So I noticed a bout 2 weeks ago when i was stuck in dead stop traffic that my car was runnign really hot, with coolent temps in the 240s so i kept an eye on it and it did it again when i stopped at a gas station a couple days later and left the car running(without the a/c on) for probably 4 minutes and I came back and it was in the 250's. It seemed to cool down if i was continuously driving but would heat up and wouldnt go back down if i stopped any period of time. I made sure the fan kicked on at 225 for the low speed and 235-9 for high speed but it didnt seem to do anything.

So I decided the thermostat must of gone bad or something because the fans were working but it still wasnt cooling the car off. So I replaced the thermostat and it seemed to run a little hot but wouldnt go over 235(high speed fan) but i get in the car today and it damn near overheats while sitting at a light, but the odd thing is that my oil tem was still at like 199 and when i popped the hood it didnt seem like the bay was THAT hot, I had coolant in tank, the system was under pressure and everything. When changing the thermostat I also cleared all the debris from in between the radiator and condenser so blockage isnt it.

I can think of only a few things left that it could be:

- Radiator blockage/malfuntion , in that for some reason the water isnt flowing correctly through the radiator. But the coolant seemed pretty clean when it came out while doing the thermostat and there was no signs of corrosion or anything like that inside it.

- The coolant temp sensor is on the fritz and giving weird readouts, not sure if this would trip a code but i'm not getting any codes so not sure if this is a possibility.

- water pump is out, not really sure how to test this as its not making noise, is spinning freely and there seems to be pressure on the system which im only assuming is being generated by the bump.

Do any of these stand out as common issues or problems, or am i missing something on the list that it could be? The issue is becoming quite frustrating considering the car is my daily driver.... any help is appriciated!

 

The radiator is most likely clogged with debris. Pull the air filter and fans out of the way and clean it out with a pressure washer. I pulled my radiator out of the car to clean it and did an okay job with water pressure and an air hose but a pressure washer would do better I think.

 

You might check the radiator flow. These are notorious for getting clogged. I can always tell when my oil temp starts running over 205 consistently, its time for a cleaning.

 

ps- that would be the outside air flow not internal!

 

A combo of things really. Most certainly their is some radiator and A/C condensor blockage (Bottom Breather). Is your highspeed fan coming on ? With the A/C on, the highspeed fan will be on.

John

 

As already mentioned, check for debris blocking the condensor vanes and check to make sure the fans are coming on. If the AC is running, both fans will be on at either low or high speed but always "both" will be running.

 

As I mentioned in the first post I took the whole intake and radiator cover off and cleaned out what debris was there so its not an issue of not enough air flow over the radiator face. For some reason I have pressure but when i loosen the top radiator hose(at the water pump) very gently when its hot that all i get is air and NO coolant, not sure if that means there is a blockage in the radiator or the pump isnt doing its job, any guesses?

 

Of course you could have trapped air in the system as you are thinking. In just taking the cover off the radiator and condensor, how did you clean things out? Personally, I use a water-wand that I fabricated to do the job which supplies enough force to blast out the tiny rocks, toward the front. Air trapped inside, air not getting through the vanes...either can cause this. I would almost say it was the coolant temp sensor itself but you say its cooling back down when you start moving. The fans are running so it isn't that. Are you running the HVAC when this happens or does it happen only when the HVAC is off? Are you the original owner of the car and I ask because I'm curious if someone could have dumped some "Stop-Leak" or similar in there, plugging up the internal radiator?

 

It was a PITA trying to flush the air out of the system when i swapped the T stat and ive tried to keep purging the system by letting it run and getting hot and slightly opening the cap and upper hose but its still doing it. Now it wont even cool off as I drive, as i've discovered tonight. I start the car and its at 150 degrees and i drive and before i could even do a mile it was at 230. Im starting to lean on the water pump going out.

When I took the radiator cover off I just pulled all the hair/leaves out from the condenser/radiator and there is a few leaves stuck in there but nothing that would cause this issue.

I was going to drive it down to the stealership and have them jsut do the doagnosis but now i know I cant drive it that far and the car wont fit on a tow truck so im down to trying to solve this problem in my garage. I guess I'll pull the radiator completely out and see if there is some sort of blockage there, and if its not that I guess it has to be the water pump. I hope its not considering the car only have 30k miles... Oh and im not the original owner, but when i drained the radiator to swap the T stat it didnt look like there were any additives in there.

The issue happens with the AC off, havnt checked with it on but im assuming that since i cant even drive a mile without it overheating it wont change if the AC was on. There is obviously a obstruction thats not allowing the water to flow into the block and back out into the radiator, just have to find out whats causing it.

 

There are a few things that could be going wrong here.
You essentially eliminated it being the T-stat by replacing that. My question for you is how many miles are on the car? A high milage car may point to the water pump so that could be something to look at. The other pretty obvious option is that the radiator is clogged or has some blockage. I know someone who had a piece of cardboard stuck in his radiator and didnt even know it. His coolant temps shot through the roof and the car actually went into "reduced engine power" mode. 200 degree oil temps are insane though, I have a 400rwhp N/A cammed C5 with 4:10's and I never get above around 160-168 oil temps and I dont have an oil cooler or anything. Might also be worth changing your oil that could help as well. Let us know how it turns out.

 

I don't think I could have got mine clean without pulling the radiator completely out. Maybe with a pressure washer.

In my experience water pumps rarely stop pumping. They start leaking if they fail but the vanes are fixed and very seldom break or come loose.

If the replacement thermostat had a bleed hole like the original you should have no trouble getting air out of the system. The system has a purge hose that leads to the top of the tank so filling it slowly and refilling it before starting should get it completely full.

I suggest you pull the radiator and clean it and the condensor again. Fill the resevoir and let the car sit 10 or 15 minutes then refill untill it stays at the correct level. THEN put the cap on and start the car. Run it for a few minutes and shut it off to check the level again. If everything is working like it should you don't have to loosen any clamps or pull any hoses to get the air out. The system is designed to self bleed with the cap off.

 

I didnt check to see if there was a bleeder hole in the new T stat, And there is a little debris left in the radiator but not even close to enough to justify going from 150 to 250 in less than a mile, I know there is air in the system and the water is not flowing I just need to figure out why. I think before I do anything im going to pull the T stat out(even though its new its from autozone and it could be faulty) and see if it still runs hot, if so i'll pull the radiator out and check that for blockages, if that doesnt work I guess i'll have to move to the water pump, but I agree i really dont think its the pump since the system still has pressure and im not getting any leaks from there, or at least that I can see.