Hi Folks,

I'm new to the forum and acquired an '84 2M4 last October. Thus far, having a blast!!!

In checking all that I can within my amateur tech. status, I have tested my Thermac air intake regulator system and it is not working correctly (damper door in snorkel not holding vacuum, etc.). That said, I want to replace the damper door unit and also want to replace the temperature sensor/bleed valve in the air cleaner housing. Does anyone know replacement OEM of aftermarket numbers for these parts? I think I'm confident with the temperature sensor number that I found (8997249) but have no idea what heat diaphragm replacement to choose even though thousands of older GM cars used this system. Your help is greatly appreciated!!!

I don't remember the number of the vacuum unit in the air filter housing I got a while back for my 84, but I went to Advance Auto and told them what I wanted. I don't know about replacing the damper door or the vacuum unit that pulls the door open. The vacuum unit looks like it could be replaceable, but I've never heard of anyone replacing it. You could try running a piece of hose from the port for that part, bypassing the temp sensor in the air filter and see if the door opens before you look at replacing the door unit. The door and attached vacuum unit are pretty rugged, my 84 has 233,000 miles on it and it still has the original air filter housing on it. Almost every time the damper door fails to open it's the temp switch in the air filter housing.

Welcome!

[This message has been edited by johnt671 (edited 08-21-2015).]

Thanks Johnt671,

Didn't think of your good idea to put the continual vacuum on the door unit to see if it stays open with constant vacuum. I'll certainly do that first and if it's all good then I'll change the temperature sensor in the air cleaner housing. Cheap enough to replace to ensure correct engine vacuum and thermac performance.

Thanks again, and for the welcome!

Also make sure that the tube that connects to the opening on the bottom of the damper and goes down to an opening on the exhaust system is there. This tube brings hot air up to the filter housing to warm the motor quicker. I found this piece at Advance Auto also.

Tested the air door in the snorkel - works perfectly with direct vacuum. Thanks for the advice! Also, although there was a heat stove tube connected - it had a hole the size of a quarter in it. Replaced that as well with a Dorman replacement from Advance.

One other question I have never found a definitive answer to - on the bottom of the temp sensor, one of the ports has a large hole, and the other port has a tiny almost pin size hole. Does the large hole accomodate the hose to the damper door or is it reverse; is the large hole connector supposed to connect directly to the vacuum source on the throttle body? It would seem that it is logical the large hole connect to the vacuum supply but the crappy illustrations I have found show that the pin hole size connector goes directly to the vacuum source.

Thanks again....

I'll go out this afternoon and check mine out to see how it's set up. I'll get a picture of how the vacuum line runs.

3 ports on switch? most I seen have 2.
1 port (Port 3?) goes to nowhere.
if numbers are visible when you take it out of cleaner.
If big hole is to side, maybe is port 1.

Alldata says (84 and 86):

quote Thermostatic Vacuum Switch: Description and Operation Thermac Secondary Vacuum Break Thermal Vacuum Switch (SVB-TVS) This switch acts as a vacuum connection for the thermac air cleaner control and a thermal control for the secondary vacuum break diaphragm. Ports 1 and 2 of this switch are always connected and port 3 is sealed when cold and connected to the other ports when warm. Thermostatic Air Cleaner Thermal Check Valve (TAC-TCV) This valve is a one-way check valve and closes at 80° F. When the valve's temperature reaches 95° F, it opens and allows vacuum to flow in both directions.

Emissions equipment list for 84 is TAC but (SVB-TVS) says 3 ports... I don't know what you have. (don't have 84 FSM)

Some sites still list the motor 25041109 for 84-86.

ACDelco: Air Cleaner Temperature Vacuum Valve
Part Number: 213-118 for 85-86 cars
Doesn't list one for 84 but might be able to make later part to work. Later ones still vent to open air but doesn't have a port.
(AC list them under Emissions and EGR Valves.)

------------------
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(Jurassic Park)

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Thanks Ogre. Im not sure what they are referring to as the third port unless they mean the port that opens and closes inside the sensor unit itself, the two hoses considered ports one and two. I have seen in various diagrams conflicting information - some diagrams show the large port on the sensor connected to the TBI vacuum source; others show the smaller "pinhole" port connected to the vacuum source. Now that it will soon be getting colder here (near Buffalo, NY); I want my hook up to be correct through the fall for better warm up and performance. She gets stored in the winter.

I didn't take the pictures today, I had an eye exam and can't stand the bright sun. I'll get them tomorrow, and also look for my 84 service manual to see what it shows.

quote Originally posted by cashmgr: She gets stored in the winter.

Help warmup but isn't only job.
Keeps TBI from freezing and that can happen in the summer depending on weather.

The service manual states that the motor assembly for the damper door can be replaced by drilling the spot welds on the strap. remove and replace the motor, and use sheet metal screws to hold the strap down.



This picture shows how the temp sensor mounts in the air cleaner housing. the C in the AC logo is towards the front of the car.



This picture shows the vacuum lines. The line under the C runs to the motor, and the line under the A comes from the throttle body.

Thanks very much John. I suspected that may be the case but wanted to be sure. I appreciate you checking your hookup for me.

Best regards,

Dennis

No problem, glad to help you out.