Overheating

So I have a new 3-core replacement radiator that I got from 4wd Hardware (I think it's bigger than the factory one too, as I had to fab new brackets to mount it). I also put in a 17" flex fan. So, the radiator has one extra core, and the fan is 2 or 3" larger than stock. I have a one inch fan spacer installed, and it keeps the fan 1" from the radiator at the bottom of the radiator (the engine sits at an angle so the top of the fan is further away from the radiator). Anyway, when I got the Jeep it didn't have a fan shroud, and I currently don't have one installed. The Jeep runs inconsistently hot and cool. Its okay for some time, then gets hot, then runs cool, then hot, etc, etc. It reaches 220 pretty easily when it gets hot, and one time it got to 235 before I noticed and shut it down. It has a brand new 160* thermostat in it, and when I fire it up for the first time and let it run, it will run right at 160*, then when it starts to heat up, it will run anywhere from 160* to 220*, up and down. If I put on a fan shroud, will this solve my problem and keep it running at 160-180? How much does the shroud help? I could also put a pusher fan on the outside (front) of my radiator, but it will cost more money, and electrical stuff does have the chance of failing. So, anyway, what do you think about the shroud, how much will it help? And where can I find one? I could make one if I have to, but getting tired of fabbing everything on my Jeep and factory/replacement shroud would be easy and look nice. Please help! I wanna go 'wheeling again this weekend. Thanks.

 

Grab your fan with both hands and turn it. If you can slip it on the fan belt then the belt is too loose. Try drilling a hole in the T-stat. You may have some air still in the system. What is your total advance on timing? Are you running stock Dist or Elect?

 

As Glenn said first thing is to verify the temperature reading is correct, a good mechanical gage or I use a meat thermometer, compare the readings on the thermometer to your temp gage.
I don't personally have experience with the 225 CID but 220 is to hot. Yes a shroud will make a difference. I don't personally run an electric fan but if everything else is ok it shouldn't be necessary.

 

To try and answer everyone's questions...I am running a Delco distributor, one of the huge ones that looks kinda like the DUI distributors. My timing was advanced 6* when the issue first happened, then today I advanced it to 12*, it runs a very tiny bit better, but still gets hot. I put a new gage in it just recently, it is a mechanical one, the temp sending unit goes in through the intake manifold on the top of it, the only wires for the gage are for lighting it during nighttime. Since the gage is new, I assume it is working correctly, who knows...The fan turns when the engine is on, and when I rev it up, the fan flattens out a slight bit, as it is a flex fan. If I can spin the fan by hand with the engine off, that means the belt is too loose? Tightening it up till it won't spin by hand, can that really be the culprit? Is there something else I'm overlooking?

 

You should not be able to slip the fan either left or right (unless it's a clutch fan) and this will cause slippage at various speeds causing your problem.

 

First off, verify if you are really gettin hot. If you are gettin hot and it is not a false reading , then I doubt your fan or lack of a sroud is causing it. It sounds like you are getting hot spots. I would remove the thermostat and see what happens. If no change , then look for air in the system. Rig up a hose adapter and run some water through the sytem until it overflows the radiator . If that doesn't help, change the water pump. I had a water pump with a loose impellor that acted similar.
If the fan shroud was an issue , I would expect it to run hot and stay hot , not vary. If you aren't getting water through the radiator consistently, a fan shroud won't help. Also, make sure the radiator isn't partially blocked.

 

Basically, it will creep higher and higher in temp until random changes in driving, and I don't know what or why. Sometimes it heats up on the road at consistent throttle, sometimes it will cool off from being hot if I drive that way. Sometimes when I'm creepin' on the trail it will get hot, and sometimes when I go from a faster road to trail creepin' it will cool off. However, I most always must change my driving habits before it will change temp. For running a hose through the system till it overflows the radiator, do I do this with the thermostat out and the engine off, or with thermostat in and the rig up to temp? What's the deal with the air bubble idea, how do I get the air bubble? Also, I installed an overflow tank and it seems a tad bit mirky now. The engine did sit idle for three years with me, and who knows how long before that, and the radiator was out for at least two if not closer to three of those years that it sat while I worked on it. Could there be rust in the block that is coming off now that it is running, and mirking up my coolant? Does my radiator need to be blown out maybe? How can I tell if the radiator is partially blocked, as Birddog said to make sure it isn't? Thanks for the help.

 

It sounds like the thermostat is not working correctly.

 

First off I'm a newbie here so this is JMHO.

Thermostats only set the Minimum Temp an engine operates at. IMHO they only help cool an engine by giving the radiator time to cool the coolant that is currently in the radiator.(My 97 TJ had no thermostat when I bought it and in the summer/traffic the gauge went UP)

You have a new radiator and new thermostat. I will assume you flushed the system before they were installed. You mentioned the overflow is getting Murky. My guess would to be check your compression(cuz its cheap and sounds like a head gasket leak if all the obvious probs. are clear)

Hope its something simple and cheap.

TCJ

 

I had the same problem. I put in a new thermostat and it started overheating then cooling back down. I changed that thermostat and i havnt had aproblem since. Sometimes thermostats are bad even if new.

 

If it has never run right with this thermostat in it my guess is that it is bad. They make radiator flush and radiator cleaner, 2 separate products that you can get at NAPA, but I haven't used it yet.

 

Lots of good advice here. I wanted only to add - did you install the shroud yet?
In order for any fan to do a good job it should be set up in a properly sized shroud so that air isnt just escaping around the fan when it really needs to be pulling. In the late's, Chevrolet would deliver L88 corvettes without a shroud because the cars were supposed to be driven fast (raced) and never stop. When joe average bought an L88 and tried to drive it on the street it would overheat. The cure was a shroud.

Is your overheating while driving? or sitting in the driveway?

Tom

 

Unfortunately, I did replace the thermostat already. I didn't know if the one in there was maybe a 190 or 210, so I went to replace it with a 160, and it already had a160 in it, but I replaced it anyway, and same thing. I have not made a fan shroud yet, gonna try to make one today. What's the chances that both thermostats don't work properly, even though both were new? If I go to a 180, and give it more time to sit in the radiator, you think it will actually keep the engine cooler overall? Also, the rig does not overheat sitting in the driveway, it overheats under load, and then if I pull over and let it idle for about 5-10 min, it will cool back down, but usually stops around 180, never really gets fully back down to 160.

 

You will run cooler with a 190/195 thermostat than with a 160. These engines run better at this temp and the coolant stays in the radiator longer