Hi all! Looking for some input on a cooling issue I’m having with the old girl. ‘02 D2, 162k miles.

I recently replaced the valley gasket, all cooling hoses, TB heater, and OEM 180 deg t-stat. Flushed the cooling system with radiator flush and distilled water, then just distilled water and filler her back up with green coolant.

I extensively bled the system over a few days following the best practices outlined on here (including elevating the nose of the truck).

Driving the truck around it was running north of 197 and got up to 210 at stop lights. Heater blowing hot air the whole time and no waterfall sounds. I rebled the system a couple of times and it continued to happen.

I felt the lower t-stat hose and it was ice cold compared to the upper hoses. I thought I had a bad t-stat. I replaced it, went through the same bleeding again. Drove it again and the temps climbed all the way to 217 where the cond fan kicked on. Felt the t-stat hoses again and felt the same temperature differential in the hoses.

I happened to change the oil after all this and no signs of coolant in it.

The truck was running fine temp-wise before the work and flush. I’m thinking the flush broke up some crud in the radiator and now it’s not flowing enough to open the t-stat.

I ordered a new radiator and water pump and plan on hose flushing the block, heater core and TB heater hoses to ensure there’s no blockage when reinstalling the new parts.

Does it sound like I’m on the right path? Anything else this could be or anything else I should consider?

I’m sick of draining and wasting brand new coolant trying to fix this. Any help is greatly appreciated. Thanks!

 

The factory Disco thermostat makes it very hard to diagnose cooling system issues. The two most common issues are bad thermostat and plugged radiator. Plugged radiator will generally idle at normal temps but run hot on the highway, defective thermostat will run hot under both conditions, sometimes randomly. The inline thermostat mod allows you to remove the thermostat completely if need be, removing it from the equation so you can diagnose the radiator separate. You can attempt to test the radiator with a garden hose but they typically do not flow enough to provide a good test. You can also replace both the thermostat and the factory tee with bushing to do a thermostat free test.

 

Where did you get the 180 degree thermo from? I had the same problems you a couple years ago and it ended up being TWO bad, new aftermarket 180 thermostats from Lucky8. I got an OEM LR 180 degree thermo from Rovers North and problem solved.

Overall observation after owning two discos for several years... the older these things get, the less reliable aftermarket replacement parts are becoming in terms of quality and consistency. I've been slowly reckoning with the thought that it's looking like OEM parts from now on for most things.

 

Sounds like a factory thermostat temperature range. Throw that crap out and go inline

 

I'll get those temps with a 180 thermo in the summer going uphill in a hot/desert part of the state (CA), but winter temps are usually 186 on the freeway, 194 in town, 199 at a stop.

Inline is certainly an option, but I'm pretty sure he has a bad, new thermostat on his hands.

 

Rovers North.

Bought the AB generic 180, which is what was in it when I got it.

 

thanks for the info. Idling fine, but running hot while driving is what it’s doing.

 

I bought the thermostat that goes on top of the radiator shroud from the link in the sticky at the top of the disco 2 forum. It eliminates the factory thermostat and makes it much more accessible.

 

Thanks for the tips all. I’ll be swapping to an inline. 👍🏻

 

I made a little YouTube video about the D2 cooling system. Maybe it will help.