Just to make sure, and I have looked at the manual dozens of times, the outside hose from the firewall attaches to the pipe to the intake. The drivers side pipe is the return pipe to the lower radiator hose, yes?

 

 

The heater core is in its own loop, returning to the hose between the thermostat and the water pump. The thermostat isn't opening if the radiator return to the thermostat is still cold/luke warm, and the other loop is hot. The opening of the thermostat shunts the bypass flow through the "T" towards the radiator inlet.

 

I've installed and am about to test what this heat sink does regarding engine temps:

 

Yep you can route the heater hoses anyway you please! It’s just a loop and there is no certain flow in or out. When my Kalahari heater core clogged up last winter I used some 5/8 heater hose line & went straight in/out.

 

I got the coolant system pressure test kit from Autozone this morning, and tested the system at 20psi. It held, and no leaks.

New Genuine 180 Degree Thermostat is on its way from Rovers North.

I'll install, and bleed again. If that does not work than the Radiator is going to have to come out, and get flushed. Hoses will have to come out and be inspected as well as the Intake/Block, and the water pump as well.

I cannot think of a reason that the thermostats are not opening, aside from they are bad. The thermostat is getting hot, it's installed correctly. You can squeeze the hoses and get the coolant to flow through it, and if you squeeze the radiator hoses they affect flow at each end.

it is possible that the temp sensor is wrong, but I don't think so. The heater is blowing hot as all get out.

 

What is going on with yours?

 

Drop the thermostat into a pot of water, and check it with a temp gun.


A friend of mine just bought a rather clean 04 (he paid for a pretty penny for it). He brought it over for me to fix the CEL (vacuum line for the SAI was disconnected), and I went about checking the usual issues. The previous owner or dealership spent a pretty penny on a new radiator, water pump, hoses, and a HG job, but they DID NOT replace the dang 14 year old thermostat!!!!!!!!!!!!!! After I saw that I grabbed my trusty Scangauge II and wasn't surprised when it was idling at 220F.....


I told my friend to change the thermostat immediately!!!! I had a spare so when he was free he brought it back and I installed a 180F Britpart Thermostat. I flushed out all the OEM coolant and replaced it with the green coolant. Added coolant and let it idle. Temp showed it spiked to 211F, but when I used my temp gun the manifold wasn't even 190F. I shut it off, let it cool a few minutes, topped off the coolant thru the reservoir and the bleed screw. Then we went for a 10 mile drive. Temps went up to 200F and then it went straight down to 188F to 193F. Got back and I had to fix his cubby coin/ash tray so while doing that it cooled down. Topped off the coolant and he's good to go.


On his OEM 195F Thermostat it was so obvious the thermostat wasn't opening. The top of the thermostat had a darn orange look to it, while the bottom was more of a tan/cream color = coolant was cooler at the bottom, but since it was stuck closed the upper part of the thermostat had the brunt of the temps and it actually changed the color of the plastic due to the heat difference. I wanted to keep his thermostat for a prime example to show people how important changing the OEM thermostat is, but he was curious and wanted to take it home and put it into a pot of water. I've got $$$$ on that sucker not opening. I'm also willing to bet that's why his D2 was either sold, then fixed with a complete HG job, but once again they didn't actually fix the cause of the HG's going out = thermostat, so my friend basically had a ticking time bomb until it blew the HG's again. It will never cease to amaze me the $$$$ people will dump into a HG job and then they skip or forget to replace the thermostat which was actually the cause of the problem the entire time.


I have seen the temp sensors give false readings before and I have replaced them.


Only other reason the thermostat might not be opening is that the coolant flow thru the radiator is poor, and it's never getting warm enough on the bottom side of the thermostat to open. My 500.00 wonder wasn't opening even after I replaced the thermostat with a spare new 195F I had. I removed the hoses to the radiator, flushed it like a crazy person changing the flow in/out, and even used a vacuum cleaner (shopvac) to get more crud out vs just the water alone. After that I put it all back together and then the thermostat opened and coolant was flowing properly thru the radiator/thermostat.


Testing the thermostat in a pot of water & a temp gun can truly be helpful in diagnosing and ruling out a thermostat issue.

 

Read my magpie thread -- last few pages.

Been dealing with the the same damn issue for weeks.

 

I highly recommend installing the cheap JC Whitney heat sink around your oil filter.

The cooler oil reduced my separate water coolant temperature by 2 degrees in the hot Alabama noonday Sun.