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coolant leaking from tank's cap

well one day some hose broke (the little one at the bottom of the water pump). i took the car to the shop because it was in the winter, and had them replace it. after that the gauge needle was showing temp a little higher. esepcially in traffic. but car was not overheating. that's when i changed the thermostat, but in traffic didnt make much difference. then one day when i was changing my clutch, my friend accidely broke the sending unit sensor for tha guage. so i replaced it, and the problem with needle going up in traffic was solved. i guess those guys in the shop damaged the sensor a little (it seemed a little loose). but why the problem with the hoses... i have no idea. all that happened in a period about 2 years ago. so i dont think any of it is related to my current problem.
 
i just spoke with Bill Jenkins. He said that there is a Low speed and a High speed relays. There's also a resistor on the fan's housing. And the ECT (engine cooling temp) sensor. any of these could be the problem.
can someone verify the exact location of the resistor on the fan's housing????? Thanks.
 
8000RPM said:
i just spoke with Bill Jenkins. He said that there is a Low speed and a High speed relays. There's also a resistor on the fan's housing. And the ECT (engine cooling temp) sensor. any of these could be the problem.
can someone verify the exact location of the resistor on the fan's housing????? Thanks.
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Trust me. You've already checked the whole circuit by verifying the fans do run with the a/c on. The only thing you have not checked is the coolant temp sensor. I don't know who Bill Jenkins is, but did you tell him the fans work normally with the a/c on. The PCM commands the SAME relays. This rules out the resistor, and relays.
 
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well the a/c probably controls the high speed relays, since both fans kick in. not sure about the low speed relay, but you might be right.
i didnt tell Bill about much of the problem. i just asked him for prices on several things that could cause this problem+part numbers. i guess i will look into the engine cooling sensor. can someone verify which one it is - the engine coolant sensor that is? thanks.
 
Don't forget the coolant tank cap (radiator cap). My low speed fan kicks on at 212 - BELOW the boiling point of water IF the cap is holding the pressure. But at EXACTLY the boiling point of water at SEA LEVEL without a pressure increase. An increase of 1 lb pressure above the ambient of 14.7 raises the boiling point 1 degree. So a 16 lbs cap, fully pressurised, will prevent the coolant from boiling until it reaches 212 plus 16 = 228.

If the cap is not sealing, then the coolant may boil at anything over 212 - BEFORE the low speed fan has a chance to kick in. The fact that your temp guage never gets high MAY mean that the coolant is NOT pressurized and MAY seem to indicate that the coolant is boiling at some temperature LOWER than the 228 for a 16 lb cap i.e. 212 degrees.
 
cliff7080 said:
Don't forget the coolant tank cap (radiator cap). My low speed fan kicks on at 212 - BELOW the boiling point of water IF the cap is holding the pressure. But at EXACTLY the boiling point of water at SEA LEVEL without a pressure increase. An increase of 1 lb pressure above the ambient of 14.7 raises the boiling point 1 degree. So a 16 lbs cap, fully pressurised, will prevent the coolant from boiling until it reaches 212 plus 16 = 228.

If the cap is not sealing, then the coolant may boil at anything over 212 - BEFORE the low speed fan has a chance to kick in. The fact that your temp guage never gets high MAY mean that the coolant is NOT pressurized and MAY seem to indicate that the coolant is boiling at some temperature LOWER than the 228 for a 16 lb cap i.e. 212 degrees.
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That is correct. That is also the reason you need to check the tank for cracks in that area. They are not apparent until the system is pressurized and can be very difficult to see; yhey blend in with the threaded portion.
 
cliff7080 said:
... An increase of 1 lb pressure above the ambient of 14.7 raises the boiling point 1 degree. So a 16 lbs cap, fully pressurised, will prevent the coolant from boiling until it reaches 212 plus 16 = 228....
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A fresh 50-50 mixture of coolant/ water should keep the coolant from boiling to more like 265 degrees

Here's a part of a article on Coolant System Basics from a August 2003 Motor magazine.

We learned in grammar school, however, that water boils at 212[degrees]F at atmospheric pressure, at sea level. If we put the water in a sealed container and increase air pressure to 15 psi above atmospheric pressure, we can raise the boiling point to about 250[degrees]F. Then, if we trade the plain water for a mixture of half water and half ethylene glycol and put it in the same container with 15 psi of air pressure, we raise the boiling point even higher-to about 265[degrees]F. (We'll use the nominal value of 15 psi, but engineers design for pressures from about 10 to 20 psi.) That's 53[degrees]F above the boiling point of plain water at atmospheric pressure. It's also above the required temperature range of a modern engine.

Mixing water with ethylene glycol and pressurizing the cooling system ensure that the coolant remains a liquid at temperatures well above the boiling point of water. This brief explanation of engine temperature and coolant boiling points illustrates the importance of the cooling system as a temperature control system.
 
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so u are saying that i might have a crack somewhere or a loose hose, which does not allow for pressure to build up, therefore coolant will start boiling below the temperature where the low speed fan should kick in?

i checked my relays with a 9v battery. used pin #1 and pin #2, contacted them to the battery and the relay was clicking. at least that's how i was told that they can be checked. all other fuses seemed ok. i just got the ECT sensor and will try to replace it. dunno if that will fix the problem though.
 
8000RPM said:
well the a/c probably controls the high speed relays, since both fans kick in. not sure about the low speed relay, but you might be right.
i didnt tell Bill about much of the problem. i just asked him for prices on several things that could cause this problem+part numbers. i guess i will look into the engine cooling sensor. can someone verify which one it is - the engine coolant sensor that is? thanks.
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The engine coolant temp sensor (for the pcm) is the one in the back of the engine just above the starter solenoid.

If you have the engine running and unplug the connector from the sensor, after about 5 seconds, the low speed fan will come on, then after about 10 seconds the high speed fan will come on. Use this test to verify the PCM is responding correctly to this input.

We are talking about a V6 (SVT) contour, correct?
 
yeah. it is an SVT. i just changed the damn coolant temp sensor and same thing happens. absolutely no difference i will go to try to unplug it in a bit. it is really hard to get your hand in there. car idles for several mins, the gauge is at the N of NORMAL, then it slowly goes to the O (that is when i see the coolant starting to move a little) then it goes between the R and M and at that point, coolant and steam is coming out of the cap. fans never kick on. if i turn the a/c, temp goes down and everything goes back to normal....
i will try unhooking the sensor while car is on, and will report back. would it be ok if i disconect the sensor and then turn the engine on?
 
OK. with engine off, i removed the coolant temperature sensor's plug. turned the engine on and both fans came on. just as a side note, i also have heat blowing from the HVAC, so the water pump should be good.

now what would all that mean?
 
8000RPM said:
OK. with engine off, i removed the coolant temperature sensor's plug. turned the engine on and both fans came on. just as a side note, i also have heat blowing from the HVAC, so the water pump should be good.

now what would all that mean?
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When you remove the electrical connector from the sensor the fans will stay on 100% of the time... This is because the PCM is getting NO signal from the sensor, it knows there is a problem, and it turns the fans on to prevent the car from possibly overheating... When your sensor is hooked up though, the PCM is getting the WRONG signal and is being fooled into believing the engine is running at a normal temperature when in fact it is overheating...

To sum all of that up - I would replace the sensor :cool:
 
i just replaced it 2 hours ago....still the same problem.
what i think. the computer is working properly, because it is able to detect that the sensor is unpluged, thus it turns the fans on by default. thus the wire is good, and ECU is working good. with a new sensor i would assume that it sends the ECU the proper signal... and is sending a signal to the fans to turn on, but they dont... the question is why??? or did i install a deffective new sensor, which sends wrong singal and fools the ECU as described above...!?!?!?!?
 
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Your cooling system definitely isn't holding pressure. No way you should be getting boiling between the R and M on the gauge, assuming it is reading correctly.
 
8000RPM said:
i just replaced it 2 hours ago....still the same problem.
what i think. the computer is working properly, because it is able to detect that the sensor is unpluged, thus it turns the fans on by default. thus the wire is good, and ECU is working good. with a new sensor i would assume that it sends the ECU the proper signal... and is sending a signal to the fans to turn on, but they dont... the question is why??? or did i install a deffective new sensor, which sends wrong singal and fools the ECU as described above...!?!?!?!?
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Yes, that is the reason I wanted you to unplug it. It tests the computers ability to turn the fan on with that input. Once again it all tests o.k. I doubt the new sensor is bad. It's possible but unlikely.

I also agree with Zorrex, it should not be boiling between R and M on the gauge, but even if it is not holding pressure, the cooling fans should kick on before it starts to boil. If I remember right the boiling point of pure water under no pressure is 212 degrees. I'll assume you are holding some pressure, and you have some anti-freeze. Your boiling point should be at least around 220 degrees, your fans should kick in by then.

See if any of the parts places (autozone, advance auto, pep boys) has a scan tool that you can rent, or that they will hook up. You need a tool that will display PID data. Check and see what the ECT is reading, it will read in degrees. If it is reading a lower temp you need to persue that.

Also, as Zorrex said, double, DOUBLE check that cap and look for any possible leaks. If it is overheating as quickly as you say there may be other issues. If possible, jack the front of the car way up when you fill the coolant, this will help alleviate any air pockets in the cooling system that you may have.

I really need to know what that ECT is sensing, then I would need to verify it with an infra-red thermometer. Too bad I don't live closer, I know we could have the problem pinned down in a matter of minutes, we just need to run the right tests with the right tools.
 
Well i am going to borrow my friend's cap (from his csvt) and see if it will make a difference but i doubt it. I will get some relays from the junk year and change them. i dont see any leaks though. and i've had leaks before but never had this problem. non of it makes any sense. i am also thinking of getting new sensor for the temp gauge and the resistor which is mounted at the bottom driver side of the fans housing. if after all that the problem still remains, i will take the sucker into a shop, coz i am already sick of it by now.

am i missing any other temp sensors/relays/fuses that i might not be aware of and need to look into?

tony2005 is usually very helpful in these things but i dont see him saying anything about that so far...
Toddio - i agree with you. if i had a scanner tool to see the real time data, i would have had pinned the problem down, but neither autozoe nor advanced offer shuch scanners (rentals i mean).
 
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