Cooling issues in my CJ7 w/ 4.6L

[LetchcoreCJ7]

After I drive for 20min or so and sit at stop lights alot the temp starts rising. Unless I get up to 30mph or so it wont stop rising. If I stay 30mph or more the temp comes right back down. I have a stock style 3 row radiator, 180 deg thermostat, fan shroud, and stock 5 blade clutch fan from a 4.0L. Take into mind it has been between 85 and 95 degrees lately in TN.

I was thinking the next step for me was a custom aluminum radiator? Anyone have some suggestions? Is there some kind of trick to make sure the fan if pulling enough air through the radiator?

[Cheromaniac]

It sounds like the clutch fan isn't pulling in enough air when you're travelling at low speed. I suggest you convert to an electric fan. Look for a fan/shroud that covers at least 80% of the radiator. The Taurus or the Lincoln Mark VIII are reputedly the best but draw a lot of current. Take a look at the Flexalite range.

[LetchcoreCJ7]

Is there any kind of running condition that would make the temp rise?

[Cheromaniac]

You said in your first post:

After I drive for 20min or so and sit at stop lights alot the temp starts rising. Unless I get up to 30mph or so it wont stop rising. If I stay 30mph or more the temp comes right back down.

That statement is classical for a cooling fan that isn't pulling in enough air. At slow speeds there isn't enough ram air cooling of the radiator which is why it needs help from the fan. Above 30mph you don't need the fan so I'd say it's more than likely that the viscous clutch of your stock fan is toast. To confirm that, try spinning it by hand when the engine's hot (ignition off naturally ). If the clutch is OK, there should be a moderate amount of resistance. If the fan turns almost effortlessly, the clutch is toast.

[astjp2]

Spal pwm controller with relay to run a ford contour. I am running it on mine an it sure is nice. Tim

[BADASYJ]

A lean condition or higher comp. ratio will make more heat in the engine. You could try running 93 octane through it and see if that helps. You could be on the verge of detonation.
An electric fan will NOT solve your problem. The mechanical fan can pull more cfm then any electric. I would first check the clutch on the fan like Dino suggested. If that doesn't work replace your thermostat. If you mud, spray out the cooling fins in your radiator. And of course you need to check your waterpump to see if the fins are gone. If none of that works and your shroud is still intact then I would suggest a new radiator. I know that Be Cool sells a direct fit radiator for a YJ (should be the same as a CJ7) and that thing sells for around $700 w/e-fan and $499 without the fan. They do sell universal radiators much cheaper but it will take a little fab work to make it fit.
Unless you are strictly racing or have a money tree I would stay away from the electric fan. The stock fan WILL pull enough air to keep you cool so long as your radiator is in good shape.

[Cheromaniac]

If you mud, spray out the cooling fins in your radiator. And of course you need to check your waterpump to see if the fins are gone. If none of that works and your shroud is still intact then I would suggest a new radiator.

His engine runs cooler at higher road speeds so that rules out the radiator. If the radiator was clogged the engine would run hotter at higher road speeds. The WP isn't the problem either for the same reason. Like I said earlier, the symptoms

After I drive for 20min or so and sit at stop lights alot the temp starts rising. Unless I get up to 30mph or so it wont stop rising. If I stay 30mph or more the temp comes right back down.

point to an ineffective cooling fan.
The cure is to either replace the viscous clutch on the existing fan (if the clutch is shot) or replace the fan with another one that pulls more air. An appropriately sized electric fan will not only pull in more air but it'll also free some HP.

[BADASYJ]

Not to get into a pissing match Dino but in my experince I have had a mud clogged radiator that would cool at highway speed but not at idle. Mud will definitly damper the cooling effieciently of the radiator. Mud is an insulator and will hold in heat, espesially at idle speeds. Get up to speed and the mud will cool drawing out more heat The same goes for the fins on the water pump they were gone but it would cool at highway speeds and not at idle. No doubt its the clutch fan, I was just sending out some more helpful hints incase a new clutch did not fix his overheating problem.