1992 Isuzu Rodeo Heat Problems

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  #1  
Old 12-15-03, 05:54 PM
SteelPanther
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1992 Isuzu Rodeo Heat Problems

I have a 1992 Isuzu Rodeo with a 3.1 V6 4x4, 112,000 miles Automatic Trans.

I was having a problem this summer with the heat guage pegging all the way up to H. So i figured Id take out the thermostat and see what happenned. After taking out the thermostat it has went up to H maybe 2 times in one month of running. Now it is winter so i had to reinstall a thermostat so I could have some heat. Soon as I turn on the vehicle 5 minutes goes by and it is pegged on H again. This hasnt happenned just once but 3 different thermostats because I didnt know if they may be faulty.

It doesnt sound like it is overheating at all, hissing boiling etc. And Id hate to run it if it is that hot but I dont know if it is. The gas guage which is right next to the heat guage in my instrument panel also bounces. It never stays in one spot unless the vehicle isnt moving. I don't know if this heat problem is merely a electrical malfunction or mechanical error.

As for heat after I put the thermostat in the heat works excellent. Nice and warm. Which Im thinking would rule out a plugged core or bad pump, or thermostat if Im thinking correctly?

Also the heat sensor on the front of the engine has been replaced twice with no luck.
 
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  #2  
Old 12-16-03, 04:45 AM
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First thoughts are that it sounds like you should try to put an aftermarket temp gage on it. You could possibly have an instrument panel problem.
Billy
 
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Old 12-16-03, 12:23 PM
SteelPanther
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Thanks I will try that.
 
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Old 12-16-03, 06:53 PM
mike from nj
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which heat sensor have you replaced twice? the 2 wire one or the 1 wire one?
 
  #5  
Old 12-16-03, 08:20 PM
SteelPanther
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I changed the front one right below the alternator, i think it is just one wire with a black connector
 
  #6  
Old 12-18-03, 06:47 AM
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you could have it scanned...

...by a technician and see if the computer sensor agrees with the engine sensor...they are separate and that's why mike asked which one you replaced. running without a t'stat isn't advised because coolant can pass thru the radiator too fast and not have time to transfer the heat to the air. probably should have had it checked then...but that's water over the dam now. get it scanned to rule out an electrical malfunction and go from there. if it's truly running hot but hasn't damaged the engine from overheating, it may well need a radiator. if it has damaged the engine, it may well need both...as the damaged engine will be the result...something else is the cause
 
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Old 12-18-03, 08:11 PM
mike from nj
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sorry, i've been a little busy lately

i guess we can assume the sender unit is good, since it's been replaced twice and it's still doing it.

the best thing is to get someone with a scan tool and drive with it hooked up, this will tell you pretty accurately the temperature of the engine. this reads off the 2 wire sensor that is bolted into the aluminum intake manifold, right under the air filter housing.

the 1 wire sensor is bolted into the cast iron cylinder head (the one you replaced??) this is what signals the dash gauge. if you want, you can put a thermometer into the radiator and watch the coolant temp. it should go up to 195 (or whatever temp thermostat you put in) and cycle up and down a little, 200-180, until everything equalizes temp-wise. this may or may not help you, as it usually overheats while driving, and i don't recommend driving without a radiator cap (that's why i said to use a scan tool)

all the sender unit does is make a variable ground for the gauge. unplug it---the gauge should read 'full cold'. hold that same wire on to the engine block(or anything metal) and the gauge should go to 'full hot'. this tests out everything back to the gauge. if the wire has a bare spot, and it touches ground, the gauge will do what you describe.

of course, if it's overheating, it will do this too. a scan tool helps big time.

let us know what you find

(ps. your grill says 'isuzu', but your engine, trans, computer, sensors and rear axle are all General Motors)
 
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Old 12-22-03, 02:51 PM
SteelPanther
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Hi all. Back with results. Bought a aftermarket temp guage and replaced the 2 wire sensor in the intake manifold with this temp guage. left it under the hood for the time being, not fully installed into dash etc. Guage in instrument panel read HOT. Got out went under the hood to the aftermarket sensor, which read 195 (thermostat temp.) Im guessing it is as you said a bad wire grounding out from the block sensor. As this guage continaully pegs on H at times even 1 minute after starting cold in 15 degree weather.

So everything seems to be fine with my water temp seems to eb finicky wiring or another bad sensor causing the problem. In any case Im going to leave the aftermarket unit installed so I can see mroe accurately then H or C.

One concern I had is what do i do with the two wires that were attached to the old intake sensor?. Do i just tape them off? My truck used to idle at around 800-900 RPM after i installed the aftermarket temp guage it idles at 1000, is this a major concern?

Thanks again.
 
  #9  
Old 12-22-03, 03:12 PM
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Well first of all you installed the analog gage in the wrong place. The 2 wire sensor goes to the computer. This is probably why you have the slight change in idle as the computer is no longer receiving that signal. Try installing the gage where the OTHER sensor is located. Like Mike said the 1 wire sensor tells the gage what to read. Not that this will change your results, just the right way to do it.
Billy
 
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Old 12-22-03, 04:48 PM
SteelPanther
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Thanks Billy,

Went out and changed that around to the correct way and tested a second time, with as youi said the same results. Do I need to remove the wire from the old junk sensor? Or can it be left in place? Everything seems to work fine now that that sensor is out of the vehicle. Thank you everyone for your help.
 
  #11  
Old 12-22-03, 05:23 PM
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Either way, Its 6 of 1 half a dozen of the other. The gage is still going to show full hot with it connected. Disconnected it will show cold. Did you replace THAT sensor or just the 2 wire sensor?
Billy
 
  #12  
Old 12-22-03, 05:56 PM
SteelPanther
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I replaced the 1 wire sensor 2X. The dealer i bought it frm said they had replaced it as well but could never get it figured out. I almost wanna say it is in the instrument panel as the gas gauge is continually bouncing up and down as well.
 
  #13  
Old 12-22-03, 06:07 PM
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Yeah, thats what I thought from the beginning.
Billy
 
  #14  
Old 12-23-03, 02:49 PM
SteelPanther
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Ok, now there is another problem. I drove the vehicle around today and when i watched the heat guage it never left 135-140 range. Im truly confused now, there was heat coming out fot he vents like normal but, no luck with the guage.
 
  #15  
Old 12-23-03, 03:04 PM
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Did it move to that range suddenly or slowly? What was the ambient temp where you are during this time?
Billy
 
  #16  
Old 01-10-04, 01:15 AM
SteelPanther
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Did some testing now for a couple fo weeks and the heat has went to 190 on a regular basis and Ive only had one abnormal day as stated earlier. Im now guessing everythign seems ok as the temp has stayed the same range for a few weeks everyday. Thanks!!
 
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