Strange overheating problem

Hello everyone,

Yesterday I changed all of the hoses and the t-stat on my 98 Discovery (70,000 miles). Everything was ok until I went to a self carwash and cleaned my engine. When I got home (15 min drive) and was let the car idle all of a sudden it started overheating. The gage just shot straight up and wouldn't go down even if I let it idle with the heat on. Sometime its a bit erratic - goes up real quick and then backs of a bit and the back up. There is no steam coming out. When i filled the system with the new coolant I opened the radiator and let the coolant flow out of it so that there would be no air in the system. So my thoughts are - bad t-stat (could be clogged), air in the system or I somehow screwed up the temp sensor when I washed the engine today. Any thoughts?

Alan

Is your electric fan and engine fan working? Could it be a bad t/stat, are you sure you got all the air out of the cooling system, most don't.

Both fans are definitely working. I THINK I got all of the air out. I basically opened the little plug on top of the radiator and poured the coolant into the tank until it came out of the little opening. I guess you don't think it was the sensor. Replacing a t-stat is easy - so maybe I will just do that and then refill it again. Is there a step by step air draining procedure somewhere on this forum? Thanks Mike!

Alan

Remove the plug from the top of the radiator, remove the cap from the overflow bottle, start the trk and turn the heat to HOT, both sides.
Let the trk run until the upper radiator hose is to hot to touch and coolant comes out from the plug on the radiator.
Keep the overflow bottle at the proper level while doing this. With the trk running replace the plug and THEN the overflow cap.
Every couple of min check the temp gauge and make sure that you are getting hot air from the heater. If you put it on "dash" you can just stick your head in the window and feel the hot air in your face and check the gauge without opening the door.
But it does sound like you have air in the system.

Alan, rebleed it and if you still have problems, get back to me.

Well - I am pretty sure that its my t-stat. I took out the plug and removed the cap and started the truck. With my hand on the upper hose I stood there for about 10-15 min and while the temp gage went all the up up I felt no hot coolant going through the hose. So basically while the gage was telling me that the coolant is hot I was still able to hold on to the hose and squeeze it and felt nothing going through it. So I am thinking its the t-stat so I will order a new one and pop it in. Any thoughts? Thanks!

Maybe you installed it backwards, flip it around and see what happens.

Son of a gun - now I am starting to question myself. Does anyone have a picture that show how the thermostat goes in? I got the rave manual but it doesnt work on my Mac. Lets see - the spring part - does it go inside the engine or outside?

I am 90% sure that the spring goes on the inside. BUT, if you mark the old one when you take it out and then put the new one in the same way...but you already replaced it.
Remove the t-stat housing and just turn the t-stat over. So if the spring is facing out then put it in. I know it can be a pain to figure out if you dont pay attention, I've done it before, it sucks.