Overheating Problems...

[Coach]

I have a strange issue with my '86 CJ7 , it overheated twice today. It was slow to build, both times were right at about 8 miles. It is blowing out of the radiator cap and nowhere else. It heats up to normal, stays there, then builds right at 7-8 miles of driving. Stop and go driving both ways and it's heating up while I drive, not when stopped.

I thought it might be a leak and it was getting low, then overheating. But I checked then level before leaving for home and it did it again.

My radiator cap seems very easy to take off and I think it had 16lbs written one top.

So could it be the radiator cap, maybe the water pump, or something else. Any help would be greatly appreciated. I hope this makes sense, is hard to describe, but I'm hoping someone has experience with an issue like this.

Thanks,
Coach

 

[firedocs]

Maybe the thermostat, it will sometimes close when it should be open, That will cause "no flow" and things will get hot. Its an easy fix if that's it.

Tim

 

[Coach]

Alright, so what temp should I get? They range from 160, 180, and 195. I can't manage to find which mint be best.

I think you are right after reading others with issues. My temp was super low for about two months, than started worked this week, followed by my issues today. I guess it could have been stuck open, then snapped shut.

Thanks,
Coach

 

[CJ007]

Hey Coach, hopefully thats all it is. I would also check a few other things. First check the bottom hose, if it's really soft and there is no spring (rusted out?) they tend to buckle and reduce flow. For the Water Pump you can sometimes can see seepeage when they are bad. There should be seep hole(s) on the bottom that will have a little water or lime/rust runoff. I would also change the cap if its old and loose.

Look in the radiator too, you may or may not see anything, but if it's old/dirty you probably should flush, even with a water hose just to see whats in there. And, if you haven't done so, pull the dipstick and make sure you oil is not whitish foamy to get an idea if it's the head gasket.

If have any other details or have worked on anything lately, post it as it may help narrow it down. Good luck!

 

[Coach]

Oil looked good and the color it should be, that was one of my first fears. My radiator does look pretty rough inside, so when I'm changing everything out, I'm going to flush it really good. Plus, I'm rebuilding my heater box, thats the only thing I have been working on in relation to the engine or cooling system.

I'm going to go over all the possible hoses under there too, since I'll be draining the system anyway and can knock out as much as I can at one time.

I appreciate all the help, that is why this is such a great site, you can always count on people for help and advice around here.

Thanks,
Coach

Hey Coach, hopefully thats all it is. I would also check a few other things. First check the bottom hose, if it's really soft and there is no spring (rusted out?) they tend to buckle and reduce flow. For the Water Pump you can sometimes can see seepeage when they are bad. There should be seep hole(s) on the bottom that will have a little water or lime/rust runoff. I would also change the cap if its old and loose.

Look in the radiator too, you may or may not see anything, but if it's old/dirty you probably should flush, even with a water hose just to see whats in there. And, if you haven't done so, pull the dipstick and make sure you oil is not whitish foamy to get an idea if it's the head gasket.

If have any other details or have worked on anything lately, post it as it may help narrow it down. Good luck!

 

[MN CJ7]

What temp thermostate got me too... the 195 F is the right one.... the water heats up the water jacketed intake and helps with the fuel atomization and steady temp. I believe to be correct and will take a look after I post.

X2 on the lower hose has the spring and without the spring the lower hose is under suction and can collaspe the lower hose... and that limits water flow. Happens at higher rpms, more flow from pump, and more suction.

The 50/50 mix helps keep from over boil. The elevated psi on cap also raises the boiling temp. So a mix of 50/50 and the proper radiator cap with 16 psi both will help stop boil overs.

The last idea... and you most likely have it is a failed clutch fan. I say you most likely have a clutch fan because you are in TX, auto Transmission , and a 86 so you may have the HD Cooling. HD Cooling has 3 core rad, clutch fan, fan shroud, overflow container so the cooling radiator stays full all the time. The Clutch Fan has a bimetal spring that grabs when the temp rises and the fan spins full speed. When under operation temp the clutch is free wheeling and uses less energy from the motor HP. When they fail they do not grab and thus do not cool right. Since this is happening at speed this might be the issue too.

I would also look at your radiator internal. The tubes / passages can be seen from the rad fill hole. If these are all caked up with minerals that is a issue for cooling and flow. If the tubes are not pretty open... another reason to do a flush and fill.


My guesses would be the clutch fan or failed thermostate

 

[Cheepjeep85]

The 50/50 mix helps keep from over boil. The elevated psi on cap also raises the boiling temp. So a mix of 50/50 and the proper radiator cap with 16 psi both will help stop boil overs.

I can't understand why anyone would pay for a 1/2 gal of antifreeze and 1/2 gal of water, I've always thought that 50/50 was a racket. I mean I have a water hose and a antifreeze checker at home, im not spending the same money as a reg gal of antifreeze for half of it to be water. Rant off.



Sent from my DROID2

 

[MN CJ7]

I can't understand why anyone would pay for a 1/2 gal of antifreeze and 1/2 gal of water, I've always thought that 50/50 was a racket. I mean I have a water hose and a antifreeze checker at home, im not spending the same money as a reg gal of antifreeze for half of it to be water. Rant off.

I agree on some and will add some caution.


I am also cautious on the Premix Antifreeze that is mixed at 50/50. I never said the poster needs to buy 50/50 mix or the 100% Antifreeze. I usually buy the full strenth and buy a gallon of distilled water and mix my own. BUT.... if traveling and need some coolant because low.... that mix is a dream to use then.

Not that it matters.... but the 50/50 pre mix antifreeze is much less expensive than the 100% antifreeze. The antifreeze company is adding 50% distilled water. It is up to the buyer i guess.

I disagree and caution the suggestion to use the hose for tap water.
The Caution...... I would never recommend tap water or water from the hose as you say. Tap water has minerals and can leave deposits in your engine, passages, and radiator. The minerals precipitate out and coat the cooling internals. The minerals comming out of water solution will coat and look like a coffee maker on the bottom. Other tap water areas can have iron, sulfur, very high calcium levels, and other issues.

Poster.... could have pluged cooling tubes from using tap water. You could too. The use of tap water and the known issues is why I suggested poster inspect his cooling tubes. This would be a great example inspecting a radiator internal and seeing the cooling tubes that make up the 2,3,4 core radiators get coated with calcium/minerals. Once the minerals coat and block / plug the small passages and lowers the coolant flow and heat dissapation. This happens often and I guess our conversation shows just that.

That is why i mention above for poster to look at the radator cooling tubes.

A CHEMICAL FLUSH can possible remove coolant deposits if this is a issue. ( this has not been ruled out for the poster yet) I am not sure how well these chem flushes work.

For poster and readers.... if the radiator tubes are plugged its a issue. Chem clean might work... A new radiator with the high price of copper will run between 200 and $400 for our CJ's. I had to buy a new CJ radiator about 4yrs ago it $200 + ship. So I guess that $5 gal of premix 50/50 antifreeze is looking like a pretty good deal. Even the $10 full stength antifreeze if a good deal compaired to replacement radiator.



50/50 Antifreeze gen info and FYI......

Water is better at removing heat from engine than water/antifreeze
Water/Antifreeze will boil at a higher temp than waters 212F sea level
CJ use a 195F thermostate so not too far from 212F.
Std Radiator Cap will pressurize the cooling system and raise the boiling temp.
50/50 Mix and 16 psi cap will boil at ( I estimated ) 240 -260 Deg F
Water/Antifreeze mix protects against corrosion (engine & radiator)
Water/Antifreeze mix lubricates the water pump
Water Antifreeze mix removes acids and impurities from engine & should be on a PM for antifreeze changes.

 

[Coach]

MN CJ7 , thanks for all the good information. I didn't realize some of that and it is good to know. I'm not sure what the PO put in the radiator over the years, but looking inside I am led to believe it may have been muddy creek water at some point.

I'm going to give it a good flush, I don't want to replace the radiator yet, since I'm planning an LM7 conversion in about a year and it will need a new radiator anyway.

I appreciate you taking the time to help me out and for the detailed information.

Coach

 

[MN CJ7]

Coach,

You are welcome. Let us know how your work moves along with the overboil.

 

[MN CJ7]

Since you will be doing motor and cooling work in the future.

This is the best tech article for cooling I have found. On another site but stilll very good and may show you a few good points. Long article but very good. HINT.... I copy such article into Microsoft WORD and then save to my hard drive. Works great and verbage and pics copy over Cut/paste.


Pirate4x4.com - The largest off roading website in the world.

The cooling system – deceptively simple yet devilishly complicated. Like many things – your rig’s cooling systems is one of those things that seems simple, that most people think they understand, but which, behind the scenes, is actually a lot of fairly complicated stuff working together in a fine balance. Or not working together well – which is often the problem.
In reality, “under the hood”, cooling systems contain a lot of pretty sophisticated engineering – laws of thermodynamics, pressure, turbulent and boundary-layer flow, aerodynamics, etc.
As a result, because cooling seems simple, even though it isn’t, a LOT of misinformation and tenacious long-lasting myths exist surrounding it.
So, let me get this out there – designing a complete cooling system is no easy task – especially if it’s for a high-performance rig that’s run hard. It takes a lot of know-how. So what are you to do?
Well

 

[Cheepjeep85]

I agree on some and will add some caution.


I am also cautious on the Premix Antifreeze that is mixed at 50/50. I never said the poster needs to buy 50/50 mix or the 100% Antifreeze. I usually buy the full strenth and buy a gallon of distilled water and mix my own. BUT.... if traveling and need some coolant because low.... that mix is a dream to use then.

Not that it matters.... but the 50/50 pre mix antifreeze is much less expensive than the 100% antifreeze. The antifreeze company is adding 50% distilled water. It is up to the buyer i guess.

I disagree and caution the suggestion to use the hose for tap water.
The Caution...... I would never recommend tap water or water from the hose as you say. Tap water has minerals and can leave deposits in your engine, passages, and radiator. The minerals precipitate out and coat the cooling internals. The minerals comming out of water solution will coat and look like a coffee maker on the bottom. Other tap water areas can have iron, sulfur, very high calcium levels, and other issues.

Poster.... could have pluged cooling tubes from using tap water. You could too. The use of tap water and the known issues is why I suggested poster inspect his cooling tubes. This would be a great example inspecting a radiator internal and seeing the cooling tubes that make up the 2,3,4 core radiators get coated with calcium/minerals. Once the minerals coat and block / plug the small passages and lowers the coolant flow and heat dissapation. This happens often and I guess our conversation shows just that.

That is why i mention above for poster to look at the radator cooling tubes.

A CHEMICAL FLUSH can possible remove coolant deposits if this is a issue. ( this has not been ruled out for the poster yet) I am not sure how well these chem flushes work.

For poster and readers.... if the radiator tubes are plugged its a issue. Chem clean might work... A new radiator with the high price of copper will run between 200 and $400 for our CJ's. I had to buy a new CJ radiator about 4yrs ago it $200 + ship. So I guess that $5 gal of premix 50/50 antifreeze is looking like a pretty good deal. Even the $10 full stength antifreeze if a good deal compaired to replacement radiator.



50/50 Antifreeze gen info and FYI......

Water is better at removing heat from engine than water/antifreeze
Water/Antifreeze will boil at a higher temp than waters 212F sea level
CJ use a 195F thermostate so not too far from 212F.
Std Radiator Cap will pressurize the cooling system and raise the boiling temp.
50/50 Mix and 16 psi cap will boil at ( I estimated ) 240 -260 Deg F
Water/Antifreeze mix protects against corrosion (engine & radiator)
Water/Antifreeze mix lubricates the water pump
Water Antifreeze mix removes acids and impurities from engine & should be on a PM for antifreeze changes.

Neverhad a problem with tap water. Thank you


Sent from my DROID2

 

[Coach]

Since you will be doing motor and cooling work in the future.

This is the best tech article for cooling I have found. On another site but stilll very good and may show you a few good points. Long article but very good. HINT.... I copy such article into Microsoft WORD and then save to my hard drive. Works great and verbage and pics copy over Cut/paste.


Pirate4x4.com - The largest off roading website in the world.

The cooling system – deceptively simple yet devilishly complicated. Like many things – your rig’s cooling systems is one of those things that seems simple, that most people think they understand, but which, behind the scenes, is actually a lot of fairly complicated stuff working together in a fine balance. Or not working together well – which is often the problem.
In reality, “under the hood”, cooling systems contain a lot of pretty sophisticated engineering – laws of thermodynamics, pressure, turbulent and boundary-layer flow, aerodynamics, etc.
As a result, because cooling seems simple, even though it isn’t, a LOT of misinformation and tenacious long-lasting myths exist surrounding it.
So, let me get this out there – designing a complete cooling system is no easy task – especially if it’s for a high-performance rig that’s run hard. It takes a lot of know-how. So what are you to do?
Well

Thanks, I have saved that into Evernote along with all the other info I'm accumulating for the future engine swap. I didn't have much on cooling, but knew that it was a complicated part I needed more info on.

Will update this weekend when I finally get to work on the Jeep.

 

[Coach]

I'm back and have a couple of more questions. Finally got some time to work on the Jeep and picked up most of the parts I need to get the thermostat installed.

I decided to finish my heater box since I would be flushing the radiator and draining everything to install the thermostat anyway.

My question is, what size hoses are supposed to run to the heater core and back to the engine? I have one that has 11/16 on the outside and the other I swear is 5/8's (nothing written on it), they aren't the same size for sure. I really don't want to pay for the preshaped ones, but don't know what size heater hose is supposed to go on there. Any help would be greatly appreciated.

Thanks,
Coach

 

[MN CJ7]

I'm back and have a couple of more questions. Finally got some time to work on the Jeep and picked up most of the parts I need to get the thermostat installed.

I decided to finish my heater box since I would be flushing the radiator and draining everything to install the thermostat anyway.

My question is, what size hoses are supposed to run to the heater core and back to the engine? I have one that has 11/16 on the outside and the other I swear is 5/8's (nothing written on it), they aren't the same size for sure. I really don't want to pay for the preshaped ones, but don't know what size heater hose is supposed to go on there. Any help would be greatly appreciated.

Thanks,
Coach

Coach,

I used 7/8" ID hose because it fit the front of engine. The 7/8 did nto want to seal over the heater core pipe. I tried several times and kept leaking.

I tried to use 5/8 and could not get it to stretch over the 7/8 on the front of engine.... and just cut my knuckles a few times.

I found a plastic neck down adapter from 5/8 to 7/8" so used the 7/8" hose for most of the lenght and then by the battery use the neckdown to 5/8" and never leaked with that combo. The adapter cost about $2 and was Autozone if I remember right. I used a couple of zip ties to the battery box so all the weight of heater hose and enclosed water was not stressing the heater core tube. 2 years and no leak.

Hope that helps,

fred

 

[Coach]

Finally got my heater box back in the jeep and all bolted up. Did the motor upgrade while I had it out and rebuilt and sealed the whole box up. Took a while to wrestle it back in through the new hole I cut and around the AC system.

Added all new heater hoses and clamps. Haven't replaced the thermostat next, but will this weekend.

But, in true CJ fashion, I buttoned everything down and wanted to take it for a quick spin around the block and it was after dark. While idling and flushing the radiator, I would turn on my parking lights to check my temp guage. All was well, so I pulled out of the driveway and looked down and my dash lights were out. Though maybe I had turned the light switch and dimmed them down, but no, they were out. So one problem solved and another presents itself. The CJ7 is proving to be a never ending hobby.

I'm hoping it just blew a fuse, but didn't feel like chasing down another rabbit tonight.