaced that a few weeks prior when the gauge went wonky and the warning light came on. Sender fixed the issue, and it was normal.
Since I new the sender was new I next suspected the thermostat. I would feel the upper hose when hot and it was limp and easy to compress. Not definitive, but a red flag. Fluid levels were fine in both the radiator and the overflow tank.
Thermostats are cheap so I grabbed one with a new gasket from a local shop, and set out to replace the thermostat this afternoon. It's a relatively easy process.
First, using the valve on the lower left corner of the radiator, drain the fluid out. Once it's drained for a few minutes you can undo the upper hose end at the radiator, then unbolt the water neck, and remove the upper hose all in one piece.
Then, remove the old thermostat and set it aside. Using a pot that the Wife won't mind you using, start some water on the stove and get it near a boil. Drop in the old thermostat and let it sit in the boiling water for 10 - 15 minutes. Inspect it, and as with mine, a bad thermostat will not open. It'll remain sealed.
That confirmed what I suspected, that my thermostat...my new Dorman thermostat from Rockauto, not even a year old...had failed.
Finally, clean the gasket surface with a long neck blade scraper, put the new thermostat on the intake, lay down the gasket, and drop the water neck...which is still attached to the bottom end of the upper hose...and install the bolts. Tighten them down good and snug to get a good seal of the gasket.
Add coolant and water, clean up your tools and such, all while letting the engine idle. I watched the temps climb up to normal, and hold at normal, for another 10 - 15 minutes. I spent that time checking all my other fluids and tire pressures.
I have had thermostats fail before, but usually it's immediately or many years after they are installed.
Top Tip: I always drill a 1/8" hole in the hat brim of the new thermostat to allow trapped air and steam to escape out of the system. If you have a pocket or air or steam under the thermostat, it'll never open, and you'll overheat. The tiny hole allows the air pocket to escape, and the hole is so small it won't affect the warmup cycle of the engine. Some new thermostats come with the hole already drilled, as was the case with the new thermostat I bought at O'reilly.
So if you start seeing a climbing temp gauge, first two suspects could be the sender and the thermostat...both cheap and very easy to replace.
