What is this part and what does it do????

It is a '84 K10 305.

I was changing the termostat and the piece on the thermostat housing broke. Apparantly it was very brittle from age/heat and broke very easily.

I will try my best to describe it. It is on top of the thermostat housing. It is tapped and screwed into the housing. It has about 1" diameter plastic cylinder that is 2" high. There are 4 male attachments for vacuum hoses. I am assume they are vacuum hoses.

As a stated it broke. The bottom portion is still in the thermostat housing and does NOT allow any fluid to come out. The top portion, white cylinder piece with hoses attached, seems to have some type of valve?

The truck starts and runs. The temp gauge works fine. I am confused?! Thanks for your help!

I think you are talking about the early fuel evaporation switch.
These switchs were usually identified by color of the plasic top and number of ports such as gray, black, and blue and ranged in ports from 2 to 4. Here is an illustration.

That's what I need! I figured it was for the emissions. So many vacuum hoses it's like a snake pit around that engine.

Do you sell it? If so, how much with shipping to Atlanta, Ga 30092?

Thanks!

This is just a guess I looked the part up and as I said there are several depending on the color code and number of ports but the part with our internet discount is around 20.00 and the shipping is no more than 5.50
As you said these engines are a snakepit of vacume hoses and harness's and some were very difficult to decipher which switch is which in the catalog, there are 3 pages with 10 different ones on each page. Sometimes GM put the actual 7 digit part number on the metal part of the switch, the number will start with 305XXXX OR 1400XXXX. Let me know. You can email at [email protected] Thank You John

I'll check and confirm tonight. I believe it is white/grey and it has 4 ports.

I'll try to find the part number on it.

Ok sounds good.
Let me know if you have any other q's I am usually
hanging around here.