2002 Venture cooling


Old 09-06-09, 12:23 PM
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2002 Venture cooling

We have a 2002 Chevy Venture with a 3.4 litre engine. The cooling system seems to be operating normal while driving however, the temp guage goes up to roughly 3/4 of full scale when idling for a long period of time and then goes to normal when driving again. It seems when you are idling and turn the AC on the temp. drops to normal also. I found the following, the radiator cooling fan comes on when you first start the engine and then goes out. I left the vehicle idling in the driveway today for about 20 minutes and the temp gauge rose to half however the cooling fan never came on( I am assuming it was hot enough for it to come on). If I put the A/C on it forces the cooling fan on to drop the temp. I have checked the fuses for the cooling fan under the hood and those look good and I am assuming that the temp sensor on the engine is good as the display gauge appears to be working fine. The coolant level is good and the waterpump was replaced about 18 months. Any other thoughts or tests that I can do to find the problem with the cooling fan. Thanks
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Old 09-06-09, 12:33 PM
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Why start a new post? Here is your original..http://forum.doityourself.com/automo...emp-issue.html

You have 2 temp sensors...one for the gauge..that changes slightly as temp goes up and down like a thermometer. The other turns the fan/fans on and off at a set temp..like the thermostat for your furnace/AC at home.

When you drive..the airflow through the radiator increases and then the stat regulates the temp...but when the stat is full open..the fans should be coming on and off as required.

You either have a bad fan temp sensor or a problem with the wiring to that sensor most likely...could also be a relay I guess..they may be seperate between the sensor and the A/C.
Old 09-06-09, 12:51 PM
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(Especially) if you find you are losing some coolant, even very slight, you lose the ability for cooling system to properly draw coolant out of reservoir at engine cool down and expansion of coolant back into reservoir during hot engine. So if there is a slight leak, the cooling system draws in air, rather than coolant, and bubble can develop behind closed thermostat, and cause engine temp to get hotter, because the stat opens late when not submerged completely in coolant.

Other than that, it is quite normal for engine to warm all the way up to stat open temp (midway these days in many cars) and then have the gauge drop down, - and to drop down even lower at highway speeds when continual cooling is at the radiator, rather than just when the fan kicks on during slower city traffic conditions.
Old 09-06-09, 02:22 PM
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I looked at this a bit more in depth with the Haynes manual I have and looking at the wiring diagram I have for the cooling fans it does in fact show the relays ahead of both cooling fans with the firing of them coming out of the PCM. When I turn on the A/C it is obviously turning both right and left fans on so that being the case the relays and power wiring should be good. I guess I'll try and concentrate on the sensor
Old 09-06-09, 03:47 PM
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Just a thought. As the vehicle is 7 years old, has the basic maintenance been done with the rad and system flushed and coolant replaced along with checks for soft rad hoses that may colapse under pressure, rad cap pressure, thermostat function etc? I have found in my own experience that sometimes when trouble shooting I often ignore the basics and jump into the other possibilities first. While it does sound alot in your case like insufficient electric fan cooling tied to a temp sensor I only wanted to mention the obvious.
Old 09-07-09, 11:27 AM
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Ok well I had a grand am with a 3100 v6 which is the same engine with different heads. So otherwise same basic design. Anyways ya mine did the same ... even if the temp goes up its not damaging it. In the red is bad but as long as you dont go any higher than 3/4.

So bassically when you drive your radiator does its job by having air flow through it to cool the engine.. and the engine can be cooled easily. But after you drive for a while then idle.. Your actual engine temp is warmer.. and takes a bit more to cool it. So as your driving and come to a stop .. air stops flowing through the rad thus giving you less cooling power. So your temp rises to 220 degrees.. in which the cooling fan comes on to lower it. Its designed not to come on until that point as it can save power on the electrical system.

As for when you turn on the A/C wether it being hot or cold the fan will come on as the A/C generates more load on the engine causing more heat. Thats why it cools. Also putting into defrost will behave the same way.

So bassically make sure cooling system is full and not leaking.. if your loosing coolant.. thats another story as you shouldnt ever loose any.

But otherwise these 3400 and 3100 v6's do this... alot of people dont pay attention to thier guages but just the warning lights... if you see it in the red stop and pull over.. but otherwise your fine.

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