Thermo valve and wax case
06-18-02, 07:53 PM
#1
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Thermo valve and wax case
Hello all, this is my first post. Tried doing a search with negative results and also can't find the info in the factory manual, chapter 4B where I am looking.
What I'm trying to find is an explanation of the thermo valve and wax case.
TIA.
pmartin
84 SE
What I'm trying to find is an explanation of the thermo valve and wax case.
TIA.
pmartin
84 SE
06-19-02, 06:41 PM
#3
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Thermo valve and wax case
Good point Sterling so here is more info:
When looking at the engine bay from the right side, the thermo valve is to the rear of, and below the throttle body and has 2 vacuum lines to it. One of them goes to the throttle diaphragm forward of the throttle body and has a "delay valve" according to the diagram in the FSM. I am assuming the system has something to do with warmup idle control. Also, integral with the thermo valve is something called a "thermo wax case".
pmartin
When looking at the engine bay from the right side, the thermo valve is to the rear of, and below the throttle body and has 2 vacuum lines to it. One of them goes to the throttle diaphragm forward of the throttle body and has a "delay valve" according to the diagram in the FSM. I am assuming the system has something to do with warmup idle control. Also, integral with the thermo valve is something called a "thermo wax case".
pmartin
06-20-02, 10:11 AM
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I'm sorry, but you're talking "13B" ...It's a whole other language to me! I don't know!
It looks like a choke mechanism...Perhaps the case is filled with wax, and at the right temp, it melts, and the piston can be pushed in?
Sorry!
It looks like a choke mechanism...Perhaps the case is filled with wax, and at the right temp, it melts, and the piston can be pushed in?
Sorry!
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06-20-02, 02:57 PM
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The thermo valve (4B-46/47) applies vacuum to the #2 secondary throttle valve diaphragm, closing the valves when the engine is cold. As the thermo valve warms up, it cuts the vacuum and the throttle valves open. The delay valve just allows the valves to open slowly, instead of flipping open when the vacuum is cut. The "choke" function is performed by the ECU and injectors. The #2 secondary valves just restrict the airflow to the #1 secondary valves behind them to keep you from over-revving the engine while it's cold.
The thermo wax rod is retracted when cold. It engages the fast idle cam, mechanically keeping the throttle partially open. As the engine warms the wax does also (water is circulated through the thermo wax assembly by a hose from the front of the engine and another short one to the rear) and the rod extends, disengaging the cam, and allowing the throttle linkage to rest on it's normal stop.
With a cold engine the thermo wax rod is retracted, but the cam is not engaged with the throttle linkage. That's why you want to tap the gas pedal before starting. Look at the fast idle cam when the engine is cold, and move the throttle linkage: you'll see the spring loaded lever engage with the roller on the throttle linkage.
-John.
The thermo wax rod is retracted when cold. It engages the fast idle cam, mechanically keeping the throttle partially open. As the engine warms the wax does also (water is circulated through the thermo wax assembly by a hose from the front of the engine and another short one to the rear) and the rod extends, disengaging the cam, and allowing the throttle linkage to rest on it's normal stop.
With a cold engine the thermo wax rod is retracted, but the cam is not engaged with the throttle linkage. That's why you want to tap the gas pedal before starting. Look at the fast idle cam when the engine is cold, and move the throttle linkage: you'll see the spring loaded lever engage with the roller on the throttle linkage.
-John.
Last edited by FJ; 06-20-02 at 03:10 PM.
06-20-02, 06:57 PM
#9
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Thanks Spinner. Guess I just didn't read that darn manual carefully enough. Actually, I didn't realize it was in there since it wasn't specifically listed in the table of contents where I tried finding it.
pmartin
pmartin
06-20-02, 08:11 PM
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Originally posted by pmartin
Thanks Spinner. Guess I just didn't read that darn manual carefully enough.
Thanks Spinner. Guess I just didn't read that darn manual carefully enough.
-John.
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