Overheating and already replaced all the usual suspects

Airflow seems an unlikely culprit to me because the fans will keep it cool, right? Airflow from motion will override fans after 30 mph or so. All I can figure at this point is pressure loss leading to pump cavitation or water flow. I might be wrong though so shine a light on one side of the condenser/radiator stack and see if the fins are jammed up. Lower skid shouldn't matter.

The fins are all fine. I spent many nights cleaning and straightening fins on the ac condensor, the radiator looks great too.

Do you know of a way to test for pump cavitation?
Thanks!
 
I don't.
What I do know is how to test for pressure loss. Go to a mechanic, or get one of these or similar. The reason you need to verify pressure capacity...
The radiator cap increases the boiling point of your coolant mix by 3 degrees for each psi it holds (if I remember correctly)
So if your OEM 16 lb cap is holding, and you have no other leaks (important!) your coolant mix is good for an additional 48 degrees.
Now, the important part is that if your system isn't holding 16 psi - for the sake of argument, say the cap is off - then coolant at the water pump / in the block can boil. Instead of a stable liquid, the water pump is now trying to move a bubbly mess - which it isn't designed to do and can't do very well. Since water isn't moving very well, it just keeps getting hotter.
Hmm.
Have we already asked if the upper & lower radiator hoses are getting really firm as well as hot? You want to feel pressure building as temp rises.
Sigh. I don't remember everything we've gone over already. I might be beating a dead horse on leaks or pressure loss. Are you losing or smelling any coolant?
 
Sigh. I don't remember everything we've gone over already. I might be beating a dead horse on leaks or pressure loss. Are you losing or smelling any coolant?

Thanks for your patience and help on this.

The only coolant leak I found was while I was back flushing everything and I had some dripping from under the heater core, Ive since bypassed the heater core with some brass fittings.

As for loosing coolant, it's been hard to keep an eye on the coolant recovery with all the burping and switching back to stock radiator etc...

I'm not smelling any coolant.

The temperature of the hoses seem to be correct as measured with IR and according to my untrained feel, I do believe them to be on the firm side.

I'll do a pressure test next and see what happens there. I am starting to feel like a mechanic would be a good idea, but I don't have one that I would trust to do anything. I just got burned by my gf's mechanic on her lexus, who tried to charge us $200 for a diagnostic that yielded no results and some b*llsh*t contact cleaning. Two weeks of googling and reading the fsm solved our problem with a clogged oil control valve filter =) I never heard of one, the mechanic never heard of one either and he claimed to be a lexus enthusiast =)

There was some question as to whether I am really over heating because there is no boiling over. A new oem temp sensor and my temp gun corroborating my gauge hopefully shows I'm not chasing ghosts

Also if anyone has recommendations for a decent mechanic in my area or within a decent driving range I'm all ears. Hell... if any forum members care to spend a saturday or sunday troubleshooting, I'll gladly pay for some beer and time.:cheers:

Well, thanks again.
 
you put the old rad back in? Are you sure it isn't restricted internally?

Your right, and I'm keeping that in the back of my mind. I will get a new oem rad after I get the new aftermarket one returned.

I just need to get back to basics on this problem. The previous posts on pressure and and a scangauge 2 are great ideas with the first one being free so I'll start there.

Hopefully the block test being negative gives some measure of security that my engine is still healthy as that's my biggest fear.
 
If you have an Android device, you can get an app called Torque for $5 and a bluetooth OBDII adapter for between $10 and $25. It will let you look at the sensor data for a lot less than a ScanGauge.
 
If you have an Android device, you can get an app called Torque for $5 and a bluetooth OBDII adapter for between $10 and $25. It will let you look at the sensor data for a lot less than a ScanGauge.

Great minds think a like. I was in the middle of ordering one when I saw your post. I wanted to do that some time ago and now I have a good justification for it. I also made a custom mount for an old droid that I have dedicated as my jeep vehicle computer. Topo maps, blm maps, ohv trails and music, now obd diagnostics =) I'm also in the middle of designing an interface from my android to my cb radio so that I can annoy my friends with bad soundboards of arnold schwarzenegger and christian bale either across the radio or through the PA =) haha good times
 
I had some of what I thought were UNDER heating woes a while back. Turned out that all I needed was a new gauge sensor. On my 96 the PO got it cheap from a kid that ran it without coolant and cracked the head. The PO is the son of a local mechanic with a great reputation. They replaced the head and the entire valve train.

I rig never got up to 190. I asked the PO what kind of thermostat had in it and he said the OEM 195. Anyway after a host of other issues, and not trusting the temp gauge, I tried a different approach and it at made all of my entire instrument panels more sensitive, though not necessarily more accurate was clean the bulkhead connector. I live in SW Florida an my rig sees a lot of water. So after changing ALL of the fluids. I then started to go after EVERY single electrical connector. I cleaned each of them out thoroughly with electrical cleaner, gave each side a dose of electric grease, then I wrapped each one with heat shrink tape and shrunk it. That alone made a difference, though ever so slight, in how rig behaves.

However, the big difference came when I cleaned my bulkhead connector. It is very easy. just time consuming. When I opened it up, it looked like somebody used asphalt tar instead of electric grease. I got as much out as I could with a small flat head screwdriver at first. Then after electrical cleaner wasn't cutting it I broke out the brake cleaner. I used a variety of picks, toothbrushes, Qtips to get all of that tar out of both the male and female side of the connector. When It dried, I put a small copper barrel brush form my weapons tool box in to the end of my dremel, then roughed up all of the male pins. Then I bent each of the male terminals just a hair. Cleaned it once more with some electric spray, then some compressed air. Applied a light amount of electric grease. Put it back together. Then sealed the outside with some RTV silicone to further protect from the elements.

As soon as I started it up, I noticed EVERY electrical component inside of my jeep was FAR more sensitive to activation/deactivation. Before my gauges were sluggish and seemed to move really slow. My oil pressure gauge is very sensitive now. Before on the highway, it would just hover and now its a lot more twitchy. My temperature gauge is reading dead on with my IR gun, originally the needle always ran at 190 and just crawl higher or lower. It immediately rose to 210 and is very active from 195-220. Even my voltmeter is more sensitive. All of my power windows are still not very fast BUT the second I hit the button to roll them down, where there was some sluggishness, now as soon as I hit a button I notice an immediate response at my volt meter. I can think of a few times now that I could have definitely cracked a head by think the temp was actually 10-15 degrees warmer than the gauge was telling me.

I know this is a little off track, but its the easiest FREE thing you can do if you want to have a little more faith in your instrument panel.
 
Great minds think a like. I was in the middle of ordering one when I saw your post. I wanted to do that some time ago and now I have a good justification for it. I also made a custom mount for an old droid that I have dedicated as my jeep vehicle computer. Topo maps, blm maps, ohv trails and music, now obd diagnostics =) I'm also in the middle of designing an interface from my android to my cb radio so that I can annoy my friends with bad soundboards of arnold schwarzenegger and christian bale either across the radio or through the PA =) haha good times

Can you post some links where you're getting this stuff?
 
Can you post some links where you're getting this stuff?

Sure,
For topo maps, blm, and ohv trails I use backcountry navigator with acuterra premium map source and blm and ohv overlays.
http://backcountrynavigator.com/
total of about $30 but worth it for me, I'm a pretty avid hiker

For google satellite view and other sources of topo maps I use mytrails
https://play.google.com/store/apps/details?id=com.frogsparks.mytrails&hl=en
about $5

The mount was a modified universal that I cut the wire that holds the suction cup and threaded the wire and put a backing plate and screwed it into the dash, it actually looks very clean and worked great
 
Ok, the cooling system pressure test was a very good suggestion. I'm still reading up on the different ways to use it. I rented one from autozone, and quickly found out on my radiator caps thats I could trust the gauge. I went to 2 different stores and ended up at an orilleys that brought out a brand new one. We just kept testing one until we found one that was accurate and held pressure.

My suggestion is that if anyone else is looking to rent one, bring in your radiator cap and test the pressure tester in the store, if your cap doesn't hold pressure correctly according to the gauge, ask them for a new cap and test that one too. If it doesn't work ask for another tester. Go home when when you finally have a good tester and cap. Bring a bottle of water to put on the seals and cap while testing too. If the store isn't ran by jerks they should understand.

So I found one leak thus far, one of my factory spring clamps seems to have lost some tension from the tstat housing heater hoses. I cut the hose a little shorter to get a fresh seal with rubber, I cleaned up the housing side a bit on the nipple, gave it a little bit of indian head sealing shellac, and put a new worm gear hose clamp on it.

It ran better but it still was getting up to 230 degrees. I think I still have another leak that I'll go searching for tonight and my radiator might have some clogs, I'll try to trace that with an IR temp gun and I still have my bluetooth obd2 coming in tomorrow for some more accurate temp readings.

It's not fixed by any means, but at least I got a small victory last night. Thanks everyone!
 
Glad the pressure test found something. Also - only pump it up to the pressure rating on the cap, 16 lbs in our case.
Hope you find the gremlin soon... Suspect the radiator, but verify before spending any more $$.
 
Is there a good reason that I should put my tstat back in, or can I leave it out until I get the cooling issue resolved?
 
You might set a check engine light (don't know if our XJs have that code) but no, you won't hurt anything not running a tstat for a while.
 
Is there a good reason that I should put my tstat back in, or can I leave it out until I get the cooling issue resolved?

Coming into this conversation late. To answer your question, put the thermostat back in. The T-stat does more than control temperature; it also controls flow through the system. Its possible that water can flow through too quickly, and not get a chance to transfer heat properly. Further, eventually, you'll need to put it back anyway, and you don't want to be introducing additional differences while you're troubleshooting.

I fought overheating issues for close to two years. Some of these things I'm sure you've done, but my eventual solution was to replace the electric fans with a stock mechanical fan, with the ZJ fan clutch, and a late model stock electric auxiliary fan I also added hood vents. My factory temperature gauge still reads high, but an separate gauge with the sender directly in the upper radiator hose reads normal.

David Bricker / SYR
 
Coming into this conversation late. To answer your question, put the thermostat back in. The T-stat does more than control temperature; it also controls flow through the system. Its possible that water can flow through too quickly, and not get a chance to transfer heat properly. Further, eventually, you'll need to put it back anyway, and you don't want to be introducing additional differences while you're troubleshooting.

David Bricker / SYR


Since a cooling system is a closed loop, (even an open cooling system is still a closed loop) it is impossible for coolant to move too quickly through the system. More flow is always better.

If the coolant was moving through the rad faster than it moved through the block you may be right, but having no thermostat won't make that happen.
 
Since a cooling system is a closed loop, (even an open cooling system is still a closed loop) it is impossible for coolant to move too quickly through the system. More flow is always better.

If the coolant was moving through the rad faster than it moved through the block you may be right, but having no thermostat won't make that happen.

THIS IS EXACTLY WHAT I WAS THINKING--therefore, I have replaced my radiator with three lengths of copper tubing, each is THREE INCHES IN DIAMETER--as more flow is always better.

Strangely, my engine is now running hotter. :D
 
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