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Unread 10-04-2012, 05:09 PM   #31
djb383
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1998 XJ Cherokee 
 
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Something's wacked, according to the chart above, 121 ohms would be give or take 300F?

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Unread 10-04-2012, 05:13 PM   #32
BlackPearl
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Oh no, that was the reading from the coolant temp sensor at the back of the engine. So it should have been around 93ohms but it was not there I didn't check the temp sending unit at the t-stat yet
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Unread 10-04-2012, 08:04 PM   #33
djb383
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Both 121 and 93 ohms r off the chart.......300-400F.
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Unread 10-04-2012, 08:27 PM   #34
Reptile
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Quote:
Originally Posted by djb383 View Post
Both 121 and 93 ohms r off the chart.......300-400F.
He's referring to the 1st chart for the sending unit. The coolant temp sensor and sending unit have different resistance tables.

Quote:
Originally Posted by BlackPearl View Post
Oh no, that was the reading from the coolant temp sensor at the back of the engine. So it should have been around 93ohms but it was not there I didn't check the temp sending unit at the t-stat yet
With 121 ohm, your gauge should have given you about 210F, which is normal engine temperature. You could double check using a 100 ohm resistor (Radioshack), the gauge should point to that kind of temp... doesn't look like it does. Out of curiosity, where did you get your sending unit? You have a brand/part#?

Don't rely too heavily on the reading from the coolant temp sensor. Remember it's located after the stat. If your stat is clogged and obstructs the flow, the sensor won't get nearly as hot as the engine. This threw me off when I was doing my testing... I believe your sensor is bad anyway. The coolant temp sensor controls the e-fan, which is set to kick in at 217F. And my guess is you must have had a good reason to bypass the e-fan.
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Unread 10-05-2012, 08:22 AM   #35
djb383
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Well duh, my bad, there r 2 charts.
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Unread 10-05-2012, 10:39 AM   #36
BlackPearl
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Yes I used the first chart, and with my sensor reading 121ohms which SHOULD be about 210 degrees, that makes me feel hopeful that my engine isn't going to explode. And at 121ohms that had my temp gauge at the 3/4 mark. So I think we are coming to the conclusion my gauge or sending unit is bad. Just to be sure I was doing it properly I'll take some photos today to show you where I was probing the sending unit.

Next order of business, I got the replacement sending unit from a Kragen/O'Reilly. But I just recently discovered there is a Jeep/AMC salvage yard not far from me and I'm sure I could find a used one there from my exact make and model.

And yes I believe my sensor is bad anyways. I just bought a replacement stock e-fan, plugged it in, my gauge got to almost redline and the fan didn't kick on...and I know the fan works because I hooked it up to power before plugging it in.
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Unread 10-05-2012, 12:31 PM   #37
Reptile
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It doesn't hurt to test both of them in boiling water and compare to the chart. That way you're testing against a known temperature which happens to be pretty close to normal engine temperature.

O'Reilly could not find the sensor and it looked like their website had universal units which I didn't want to gamble with. At the store they looked at me funny... They had no clue what I was talking about.

When you disconnect the sensor and engine is warm does the gauge move at all? Im thinking you could have a wiring issue between the gauge and the sensor. It occurs to me that the default gauge reading is close to where you describe it, as if it wasn't receiving an input signal... Just a thought.
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Unread 10-06-2012, 09:13 AM   #38
BlackPearl
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When the engine is warm and I disconnect the sensor at the back of the engine the gauge in on the dash drops to zero...

But I'm going to be doing work on the Jeep all this morning. Hopefully things come together
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Unread 10-06-2012, 12:29 PM   #39
BlackPearl
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So I just pulled my water pump and I'm pretty sure I found my problem, I don't see an "R" tramped on it...which means the water was being pumped the wrong way
image.jpg  
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Unread 10-06-2012, 12:43 PM   #40
Reptile
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I don't know how you can visually tell whether it's a reverse rotation pump... I suppose the direction of the impeller? But it does look like the one I replaced not so long ago...
dsc03406.jpg  
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Unread 10-06-2012, 01:28 PM   #41
BlackPearl
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From what I've been reading it should have an "R" stamped on the blades
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Unread 10-06-2012, 02:08 PM   #42
Millermagic
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Did you get the 3 e-fan kit from ebay? Buddy of mine has one on his cherokee and it constantly overheats.
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Unread 10-06-2012, 03:19 PM   #43
BlackPearl
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So after everything that has gone on, I just found a crack on the block. It's on the coolant side, outside of the engine. This picture is the opening for the water pump, and it extends to outside of the engine. Other than causing leaks would this be the contributing factor to overheating?
image.jpg  
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Unread 10-06-2012, 03:20 PM   #44
BlackPearl
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And yes those were the fans I originally bought but have since see back to the original stock fan
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Unread 10-06-2012, 04:43 PM   #45
Pats94
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Quote:
Originally Posted by BlackPearl
So after everything that has gone on, I just found a crack on the block. It's on the coolant side, outside of the engine. This picture is the opening for the water pump, and it extends to outside of the engine. Other than causing leaks would this be the contributing factor to overheating?
How far does the crack go? Is it leaking?
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