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Overheating with curiosity

T

Tony8470

NAXJA Forum User
Location
Murrysville, PA
I think i know what the problem is but since I don't know this jeep very well I'm not too sure.


When I first got this thing 6 months ago, the electric fan was unplugged. I plugged it back in. It would ALWAYS be on, as soon as i turned the ignition on, even before cranking the engine over.

Today, I overheated on a long trip, fan wont turn on at all. Also, the coolant reservior has a crack along the back. But wont leak untill it get to really high temps. Under normal temps its fine. (it will be replaced)

Real question:
The jeep HEATS UP going downhill (no gas). When I get on the throttle it starts cooling down again. And forget stop lights. Thats when the real smoke show happens.


WTF?
 
So......Would you assume that the headgaskets went if you saw steam coming out of the valve cover?

How hard is it to do them in these jeeps? Do I have to disconnect all kinds of accessories? Anyone want a jeep with a blown head gasket?
 
Tony8470 said:
When I first got this thing 6 months ago, the electric fan was unplugged. I plugged it back in. It would ALWAYS be on, as soon as i turned the ignition on, even before cranking the engine over.
Click to expand...

Sounds like the relay.

Tony8470 said:
Also, the coolant reservior has a crack along the back. But wont leak untill it get to really high temps. Under normal temps its fine. (it will be replaced)
Click to expand...

It is NOT a reservoior, it is a pressure bottle and must hold pressure to allow the cooling system to work. Until you replace it, all bets are off.

Tony8470 said:
Real question:
The jeep HEATS UP going downhill (no gas). When I get on the throttle it starts cooling down again. And forget stop lights. Thats when the real smoke show happens.
Click to expand...

Check fan clutch as described above. May not be a bad idea to flush and fill the coolent.

Rev
 
>it is a pressure bottle and must hold pressure to allow the cooling system to work. Until you replace it, all bets are off.

I'll second that! I had a similar problem with boiing over...it turned out all was needed was a new cap!

Are you sure the bottle is cracked and not just the cap leaking?
 
Yeah its cracked in the back. There is debris in it so I can actually see it.

Where is the electric fan relay? I replaced the fan clutch, but it won't engage because for some reason the radiator isnt heating up. Im guessing thats because I need a new coolant bottle. I'll get that tomorrow.
 
Tony8470 said:
Yeah its cracked in the back. There is debris in it so I can actually see it.

Where is the electric fan relay? I replaced the fan clutch, but it won't engage because for some reason the radiator isnt heating up. Im guessing thats because I need a new coolant bottle. I'll get that tomorrow.
Click to expand...
the fan relay should be on drivers side inside fender, real easy to get to. About 25 dollars at the dealer
 
You didn't say what year it is, but the coolant bottle indicates it's the older closed system (like my '88). You need to change the bottle ASAP. Once it fails completely you could get stuck somewhere. (I did!)

When you're coasting downhill, the engine speed drops and so does your waterpump speed. Since you've been leaking coolant, there's likely air trapped in the radiator so it's not full. Therefore, you have less coolant circualting and it moves slower. Once you speed the engine up, the coolant flows faster and cools down everything.

Once you change the bottle and refill the system, you'll need to "burp" it.
 
Just get a thermistat thats 190 Degrees, test it in a boiling pan of water first to make sure it opens, (lots of bad brand new thermistat stories out there.) make sure you install the thermistat with the spring facing in, sometimes in a rush they go in backwards:), And remember to burp the system when you are finished. Good Luck
 
Ok. Replaced the coolant tank and it works now. But I want to get that fan relay fixed too for safe keeping. Its on the drivers side you said? I saw one relay next to some vacuum tree. next to the air filter. Is that it?
 
Tony8470 said:
When I first got this thing 6 months ago, the electric fan was unplugged. I plugged it back in. It would ALWAYS be on, as soon as i turned the ignition on, even before cranking the engine over.
Click to expand...

I don't know if this applies to the Jeep system, but I have an '87 Camaro that had this same symptom from the day I brought it brand new. I thought it was normal at first but after I had the car a while I was poking around under the hood one day and I discovered that the plug going to the AC sensor (on one of the refrigerant lines) was loose, and when I went to re-seat it I saw that one of it's pins was crushed over and never made contact with the sensor. Apparently this "open" made the ECU think the AC was always on, and therefore kept the electric fan on constantly. Fixed the plug, fan runs only when needed now. But like I said,I don't know if the Jeep system works this way or not. Anyone else know?
 
Well, the problem is still there. Highway it overheats. But at idle and in the city its fine. I actually heard the electric fan kick on when I was sitting in the jeep waiting. I'm thinking its the radiator? Anyone else think otherwise before I shell out $140 for it? I also had the cooling system flushed.
 
I am having the same issue, I have changed everthing but the radiator. Oh well, what choice do we have.

Try this number 800 874 0551, I think the name of the company is "1800 Radiator"
I am getting a 3 row CSF radiator for my open conversion for about $101 shipped with warranty.
 
If it is overheating at highway speeds, and you say you had steam/smoke coming from the head, I am going to guess it is a blown headgasket which would also result in high speed overheating.

Yes, definitely go with the OEM t-stat. $13 bucks and built right.
 
Tony8470 said:
So......Would you assume that the headgaskets went if you saw steam coming out of the valve cover?

How hard is it to do them in these jeeps? Do I have to disconnect all kinds of accessories? Anyone want a jeep with a blown head gasket?
Click to expand...

Yes, steam coming out the valve cover not only indicates a blown gasket, but I'd say the head is either warped or cracked. This warping/cracking let combustion gasses and pressure into the cooling system and probably contributed to the cracked pressure bottle. The exact same thing happened to my old '90 XJ.
 
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