2003 Montana (Venture) Thermostat replacement/Thermal bypass pipe
 

I hope someone can help me here with my 2003 Pontiac Montana (Chevy Venture) FWD

1. I got a "Check Engine Soon" light.
Noticed my coolant temp was very low. Although it is cold outside, I've been driving several hours on the highway. I didn't notice a lack of heat, but I thought the temp gauge was unusually low.

2. Plugged in my OBD2 scanner, it read P0128, which from what I can tell, is a problem with the thermostat.

3. Decided to replace the thermostat. I've read a lot of posts about how difficult it is to access the lower bolt on the thermostat housing. I decided to go with the option of removing the throttle body to gain access to that lower bolt.

4. After removing the air ducts and partially draining the coolant. Here's what I did to the throttle body: Disconnected all the electrical connections.
Removed the throttle cable bracket.
Disconnected the two small coolant bypass hoses from the metal thermal bypass pipe.
Removed the bolt on the upper left of the throttle body.
Removed the nut that secured the metal thermal bypass pipe bracket to the throttle body.

Now here's where I'm stuck, I tried to remove the throttle body, but realized there's another nut that was on the same stud that the metal thermal bypass bracket was attached to. It's behind the bracket and I can't access it because the bracket is in the way.

The only way I figure I can access that nut is to disconnect the metal thermal bypass pipe from the hose coming out of the firewall, if I can do that, there will be just enough room to squeeze a deep socket onto the last remaining nut to remove the throttle body. I'm not familiar with this kind of connection. The metal pipe leads into a black plastic connector that has two yellow tabs inside of it. Then there's a silver metal connector and then the hose. I'm not sure if it needs a special tool. I didn't want to poke around and break it.

Does anyone know how to disconnect the metal thermal bypass pipe from this kind of fitting?

I posted a photo of it. Thanks.

Are you referring to the connector with the yellow tabs?
If so, you only need to pinch the tabs and push down and then back up on the connection to get it to release...

Thanks. I solved the issue by disconnecting the thermal bypass pipe on the other end, near the battery. It was easy, I just removed the 8 mm bolt and popped the pipe out by tapping under it with a soft hammer. As soon as the o-ring loosened, it popped right up. (didn't have to disconnect the hose). That gave just enough slack to get at the lower right bolt on the throttle body.

I was almost tempted to cut off the bypass pipe bracket that was blocking the lower throttle body bolt. Finally got the throttle body off, which allowed access to the lower thermostat housing bolt. Replaced the thermostat, now I just have to reassemble everything. Just have to clean the throttle body while its out. After this experience, I don't think I'll be removing the throttle body again anytime soon.

Hope my miscues will help someone else. I don't know how much more (or less) work the other option would've been to get at the lower thermostat housing bolt, which is removing the crossover exhaust pipe. I bought a premium thermostat replacement, hopefully it'll last until the car dies.

thermostat
 

gotta say.. I have never met a design as bad as the venture for things. The thermostat was a pain. after 3 frustrating hours I finally got if off... and 3 hours back on. the bottom bolt on the housing has an open end like you should be able to slide the housing back onto the bolt but I found it was easier to BARELY slide two hands around the area and work it in. it was VERY difficult. I think if you had huge hands it would be impossible. I have medium size hands and I was able to get my fingers in over the manifold and then slide my other hand up underneath and guided the bolt in with the tips of my fingertips of both hands. Required tremendous balance and care and frankly surprised it worked. I put in a premium one too and hope it never needs replacing. now I know why they wanted 250