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Discussion Starter #1
Okay so I've read just about every thread about cooling system problems. I can't get it to stop overheating.
I recently changed the thermostat (purchased at AutoZone) and filled the coolant system. Burped the houses, tried the bleed bolt under the distributor but nothing came out (running or off) it only overheats when driving, but sometimes it will go back down to normal operating temp, then back up. How do I bleed this coolant system? Also I have replaced temp sensor on top radiator house.
 

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09 Altima 3.5SE 6MT Sedan
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If you (temporarily) remove the thermostat altogether...how does it behave? If it still overheats you have a water pump or head gasket or clogged/dead radiator issue.
 

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Discussion Starter #3
If you (temporarily) remove the thermostat altogether...how does it behave? If it still overheats you have a water pump or head gasket or clogged/dead radiator issue.
Everything worked fine before I changed thermostat other than the thermostat was stuck open
 

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09 Altima 3.5SE 6MT Sedan
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Everything worked fine before I changed thermostat other than the thermostat was stuck open
Yeah, so my test was designed to see if you'd put it in upside down, or if the 'new' one was defective too.

Whenever I change a thermostat (so far only twice in my life), both times I have heated the new one in a pot on the stove to check what temp it opens at.
 

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Discussion Starter #5
Yeah, so my test was designed to see if you'd put it in upside down, or if the 'new' one was defective too.

Whenever I change a thermostat (so far only twice in my life), both times I have heated the new one in a pot on the stove to check what temp it opens at.
I understand that, but it is not so easy as taking it out and bolting the housing together. Have to let permatex setup. I made sure and put it in correctly as I checked before I took the old one out. Pin at the top. I might try and take it out and run it with no thermostat, just not put the permatex on. Nissan service guy said it definitely sounds like an air bubble but no matter what I try I can't get it out.
 

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09 Altima 3.5SE 6MT Sedan
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Hey, thanks for letting us know the problem and the fix. Glad you got it running again.
 

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If you (temporarily) remove the thermostat altogether...how does it behave? If it still overheats you have a water pump or head gasket or clogged/dead radiator issue.
Have the same problem as described
If I temporarily remove the tstat it doesn't overheat but engine run cold which the ecm gives a trouble code related

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09 Altima 3.5SE 6MT Sedan
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Two things...you could have installed it upside down which would cause the issue. It could also just be a defective thermostat...fill a pot with water and heat it up on the stove...it should open fully before the water starts to even gently boil.
 

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Two things...you could have installed it upside down which would cause the issue. It could also just be a defective thermostat...fill a pot with water and heat it up on the stove...it should open fully before the water starts to even gently boil.
1. Am sure, I installed it with the top nod upside.

2. I cooked it and it opened before I installed. The inscription on tsat is 82c but when I installed and monitored with my scan tool I felt it open at 208f is it normal?
Because fan kick in at that time and I felt lower radiator hose and discovered it's also heated as well as the top one which was not when the engine hasn't reached 208f

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09 Altima 3.5SE 6MT Sedan
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No. 82'C is 180'F If you have the QR engine...many of them actually have 2 thermostats, one to the in-car heater, the other to the radiator if I recall. You may have an issue with that second tstat.
 

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09 Altima 3.5SE 6MT Sedan
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Have a look at this video, around 6:18 the installation guide is shown...along with the location of the two tstats.

 

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No. 82'C is 180'F If you have the QR engine...many of them actually have 2 thermostats, one to the in-car heater, the other to the radiator if I recall. You may have an issue with that second tstat.
Ok
I know
But with regards with the opening of the tsat which one does the engine consult before opening; the lower tsat or the upper water valve also called tstat

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09 Altima 3.5SE 6MT Sedan
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So are we still talking about your 2008 2.5 Altima...or an ealier one...as you posted in the 93-01 Forum...?
 

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09 Altima 3.5SE 6MT Sedan
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I always wondered how those tstats worked together, so in a nutshell, here is how it goes:

1. Cold, both closed, water pump circulates coolant around ONLY the cylinder head.
2. Warm, thermostat opens, coolant now flows as above, but return path is now through radiator.
3. Hot, water control also opens, coolant now flows through engine block in addition to above

So if the coolant doesn't start flowing until the engine is stupidly hot it's the thermostat causing the issue. If the water control valve was not working, then it should only really overheat under heavy load as the engine block would not be cooled (but the cyl head still would and so the rad would still be hot).
 

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I always wondered how those tstats worked together, so in a nutshell, here is how it goes:

1. Cold, both closed, water pump circulates coolant around ONLY the cylinder head.
2. Warm, thermostat opens, coolant now flows as above, but return path is now through radiator.
3. Hot, water control also opens, coolant now flows through engine block in addition to above

So if the coolant doesn't start flowing until the engine is stupidly hot it's the thermostat causing the issue. If the water control valve was not working, then it should only really overheat under heavy load as the engine block would not be cooled (but the cyl head still would and so the rad would still be hot).
But honestly
The overheating is not at alarming rate (Not close to the red line)
Mostly is one level above the average, worst case two level about the average when on highway and speeding.
Can it be air bubbles?
Because I didn't bleed the air out,don't have the equipment and the know how but I DIY for tstat lower fixing though.
Do you think it's a cause for concern as per the levels it's heat as explained above ?

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09 Altima 3.5SE 6MT Sedan
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Yes, it's cause for concern...as the temp can be significantly higher inside the block if the coolant isn't flowing, compared to where it's measured (which is probably only the cooled head fluid). You could temp remove the water control valve to test the theory--that way the rad gets switched in/out based on the thermostat, but you never differentiate between cyl head and block flows.

Imagine the block fluid is boiling...leaving steam vapour only around the uppermost part where the head gasket is...
 
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