I have totally gone through the cooling system of this Jeep many times...I can't get it to stop overheating at freeway speeds. It is a CJ7 with a chevy 350. The engine is stock with the exception of headers, intake and holly carb. It has the 4wd hardware conversion radiator that is three core I believe. The water pump is new, thermostat has been replaced twice, 180 degree. The engine is rebuilt with less than 1000 miles on it. The fan is a large, 18" or so, fan clutch is brand new. All I can figure is the radiator is not big enough. The Jeep won't start heating up until I get up to freeway speeds, 70mph. I can drive 50mph all day long at it stays just a little above 180 deg. It will idle all day long with the gauge pegged at 180, the gauge is mechanical by the way.

I am looking at aluminum radiators in the Summit catalog. Are these any good? The one I am looking at is a "universal" chevy radiator with 2 rows of 1" tubes or something like that. Do you think this would solve my problems??

sorry for the long post

Dan

I never overheat, and I run a 350tbi with a '79 304 CJ. Just had the neck moved for the 350

do you have a fan shroud? if not get one.


i have a howe alum rad. from summit. it is a nice unit

I have a shroud but it is kinda a half arsed one...I am making a better one...I thought a shroud was not important when cruising down the highway?
Basically you guys are saying that the 4wd radiator I have should be enough for this motor?

By the way, when it heats up on the highway the gauge just keeps rising until I slow down...and I already checked and rechecked the timing because I thought that might have been slightly off. I run about 2000-2500 rpm's on the highway, no overdrive.

What am I missing?!!?

Dan

Originally posted by camo
do you have a fan shroud? if not get one.


Get a radiator shop to order you an OEM spec. replacment 3 core (w/AC) (off-set cap) CJ radiator and a Stant 15 lb. cap.
These rads are the style that are a thin 3 core that steps toward the front and will allow you to re-use an OEM CJ shroud.
If you can't find one, Johnny's Radiator in Farmington NM will know what you are talking about.
(ORC Land Use) Brad turned me on to this.
You get back that lost inch of fan clearance too ...
;)

If it overheats at hwy speed, but not at 50 mph, it probably, needs more radiator or better coolant flow thru the radiator. Unless the radiator is blocked with dirt or a winch, the air flow should be enough with or without a fan shroud....Does the upper hose have a lot of vertical rise ? I had tall valve covers once and I routed the upper hose with a straight up fitting, it gave me overheating trouble.

call up 1800-Radiator. They have a place around here where I was able to pick mine up instead of mail order. They said a CJ w/ a 350 is not a problem and they sell them all the time. Their radiators are also lifetime warranty and they even warrantied mine out when the fan caught it due to a bad motor mount.

Dirtrod-
Hey I am in MI too...
This Jeep is just fresh off a frame off rebuild, so there is no dirt or anything cloging up the radiator. The only thing blocking airflow is a small tranny cooler...and usually the tranny runs cooler than the coolant would be.

The upper hose is just about a straight shot to the radiator. The hoses are the "universal" fit ones that are ribbed though. I can't imagine that something that small is causing my problems...

Please help before I drive myself crazy!!!

One more thing I thought of...on a day that is cooler than say 70 degrees the Jeep really won't heat up either.

Dan

Originally posted by dcmsu
Dirtrod-
Hey I am in MI too...
This Jeep is just fresh off a frame off rebuild, so there is no dirt or anything cloging up the radiator. The only thing blocking airflow is a small tranny cooler...and usually the tranny runs cooler than the coolant would be.

The upper hose is just about a straight shot to the radiator. The hoses are the "universal" fit ones that are ribbed though. I can't imagine that something that small is causing my problems...

Please help before I drive myself crazy!!!

One more thing I thought of...on a day that is cooler than say 70 degrees the Jeep really won't heat up either.

Dan

Have you tried running without a t-stat ? ...is the radiator hot or just the engine ? Is the radiator clean inside ? You might want a to go to a 4-core, but I've seen 350s with 3-cores do fine. Could it be running lean ?

I have heard that running without the thermostat really isn't a solution. The engine should be able to run at 180...Would a 160 degree thermostat help or hurt?

The radiator gets hot as well as the engine...it is clean inside I hope, as it is brand new with less than 3 months use on it.

Would a lean running motor have these symptomes? I never thought of it before but if the timing isn't right it would be working against itself, especially at higher revs.

I really don't want to go to a 4 core if I can help it because I already spent the money for the 3 core...

Dan

Originally posted by dcmsu
I have heard that running without the thermostat really isn't a solution. The engine should be able to run at 180...Would a 160 degree thermostat help or hurt?

The radiator gets hot as well as the engine...it is clean inside I hope, as it is brand new with less than 3 months use on it.

Would a lean running motor have these symptomes? I never thought of it before but if the timing isn't right it would be working against itself, especially at higher revs.

I really don't want to go to a 4 core if I can help it because I already spent the money for the 3 core...

Dan
Running without a t-stat (or one with the center cut out) just eliminates one thing from the puzzle.
Yes, lean can cause overheating, is the carb clean ? have you run that carb before ? Headers can make a small difference (making it run leaner) , but a plugged main jet could cause big trouble.
Is the timing advancing ? is the vacuum advance/centrifugal advance working ?

The carburator is a holley that I just bought new from Summitt. The vacume advance is working as far as I know...It is hooked up to the carb in the right location, I checked that. The distributor is also a new/ reman unit so I would think the mechanical advance would be working properly. It is a non-HEI distributor if that makes a difference. I just don't think the timing could be that far off because the Jeeps starts right up and runs great.

What else could it be besides an undersized radiator??

Dan

How hot is it getting ? My 454 ran over 220 deg. for the first 10 or 12 years :) Now it runs 180-200

My buds 350 with a industrial 4 core will run 200-210 after a work-out.

BTW...just because something is new, don't make it right...It's actually the other way around...don't trust anything until it has been proven to work.

You can ck the advance with a timing light, rev it up and watch the timing mark go into advance.
Most "mechanics" now a days just try known good parts until they find the problem. Try another carb, check for exhaust in the radiator (head gasket), Are the brakes dragging ? Hell man, I don't know, show that fawk'r who's boss.

I don't mind if it heats up when I am running it hard...but when the gauge rises to 230 when just cruising down the highway that is another story.

I agree just cause its knew doesn't make it right...but what could be faulty to cause this?? Everything seems to be working, just not enough.

Well, hopefully I'll figure it out

Thanks

Dan

Just because the rad is new doesn't mean it's gonna werk!There are different mfg's which means quality can vary.Sounds like the flow is being restricted some how.Going down the road at at frwy speed should be sending enough air through the radiator running shroud or with out a shroud.I just recently had my CJ7 radiator rebuilt from a 2 core to a 3 core.The radiator doctor replaced the core with a brand new Modine 3 core.He said there is a big difference between brands.You said the engine is new,how about the water pump?Possibly a new high volume water pump could work?Have you considerd a coolant treatment that lowers the coolant temp?Good luck!

check out www.radiator.com, i have used them many times they have great tech support and will ship your radiator overnight for no charge.... and there prices blow everyone out of the water...... just my .02 :smokin: