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.

[stezie]

I had similar problems with a civic years ago. especially when you mentioned rusty water after giving it a flush. The previous owner to me ran the car on plain water. no coolant. this rusted the fins away completely on the water pump. the water pump was unable to circulate enough water to cool the engine so over heated. You might need to take your water pump out.

[derolph]

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.
Do you know the age of the radiator? Maybe it's partially clogged and needs to be replaced.

[2oodoor]

I had similar problems with a civic years ago. especially when you mentioned rusty water after giving it a flush. The previous owner to me ran the car on plain water. no coolant. this rusted the fins away completely on the water pump. the water pump was unable to circulate enough water to cool the engine so over heated. You might need to take your water pump out.

Good point, when I got my motor it was guaranteed to have 50k or less miles on it, the thing was mint. BUT, I did replace the water pump because that is just what you do when you buy used motors. Good thing I did because even with low miles, from sitting around, the impeller and housing was like red clay. Those impellers are stamped steel, little rust breeders...(some were actually cast iron!)
That sediment can hide in the radiator too, no matter how much you flush it as long as some little bit remains it breeds like an infection.
The PH will be acidic, and just the flow of the coolant thru the radiator and engine can make it actually take on electric charge. Want to see that? just hook your DVM to ground and set the positive lead in the coolant.

[Buzo]

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


Well, you already replaced the thermoswitch in the bottom of the radiator, so you are familiar with how the connector looks like.
IMAGINE this is the connector (sorry don't have a pic of the actual one), take a metal clip, make an "U" and insert one tip in each side, just like shown in the picture. Open your ignition Key and the fans must kick in immediately. If so, then your new thermoswitch might be defective or is not rated for the car.

http://i1295.photobucket.com/albums/b624/Buzo3geez/fansw.jpg

[CzEcHy]

K I will check the switch and coolant tonight.

[g.frost]

Xerex G5 is a good long life coolant to use. Many problems with cooling system corrosion, rust, rusted pump vanes, plugged radiators, blown head gaskets,,, can be traced to not changing the coolant, running only water, etc. The important function here is not just keeping the engine operating temp, but very important corrosion inhibitors with all the various metals exposed in the system. It is what drove the industry to develop long life coolants; nobody paid attention to the fact you had to change your coolant every 2 years! Now we are about 5-10 years for coolant flush and replace for long life coolants.

...lets not complicate the problem here though with more issues: the engine temp overheats only when the car is not moving and the fan does not come on when it should. Also, turning on the A/C, (which turns on the fan) will bring the engine temp back down. This all points to the fan thermo not working. Plugged radiator, or faulty water pump possible but should wait until the fan is fixed first.

[CzEcHy]

Jumped thhe rad thermo switch and... fans turned on.

Jumped the thermo on the thermostat housing, small fan kicked on (with key OUT of ignition)





Rad switch bad? It was brand new

[2geeSEi]

Either that, or you aren't getting enough circulation. The only way to test the switch is to use wire to suspend it over a pot with the probe in water, then heat the water on the stove with a thermometer in it, use a multimeter to see when you get continuity. I should kick in between 195 and 200 degrees. Earlier though, you were saying that the bottom of the radiator was cold after you flushed it. Is it possible that you flushed rust into the tops of the little cooling tubes in the radiator? If so, the best thing to do while you have the coolant drained, is to remove the radiator, hold it upside down, and run water in the lower radiator hose opening (which will now be the one on top) full blast while tipping the radiator back and forth. This will dislodge anything that isn't really stuck in the tubes.

[Buzo]

Is it possible you are getting paranoic? What do you mean with car overheating? Is it blowing water vapor through the radiator cap?
Fire up your car and let it get to the max temp, the fan should kick in sooner or later.

[Dr_Snooz]

An infrared thermometer from Harbor Freight can be enormously helpful in seeing what engine temps are really doing. Both fans should be turning on when the radiator fan switch gets to 194* F.

For what it's worth, you might start budgeting for some cooling system repairs in the near future. I had a rusty system like yours and by the time I was done, the heater core was about the only thing I hadn't replaced.

[2geeSEi]

Yeah, the infrared thermometers are highly useful.

[2oodoor]

Well CzEcHy if you never get the issue resolved we certainly have enough material in this thread for anyone else's overheating issues. Keep it going all the way to a intermitant head gasket leak, which can have this symptom as well.
Infrared thermometer is one of the most usefull tools ever, use it in any trade out there.
I could start a thread just on what all it could be used for!

[CzEcHy]

Forgive me for sounding 13 in the video. I let the car sit at idle for ten minutes till the gauge started moving then started recording

http://m.youtube.com/watch?v=qY1gfOZDeO0

[g.frost]

Forgive me for sounding 13 in the video. I let the car sit at idle for ten minutes till the gauge started moving then started recording

http://m.youtube.com/watch?v=qY1gfOZDeO0

OK, I'm stumped; Unable to open, load, play, or punt with that video in your link.

[CzEcHy]

Try removing the m and .

[2geeSEi]

I saw you touch the top hose, have you felt the bottom one at that point? Is it cold, warm, or hot?

[CzEcHy]

Very hot.

[2geeSEi]

You said that you replaced the cooling fan switch in the radiator. Are you sure you got the A-90 (194 deg) and not the A-108 (226 deg)? Or could there be debris (rust) caked around where the fan switch goes inside the radiator. If both hoses are very hot, it seems that the circulation is good. If you can get or borrow a non-contact thermometer, you can monitor the temp of the sensor directly to see at what temp it is really coming on.

[2geeSEi]

Just a thought, also check your battery ground to transmission. If the ground is not good, it can cause random problems like that.

[g.frost]

+1 Most likely it's still the fan thermostat in the bottom of the radiator. It's defective or the wrong temp rating.
If it was a circulation problem (clogged radiator, bad pump, or thermostat stuck closed), the temp would not drop so effectively once the fan came on and the lower hose would be cooler than the top. Reving the engine above idle (2-3K rpm) will increase coolant circulation and bring the temp down quicker.

It's tough to diagnose when you replace a part with one that does not work right... one reason I much prefer to order OEM parts from Honda. Usually Majestic Honda.

[2geeSEi]

He said that he replaced the fan thermostat switch. That was why I questioned which temp rating he put in.

[dieselgus]

Just went through this a couple days ago. It turned out to be a bad/lazy crusted up thermostat. On a whim I also replaced both fan switches (the one on the thermostat housing with the black connector and the one on the rad with the grey connector). I did check the new switches with boiling water and a multimeter to make sure they were good. Even with a hinkey thermostat both hoses were getting hot after 20min of running but still no fan action (one can force fans by flipping on the AC). Was a bit of a head scratcher. I shall meter both old switches when I have some time over the next couple days and post up the results for your general amusement.

I seem to think the two aren't interchangable connector-wise as well.

Sent from my rooted Samsung

[2geeSEi]

I was wondering about that with the connectors, but my 2g only has the one on the radiator, so I couldn't go check it out. He did say that he replaced the thermostat though. If it were me, I would test the new radiator switch with the multimeter, thermometer, hot water.

[2oodoor]

Thermostats can be put in backwards too. It can drive you crazy if it's not discovered.
It is weird though how many of these car's fans come on at differnt temp readings on the dash guage.

[g.frost]

.............. If it were me, I would test the new radiator switch with the multimeter, thermometer, hot water.

That's what I would do as well.

Looks like the fan does finally turn on, (in the video) but way too hot already. Either this thermostat is not turning on at the right temp or there is poor circulation of the coolant. (the test in the video points to the thermostat as the temp comes down quite rapidly once the fan is finally turned on)

...we would all like to hear how this is finally resolved. for future reference.

[CzEcHy]

Will be reworking on this within the week. Guess Ill need to test the switch.

Also, what is the correct way for the tstat? I put new one in same as the old tho..

[2geeSEi]

The spring part goes toward the motor. I don't even know if it would fit the wrong way on these cars.

[2geeSEi]

That's what I would do as well.

Looks like the fan does finally turn on, (in the video) but way too hot already. Either this thermostat is not turning on at the right temp or there is poor circulation of the coolant. (the test in the video points to the thermostat as the temp comes down quite rapidly once the fan is finally turned on)

...we would all like to hear how this is finally resolved. for future reference.

We have already determined that his circulation is good. The upper and lower hoses are very hot and the fans are not on, but when he turns on the A/C, it goes down quickly.

[2oodoor]

Will be reworking on this within the week. Guess Ill need to test the switch.

Also, what is the correct way for the tstat? I put new one in same as the old tho..

The copper slug always towards the motor

[88Accord-DX]

Spring goes toward block on the thermostat. After all is said & done. If you still have overheating problems after replacing the thermostat, look for bubbles in the radiator.. You need an exhaust gas analyser to sniff the radiator.

[g.frost]

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

Looks like the fan does finally turn on, (in the video) but way too hot already. Either this thermostat is not turning on at the right temp or there is poor circulation of the coolant. (the test in the video points to the thermostat as the temp comes down quite rapidly once the fan is finally turned on)
................

Just realized I'm playing loose with technical words here; not a good idea.... The 'thermostat' I refer to is the fan switch 'thermostat' in the bottom of the radiator, not the (commonly referred) 'thermostat' which controls coolant flow on top of the engine head. OK