Cooling fan question

[bilgamesh]

My truck is not overheating. It usually runs between 210 and the mark below that, I'm guessing around 190. Occasionally if I go 75 on the highway for a few minutes, it will get up to 210 or just over, and stay there for awhile. Anyway, when it was running today at this higher temp, I stopped at Starbucks, got a coffee and popped the hood to see if everything looked okay. I noticed the electric fan was not turning. Honestly I am not sure whether or not it has ever turned on since I have owned it. The little manufacturers notice on the fan says it can turn on at any time, so I am now wondering what makes it turn on. I assume it is activated at a certain temperature or under specific operating conditions. I would appreciate any thoughts or insight.

 

Thanks,

Bill

[chicofuentes0224]

I know on mine the electric fan would only turn on if the temp at the sensor at the radiator got to 220 or 230*.

I know it turns on also when you turn the AC on. To test the fan to see if it worked I jumpered it directly to the battery for a second (I know not smart) but I needed to make sure the fan motor actually worked because it would never turn on when it was cold out. Come summertime it actually started turning on for a couple of minutes when my temp gauge would reach a little below the 3/4 line. I needed it to come on earlier to keep my temp down at 210* so I put it on a manual relayed switch in the cab so I could run it full time. Hope that helps a little. The sensor for the fan is screwed in on the driver's side of the radiator.

[DirtyComanche]

Stop worrying about a 4.0 being hot... It is intentional.

 

 

However, the factory e-fans can be whacky as far as coming on or not. I popped the hood on my old XJ in the middle of winter once, ambient temperature was about -20, the engine was nowhere near warm (not even reading on the gauge yet) and the fawking fan was on. The problem with a manual switch is you have to remember to turn it on...

[chicofuentes0224]

Stop worrying about a 4.0 being hot... It is intentional.

 

 

Yes, but I get 1 MPG better (from 12 to 13) if I keep the temp at 210* instead of 225* :rotfl2:

[mvusse]

Chico, you must have other issues as well. Even with 4.5" of lift catching more air on the highway I still get 17 around town, 24 going 65 down the freeway. It does drop rapidly above 65, though. About 22 at 70, 19 at 75. And that's with a Renix 4.0/AW4, just like yours.

 

I got 13-15 when I first got the truck, but it was running on 5 cylinders with a broke spark plug wire.

[chicofuentes0224]

Chico, you must have other issues as well. Even with 4.5" of lift catching more air on the highway I still get 17 around town, 24 going 65 down the freeway. It does drop rapidly above 65, though. About 22 at 70, 19 at 75. And that's with a Renix 4.0/AW4, just like yours.

 

I got 13-15 when I first got the truck, but it was running on 5 cylinders with a broke spark plug wire.

 

I'm sure I have issues :rotfl2:

Maybe it's because I'm running 31's on 3.55 gears.

Maybe it's because my engine has 220,000 on it.

Maybe it's because I rarely run it on the highway.

Who knows man. I gave up on throwing parts at it.

Oh and sorry bout the thread high-jack dude.

[mvusse]

Let's take the high-jack 1 post further:

 

Chico, if your stock tire size is the same as mine (which I assume), and you're getting 13mpg from your odometer without compensating for the larger tires (assuming also you have not changed the speedo gear), you're actually getting 15mpg with 31s.

 

My buddy's 90 XJ with 31s gets 15 around town, so that sounds about right. (I drive like a grandma, which might account for the additional 2 in my case).

[chicofuentes0224]

Let's take the high-jack 1 post further:

 

Chico, if your stock tire size is the same as mine (which I assume), and you're getting 13mpg from your odometer without compensating for the larger tires (assuming also you have not changed the speedo gear), you're actually getting 15mpg with 31s.

 

My buddy's 90 XJ with 31s gets 15 around town, so that sounds about right. (I drive like a grandma, which might account for the additional 2 in my case).

 

High jack 2 posts further.

I changed my speedo gear to whatever BLHTAZ and Eagle told me. I can't remember the tooth count right now. I got it from BLHTAZ when he worked at the dealer. And I drive like a grandma's grandma :rotfl2:

[Randy in Maine]

Every do a compression test on the engine?

 

Fully charged battery + a jumper if you nfeel the need.

Warm engine.

Remove a spark plugs.

Wide open throttle.

No coil wire.

10 compression cycles and write down the number.

10 compression cycles and write down the number.

10 compression cycles and write down the number.

One tablespoon of oil in the hole.

10 compression cycles and write down the number.

 

Move on to the next cylinder.

 

 

If nothing seems out of th eordinary you may want ot test out the FI components this way

 

http://www.lunghd.com/Tech_Articles/Eng ... ostics.htm

 

and also have your injectors cleaned and calibrated.