Engine temperature going up & down, bad thermosta?

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Originally Posted By: Rohan
2002 Honda Odyssey 421k

I installed the new thermostat (not OEM). Both fans are coming on at 235F then it will goes back to normal temperature which is 180F until the fans turn off. Is this normal? I did changed the coolant and bleed the air so many time. Yes, I did the combustion leak test and the results was negative.

Parts that been changed;
Thermostat
Thermostic switch A (on thermostat housing)
Thermostic switch B ( NEVER been changed, located somewhere on passenger side of the engine)
Upper & Lower Radiator hose

Why in the world would you install an aftermarket thermostat in a Japanese car?? Aftermarket thermostats are junk. Replace it with an OEM thermostat before your engine blows up. Also, make sure that the jiggle valve points up if there is one.
 
Originally Posted By: Vikas
Quote:
I don't think I need the Vavle adjustments because it not making any noise on the valve
That is NOT true. No noise means valve could be too tight which is very bad.


I can say it making some little noise but not to noisy. I believe it not getting enough air/fuel on the bank 1 sensor 1 (front 02 sensor upstream). That sensor never been changed. I might swap it out from Acura TL 2002 same part number. But first I would like to solve overheating problem at idling. It seem like it not getting enough flow from the fans. Maybe bad motor on the fan that make not to push enough air flow. But I'm having other mechanic look at it soon.
 
Originally Posted By: Gokhan
Originally Posted By: Rohan
2002 Honda Odyssey 421k

I installed the new thermostat (not OEM). Both fans are coming on at 235F then it will goes back to normal temperature which is 180F until the fans turn off. Is this normal? I did changed the coolant and bleed the air so many time. Yes, I did the combustion leak test and the results was negative.

Parts that been changed;
Thermostat
Thermostic switch A (on thermostat housing)
Thermostic switch B ( NEVER been changed, located somewhere on passenger side of the engine)
Upper & Lower Radiator hose

Why in the world would you install an aftermarket thermostat in a Japanese car?? Aftermarket thermostats are junk. Replace it with an OEM thermostat before your engine blows up. Also, make sure that the jiggle valve points up if there is one.


We didn't, mechanic did , and I did installed OEM thermostat with jiggle valve facing up in the right direction.
 
It could also be a bad radiator (rusty) or cap. Cooling fans should be OK as long as they are rotating normally. Or perhaps your ignition timing is way off.

The coolant temperature should be between 82 C (thermostat starting to open) and 95 C (thermostat fully open). Above 95 C is not good.
 
With Japanese autos its best to stick with OEM parts, but you could buy any non-China made radiator.

I had a long history with temperatures going up and down in my Maxima, did a lot of replacements, flushes, thermostats etc.

Finally with a stroke of luck (for $149) I bought OTC radiator (a good one) and wow, no more hot swings. You will be surprised how often partially clogged radiators go undiagonized that can be quite frustrating.

Now how to diagnose a partially clogged radiator, very simple (if you intent to reuse the coolant), remove the bottom shields, clean the drain bolt cleanly with brake fluid, get a brand new pan, and then take the radiator cap off and then open the drain bolt. A unclogged radiator will drain 95% of the coolant in no time, clean constant flow. If it flows, thinks, flows, thinks, you have a partially clogged radiator.

No ASE certified tech to determine that in the Nissan stealership, it was a chance of luck and thinking out of the box that resolved the heating of my engine.

Good luck, do this experiment and most certainly it is a partially clogged radiator. OTC radiators are quite good and don't have to go OEM.
 
I did read all of your posts. The code I'm getting I believe I have faulty front upstream 02 sensor. The car stall today on me during the warm weather it look like 02 sensor is going out. I'm going to replace the front 02 sensor whenever I get a chance. During the cold weather cel will come on and during the warm weather cel will disappeared. For me it seem like to be bad front 02 sensor. For overheating issue while I was looking at the radiator fan vs a/c fan. When it was running I can see radiator fan has play in it moving back and forth and when a/c fan is running it doesn't have any play while it running.

So is my radiator fan is bad?

The reason I want to replace front 02 sensor is because that read air/fuel for the engine and has never been replace.
 
Since you have a serious overheating problem, not just running slightly hotter, it's probably either the radiator or water pump. Wobbly fan shouldn't cause any problem. All the fan needs to do is to rotate at a certain speed so that it can move the air at a certain flow rate. In fact, even with the A/C fan running alone, the engine shouldn't overheat. (I had a complete main-fan failure once in my Corolla and the A/C fan alone was sufficient to cool the radiator -- it just took longer to cycle.)

I am guessing you've already checked the hoses, coolant-temperature switches, radiator cap, any leaks and cleaned the radiator outside.

So, check your water-pump belt, water pump, and radiator. I had a clogged radiator once. It wouldn't overheat but it was running hotter.
 
Originally Posted By: Rohan
Both fans are coming on at 235F then it will goes back to normal temperature which is 180F until the fans turn off. Is this normal?

No, this is not normal at all. The fan is supposed to come on above about 90 C (194 F) and stop below about 83 C (181 F).

Do these tests:

(0) Make sure that your thermometer is working. Check the temperature of the boiling water with it -- 100 C (212 F).

(1) Remove the temperature-switch connector while the engine is running and fan stopped. Fan should start turning immediately regardless of the coolant temperature.

(2) Remove the switch and insert the sensor part into hot water and check the operation with an ohmmeter. There should be open circuit (near infinite resistance) above 90 C (194 F) and closed circuit (near zero resistance) below 83 C (181 F).

If the switch is fine, there may be a problem with the fan relay or fan motor.
 
That what I was thinking about the fan motor. The thermostatic switch I have in there is made in China order it from Amazon.com. Maybe I need to put in Honda switch or from part store advance auto part store that has label on it that said made in Japan. If I turn on the A/C it will cool down so that fan is working.

Yes I already checked the hoses, clean the radiator and make sure coolant is all the way to top. No leak.

I'm going to look into all of the details u gave me it will take me sometime to look at this.
 
I did test the thermostatic switch on the thermostat housing and both fan is coming on when I put the paperclip in there with the key "ON" position. Is this mean switch is bad?
 
Last edited:
Originally Posted By: Gokhan
I would replace that switch. It's obviously not switching at the correct temperature, assuming that your thermometer is working fine.


How come brand new switch is bad? This is brand new switch maybe because it made in China. Just want you to know that I did not take off the switch from the car. I only did the paperclip test on the connector with the key to "ON" position.
 
Originally Posted By: Rohan
Originally Posted By: Gokhan
I would replace that switch. It's obviously not switching at the correct temperature, assuming that your thermometer is working fine.

How come brand new switch is bad? This is brand new switch maybe because it made in China. Just want you to know that I did not take off the switch from the car. I only did the paperclip test on the connector with the key to "ON" position.

I don't think I would ever put a made-in-China part in my car unless there is no other reasonable alternative or it's an OEM part.

All the switch does is to turn on and off (or off and on) at 90 C and 83 C. You've checked that the fan motor and relay are working by shorting and/or opening the switch. If the fan is starting at an incorrect temperature, it can only be a faulty switch. However, first make sure that your thermometer is working.
 
Bad new car die on the way home today. It will keep on cranking but no start. I need to get it home in order to look at it.
 
Originally Posted By: Tosh
PGM-FI 'main' relay?


Need to look at that whenever I get off from work. This is what are my symptoms; it start up fine when engine is cold , loss all off the power, and engine will shut off when it get hot.
 
Your engine has experienced serious overheating due to the Amazon made-in-China temperature switch. I'm surprised that it hasn't blown up. I'm also surprised that you have been running an overheated engine. I would first replace the made-in-China switch with an OEM one and then go from there. Let's hope that your head gasket is still in one piece and nothing has warped.
 
Originally Posted By: Gokhan
Your engine has experienced serious overheating due to the Amazon made-in-China temperature switch. I'm surprised that it hasn't blown up. I'm also surprised that you have been running an overheated engine. I would first replace the made-in-China switch with an OEM one and then go from there. Let's hope that your head gasket is still in one piece and nothing has warped.


I try to avoid overheating problems by reving a gas a little and I overheated four times but I did turn off the engine at that time. I can understand that but wouldn't first I need to figure it out why engine is dying? I'm going to check the fuses and main relay tomorrow if I get a time.
 
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