overheating, seeking advice asap...please

[camruhman]

1041383

Hi

A friend and I recently rebuilt the 400 Chevy small block engine on my 1985 CJ-7.

(The Radiator on this Jeep was replaced last sept 11th with one from a Nissan. The old one was off of a Ford and had been leaking badly)

I never had a shroud around the radiator, so my friend who helped me with the rebuild suggested that we leave the orignal fan off and we put a 14 inch electric fan in, mounted to the radiator.

Since the rebuild, if you are driving normally, the temp stays pretty good at around 190.

(it has a 180 thermostat in the enine)

But if you sit at idle very long, like in rush hour traffic, etc....the temp goes up to 230 and even around the 240 area.

I've been just shutting it down and letting the fan cool the water for a couple minutes then starting it back up and letting the cooler water circulate a bit and repeating that process until the temp seems reasonable to continue.

But this situation has got to go.

We are not sure if maybe it is wanting to run a tad hot due to the new engine breaking in, or what.

I have a suspicion that the 14 inch electric fan is not big enough to cool things down correctly.

A guy at a radiator shop suggested that I bring the Jeep into his shop and let him put the original fan back on and make a shroud for it out of aluminum....and he seems convinced this will totally solve the problem.

I hate to spend even more money....but as my 16 year old son will be driving this a lot for a while, I need it to be safe for him to drive and not have to worry about warping heads and overheating in general.

If anyone here has ever experimented with smaller electric fans or has a simliar set up and can give me some good advice, I'd sure appreciate it.

Thanks

Mark

INphotogr4@aol.com[addsig]

 

[MudderChuck]

1041386

I don´t know about the Nissan radiator (size and volumn). I´ve had good luck using old Dodge or Ford (depending on inlet and outlet) radiators, especially fron the extended vans (automatic) with air. They are pretty much enough radiator for anything and easy to mount. If it fits between the headlights and you can close the hood it´s about the right size. And are usually pretty cheap at a junk yard.

I´ve had good luck with the electric fan off of a full size BMW with air conditioning (older models) it is a two speed fan and really sings in high (push type fan)

Make sure the fins arn´t plugged up with dust, pollen or mud (a flashlight shone through rear to front will tell how clean things are).

Look in the filler hole with a flashlight and check to see if the inside are restricted.

Make sure and check if the water pump you have in there, isn´t reverse rotation. Contrary to popular belief, a reverse rotation, won´t pump backwords but will pump very poorly top to bottom, while the proper one will get a considerable flow going.

Make sure and check the fan, a push fan doesn´t work well in a pull position and vise versa.

An excepetionally lean motor (bone white plugs) will run hot (vacuum leak). As will one with a very small compression leak (which Chevy´s are notorious for)bubbles or foam in the radiator. The clearance between the water jacket and the cylinder in some Chevs is about 3/16 of an inch. And the intake manifold bolts have a tendancy to loosen up (re-torque).

On some motors it´s possible to put the thermostat in upside down, also for proper function the heater hoses have to be connected or put in a loop to bypass the thermostat (some) and keep a good flow of heated water flowing so it opens and closes properly.

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