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fluctuating temps/coolant smell

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Old Dec 3, 2010 | 07:05 AM
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Default fluctuating temps/coolant smell

The last couple of trips in the 02 coupe, my coolant temps would fluctuate between 196-205 at cruise speed. Usually stays right around 196-198. This was the first time I had the heat on also.
Yesterday, after pulling in the garage I smelled a slight coolant odor, not inside but under the hood. No visible leaks from the top and nothing on the ground. Any thoughts.

Thanks.
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Old Dec 3, 2010 | 08:07 AM
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Any number of possibilities but the usual is the water pump bearing is starting to go bad and your've got coolant dripping onto the belt. Another is the nipple from the tank will crack right at the tank itself and start dripping. The tank is around $50 so if this is the case, just replace it.
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Old Dec 3, 2010 | 08:22 AM
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If so, what would the procedure be to replace the tank?
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Old Dec 3, 2010 | 09:06 AM
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The coolant cap could be venting coolant vapors if it's defective.

You would be able to smell the coolant odor from it.
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Old Dec 3, 2010 | 09:46 AM
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If the tank is cracked, its real simple to replace. Remove the mounting screws and disconnect the rubber tube. Make sure the engine has cooled down totally of course as the tank would be pressurized.
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Old Dec 3, 2010 | 09:57 AM
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Originally Posted by dgrant3830
If the tank is cracked, its real simple to replace. Remove the mounting screws and disconnect the rubber tube. Make sure the engine has cooled down totally of course as the tank would be pressurized.
no drain of the coolant system required?
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Old Dec 3, 2010 | 02:38 PM
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The tank is up high...remove it, pour out the coolant into a container, install the new tank and connect, then pour the coolant back into the new one.
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Old Dec 3, 2010 | 03:03 PM
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I was looking at it today, found no sign of a leak at reservoir or under water pump. I think I may just replace the cap first and see if that may be it.
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Old Dec 3, 2010 | 05:27 PM
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Originally Posted by guido7834
I was looking at it today, found no sign of a leak at reservoir or under water pump. I think I may just replace the cap first and see if that may be it.
At least you can rule out a bad cap for less than $10 spent.
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Old Dec 3, 2010 | 05:37 PM
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If the cap was leaking, you would see the evidence around it. The fact is you are smelling coolant, so you have a leak. I don't remember exactly there the lines go through the firewall to the heater core but they are probably behind the battery or close to it.
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Old Dec 4, 2010 | 08:13 AM
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Originally Posted by dgrant3830
If the cap was leaking, you would see the evidence around it. The fact is you are smelling coolant, so you have a leak.
Not necessarily true.

If the pressure/vacuum diaphragm inside the cap is defective, hot coolant VAPORS are released. These vapors can have the smell of coolant without any evidence liquid. A defective cap seal, at the coolant tank neck, will also release hot vapors.

I still say replace the cap first.
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Old Dec 4, 2010 | 08:33 AM
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Originally Posted by Quicksilver Vert 01
Not necessarily true.

If the pressure/vacuum diaphragm inside the cap is defective, hot coolant VAPORS are released. These vapors can have the smell of coolant without any evidence liquid. A defective cap seal, at the coolant tank neck, will also release hot vapors.

I still say replace the cap first.
I agree with you. The caps seem pretty sturdy to me though as I've got over 300K miles on my original cap and its still working. That doesn't mean the OP's won't fail, of course it can. Certainly a cheaper item to try first.
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Old Dec 4, 2010 | 08:41 AM
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Just to possibly rule out the heater core, wouldn't it smello inside the car if it was the core? There is no odor in the car. Just when I open the hood. Also, would a bad cap or leak make it run slightly hotter and fluctuate like that?
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Old Dec 4, 2010 | 09:37 AM
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A leaking heater core will definitely be noticed inside the car. First by smell, and usually with a wet carpet as well.

It the cap isn't holding pressure, coolant temperature fluctuations are possible.
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Old Dec 4, 2010 | 09:44 AM
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OK. Will try the cheapest route first. Will pick up a cap today and go from there.
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Old Dec 4, 2010 | 09:45 AM
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Agreed, you would smell it inside if the core was an issue. All of the remaining coolant connections are outside in the engine compartment. I'm thinking your water pump bearing is starting to go. It'll barely leak and evaporate before a puddle is created. Under the higher pressure while driving, it'll leak more and when you shut it down in the garage, its still pressurized for a little while.
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Old Dec 4, 2010 | 11:31 AM
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Originally Posted by dgrant3830
I'm thinking your water pump bearing is starting to go. It'll barely leak and evaporate before a puddle is created.
Good possibility too. How many miles on the water pump Guido?
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Old Dec 4, 2010 | 11:52 AM
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Originally Posted by Quicksilver Vert 01
Good possibility too. How many miles on the water pump Guido?
A little over 60,000. Doesn't seem like a lot. I've never had a water pump go on any vehicle I've owned. 127,000 on my Ranger original water pump.
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Old Dec 4, 2010 | 12:47 PM
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I noticed some coolant on the passenger side of the radiator support when I replaced my harmonic dampener.
Upon investigation discovered the rubber hose going to the radiator side tank at the top was old and splitting.
I cut off an inch and secured it back to the radiator.
I was careful not to break the nipple off the side tank of the radiator.
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Old Dec 8, 2010 | 08:36 PM
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Originally Posted by guido7834
OK. Will try the cheapest route first. Will pick up a cap today and go from there.
I replaced the cap and no change. Still same symptoms. If thermostat was bad could it be leaking from there? No visible coolant.
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