First of all, thanks for having me here at jeepforum. Secondly, maybe you guys can help me with my overheating issue. Jeep started overheating, top hose hot, bottom cold so i replaced the thermostat...twice and still overheated. I have since replaced the water pump, radiator and all hoses and it still overheats. Ran nice and cool without a thermostat, but if i put one in it overheats. I have tried 3 different 195° thermostats. Any ideas? What are tbe chances of three bad thermostats?
Did it just start or was it after some other maintenance? Unlikely multiple back T-stats.
Interestingly enough mine overheated on short trip and purged out the fill tank. Replaced the t-stat and upper hose. No more problems. Tested the t-stat in hot water with thermometer and it was working fine. May have just developed a vapor in coolant. Sounds like you have blockage somewhere.
It just started out of the blue. I tested the third thermostat on the stove. It opened just before the water boiled so it seemed ok. Without it installed i see flow from left to right. I did make sure i had the correct water pump.
Yep, spring side towards the block. I swear I think it's a third bad stat. I'm not seeing any flow inside the radiator when the engine warms up but I do when it's running without one.
Runs nice and cool without a stat. I ran it for a week without it without an issue. I used an aftermarket temp gauge and I was getting over 220 degrees at the radiator fill cap after running it until overheating. I cant find a fitting that matches the threads on the head to permanently mount it. The ones that came with the gauge are too big.
We need some help from YOU. Fill out your profile first.
What year is your CJ, and what engine do you have? If you have a 258 I-6, they run warm as a matter of course. 205-210° is not rare and many run warmer. Lumpy is right; the onboard factory gauge is almost worthless.
Knowing the year of your Jeep can help us with the sender location for the gauge. If you have an aftermarket gauge, you need the correct sender. (We don't know your skill level. Don't take offense if I'm stating the obvious to you.) The sender could be up front towards The T-stat cover or back at the firewall. You can always pull the sender and bring it along with you to the parts house to match.
If you have a V-8 or an I-4, things are different.
Its an 82 with a 258. The sending unit is on the driver side rear of the head. I have a bosch gauge but cant find an adapter. The ones that come with it are too big. I also used a laser temperature gauge. Reading 220ish at the thermostat housing.
I had a Jeep 258 in the shop with a similar/same problem. A shop fan got knocked over and hit the radiator, so I took it to my local radiator repair shop to be fixed. He took the tanks off and found the tubes were "rolled" inwards restricting the coolant flow. I would have never guessed that as it was a new radiator.
The radiator shop fixed the cooling tubes and runs at 195, the same as the stat.
FYI
Get a thermostat housing for a 4.0. Will be around $10 and available at any parts store. It has a place for the sending unit on it. Take the sending unit to parts store to ensure you get the right bushings to marry the sender to the housing. Also get a plug to seal the head or you can use your old sending unit.
Yeah agree. I used a 4.0 thermo and have two gauges wired up. Original from sender at rear of head and and a possibly more accurate one with a degreed scale from the Thermostat housing as pictured. Think port on thermo is 3/8 npt from memory.
Well, when I had that problem, I had a slight head gasket leak. The jeep would drive normal at first, but I kept getting air in the system. When that happens, the thermostat does not open, causing the engine to overheat. I could bleed it and it would work for a little while, until air formed back in the head.
I literally replaced every other part before I realized that. I did a test where I ran without the thermostat, and it ran fine, no overheating. Without the t-stat, the pump is able to push the air right out of the system. So I replaced the head gasket, put back in the thermostat, and now it works great.
But the first step is bleeding the system. Loosening the temp sender is one way.
IF, you are running an OEM type brass core radiator.
Find somedangbody that can do a 'rod-out' to be sure it flows freely.
You SURE you have the correct flow WP installed?
This is a classic sign that you do not-Pull the pump and check the impeller with your old one.
LG
Just thinking out loud here. With out the thermostat he stays cool. With it it overheats. It opens on the stove. Flow from left to right with no thermostat, no flow with it in place. The thermostat adds a restriction to the flow which in turn will cause back pressure on the pump and less flow through the system. So at the pump suction, I would expect there to be a higher level of suction.
Check the lower hose, sounds like it's collapsing.
Ok, finally fixed. I bought a 4.0 housing, stat, and another (better) aftermarket temp gauge. Installed everything and it's running perfectly at 195, stat is opening and coolant is flowing. My factory gauge is reading just under hot so it's obviously wrong. I think this was a combo of bad thermostats and my gauge. My gas gauge also stopped working around the same time, so there's that too. Thanks for all the help, guys!
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Related Threads
?
?
?
?
?
Jeep Enthusiast Forums
18.5M posts
726.7K members
Since 2000
A forum community dedicated to all jeep owners and enthusiasts. Come join the discussion about performance, engine swaps, modifications, classifieds, troubleshooting, maintenance, and more!