I have a 2003 s-type v8 sport with 150k on it. When it started getting hot out I started using the A/C. The A/C blew hot out of the outer vents and cool in the center vents until the car reached half on the temp gauge, then it blew hot air. I read on the forum that it was the heater valve located out by the radiator. so I take the car to the shop to make sure that is what it is and they said it was probably the valve because it had corrision around it. I took the car back to drive until the part came in. When I drove the car it drove great until about 30 mins in when the car started over heating. I pulled over turned car off and let it cool down, which only took a couple of mins. I arrived at my destenation and stayed for about a hour and a half. Got back in the car with the heater on and drove it back to repair shop. the temp gauge never went over half on the way home.

The repair shop put the new valve on and checked car out saying that the air worked and no over heating. drove it that night for about a 30 min trip. Air blew cold until i got to hwy speed. i drove again 30 min trip on interstate, when i slowed down to stop and go traffic it over heated. stopped let cool down turned heat on and temp gauge didnt go over half. let car sit for about 2 1/2 hours drove interstate home with heat on with temp gauge at half the whole time. get into stop and go traffic it overheated again.

talked to repair shop and the said they have no clue what is wrong!

I haved changed thermostat housing and thermostat, along with the over flow bottle.

any ideas as to what is wrong?

 

Blown head gaskets.

 

you think head gaskets even if car is still running strong?

 

Could be the fan not coming on?

 

Are you losing coolant?
Do you hear the fans kicking on max speed?

 

only time i lost coolant is the first time it overheated and it leaked out of the cap area but has not done it since. fans are kicking on.

 

You can possibly have trapped air in your cooling system. There is a bleed valve hose by the master cylinder with a plastic cap on it. Did the shop bleed the cooling system to get the trapped air out after changing the DCCV?

I would check there first - be careful opening up that bleed screw - it is plastic and are notorious for breaking.

PS - Find a new shop!

 

i will look for this and try it. my guess is that they did not bleed properly!

thank you for the options!

 

Because of this, you now have blown head gaskets.