my wifes 2005 mdx is overheating at idle now. if i turn a/c on speed 3 or more it actually overheats faster. i tried turning the heat on to see if that would bring it down and the heat didnt' even seem like it is working. i looked at both fans the cooling fan and condensor fans and they are turning on and seem to be working properly. my wifes notes eventually the a/c at idle doesn't work either but i didnt fiddle with it that long i guess.

my thought is maybe thermostat is sticking? no leaking i dont think from water pump.

i have 98K on the car

any ideas

 

I would suspect the thermostat first because you don't have any heat. This would indicate a stuck thermostat which is not allowing the water to circulate through the heater core.

I'm not sure about the water pump design on the Acura. On some brands, it is possible for the pump to wear and not push the water/coolant through the engine properly. This would also result in no heat and overheating. If it is worn internally, there would be no indication of leaks on the exterior.

 

i'm going to try thermostat, i'll let you know if it works.

thanks

 

Unless it has already been done you will be due for the timing belt maintenance soon. Most folks get the water pump replaced at the same time (labor savings), but the thermostat is most likely your culprit.

 

Since you said both of your fans are working, start with the thermostat. If you are handy, go ahead and do your timing belt (with new waterpump) on the same day. Since you will be draining the coolant anyway, it would be a great time to throw a thermostat in it.

 

Just a quick thought. I don't know where the thermostat is on an 05 MDX or how accessible it is, but seeing we are now getting into June you could just pull it out and close it back up without the thermostat until you decide how to proceed. If having it out solves your problem, you know how to fix. Again just a thought.

 

thermostat or low coolant.

 

You do not want to be running a car without a thermostat with the advanced electronic controls on today's modern engines. There are various sensors which control air and fuel mixture, idle speed, throttle position openings, etc.

Many of these sensors obtain the coolant temperature in order to make the proper adjustments. Without a thermostat in place, the engine will not reach the temperatures these sensors use to make the correct adjustments. You could be running rich, idling fast, and producing more emissions than normal. You may very well set the Check Engine Light by doing so.

Removing the thermostat and running a little to see if your overheating went away is one thing, leaving it out until you decide what you want to do is not the right way to do it.

 

ls -

While I certainly agree with you from a high level, my points or counterpoints are as follows:

1) We are in June and while the OP doesn't say where he is from, one can reasonably assume that median temperatures are in the 70s, 80s and with some of the unseasonably warm weather for most of the country - in the 90s or above. With this being said the MDX is going to reach normal operating temperature very, very quickly so a working thermostat is going to open correspondingly quickly. What I suggested by pulling the thermostat is essentially an open thermostat.
2) As noted the MDX is overheating and as such, several have suggested it is a stuck thermostat. With the thermostat being stuck and coolant temps being too high, what do you think the sensors are picking up and what adjustments are being made because of them?

Again I don't disagree with you but I don't believe the impact is as big as you are portraying it. If we were in the middle of Winter, it would be a different story as it would take significantly longer for the engine to reach normal operating temperature.

 

I might drive without the thermostat for a day or so just to see if the overheating went away. I really doubt that I would even do that though, seeing as a thermostat wouldn't be too expensive to replace to begin with.

There is no way I would drive more than a day or two without a thermostat, regardless of the season. These engines need to run at a certain temperature range, and they must be controlled by the thermostat.

As for running overheated and what that might do to the sensors and their adjustments of other components, I would be more concerned about warping the head or causing other major engine damage. I'm not sure if the MDX has a fail safe "limp" mode to reduce the engine power in case of overheating.

Remember when there used to be a variety of different thermostats available in different temperature ranges. I think they used to be 180,185,190,195 degrees or right around there. Now many are using 210 or 215 as standard equipment.

Maybe I'm just being overly cautious, but it is something I would not do.

 

An overheating condition is nothing to mess with. I warped the head on my old Datsun B210 back in the day. Stuck thermostat just occurred on one day in the summer and that was all it took with a little driving around town. I Also turned on my heater full blast to help remove heat from the cooling system (imagine that when it's 100-deg.F outside!). Wasn't enough to help though...

 

Like I said - I agree. Just offering up a short term quick solution. I don't see the thermostat closing much (if at all) after reaching operating temp in the Summer.

We need the OP to update this thread to let us know where he is today.

 

Well I feel like a doto, low coolant was the cure. I figured I check the level and it needed almost a liter. Must have evaporated through cap I have no leaks. Thanks for all the input everyone.

 

Lucky you. Hopefully there was no damage caused by the overheating. Definitely get a new cap. They routinely go bad (spring gets weak) and are cheap.

 

About 4 months ago I got to the route of coolant that kept getting low, I had a leak in top of radiator that was hard to find. New radiator and now no more loosing coolAnt

 

here a pic of radiator

 

Thanks for updating us on your progress / fix -