overheating

[CzEcHy]

K here's my problem.

About 3 weeks ago the car started overheating after driving a while then letting it idle.

Found out the cooling fans don't kick on unless you tirn a/c on. Then it cools backk down.

So today I flushed the system. Had rustcolored water so I flushed for over an hour till it was all clear.

Refilled with new coolant, bled it. Started to overheat again.

Then I noticed the lower rad hose was cold even after running. For 20 minutes, and now my a/c isn't as cold aas normal (waas warm when ii first tried).

When flushing I had the upper hose off the radiator and flushed till that hose.ran clear

Any ideas? If its the tstat where is it locsted so I can replace
Thx

[ShyBoyCA6]

could be the tstat. follow the upper hose, there will be water outlet housing. remove the 2 bolts and water outlet cap and tstat would be there. as for the fans check the fuse and rad fan switch, located on the rad next to the lower hose. i suspect a bad tstat and fan switch.

[g.frost]

....................

Found out the cooling fans don't kick on unless you tirn a/c on. Then it cools backk down................

Start by fixing this problem. The cooling fan should come on whenever the temp gauge climbs near middle of the gauge. Start by checking the (electrical) thermostat in the bottom of the radiator.

...sounds like your problem will be solved if the radiator fan works.

[CzEcHy]

Start by fixing this problem. The cooling fan should come on whenever the temp gauge climbs near middle of the gauge. Start by checking the (electrical) thermostat in the bottom of the radiator.

...sounds like your problem will be solved if the radiator fan works.

Exactly. Only overheats cause the fans wont kick on by themselves.


So how can I check the radiator thermostat?

Edit. I replaced the upper hose tstat and it still overheats. Still fan related

[g.frost]

If you haven't already, download the manual here;
http://www.pauldesign.ru/honda/shopmanual.html

Follow the section on cooling system; as you already know the fan works, comes on with A/C, follow procedure to check cooling fan thermostat (in bottom of radiator); jumper it out of circuit and see if the fan comes on (watch your fingers).

[King Peetis]

im no expert but i can tell you that i have experience with just about every kind of hot engine issue this little car can dish out. there are several sensors designed to manage coolant temp. i did the same as you for my first troubleshoot. first thing for you need to do now is to determine if your fans work. watch a youtube video to learn how to do that; its pretty simple. second, if your fans are working, start the car and wait till the temp comes up. check your fuse box under the hood. you have two relays in the box that control the fans. typically the two that sit the furthest back in the box, but check the diagram. they should be warm to the touch. if one is cold and the other is warm and they are identical relays ie RC-2203, unplug and swap positions. if the engine is hot enough, the fans should kick on immediately. if they do, then you have a bad relay, simply replace. i spent lots of money and time trying to figure out my temp issues. out of frustration, while watching the gauge and the car began to get hot, i popped the hood and ripped open the fuse box and rested my hand on the relays, feeling defeated, i noticed one of the relays was cold. i said wtf and swapped them. that one little effort could have saved me about 300.00 bucks and about 20 hours of research and labor. good luck and keep us posted.

[Buzo]

The easiest test is to check the rad fan sw located near the lower rad hose.

1) open the ignition key (don't fire it up)
2) unplug the connector of the rad fan and short-circuit the connector with a small piece of wire.

The fan must kick in immediately and you can do this while your engine is off and cold.

If the fan doesn't kick in, leave the short while you swap relays and do the rest of troubleshooting.

[POS carb]

Like buzo said, jump the fan switch wires to make sure the circuit is good.
if you are not getting circulation I would fix that first, change the thermostat. If there is no circulation the fan switch won't get hot and won't trigger the fans

[g.frost]

Manual section 10-9 describes the procedure to test the fan thermosensor; how to jumper as Buzo, POS carb have described. It also describes the procedure to test the relay and fuse if the fan does not come on when thermosensor is jumpered out. (the fan motor must be ok as it comes on when you turn on the A/C)

[CzEcHy]

My phone wonnt let me load the manual. How can I test the. Rad tthermo switch exactly? Never have had to do that

[POS carb]

to test the switch you need to take it out and put it in boiling water and check continuity, this would involve draining the cooling system.
I'd check the circuit first, just unplug it and short the plug with a small paperclip or piece of wire. the fan should run with the key on if everything is good. It is located on the passenger side near the radius arm
If the fan runs then you will know 100% the fan switch is bad or there is no circulation of the coolant
if the fan still doesn't run there is an electrical issue, like bad relay, blown fuse, bad fan motor. On my car there are at least 2 fuses for the fan system, under the hood and under the dash.

[CzEcHy]

Fans come on automatically when temp gets 3/4 to red.


They used to come on when temp was barely 2/4 to red (month ago)


Sensor I can check maybe?

[MessyHonda]

if the fan turns on its going to be your thermostat. it might close up and not let the coolant reach the temp sensor in the radiator so thats why it turns on soo late because its starting to overheat. does coolant come out of your cap when overheating? feel your lower radiator hose to see if its hot when running the car

[CzEcHy]

Lower hose.gets hot sometimes. Other times its cold.

I replaced the tstat tho. So that's two tstats.

What about the sensors behind the dist? By the bleed screw

[Dr_Snooz]

x5 on the fan switch. There are three sensors on the head. One goes to the gauge. One goes to the ECU and the other switches the fans on after the car is turned off. Your problem is when the car is on, so you're looking at the fan switch in the bottom of the radiator.

[CzEcHy]

Any part numbers or technical nnames for it? Autoparts places are dumb

[POS carb]

Oe
37773-ph2-004

beck
201-1374

standard
ts187

[CzEcHy]

Replaced radiator fan switch. Still starts overheating.

One issue I noticed is rusty coolant still comiing out even after I flushed the entire system for over an hour till every main hose and radiiator ran clear a few times.


Any other ideas?? Any other sensors that control the fans?

Remember - the fans DO engage when ac is switched on.

Also, both upper and lower hoses get hot, so it is circulating

[CzEcHy]

Bump.

[zenapup]

Could possibly be a bad sending unit causing the gauge to read incorrectly

[g.frost]

So you replaced the fan thermo switch in the bottom of the radiator? Does the fan come on now when the temp gauge climbs to midway on the gauge? If not, does the temp come down when you turn on the A/C (ie; manually turning on the fan?)
If not, does revving the engine help? (water pump working and thermostat open) with the cap off (careful not to burn yourself!) You should be able to see the coolant flowing through the radiator when the engine is warmed up.

Re: rusty coolant. what kind of antifreeze are you using? Don't use just water here.... Once it's flushed a good corrosion inhibitor coolant should stay clean.

[CzEcHy]

Umm. Let me sum everything up in a post as current conditions.
Car starts overheating when idleing (no air being forced through radiator via driving).
When driving, temp stays at a little over a quarter from the bottom of gauge.
Replaced - thermo fan switch AND thermostat.Also switched out relays to test relays.

It only overheats because the FANSS wont turn on when starting to overheat.
Fans DO turn on when A/C is on.


Something isn't telling the fans to engage when they need to.

The problem is the something that controls the fans.

[g.frost]

Per the first test as outlined above by Buzo, POS carb and myself: When you put a jumper across the fan thermo switch. (the one in the bottom of the radiator), Does the fan turn on? This is the only temperature control point to turn on the fan.
If the jumper turns the fan on, check the function of this switch in boiling water or use a multimeter to check when the engine is hot. The switch should close when the coolant in the bottom of the radiator is hot... turning on the fan. Full Stop.

[CzEcHy]

I am unaware how to jumper the switch properly. Sorry guys
,
If somone can howto it for me in their post I will do it
Detail preferred

[2oodoor]

Czechy just unplug the wires and stick a small piece of wire to connect those together, thus taking the switch/sensor out of the equation.