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2004 Nissan Sentra- Coolant overflow is overflowing after ten minutes of driving?

I have replaced the thermostat, radiator, coolant temperature sensor, and coolant. The gauge on the dash shows normal operating temperature, but the overflow keeps filling up after about ten minutes of driving? I noticed that the coolant fans do not come on at all unless you turn on the air conditioner? Can anyone help?

Have you replaced the radiator cap? A bad one will cause the symptoms that you are experiencing.

Does it blow coolant if u leave a/c turned on?

In addition t o missileman’s point, with which I agree, you should know that one of the fan’s is operated by a temp sensor and should be coming on regardless of the AC operating state.

Also, IMHO you may be blowing gasses into the water jacket despite the temp indicator’s reading normal. Especially if it’s been as freezing cold where you are as it is where I am. It might be a good idea to do a cylinder leak test, or at least check the coolant for evidence of hydrocarbons. There are lab strips at the parts store for about $10 that’ll turn color in response to hydrocarbons. They come with instructions.

Post with the results. If you do have a breech in your headgasket and you don’t address it now, it could do serious engine damage. I’m not trying to scare you, only to get you to take a look.

I have not replaced the radiator cap since last year, but I will now. When I have the air conditioner on the overflow box still leaks. I did recently replace the temperature sensor, but the cooling fan does not come on at all unless the air conditioner is turned on. I will get those strips at the auto parts store and try that also. Thanks for the help guys. I do not know if you are receiving this message or not because I am new to cartalk and I do not see a “reply” option for leaving feedback. Let me know if you are, if you do not mind.

We have received your message.
Good luck and let us know how you make out.

I’d expect the normal operation for you car, the radiator fan would come on during long idle conditions, like if you are parked in a Taco Bell drive through for 15 minutes. AC or no AC. It doesn’t even then? Under those conditions (unless it is very cold where you live, like teens or less) the coolant temp gauge should start going up. Does it? It may be it is so cold there the coolant never reaches the temperature for the fan to come on.

You may have a head gasket problem as described above. But if you don’t, I guess one explanation is that you just need a new radiator cap. Another is that the dash temp gauge isn’t accurate, and the coolant is getting hot during long idles. What’s supposed to happen then is that this condition is detected either by a coolant temp switch which turns the radiator fan on (using a relay) or the ECM senses the temp using the coolant temp sensor and the ECM turns the fan on (again, using a relay). Maybe there is something wrong with all that. Either the temp switch has failed, the ECM’s temp sensor has failed, or the fan relay or its fuse has failed.

Last summer I had the fan temp switch fail on my Corolla, so I know that is a failure mode which is possible. Fortunately the sol’n is simple and inexpensive, install a new fan temp switch.

If a new cap doesn’t fix it, then somehow you got to determine if the coolant is actually getting in the red zone when this happens, even though your dash gauge says it isn’t. I’d start by remove the ECM temperature sensor and testing the sensor resistance vs temperature. See if it matches the chart in the shop manual. Remember there are usually two coolant temp sensors, one for the gauge, and one for the computer. Make sure you are testing the one used by the computer.

It’s also possible the coolant is just overfilled too I guess. Best of luck.

If it isn’t the cap I’m guessing a blown head gasket. A cooling system pressure test is in order.

I replaced the radiator cap and no luck, the overflow still leaks. The cooling fan never comes on, ever, and the dash gauge never goes above operating temperature. The only time the fans come on is when I turn on the air conditioner, but the overflow leaks then also. I replaced the coolant temperature sensor, but is there another one, or a switch that I am missing? If I sit at an idle in front of my house and do not drive anywhere the overflow takes a lot longer to leak than when I drive the car? I live in Texas so it is not that cold on the days that I do drive, maybe around 30 or 40 degrees. If I do have a head gasket issue can I use that Bars block sealant? I had to use it many years ago on my Subaru for a cracked block and I was able to drive that for another 12 years. Any other suggestions would be appreciated. I cannot afford to take it to a garage, as I have already done that 4 times and they could not figure it out, after paying out $700 already, and I cannot afford to buy another car right now. How about some super glue, paper clips, and rubber bands?

Also, the manual says to check the timing and water pump belt(s)? Does that sound right? Where is the ECM temp sensor, it does not even mention that in the manual I have? Thanks.

There is a relay that feeds the fan. Temp sensor feed ECM and ECM turns on fan through the relay,

I had a similar problem with a 1993 Oldsmobile 88. The overflow tank was spilling over, but the low coolant light would come on triggered by a sensor in the radiator. It turned out that when the car was turned off, the hose between the radiator and the overflow tank would collapse and the partial vacuum created in radiator couldn’t draw the coolant back in. The hose was acting as a one-way check valve. A dollar’s worth of new hose and 5 minutes of work solved the problem. Maybe you will be this fortunate.

Very good suggestion @Triedaq. With a collapsed hose like that, it acts like a pump, and simply pumps the coolant out of the radiator and out the overflow bottle over time, with each heating/cooling cycle. A collapsed hose like that would actually be worse than no hose at all. With no hose at all, that’s how cars were configured 40-50 years ago, eventually the level in the radiator would get low enough it would stop overflowing naturally, all by itself. It couldn’t pump any more out.

Maybe that’s an idea for diagnosing this problem. If the hose is removed between the radiator and the overflow bottle, does it eventually stop overflowing from the radiator? Checking the radiator level from time to time of course to assure it doesn’t get too low.

Using a hand-held vacuum pump each direction on the hose might be diagnostic also.

I have to add coolant to the radiator after every drive now. It just empties the radiator and overflows from the overflow box. The cooling fan never comes on, and the overflow fills up and leaks after ten minutes of driving. The coolant never goes back into the radiator from the overflow box? I have already checked all of the fuses and relays and they are good. If I have a blown head gasket what is the cheapest solution to solve this issue? Can I use one of those aftermarket bottles of engine block, radiator, head gasket sealant? I cannot afford another garage bill.

Have you had a pressure test done? It’s cheap and fast, and will help determine whether you have a blown head gasket, instead of a problem with the fan turning on.

You do just need to test for the blown gasket. Find the test strips or use a block tester. A block tester you can get from the loaner tool programs at auto parts stores. You “buy” it and then get a full refund after returned (often 90 days). You will have to drop $10 or so on a bottle of test fluid.

If it does turn out to be a head gasket, the head “fixes” in a bottle are unlikely to work because you have combustion gases blowing OUT INTO the cooling jackets at really high pressure (figure 100-200psi or so). The head gasket “fixes” rely on cooling system pressure (16psi or so) to push the “fixer” fluid into the breaches where it sort of hardens up like glass after it cools. I very much doubt it will work at all for this kind of leak - if it is the head. So there’s probably not a cheap short-cut.

Now the darn car wont even start! It tries to turn over, but just wont kick over. Battery is good, starter good, plenty of gas, windshield wipers work LoL. Could this be a problem because of a blown head gasket?

Yes. If the head gasket is bad enough you won’t have sufficient compression

A blown headgasket will generally only affect one cylinder, and the engine will run, albeit poorly. And engine will run on three cylinders. The exception being if the breech has caused a seized bearing due to the breech involving an oil passage and the coolant having polluted the oil or due to an extreme hot spot that caused seizure. The former isn’t uncommon, the latter is uncommon but possible.

When you say the engine “won’t kick over”, do you mean the crank won’t turn? If that’s the case, the engine is likely now a good boat anchor.

If the crankshaft is turning when you try to start it but it won’t fire, pull the plugs and see what they look like. If they’re wet with gas, you’ve lost your spark. If they’re dry and normal looking, you may have lost your fuel.

Post your findings.

Okay, now it start’s again! Thanks for all of your help everyone. I am going to have the pressure test and block tested. Anybody want to buy a boat anchor? Lol!