Well it has been some time now that my engine gets a bit warm without overheating. Symptoms:

- Not overheating, but higher than norm
- Fan ALWAYS on once warm (not just because of A/C)
- Can't see flow across radiator even when warm
- when stopped, temp goes up slightly, but when i move it seems to go almost back to normal, but never cool enough to shut off radiator fans
- A/C works fine, heat works fine

OK, now for what I have "tried". My thought was lets start easy...

1. Full flush from a shop
2. Thermostat (new fluid)
3. Replace temp. sensor
4. Check water pump (new fluid)
5. Make sure new thermostat works with boil test (it does)
6. Check radiator hoses for clogs... none.

At this point the only thing left in the cooling system that I can think of is the Radiator itself. My initial thought was that it could be clogged. Problem is, whenever i drain system to work on it, it drains fine. There does not seem to be an issue with fins or being clogged (and should not have an effect on flow).

Any help with this would be VERY much appreciated. I am right now!!!

 

If engine coolant temperature is at least 200 degrees, this is perfectly normal.

This is not good. Your statement can be interpreted 2 ways.

1 - there is no coolant visible in the radiator - The radiator should be full to the top and actually spill over the top when the engine is warm and running. Possible causes: Air pockets left in engine when you had it flushed. Or you have a leak somewhere.

2 - Coolant is visible in top tank of radiator but no flow is apparent. There has to be flow, otherwise the engine would definitely overheat. If the amount of water flowing is low, possible causes are bad water pump or a thermostat that is not opening up as much as it should or not opening at the correct temperature.

This is seen most commonly in a car where the coolant level is low.

 

Last summer, when it got hot outside, sitting at idle, my engine would overheat somewhat. If I was driving, it wasn't an issue. I could hear the radiator fan on, but finally realized that at certain times, only one of the fans was running. I swapped out that motor and problem solved. I know it's obvious, and you've probably already confirmed, but check and make sure both fans are running.

 

It is more like your "2"... but both the water pump and thermostat seem to work...

Both fans are running.

Thanks for the feedback, I think I am just going to wait until it gets worse. Hopefully then it will be more obvious as to what the problem is.

As my wife put it... "no one else would even notice it, you are just OCD about your cars".

 

One quick check for you. When the engine is cold and you remove the radiator cap, is the coolant level right at the very top, maybe even spills out?

 

yes it is.

 

Maybe yur coolant Passages are clogged or your radiators rusting from the inside. Are you using 50/50? Ir straight coolant

 

T.One jogged my memory - Check the space between the radiator and the a/c condensor core, it may have leaves and junk built up in there. Also try spraying the radiator with a hose to wash out the cooling fins.

 

Does the car leak or burn coolant? Check your heater core hoses. With heater on hot feel the hoses and they should feel about the same temperature. Its obviously not a bad water pump. If it was it would overheat at all speeds. In my experience partially clogged radiators overheat more when driving, not idling. Do both fans work? Whats your mileage? Just thinking aloud. As Dennis said, clean the front and rear of radiator with LOW pressure water. High pressure will just fold the fins over and reduce their ability to disipate heat.

 

Perhaps I missed it, but when you say temps are higher than normal, what is it reading? Where does gauge sit? When warm, mine sits on the fourth line (counting the lowest line marked "C" as 1.)...one below half way.

Did you do something before you noticed something to be wrong? I'm just wondering if perhaps your wife is right about the OCD thing? LOL! If you drained the fluid prior to your observation, did you bleed the coolant system to remove air pockets?

 

Have you had your radiator cap tested? Bad radiator caps can cause a slew of cooling issues.

If you're not seeing water moving, it could mean that the water pump is bad in some way. I've seen a water pump damn near disintegrate due to corrosion over the years, but that was a ~20 year old car, so I doubt that's the case.

 

Wow, a lot of great replies... here we go.

I am definitely using 50/50.

There is nothing really blocking it... some gunk on the radiator. I will clean that off good. If that is it, that would great, but doubt i will get off that easy

No leaking or burning. I did pull the waterpump and the fins looked brand new. Is there something else that would make it fail (again no leaking).

Both fans do spin... not sure if both "high" modes work. Was going to check all the fuses tonight.

I have 106k.

It warms up to the fourth line, then can raise to right at the 5th line. Never goes above that, just fluctuates between the two.

I am pretty sure there are not air pockets.

I might just buy a new cap. not sure how to test it... only a couple bucks for that, but looks good from what i can tell. It springs back into position when moved.

I do appreciate all the feedback here.

 

You can take it to a shop to have the cap tested. Just need a radiator pressure tester kit. Would be cheaper to just replace it though.

 

I just replaced my radiator with a performance radiator, upper and lower hoses. Honda genuine coolant and the stock fans, it idles all day here in the 95 degree heat of tampa bay.

 

Yeah, it is looking the the radiator is the last link in my situation... could you send a link to what radiator you used?

Yesterday I cleaned the front of the radiator and replaced the cap... did not fix it. Here is a picture of the "high" level it gets to... sometimes just a little higher but not much. It fluctuates between the line and the line below.

 

sorry for the large picture... not sure how to resize it.

 

I just finished going through all of this...
2001 Maxima SE.
Overheating (slightly).
Replace thermostat and flushed...no fix.
Replaced water control valve...no fix.
Flushed coolant...no fix.
Replaced radiator...all better.

With all of the years and all of the corrosion the radiator turned out to be the culprit.

 

Just got back from some vacation, and i am going to try the radiator next... HAS to be it. Will update post after I do this. Thanks again everyone for the input.

 

Replaced the radiator last night. Seems to be working better, but will update again after a longer trip.

Side Note: I bought a Koyo radiator, and WOW the build quality is way better than the factory OEM radiator. Highly recommended.

Hopefully this fixed the problem... if not, I am at a TOTAL loss. I have systematically check every component of the cooling system.