Temp Gauge Reads Cold Unless Idling

[AccordWarrior]

Hi all

Weird problem for you guys. When I started my car up and was driving out today, I noticed my temperature gauge wouldn't rise up into the normal operating temperature. I also noticed that my idle wouldn't drop below the cold idle (~1500) and my heater wouldn't blow super hot air.

However, when I sat idling for an extended period of time, the temperature gauge rose up into the normal zone. My heater got nice and hot again. However, when I took off again, the temperature dropped back down to cold, and the idle wouldn't drop lower than like 1500 or so. The heater also didn't blow as hot air anymore.

Now...a few days ago I had to leave my car in a Park and Ride, and since I'm paranoid of leaving the car anywhere, I pulled the ECU fuse. I'm wondering if that had anything to do with it. I know that when you reset the ECU, its supposed to be warmed up and then the fuse is pulled and the its reset correctly.

That's the only think I can think of that's causing it is the ECU fuse being pulled, but my question is how can I reset it for the idle and temperature to be correct.

I'm leaving the car for college tomorrow, so its not like this needs to be addressed yesterday...any ideas?

[91accord4door]

thermostat...change that its cheap. i never had that problem after pulling the ecu fuse on any of my cb7s. but to reset it pull the negative battery cable off for a minute or 2. that resets the ecu. but i doubt its from pulling your ecu fuse. sounds like a thermostat problem to me and the stat is only opening when you idle becuase your engines not getting hot enough while you drive, just hope its not stuck closed (not good).....good luck mike..

[owequitit]

Like 91accord4door said. Thermostat.

Your thermostat is stuck open. Or it may just be beginning to stick. Sometimes they stick closed too, so be careful. If all of the symptoms point to cold coolant, and it happens when you are moving, then it is the thermostat.

The ECU should be fine because it has nothing to do with the functioning of the thermostat.

[AccordWarrior]

Thanks guys.

I'll fix that when I get back from school. I'm only driving it like 2 more times before I head off, so I'll just be super careful with the gauge.

[HondaGuy1212]

Thanks guys.

I'll fix that when I get back from school. I'm only driving it like 2 more times before I head off, so I'll just be super careful with the gauge.

is it hard to change the thermostat and how much do they cost

[91accord4door]

is it hard to change the thermostat and how much do they cost

are u serious? if u are its very easy....follow the upper coolant hose to the thermostat housing...remove the housing (2 10mm bolts) coolant will spill a little bit so have a rag handy. remove the old thermo along with any traces of the old crappy gasket....clean the housing up a bit and reinstall the new gasket that came with your new thermo.....install new thermo...make sure you dont install it backwards.....and retighten the thermo housing back, finally top off the coolant. u may be able to do it without removing the upper coolant hose, i always was. (if not just undo the hose clamp and tiwst). good luck and have fun.oh and they cost under $10 at autozone and advance auto .....gasket included. whenever i replaced mine i always did a flush and fill and blead the air out of the system.

[NAiL05]

Isnt it the lower radiator hose? When i changed mine i followed the lower. The upper housing looks like a t-stat housing but its actually in the back. A lil razor blade helps remove remaining gasket thats left on there.

[HondaGuy1212]

are u serious? if u are its very easy....follow the upper coolant hose to the thermostat housing...remove the housing (2 10mm bolts) coolant will spill a little bit so have a rag handy. remove the old thermo along with any traces of the old crappy gasket....clean the housing up a bit and reinstall the new gasket that came with your new thermo.....install new thermo...make sure you dont install it backwards.....and retighten the thermo housing back, finally top off the coolant. u may be able to do it without removing the upper coolant hose, i always was. (if not just undo the hose clamp and tiwst). good luck and have fun.oh and they cost under $10 at autozone and advance auto .....gasket included. whenever i replaced mine i always did a flush and fill and blead the air out of the system.

ok thanks man for explaining that to me i thought it was gonna be a messy job but i guess not

[91accord4door]

ok thanks man for explaining that to me i thought it was gonna be a messy job but i guess not

your welcome.no its not bad. only a little bit of coolant spills out. just have a shop rag handy.

[crewfish13]

Also, I always make it a practice to check the thermostat before installing it. Heat some water to near boiling, and submerge the thremostat in it. After a few seconds, the thermostat should open up. Once you remove it from the water it should close again. Aside from saving you the trouble of installing a bad thermostat, it's pretty cool to see in action.

[NAiL05]

Also, I always make it a practice to check the thermostat before installing it. Heat some water to near boiling, and submerge the thremostat in it. After a few seconds, the thermostat should open up. Once you remove it from the water it should close again. Aside from saving you the trouble of installing a bad thermostat, it's pretty cool to see in action.

Most people dont do that but its a good safety precaution. Of you can take a lighter and light up one end and see if it expands but the water method works better and you dont burn yourself.

[cp[mike]]

yeah mike, the thermostat is stuck open

if you get stuck while replacing it ill be on aim.

[owequitit]

Just a quick of tip when replacing it.

You will see a pin little pin placed in the frame of the thermostat, it is impossible to miss, it is out all by itself and the gasket is designed to clear it.
That pin must go straight up at the top of the housing. Honda didn't really say specifically why, but I imagine it is the air orifice that allows the system to bleed correctly. It also apparently has something to do with allowing the coolant into the intake manifold correctly.

[4CYLPOWER92]

This doesn't make a whole lot of sense. If the thermostat is stuck open, and your engine has warmed up completely, you should have not fluctuation you speak of.

The theory only makes sense if your engine hasn't had time to warm up. And with the thermostat stuck open, it should take a long time to warm up.

Actually, it makes no sense either way.

[F22-GURU]

This doesn't make a whole lot of sense. If the thermostat is stuck open, and your engine has warmed up completely, you should have not fluctuation you speak of.

The theory only makes sense if your engine hasn't had time to warm up. And with the thermostat stuck open, it should take a long time to warm up.

Actually, it makes no sense either way.

Like the others say "Replace The Thermostat"
..and yes the little hole in the thermostat is there for a bleeding purpose, if you notice it is like a one way valve.
...and yes it does face upwards for that reason.

BTW: Use 50:50 Coolant mix and don't forget to bleed the system.

TIP:

Get a The Largest Funnel you can find which will fit snugly into the radiator.(or a Plastic Coke Bottle with the arse cut out).
Fill the Funnel Up with coolant and crack the bleeder nipple open.
Keep topping the funnel up until bright green coolant is flowing freely.
Then allow the coolant to drop to the bottom level of the funnel and tighten the bleeder nipple.
Remove the Funnel - Don't worry about the spillage. Just use fresh clean water to disperse it.
Run the engine until the Thermostat opens or after the Aux Fan cuts in, keep an eye on the coolant level. Top up if necessary.(The bottom hose will be cold until the thermostat opens)
When the Aux Fan cuts in top up the radiator if the level drops then put a NEW Radiator Cap on.
Before Starting in Morning Recheck Coolant Level. Top up if necessary.
Don't forget the Overflow Reservoir.