No Heat at High Speeds

fotojosh · Post by **fotojosh** » 13 Feb 2011, 14:44

I have a 1998 V70 Non Turbo that I just picked up with 127K miles on it. I live in the city and took it out for its first long drive this last weekend. IN town the engine heats up like normal and the heat blows hot. As you get up to speed 55-70mph the Engine temp slowly begins to fall until it registers cold on the gauge and the heat blows cold. I drove for 100 miles and got out to check the engine. The engine was so cool that I was able to place my bare hand on the exhaust manifold and top radiator hose. Both were warm but not hot. It was about 10F out. I then let the car sit and idle for about 15min and the engine heated right up and the heat worked fine. Could a thermostat cause this if it was stuck open?

fotojosh · Post by **fotojosh** » 13 Feb 2011, 14:46

Also, I can repeat this at anytime like clock work.

Post by **JRL** » 13 Feb 2011, 15:02

You need a new thermostat and possibly a coolant temp sensor.
I can guarantee you that this is your problem

fotojosh · Post by **fotojosh** » 13 Feb 2011, 15:09

Thanks! I'll throw a new one in tomorrow.

billy · Post by **billy** » 13 Feb 2011, 15:11

What about the thermostat? Going in the opposite direction (my favorite direction) even in the hot florida summers my cooling fan is not needed much to keep the engine cool as long as I am trucking along pretty good and the air is moving through the engine bay. But in a long idle or slow city driving it is needed and the fan relay will do what it's supposed do, even to keep the cooling fan running for a short time after shutdown. I don't live in cold country, possibly defective thermostat...Hek...who knows...maybe once upon a time your car lived in Florida, and somebody ( a previous owner or a not so pro) took the darn thing out completely. ....But in your world ( and everybody elses for that matter) we've got to have proper functioning thermos. Have you checked that out? If that doesn't work, I've got a small propane Char Broiled grill I would sell you on the cheap and you could stay warm and cook burgers in your passenger seat while you're headed down the road.

billy · Post by **billy** » 13 Feb 2011, 16:20

if your temp guage gets in the approx. 3 o'clock position and your warm and snug inside, but when your cruisin at 70 mph and the temp gauge drops, and your teeth are chattering, the sensor is O.K., it's the thermo. Last possibility...you're driving around with back window down after drinking too much