: 97 DeVille Concours still runnin hot

07-20-05, 10:19 PM
I have already replaced the radiator, water pump, water pump tensioner, and the hoses. The car ran hot 278 degrees and then I replaced the thermostat. It seemed to run okay, but then after about 2 days it still runs hot after driving it hard or for longer than 30 minutes. I unscrewed the purge line from the surge tank trying to determine what else it could be other than heads. When I started the car with the purge line unattached from the surge tamk there is no flow coming out of the tank or the hose coming from the water pump. Both fans seem to be working fine...Does anyone know how or which way the flow should be moving in the purge line? Or can anyone tell me what else to check? I really do not want to get into the heads if I don't have too$$$$$$$$

07-21-05, 11:11 AM
you need to go to a radiatorshop and have them pressurize the system they should be able to tell u the problem

07-21-05, 01:16 PM
The flow should be coming from the water pump to the surge tank. If there is no flow you likely have air in the system and that is why you are running hot. Remove the line and blow it out. Also check the hollow bolt that it connects to at the pump housing and be sure that is clear.

If nothing came out of the surge tank, then it too is plugged or dry. Pour some water in it with the purge line disconnected and see if it runs out. If not, clear the obstrucsion and refill it when you get it back together.

If you ran 278 deg. you may have damaged the head gaskets.

07-21-05, 01:25 PM
Thanks Ranger...i'm working on it right now...i'll check back in a few...if that doesnt fix the problem, do you recommend that i drain and flush the radiator and add some bars leak to the radiator hose and see if that fixes any possible head problems? i just put a new pressure cap on the surge tank just because...

07-21-05, 06:39 PM
Nope. Barsleaks does not fix a head gasket. There is only one cure for that.

07-21-05, 10:32 PM
I did all I can do...when I drive it now with Dexcool in it and the new pressure cap and after I flushed the system and blew it out with a shop vac, it still runs hot. As soon as I start moving at low speeds or on the highway at about 75-80 mph the temp goes back down. I can run the AC on high and everything, but as soon as I come to a stop, the needle starts going up....I checked to see if I could see any coolant leaking out from anywhere and I could'nt...there is no steam at all, but I do hear a slight hissing sound from the upper left (when facing motor) part of the engine...ugh! Looks like its the heads.....damn it!!!

07-22-05, 02:37 AM
Are the fans working? They do come on when the AC is on. If they're not working that would explain it overheating at slow speeds.

07-22-05, 02:32 PM
Last night when I test drove my car it still wanted to run hot like I stated in my last post, but this morning I checked the coolant and put some wetter water in the surge tank and put the pressure cap on so where the arrow on the cap lined up with the overflow hose. I drove it all day with the AC on blast, stopping and starting in traffic and everything and the temp gauge hardly budged!!!!!!! Yeah!!!!Please pray that it stays like that.....Yeah!!!!!

07-22-05, 06:39 PM
By jove I think you've got it! I think maybe you've purged the air out of the system. Just for the hell of it, remove that purge line at the surge tank. Put the end in a coffee can and have someone start the engine for a second or two. See if it is now flowing coolant. I think that was your problem all along but I'd still be concerened about that 278 deg. temp. If it is, then I think you are out of the woods. Pour that coolant back in the surge tank and keep a close eye on the temp guage. Keep me posted.