I've been reading up about this a lot lately so here's what I understand about the thermostat/cooling system in the D2 and how the thermostat works. When you turn your truck on the coolant pump starts to circulate the coolant in the block which gets heated up, on the way out of the block it passes the temperature sensor before going in to the thermostat. In the thermostat there is a spring and a wax plug that holds a valve shut. The valve has holes in it so some coolant ~10% is always allowed through, even when the valve is shut. When the valve is shut 90% of the coolant is shunted to the heater core, according to the RAVE this allows the heater to come on line faster for passenger comfort. When the coolant passing through the thermostat reaches 180 F the wax holding the thermostat spring and valve shut starts to melt, allowing the valve to open partially which starts to divert some of the coolant to the radiator where is it cooled (hopefully) and then returns to the engine block. The wax continues to melt until 205F where it is fully melted and allows the valve to be 100% open which should be diverting nearly all of the coolant flow to the radiator for maximum cooling. It should also be noted that the spring holding the valve shut is a so called "hard spring" in the stock thermostat so even when the wax is fully melted the valve doesn't fully open because the coolant pressure at idle RPM isn't enough to push it open. The warm weather thermostat, which is the recommended replacement opens at a lower temperature and is a soft spring so more coolant goes through the radiator at idle engine speeds.

Hopefully that sheds some light on the workings of the thermostat. As for the pinch tools, I found this image on the forum and saved it- you can make your own!

 

That's rather brilliant. I'm going to try that with U-bolts and see how it goes.

I went ahead and bought the Britpart 180 degree thermostat and will see if I can wrestle it in in the next couple days.

 

Update: Apparently the plastic tee is leaking coolant directly onto the serpentine belt, which is probably not helping anything. Still need to put in the thermostat, but I'll probably drain the system and replace what I can while I'm able.

 

You can capture and reuse the coolant. I have done so a couple times. Just put a drain pan below the radiator area, then use an old T-shirt or other piece of fabric to filter the coolant before pouring it back into the reservoir after you have finished replacing the thermostat.

 

How did you bleed it?

Do you hear any waterfall sound?

You can hook up a garden hose and run some water through the core to see if its flowing.

If you can, grab a laser thermometer and see if you have a warm radiator through the whole radiator. If corners stay cold the flow could be reduced in those areas...

Switch to green coolant. Change your coolant every 5 years.

 

So I did some research, and apparently the way I bled it was the wrong way, which is to open the bleeder screw with the engine running. There's no waterfall sound though, and the heat seemed to improve when I topped off my coolant.

I'm also using Zerex G-05, which I like better than green coolant, but I've certainly got a schedule for flushing it.

At any rate, I took out the old thermostat, and it pretty much crumbed in my hands. The hoses appear to be new, but I'd be surprised if this was ever changed, so it was definitely time for it to go.



I'll have to drive it around a bit a rebleed it before I can call it fixed.

However, I did notice a leak coming down the outside of the radiator support. So I get to add potential cracked radiator side tank to my list.

 

OMG
it's supposed to be white.

As far as a cracked plastic tank on the rad, get a dremel and valley it out, fill with JBWeld, you may get a couple more years out of it.

 

Yeah that thermostat looks NASTY!!! I bet the T is just as brittle & I’d highly recommend replacing it.

 

The upper radiator hose appears to have been replaced, but I think I may have stripped the bleeder screw, which is great. I'm putting in a brass screw, and I've got my eye on the metal tee so I don't need to worry about it again.

The other thing that's baffling me, and makes me worried about the radiator, is that the coolant is going in a fairly normal yellow color, and is coming out a very clear, very bright, purple. I've flushed the system a couple times before filling it and added (I think) a UV dye, and it has none of the hallmarks of a head gasket leak, but I'm nervous that there's ATF somehow getting into the cooling system (and vice versa). That said, I was under the impression that the transmission cooler was separate from the radiator, so I'm not sure how the two would mix.

 

So I took it for a test drive and things do not appear to have improved. It now sits at 206 on the highway, there's no heat again, and it hit 215 sitting in traffic. Putting it in neutral and revving it at a stop light brought temps down to 203.

I'm going to try bleeding it again, but if anyone has another idea what's going on, I'd really appreciate the help.