rekomstop209

I have a 99 EX Automatic with a 1.6 SOHC Vtec.

The car drives well but when I'm on the freeway and I floor it to merge or to get in the passing lane, my engine temp gauge goes up to about 70-80% on the gauge but when I stop accelerating and just coast it goes back down to normal.
The same thing happens when I go up a hill. If I dropshift and try to keep my speed or accelerate up a grade, the temperature gauge goes up slowly to about 70-80% but when I just coast it gradually goes back down to the normal temp.

Also the radiator has plenty of fluid and was flushed about 5000 miles ago.
Water pump was also replaced about the same time.

I don't know a whole lot about cars, but I'm trying to learn and I have a suspicion this may be the thermostat, but I would love some imput! Thanks.

gearbox

iTrader: (95)

i would start by replacing the thermostat with a new oem honda part. its possible the old one is stuck partially closed and the coolant is not moving fast enough to cool down.

rekomstop209

I have the weekend off so I will replace this part, I see it only costs about $20 for the thermostat and the gasket.

Do you know a good site that has step by step instructions on replacing the thermostat? Do I really need to drain all the coolant? I have a Haynes guide but it is very brief and technical on that subject.

gearbox

iTrader: (95)

maybe 1/2 the coolant, so you dont have it pouring all over when you remove the hose. there isnt much of a diy, other than opening the housing and replacing it. honda part is keyed so only installs one direction.

jidayqc

if fan starting and theres no problem there
to do a nice job : change all fluids, change thermostat, after that see if something changed, if not, change ect. tell me if u resolve the problem! i got the same one on 2 of my old ek

jidayqc

i got my night off ill do a video for you buddy! thermostat about 15 minutes, drain coolant, 10 minutes.. ill show u the essential to do in a 5 mninutes video.

shytvic69

I have been doing some reading, it seems that when you press the pedal down harder it uses more gas and causes more heat to be created. As long as it is cooling down after then it shouldn't cause any damage to your internals. Could be a thermostat problem but check you fluid levels as well. Not enough coolant could mean that its not running through your entire radiator and not distributing the heat fast enough.

palsana

It could be a water pump leak!!!!!!!!

jidayqc

sure but before buying a new waterpump, lets check the engine coolant system first with little this that dosent cost much

rekomstop209

Okay I have ruled out the thermostat now because all the hoses going to or from the radiator are hot. The radiator appears to be full of fluid and the extra fluid reservoir is filling up about halfway when the engine is hot, so I know the pressure in the radiator is good and the coolant is cycling through the engine.

But the temperature gauge is still jumping erratically-even more than ever now. Today was the worst day of all. Today it seemed that the gauge was moving randomly. Sometimes when I accelerated, it would go up, sometimes it would go up and down when I would just be driving steady at 50 mph. The longer I drove the car, the hotter the average temperature seemed to be and remain. The temp gauge at first would go up and down between 45-70%. But then it leveled out at about 50% and then started going up and down, getting hotter and hotter everytime it would rise. And then at one point the gauge was steady at like 75-80% and even got as high as 90 or 95% but no steam came from the engine compartment.

When I finally got to my destination, I left the car running and opened the hood and found that even though the temp gauge was at like 70-75%, the radiator fan was not even on at first. After a couple minutes of watching the engine run the fan did come on and I looked at the temp gauge and it was still at 70-75%. Like I said before, all the hoses to and from the radiator were hot, I checked. And also I see no external leaks anywhere.

I have been driving the car like this for weeks now, but today was the first day the gauge got what seemed to be dangerously high. So I would say that whatever problem is occurring has been getting worse. WTF is going on with my car.

gearbox

iTrader: (95)

did it seem hotter than normal under the hood? usually overheating would be way hotter and you can smell stuff burning. its possible the car is running fine but the gauge is messed up. another possibility is the ECT (engine coolant temp) sensor may be bad, which is the part that tells the gauge (and the main computer) how hot the coolant is. but usually for that the check engine light would come on and the car would not drive the same, since ECT supplies info used to calculate fuel trims. you may also have air in the system and when an air pocket reaches the sensor, it will throw off the readings.

rekomstop209

Okay I went ahead and replaced the thermostat anyway but the temp gauge is still going very high when I'm accelerating. After replacing the thermostat I took my car for a drive, riding it pretty hard to see if the temp would remain constant, but it started to go way above normal, all the way up to about 95% and then slightly back down as I coasted back to my house, where I popped the hood to check for leaks. The temp gauge had gone back down slightly to about 75% and when I looked under the hood, the radiator fan wasn't even on. I hit the A/c and the condensor fan came on, and then a couple minutes later the radiator fan came on...but the temp gauge never went down any further. In fact, when I turned the A/c off, I swear I saw the temp gauge jump a tiny bit higher even, which just plainly makes no sense to me.

gearbox

iTrader: (95)

hmm im pretty sure both fans should come on together when the a/c is turned on. altho having fans on is only good for cooling the engine at idle. while driving, all you need is a functioning radiator.