Jeep Enthusiast Forums banner

Cooling Question 258 - high temps!

6K views 68 replies 22 participants last post by  valkadesh 
#1 ·
I recently put a rebuilt 258 in my 85 CJ7. It was performed by a local shop and a new water pump was installed at the same time. After i got everything back, i went ahead and installed an autometer electrical temperature gauge so i could see exactly what i was running at.

Driving around town, i'm sitting pretty constantly at 210. My sending unit is on the drivers side of the of the engine block right near the firewall. EGR is hooked up

However, when i get going at a good speed ~60 or so, for any period of time, the temperature starts to creep up. After a brief 5 minute drive at that speed, i was already up to 225 and climbing.

I'm assuming the thermostat is working (and new), because when it heats up around 210, i can see it move back a bit telling me the thermostat has opened up and coolant is flowing.

I have what looks like a 6/7 blade fan (not sure if it's a clutch fan or not). Shroud is installed.

I'm really scared to take it on the interstate for any period of time. Prior to putting in the new engine, my last motor overheated on the interstate and boiled coolant everywhere!

I'm thinking it's the radiator perhaps, but i'm not sure. Also i have a warn 8274 up front which sure isn't helping the air flow.

Ideas? bigger radiator?

Thanks!
 
See less See more
#2 ·
This is a basic question, but I didn't see it addressed in your original post. Has the radiator been boiled out? New hoses? Have you taken the thermostat out and run for a while and watched the gauge. My first thought is that the radiator is partially plugged or the fan is not movinig enough air. Air movement is not as a big an issue at highway speeds though. Good luck and God bless.
Jon In Tucson
 
#7 · (Edited)
Well i did some research tonight. First i took the rad cap off and warmed up the engine, i can see the coolant moving up and down so i'm assuming that the thermostat is working correctly. Also with the cap off, my gauge was on 195 with the engine warm.

I replaced the cap and the temperature immediately moved up to the 210 range when it stayed indefinitely when idle.

I then took it out on the interstate and ran it for about 5 miles. I was near 225, and when i exited the interstate it shot up to 240. Once i idled for a while at a nearby gas station is returned to 210.

I also picked up a temperature gun tonight and shot the thermostat housing while it was idling (temp gauge showing 210), the housing read between 195-200. Assuming the coolant inside is a bit warmer, i assumed this to be correct.

Going through receipts tonight, apparently i put in a new radiator about 2 years ago with new hoses, and i had only put 2500 miles on the jeep since. The radiator is the kind with the drivers side off-center fill cap. It appears to look like new upon inspection. I also appear to be running a clutch fan.

Any other thoughts? I'm kinda stumped at this point as to next step....
 
#11 ·
Going through receipts tonight, apparently i put in a new radiator about 2 years ago with new hoses, and i had only put 2500 miles on the jeep since. The radiator is the kind with the drivers side off-center fill cap. It appears to look like new upon inspection. I also appear to be running a clutch fan.
When you replaced the radiator, I assume you replaced it with another 2-core? That's your problem.

From what you have posted about the Jeep getting hot when on the highway (when coolant is passing though it much faster than when at idle), I suspect you have insufficient heat exchange occurring due to insufficient dwell time. That means that the coolant is not remaining in the radiator long enough to be cooled due to the increased coolant circulation rate. Doesn't matter how much air you try to move across the radiator at this point. Your radiator just doesn't have the required cooling capacity. You need more surface area and more coolant volume. The only way you're going to get that is by installing a larger radiator.
 
#8 ·
The problem might not be the cooling system. If the engine is leaning out at highway speeds, chamber temp rises which would drive overall system temps up. I would think about an aftermarket AFM and o2 sensor. Not a bad investment to aid in tuning.
 
#10 ·
Well i thought I'd update this and solicit some more help. As you can see from my profile, I've got a Warn 8274 winch installed which is massive. I took the winch off and took the jeep for a drive, temps stayed constant at 210. So I'm guessing at highway speeds i'm not getting enough airflow through the grill and the clutch fan is not working hard enough.

So i went ahead and spent the big bucks and ordered a flex-a-lite 575 which is supposed to be fit the CJ like a glove.

I removed the clutch fan and shroud, and I went to install the new electric fans. Problem: I've got maybe 1/4 to 1/2 inch clearance between the water pump and the fan grill, and there is a big gap at the top of the radiator. Any thoughts? I'm stumped at this point. I've read the directions about 10 times and i'm pretty sure i've got everything setup correctly....

pictures enclosed (the wiring isn't hooked up, so ignore that)



 
#12 ·
I believe that i have the "high performance" 2 core model (with the driver's side rad cap). There is a 3 core that is actually cheaper, but people claim the 2 core actually works better. I know the 3 core is quite a bit thicker and has a center cap.

I guess i could drop the $200 on the 3 core radiator, but even then i don't think my new fans will fit. I'm assuming the 3 core will have the same..or less clearance!

Maybe i'd be ok with the clutch fan and the new radiator. I'm about out of options.

You'd think a stock 258 even with a big winch wouldn't be this complicated :(
 
#18 ·
but people claim the 2 core actually works better.
Where did you see that?

I guess i could drop the $200 on the 3 core radiator, but even then i don't think my new fans will fit. I'm assuming the 3 core will have the same..or less clearance!
You probably won't need the new fans anymore. Plenty of CJ's came with 3-core radiators. If you buy the correct unit and it is all assembled correctly, there should not be an issue.

Maybe i'd be ok with the clutch fan and the new radiator.
That's what I would expect, but I'd add a shroud. If you still want to utilize auxilliary fans after reconfiguring, you can still run them in front of the radiator. Push/pull does not matter - there is no difference. Airflow moving from the front of the radiator into the engine compartment is all that matters.

However, I would check on a few of the other things that people mentioned, such as making sure that your hoses are not sucking shut and that you do not have pressure leaks that surface once you get rolling.
 
#13 ·
One way to get more fan clearance is to remove the studs in the water pump pulley flange and use short bolts to keep the pulley on.

I'd agree about the radiator capacity though. I have the 3core on my '75 with an 8274 in front of it. My engine is the 258 with EFI and never has a problem with cooling even in 100°+ temps wheeling in Moab.
 
#16 ·
You have the "heavy duty" radiator. I have the same one with a winch and tranny cooler in front of it and Contour fans.She runs cool as a cucumber. I wonder if your rebuild shop put in the wrong water pump. The serpentine pump runs backwards.
 
#17 ·
I'm having the same issues, same deal with the 8274 mounted. I run the mopar mpi.
If you change to the 3 core radiator and fan clutch you stand a good chance to put the fan clutch into the radiator core (ask me how I know).Not enough clearance.
Do you have a spring in the lower hose to keep it from collapsing?
Was your rebuild stock?
The mopar kit tends to suck a little oil into the throttle body which raises cylinder temps. any issues with that?
Do you have an overflow bottle?
Have you pressure tested your radiator cap?
Check out Novak, they have a cooling section with some good info.
 
#19 ·
I'll try and answer a few of the above questions:

--Not sure on if i have a spring in the lower hose, i kinda doubt it.
--my 258 rebuild is completely stock as far as the motor is concerned
--I do have an overflow bottle hooked up, rad cap is new (tried 2 caps to be sure)
--I'll have to check with my shop to see if they kept any record of the part number for the water pump, is there any way to tell with it installed?

I was going to get a 3 core radiator, and try hooking up the clutch fan and shroud, but it sounds like there might be clearance issues with that too.

With my 2 core in, there is a decent "gap" between the front of the radiator and the grill. I guess i just assumed the 3 core would fill that gap and leave me with similar clearance...
 
#20 ·
Clutch fans can wear out... Then the Fan does not read the temp correctly and will not "lock up" to spin the fan blades. When the Clutch Fan fails it will not pull the correct amount of air and can over heat. There is a test process in the Jeep FSM for the clutch fan. The idea is the clutch slips when you hit the gas and yields quicker rpms and more pep, but when hot the fan clutch does not slip and maxes the cooling.

The lower hose needs to have a spring installed to keep the hose from collasping. You have 2+ year old hoses so they are softer and could be sucked shut at highway speeds and higher rpm running,,,, just the wrong time to suck closed when you need cooling. For this reason, your post on hwy overheating, I think this is part of most of the issue.

The 3 core is thicker than the 2 core. I have the 3 core in a 78 and fits fine. So that could be an option for you.

Inspect the radiator.... if the top of cores are blocked with mineral deposits then there is limited water flow. This is why it is suggested you use distilled water and antifreeze in the radiator. We have hard water here in MN and every house has a watersoftner. YOU SHOULD ALWAYS use distilled water in radiators. The top of the verticle flow tubes is one of the locations the radiator likes to plug with minerals and cuts down your water/collant flow.

I have read.... The water pumps are two styles the std and the reverse flow for the serpentine belt. The inlet hose is mounted in different spots on the water pump and should be able to tell that way. Also the flow should be comming away from the top inlet hose with the cap off.

MY VOTE is your bottom hose is collasping and you may have mineral deposits. The problem in the first set up the clutch fan was worn out and not cooling properly.

Fred
 
#21 ·
Just a quick update. I drained most of the radiator last night and took a good look inside, it's really clean. I also inspected the water pump closer and found a part number stamped on the outside (31178 A) or (31176 A), it could be either a 6 or an 8 for the last number. I know my builder got the part at O'reily, but that number doesn't come up on their site or anywhere on the internet!

I guess i'll be making a trip down there to see if they are willing to open some boxes for me so i can match that part number. I'd like to ensure i've got the correct "V" style water pump on there.

If it's fine, i'm going to get the radiator checked, go ahead and replace both radiator hoses, and potentially change out the fan clutch.

The fun continues! Thanks for all the great suggestions so far!
 
#22 ·
Another update. To make a long story short, i'm pretty sure it's the correct water pump. Going to pull the radiator out tonight and get it checked, and i'll probably go ahead and replace the fan clutch and upper/lower hoses. I'll update again in a few days.
 
#23 ·
forget the clutch fan. you have a awesome electric fan to use. the three core radiators are thicker, but they are thicker towards the grill and not the engine, so clearance isnt a problem. you might have a air pocket in the cooling system that is causing the overheating problems. i have heard of this happening before and there is a way to burp the air out, but i dont know how. maybe someone who has done this before can provide some more info.
 
#24 ·
How many miles on the rebuild? New engines will run hotter for awhile until they break in. Both of my rebuilds ran really hot then settled down after 1500 miles or so.

I agree take the studs out of the water pump and replace with bolts IRRC 5/16 fine thread and route your wiring away from the sheave.

Run your current setup and see how it goes before going to another radiator.
 
#25 ·
Thanks for the tips. I'd still like to get the radiator "checked" it won't be expensive. I've heard of people with the clutch fan and the 3 core (with center cap) having clearance problems with that setup. One step at a time i suppose....

Oh the rebuild has about 500 miles on it i suppose, so that may be a cause as well.
 
#27 ·
Check your exhaust for restrictions. My 5 ran really warm from the day I bought it, and I tried everything, I finally got it to stay around 220 with a 160 degree thermostat. Then when I had new exhaust installed, we found an old blown out donut gasket turned sideways and dropped down inside the exhaust pipe. Now she stays nice and cool.
 
#28 ·
fwiw from a newbie, i adjusted my timing from 1 degree btc to 5 degrees and the cooling was immediate. the dash gauge dropped from halfway in the middle from c(old) to h(ot) to a little bit above c(old) but on the red line that connects "c to h". power was much improved.
 
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top