Engine light & overheating

[box091]

Hi,
I need some help running down what is wrong with my 99 GA GT.

My husband is a truck driver, and loads at his company are not so well at the moment...so we have got to try to figure out what this is on our own and fix it this weekend when he comes in.

The problem started with the loss of coolant, and the low coolant light coming on. I would put more coolant in, and be ok for a few days. I found a crack in the overfill container. I had to JB weld the crack until our local parts store could get the container in. There would be times the temp would climb... and I would turn the heater on full blast and the temp would drop... but most of the time the air blowing is cold.
The overfill container got here this weekend, and we put it in.
We were on our way back from the parts store when the engine light came on. It blinked, then it went solid. The temp would climb.. but I blasted the cold heater and it would drop.
When my husband put in the new overfill container, he also replaced the fuel filter. (When he had done our tune up, the clips broke.. and well, now the new one is in after a lot of cussing and the help section at the parts store)

I start the car and being cold out, you would think it would take longer to warm up.. but no sooner did we get out on the highway... the tempature shot right into the red within 5 minutes only giving us enough time to get into the shoulder before it dies. We waited a few minutes, and with the heater on full blast start it up again. It may take 2 or 3 times, but something kicks in and the temp goes down.(cant tell weather it was the fan or the heater bringing the temp down)

On top of that.. the heater blows luke warm for a few seconds, then goes ice cold. And then for the most part it stays cold.

Now one more problem to add to this is... at an idle the car is now rough. If you are in gear it's even rougher. Once I get the temp to go down and can get up to highway speed however, it drives fine... until I come to a stop and then it is rough again. (unless we are talking when we first start the car and start driving and thats when it tends to do the overheating and stalling)
Now.. I know I should not have driven the car.. .. I HAD to take my husband back to the shop so he could leave back out, and he stayed at the shop until I called and told him I had made the 60 mile trip home. It was cold... but we made it.
Now the car is sitting because I am afriad to go anywhere with him now not being in the area... and I do not want to damage anything.. or worse case be stuck on the side of the highway with my children, with no family to call to help..

He is racking his brain trying to figure out what it could be.. oh and I also went thru 2 gallons of coolant going up there and back to drop him off.
The hoses are tight, there is nothing dripping in the driveway though.

A rundown:

Engine light both blinking and solid... it will just start blinking randomly
Running rough under 15 MPH (actually sounds and feels like it will die)
Eating up coolant
Heater blowing cold 85-90% of the time.

Sorry so long... I just wanted to be descriptive.

Oh.. my husband is thinking it is the oxygen sensor and the theromostat.

I am thinking heater core and thermostat.

Are one of us close? Please help!

Thanks for all help in advance!

[GTP Dad]

Welcome to AF!!

Start with the thermostat. It sounds like it is stuck in the closed position, that is why you are heating up so fast and there is no heat coming from the heater. I don't think the heater core has an issue you just need to get heated water to the core so that the heat will work. However, since you did go through so much coolant it must be going somewhere. There is a drain on the firewall near the front of the engine. If you are loosing coolant from the heater core area it should come out that vent. There is usually a rubber elbow on the vent that directs any fluid onto the ground.

Changing the thermostat is not hard but you will need to bleed the air out of the cooling system which can be hard. To bleed the system, fill the system and open the bleeder valve on the thermostat housing until you get coolant. Start the car until the thermostat opens. Refill the fluid and bleed the system until you get coolant again. This is a pain but it must be done. Make sure you bleed the system with the heater on high so that you get coolant into the heater core.

Changing the heater core is a different story however as it is tough to get to to change. If you find it is leaking it will need to be changed so Good Luck!

[box091]

Thank you so much for your reply!
It seems with these new cars you have to release the pressure from everything before changing something! That it what caused my husbands problem changing the fuel filter. It seems the small things can be the biggest problem...thats why I am on here BEFORE he gets home lol.

The thermostat would cause the rough idoling too I am assuming if the coolant is not running thru, right?

I am ordering it today and will post back Saturday after he gets home. Unless it comes before the weekend and I go out there myself! lol

On a problem like this will the codes have to be reset to get the engine light off? Or will driving a few miles make it reset?

Thanks so much for your help... these new car are not "fun" to work on like the oldies were. At least not to me!

Lynn

[J-Ri]

Unless it it overheating so much that the engine is pinging and doing all that other fun overheating stuff, the thermostat is not your only problem. It may have been, but it sounds like you're looking at a head gasket now. If an engine overheats, it is very possible to blow a head gasket. If you used 2 gallons of coolant, and there are no external leaks, you definately have an internal leak. It sounds like probably a head gasket is leaking into one of the cylinders, causing a misfire, causing the SES light to come on/flash. The only thing I know of that will make it flash is a multiple cylinder misfire.

Check the oil. If it is milky looking, you could have an intake or head gasket leaking, but more likely intake. Coolant in oil could be caused from a leaking timing cover gasket, but they almost always leak on the outside first. If the oil is normal, it is probably a head gasket.

[box091]

Thanks a bunch for yor reply. I am making a list of possabilites we will have to work with Saturday. I went out and started it earlier, and found a hose that was slightly loose. The temp stayed low on me.. but we stayed here instead of getting onto the highway, and I ran it for only 2-3 minutes... then shut it down, tightened the hose, and started it back up for about 5. Tonight the engine light blinked when I first started it then went solid and stayed that way... but, like I said I didnt run it that long though. But... bo leaks in the driveway... which should be a good sign! ( i hope)
Thanks y'all again for helping me with this!

[box091]

ok "J" I just re-read your post. Lol.. I have to laugh at this point.. ok so maybe no coolant on the driveway is not a good sign.. if.. it is internal. Man I hope not...

[GTP Dad]

Make sure to check the oil to see if there is water in the oil. If not spend the money to rent a compression tester and do a compression test on all cylinders before getting into a head gasket replacement. Do you see a large plume of smoke coming from the exhaust? That is a good indicator of a blown head gasket but there are others so the compression test will tell you a lot. Also when you pull the plugs check for contamination as that can tell you where the leak may be if the head is truly cracked or the gasket is damaged.