Temp gauge is in normal, 200 degree, range when starting. Within a few minutes of driving goes up to 250, right below orange line. No leaks found, coolant level appears fine. Any ideas?

The impeller could break loose from the shaft. You would have to remove the pump to find out for sure.
Could be a blockage in one of the passages too.

There are many different temperature ranges of thermostats. The old one may have been a 165 degree thermostat. The new one may be a 195 degree one. You will then notice that the gauge will run higher than it used to.

Souds like it's way low on coolant. The heater will blow cold air when the cooling system is so low that there is no water (coolant) running through the heater core. Then the thermostat opens, it trys to be normal but the system is low so it gets too hot in just a few minutes. If its that low, there must be a leak somwhere.

The range should be in the temp range of your thermostat within in a few degrees, you probably have a 190 degree thermostat. As the outside (ambient) temp rises it's normal for the engine to run a little hotter 200 degrees is safe with coolant, water boils at 212. Your fans should cycle, so it sounds like your temp sensor is faulty. if you haven't flushed your radiator and changed your thermostat lately, now would be a good time to do so. Hope this helps,

Honda used to put the temp switch to turn the fans on in the bottom left side of the radiator. Not sure if that is the case on yours, haven't worked on a Honda recently. Anyway, the switch operates a relay, not the fan directly. The fans would normally come on around 200 degrees. Also, one of the should come on when the A/C is on to move air through the condenser. Hope this helps... good luck.

Hi!

If by red lined you mean it went over the 250 psi range??

Assumiing that the answer is yes. This is what I think.

The Hi and Low pressure switches prevent damage to the compressor if the pressure is out of range.

Before going any further, check A/C Relay and fuse.

With the engine off, check pressure on both, Hi and Low. Both gauges must have same reading. It should be between 175-200 psi at about 80 degrees temp., if pressure is over that range, the Hi Pressure switch is preventing the compressor clutch to engage, gas needs to be removed by a qualifying A/C Technician.

If Pressre is between range, and both gauges read the same, start engine and turn compressor on, check gauges, The Low side should read about 38 psi and the Hi side should be between 250/275.psi.

Any more trouble shooting should be performed by a Qualified Tech.

Don't forget to rate this post!! Good Luck!!

195 degrees is the typical high end on the thermostat (when the thermostat opens), so the temp gauge should read a max of 195 degrees, give or take a few degrees. Some people replace their thermostat with a lower temp one, such as a 180 degree one. Then the gauge will read lower (approx 180 degree max). So the range is typically from cold at start to just under 200 degrees.

It has a leak. Fill up the radiator and the coolant tank. Then restart it and check for leaks.

Check to make sure your thermostat works right by monitoring the warming up of your engine. With a completely cold engine, start and run the engine for a few minutes, then put your hand on the top radiator hose to monitor if and when it gets warm as the thermostat opens more and more and note the gauge reading( if it works) the top radiator hose should be unbearably hot within 5-8 minutes. If the therm. opens right it should close right aswell, staying open a little while eventhough the radiator may have cooled may be what you are experiencing causing the rapid cooling and is nothing to worry about. The Hose should not get warm very soon after starting the engine. Regarding you gauge, lets take one step at a time, verify proper op. or the therm.

My mechanic in our town did a quick computer check. Car computer indicated a low level of antifreeze, he topped it up, cleared all messages off the car computer and said to watch the the heat guage for any further irregularities. I'll keep an eye on it, love the car, great mileage fun to drive.