Over Heating

My cj6 has a 225 with an hei distributor. I put a new thermostat and hoses upper and lower. It also has a new core in the radiator. It does not leak . I have been driving it around town for 3 days now and the temperature has been steady at 190 degrees. My question is that when I take it on the highway at high speeds it starts to get hot. It went as far as 240 degrees. What could cause this? I havent checked the distributor to see if it is an odd fire one yet. It was installed by the previous owner. This is what I'm going to check when I get home. Is there anything other than that I need to look for? Should I take the thermostat out? It only runs hot at high speeds.

 

If the timing (distributor) is to far advanced the engine will run hot. Might get some cleaner for the radiator and water jackets and flush the block and such with it.

 

Timing won't cause it to run that hot. I would think you have a lack of circulation problem. Could be a bad thermostat, not opening, radiator, ( I know you said you just had it recored), or maybe air in it somewhere. Was it running hot before the recore? With the cap off and the engine running, is the water flowing freely. You should be able to tell by the difference in the water temp when the thermostat opens. The water should also flow freely at that point. If its not flowing freely, I might remove the thermostat and just see if it flows better. Typically, high temps at speed are caused by low water, lack of water flow through the system, or lack of airflow. If you can, look for signs of lack of flow. When the thermostat is open, place your hand on hte radiator, and feel for cool areas. IF you find one, when the engine is up to temp, you have a lack of flow to all the parts of the radiator. Whoever recored it will have to fix that. Good luck

 

What type of fan are you using?

 

I watched my boat engine (302 ford) overheat with a 138* thermostat in it after some idiot at the boat shop run my distributor around more than 30*, boat started easy and would overheat in a matter of about 20 minutes of running, reset the timing and it ran fine.
I agree it is probably a stopped up radiator or block but the timing has alot to do with engine temp and can very easily cause it to overheat..

 

I think thats the exception and not the rule however. The 225 is an easy engine to cool, assuming its stock, and its more peculiar with regards to timing. I Run mine with 12* initial advance with an HEI unit, with about 32* total advance. Doesn't get above 190, even crawling in L/L. Most of the time it hovers about 165.

 

Lets start with the simple stuff.
Get it up to temp and see if a hose is collapsed.
Could be a air pocket stuck. Does the tstat have a weep hole?
Dont dicount the timeing all together. It'd have to way adavanced to run that hot just at rpm though.

 

Dave,
If you need it I have a tester for pressure testing the cap and system. Also a timing light if needed.
PM me and I'll send you my phone number.

 

During a winter trip a couple of years ago my fan clutch launched the fan into the radiator. It was replaced with an inexpensive one and I was on my way the same day.

Things went well until several months later when things heated up here in AZ and I started running waaaay hot. I replaced everything except the radiator, the newest part.

Come to find out, all four core radiators are not created equal. Your radiator may fit according to the "how-many-vehicles-can-I-cram-this-into" guide and not really be the best choice. You know, it works, but ...

I also layed a fan clutch on it's face once while replacing a rear main. Drove me nuts trying to figure out why the engine couldn't recover. Come to find out, a small amount of oil leaked out of the fan clutch (I noticed it at the time) and it took me months (and aggravation to put the two together.



Those who beat their swords into plowshares and spears into pruning hooks;
Will plow and prune for those who don't.

 

Ok, here is what I did so far. I took out the new thermostat I put in and threw it away. Then I flushed the system. I bought a new thermostat(180) and installed that, But before I did that, I boiled it on the stove and used a cooking thermometer to see if it would open at 180 degrees and it did. I took it for a drive and it was around 190 on the city streets. I got on the freeway and drove at about 65mph going slightly up a grade and it got to a steady 210 degrees . Last time It got to 245 on this same path. When the freeway levels out it drops back to 190. Its a very hot day out here today as well. 95+ degrees. I'm gonna wait and drive it tonight when it cools off and see what it does. Its not a fun drive when I keep stairing at the temp gauge all the time. Some thing I did notice is that my fan is not centered to the radiator and I have no shroud on either. What I may do is run an electric fan. Any suggestions guys, let me know. Thanks all for the advice.

P.S. I checked my timing and it was set at 12 degrees with hei distributor just like m38willys has his, so I left it alone.

 

Dave:
I ain't a Jeep guru, let me get that out there, but systems are systems.

Is the fan running concentric or eccentric?

I'd install the shroud if the vehicle was designed for one before I purchased an electric fan. An electric fan will move as much air as your pulley driven one (unless you get a bigger/more aggressive fan for electric). You'll hear a more aggressive fan, so you gotta ask if you want to listen to it.

The fact that it cools down when it's not working hard says the system probably flows.

It sounds like your problems started when you put the new radiator in, or did I miss something? Are the cores in your radiator the right size? The radiator may fit in the Jeep, but the surface area that allows cooling may be smaller than your old one.

 

Red, I never started it with the old radiator as it was in terrible shape, I had that thing recored right away. It ran fine for a few weeks but only in the city streets and the dirt roads behind my neighborhood. I think it needs a shroud. I'm gonna check the jeep salvage to see if they might have one tomorrow.

 

mine ran steady 190* w/mech fan and now 195* w/electric one.

 

Oil system is good?

 

Yep, I got good oil pressure

 

Aluminum radiator Love mine.

 

I use to have the same problem, ran at 180 all day long on the trail and around town, got on the freeway and it would overheat. I just replaced my waterpump (mostly because it looked like it need to be) and it solved the problem.

 

I would start with a fan shroud. Without one of these there is no way to direct air thru the radiator. Would draw air from above/under the radiator rather than thru it. Dont disreguard the timing either. It is a common cause of overheating. Advanced timing caused predetionation which causes alot of heat as well as mechanically damaging to the motor.

 

I think I'd check the timing, pull and test the thermostat in a pan of hot water with a meat thermometer and use a $8 Prestone backflush kit to flush the system. I think the lack of a fan shroud is much more likely to hurt you at low speeds.

Also, consider what's on your bumper? A big 8274 standing up in front of the radiator and a bug screen could be problematic as well.