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Running Hot in Traffic


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My 94XJ 4.0 is running hot in traffic but as soon as I put the heat on it drops right down. It tends to run about 210* w/ the 195* thermostat during regular driving. I just put a new (used) radiator and a new 195* thermostat in. I noticed the cap is leaking a little so I will replace that tomorrow. Will an OEM thermo with the hole in make a difference since it is only running hot in traffic? I just got this jeep so I'm not sure if this was a problem previously. Any suggestions?

 

I also have an elec fan but the AC isnt working. Is there a write-up anywhere on how to wire a switch to the dash for it?

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It is running 210 degrees in traffic? That's not hot and is perfectly acceptable.

 

Willy

 

No, it runs 210* in normal driving; I have also let it idle in the driveway for like 25 min when i put the rad and thermo in and it didnt go over 210* . It started creeping up towards 230*-235* in traffic before I put the heat on to drop it back down.

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Question is........Why use a Used radiator?????? :hmm:

 

So from what I read, your running at a normal temperature (210) and when you stop for traffic, like at a red light, your temp climes up, you put the heat on to use the heater core for an added expulsion of the "hot" water, right??

 

My first though........Bad, plugged radiator. Could be the fan clutch, but I'll take the "used" radiator first.

 

I know, it's temping.........but some things, like use brake lining, and use radiators don't Need to be reused, and with new ones less than $100.

 

And........I think this is what your looking for -

 

viewtopic.php?f=2&t=3912&hilit=electric+fan

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It has been fine driving around town at red lights and stuff and when i let it idle in the driveway for a while. It started to run hot today when i got stuck in traffic on the highway and earlier when the wife took the baby to the zoo, also requiring stop and go on the highway. Its that damn highway :fs1:

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You could try a flush and fill to see if there was anything in there to get out... Do you have a Rad shop nearby to pressure test it?

 

My MJ will creep up in temp on the freeway if I push it above 70 for any length of time in the summer. Sitting in hot city traffic in the summer will also do this. Mine is brandy new and a three core with a 190 T stat and new fluid all last year. But I have a winch up front partially blocking the rad... A AC cooling fan wired with a switch helps ALLOT!!! Head to the junk yard and get yourself one.

 

They just have marginal cooling IMHO...

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They just have marginal cooling IMHO...

 

That is true, looking at a stock MJ or XJ, the stock fan only covers about 1/2 of the radiator surface, and the electrical fan (Option) cover about 1/2 of the surface of the radiator.

 

Using both fans would help if your in the "warm" belt.

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This XJ has the electric fan already in it but since the AC doesnt work it never kicks on and is probally doing more harm than good at this point. I will try and wire a switch up to it.

 

My 89 MJ, which doesnt have an elec fan (no AC), never goes above 175*-180* with a 195* thermostat

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A factory installed electric fan should also kick on around 200-210 degrees, regardless of AC being on.

Yep - IF the fan works, and IF the temp sensor in the radiator works, and IF the relay works, and IF the wiring is hooked up and IF the connections aren't corroded. On a 20+ year old MJ there are a lot more reasons why the aux fan probably doesn't work than there are reasons to think it might work.

 

The fan didn't work on my '88 when I first got it. I found that the connections where the wiring plug went onto the relay were so badly corroded that one tab of the relay simply didn't exist. I had to cut all the wires, crimp on new female connectors, and attach each wire individually to a new relay.

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A factory installed electric fan should also kick on around 200-210 degrees, regardless of AC being on.

Yep - IF the fan works, and IF the temp sensor in the radiator works, and IF the relay works, and IF the wiring is hooked up and IF the connections aren't corroded. On a 20+ year old MJ there are a lot more reasons why the aux fan probably doesn't work than there are reasons to think it might work.

 

The fan didn't work on my '88 when I first got it. I found that the connections where the wiring plug went onto the relay were so badly corroded that one tab of the relay simply didn't exist. I had to cut all the wires, crimp on new female connectors, and attach each wire individually to a new relay.

 

I didnt know this, I thought it only worked with AC. I will turn the AC and see if it kicks on that way, atleast that will give me an idea if it works at all. Where is the relay located, I will check all the wiring for it. The PO has done some "modifications" :wall: to some of the wiring so I can add this to the list. When I changed the thermostat half of the temp sensor for the fan was coveded up with a pile of s#*t from the sealant he used on the housing

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I'm a bit confused. Did only XJ/MJ with an AC come factory with an aux fan? Because my MJ has an aux fan with the factory wiring/connector in there with no AC. Based on the work I've seen from the PO, he didn't add it with how clean it looks. Which options came with the aux fan?

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This XJ has the electric fan already in it but since the AC doesn't work it never kicks on and is probably doing more harm than good at this point. I will try and wire a switch up to it.

 

My 89 MJ, which doesn't have an elect fan (no AC), never goes above 175*-180* with a 195* thermostat

OK here is another angle... is the gauge reading correct temperatures? How could your other jeep run at a lower temp than the stat? I mean your engine will EASILY surpass this temp if the flow is blocked as it is when a stat is in place. SO, either your stat is stuck open, its not a 195 stat or your temp gauge is not reading correct temps.

 

CW

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I have the aux fan and a Ford Taurus 2 speed fan, I just use the Taurus lower speed for normal driving and stop and go trafic with out any problem, when I use the 4x4 I turn on the aux fan to keep and adecuate temperature and everything it´s been ok! and I still have the high speed of the taurus fan free to be used just in case.( I took off the fan clutch and since I have no A/C I took off 3 of the pulleys that I don´t need with my no A/C set up) :clapping:

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This XJ has the electric fan already in it but since the AC doesn't work it never kicks on and is probably doing more harm than good at this point. I will try and wire a switch up to it.

 

My 89 MJ, which doesn't have an elect fan (no AC), never goes above 175*-180* with a 195* thermostat

OK here is another angle... is the gauge reading correct temperatures? How could your other jeep run at a lower temp than the stat? I mean your engine will EASILY surpass this temp if the flow is blocked as it is when a stat is in place. SO, either your stat is stuck open, its not a 195 stat or your temp gauge is not reading correct temps.

 

CW

 

Very good points. I had wondered this about the MJ, since I put the 195* stat in there. I think my other job has one of those point and shoot digital thermometers, I will try and find it and do some testing. The gauge could easily be reading low.

 

The XJ tho, I think may be accurate because it reads normal most of the time, only runs hot in traffic on the highway. I will also check this if I can find the thermometer at my other work.

 

Neither of the stats are the OEM style with the hole in them.

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