|MARK’S CORNER – AUTO REPAIR HELP|
THERMOSTATIC AIR CLEANER (TAC)
The typical TAC system uses a vacuum motor to actuate an air flow door, located in the air cleaner inlet. The vacuum motor is operated by a signal from a thermostatic switch located in the air cleaner assembly. Warm air is supplied to the air cleaner via a hose that connects from a shroud mounted on the exhaust manifold, to a port on the underside of the air cleaner inlet. During cold engine operation, the actuator closes the air flow door and warm air is drawn into the engine from around the exhaust manifold (take special note of this during a diagnosis of the TAC system). As the engine warms up, the vacuum signal is removed from the actuator and the door slowly opens to allow cooler air to enter through the air cleaner inlet, while at the same time, blocking warm air from the exhaust manifold.
Some TAC systems do not use a vacuum actuator to control the air inlet door. Instead, a sealed actuator containing wax is used. When the engine is cold, the wax solidifies and contracts, causing the door to close. As the engine warms up, the wax liquefies and expands, placing pressure on a piston that is used to actuate the door. The TAC system functions well to aid in cold start up. However, if the air cleaner door were to stay in the closed position after the engine reaches operating temperature, lack of power and hard starting could result. Visual inspection of the TAC system can usually determine if this is the cause of these symptoms. If you are doing the auto repairs yourself or if you have hired your local auto repair mechanic to do it for you, the first step should be to visually inspect the TAC system.
(Mark gave up on sports when the Browns left Cleveland and now spends his Sundays working under a shade tree in the back yard tuning his son’s soap box derby car.)
Can a open air cleaner be used on a 2.8 TBI
Thank you for this information. Moving forward, we’ll always inspect our thermostatic air cleaner.
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MARK, ON MY 1988 GMC SIERRA K-1500 W/ 5.7LITRE V8 I HAVE THE WAX PELLET ACTUATOR, (THERMAC) THERMOSTATIC AIR CLEANER. THE EMISSION MANUAL STATES THAT THE ACTUATOR ASSY. CAN BE REPLACED IN THE SNORKEL AIR INTAKE. THE PLASTIC THAT HOLDS THE WAX PELLET ACTUATOR IS SECURED BY TWO RIVETS AND A PART # 25095945 IS STAMPED INTO THE PLASTIC. MINE IS STUCK CLOSED! I CANNOT FIND A REPLACEMENT ANYWHERE, NO ONE EVEN SAYS THE PART # IS GOOD. SEEMS A PART # 25097956 IS FOR THE ENTIRE AIR CLEANER. ANY HELP FINDING THIS WAX PELLET ACTUATOR WOULD BE GREATLY APPRECIATED.
i have a 1998 gmc 1500 truck 2wd and i am getting trouble codes P0420, p0430 AND p0440 ALL EMISSIONS I GOT THE CAT LOW EFFICIENCY BANK 1 AND 2, I PLAN ON REPLACING THE CAT…. BUT THE NO FLOW DURING PURGE IS HAVING ME THINK TO REPLACE THE PURGE VALVE COULD THIS FIX MY PROBLEMS OR IS THERE ANY OTHER TESTING I SHOULD DO BEFORE REPLACING THESE PARTS…. THANKS
These Air Cleaner Thermostatic switches are getting harder and harder to find and the few that are left are way over priced plus these old parts may no longer function. One idea I had is to purchase an air pressure toggle switch and manually control the damper door from the dash. That may be the only solution left. You can always wire the damper door open and just use 100% outside air.