Exhaustive cooling problem thread.

I know the is another one posted tonight, but i didn't want to muddy the waters in that thread. I am about to blow this thing up, I am so fed up. this is going to be long!
This is the 3rd summer since a ground up rebuild of this Jeep and I still can not solve the overheating issues. I built this to camp and explore but I am afraid to take it beyond cell service.
When I say EXHAUSTIVE, I mean it.
I have built several XJ's before this one and knew exactly what to do and how to solve all the problems.
This is a 98 with a completely rebuilt drive train. Motor and head were rebuilt, aw4 was rebuilt along with the tcase. Axles are stock JK 30/44 running stock JK tires and 3.73 gears.
Currently running CSF radiator, locked fan clutch, stock efan, hayden trans cooler, FlowKooler pump, 50/50 mix w/redline additive, 180 thermostat, and hood vents. I have no cat and all new exhaust. There are no signs/indications of head gasket leaks. I have burped it every way possible. Performance is what you expect for 33's and 3.73's.
Temps have been checked with a laser gun and 2 different sensors. Read via OBDII and Torque app.
My normal commute (13 miles in SLC) temps run 225-238!! Surface streets or freeway at 70, AC on or off, makes no difference. Will drop to 220ish if left to idle. Under 80 days it is fine and runs about 210. Winter about 190-200.
Plugs look good, running full synthetic, not using any oil, timing and vacum seem correct via obdII.
I have tried every combo of the following parts. Stock HD aluminum rad, stock water pump, new XJ fanclutch, new ZJ fanclutch, 160/180/190 thermostat (the good ones), 2 different new caps, and bypassing the heater core.
I have flushed it so many times that I would drink the water out of it. (waterpump off and pressure washer in the block) I even pulled the CSF radiator and had it checked and flushed at the best shop in the state.
I am seriously about to put a stick of dynamite under this thing!! I am beyond frustrated!!
I would LOVE any ideas you all have. I am very experience and tried everything I can think of. I went to the forums and have read hundreds of posts. I am at the end of my rope!!!!hasta

I would put on list of questionable parts -CSF radiator and the Flow-cooler pump. CSF radiators have all of complaints. It's a lot hotter here and mine (2 2000's) don't have any issues!

BTW - those gears are not helping the situation.

RCP Phx said:

I would put on list of questionable parts -CSF radiator and the Flow-cooler pump. CSF radiators have all of complaints. It's a lot hotter here and mine (2 2000's) don't have any issues!

Click to expand...

I ran a stock pump and radiator, issue remained.

Which trans cooler do you have(type/size)? And is it a stand-alone cooler?

X2 on the trans cooler. What does your ATF fluid look like?

Listed are some low cost things to help you out. Even if they seem dumb just do them.

-measure the resistance of your E-fan.
-block test your engine. Make sure to pour a control sample into a glass (clear shot glass will do) to compare side by side of the test sample. If you are unsure of what a positive test looks like you can blow into the tester fluid and it will change positive.( You make co2)
-what do your short and long term fuel trims?

The other thing you can look at is the A/C condenser , check to see if the fins are plugged and not letting air get to the radiator . be careful cleaning the fins they can be damaged easy soak it with a good cleaner and rinse it and see if it gets better , you should be able to see though it to the radiator .

Back after vacation and other projects. I have now moved the trans cooler to below the radiator. It is not blocking any flow. I have cleaned and assured flow through the ac condenser. I can see light through it. Checked for exhaust leaks and vacuum leaks.
I have gone through everything here and in other threads. Nothing seems to change it at all.

Seeing as how you have gone through most of the obvious culprits maybe try something exotic.

Read your plugs. Make a run up the interstate at 1000-1200 RPM. pull into a rest stop and pull some plugs hot and take a look. Do the same at 2000-2200 and compare. Hot plug readings can be different from cold tradings, differences can be subtle but noticeable. Take some gloves, long sleeve shirt and some extra plugs just in case you crack one.

Find yourself a thermocouple type type thermometer rather than IR. Measure your exhaust pipe temps as close to head as you can (two inches if you can reach). Again at idle, 1200 RPM, 2000 RPM and higher and see if you can find a lean spot (hot spot). Compare to a known well running XJ. That's how we used to jet carburetors and guess fuel ratios before all the wiz bang stuff was available. A lean burning motor will generate a lot more heat than a rich running motor will. And with the EPA mandates the newer the model, the closer it runs towards too lean. Due to the nature of the programming and possible faulty info from sensors (O2) you may be running lean at certain RPM's, usually near peak torque.

I've used old school thermometers, much easier with a thermocouple a long dowel so you don't burn your fingers and a dab of heat paste. Many of the digital volt meters have a thermocouple plug on them.

I'm just thinking you may have a perfect storm, at certain RPM's, throttle opening a bit more due to the tire load and lowering vacuum some, the programming could be running your motor too lean.

Just a guess, but it seems you may be at the grasping at straws phase in your troubleshooting-

I had persistent freeway speed over heating in one XJ, actually multiple times over many years. Once was I neglected to put the spring in a new bottom radiator hose and the more the water pump pumped the more the hose would collapse. Then again years later the spring that I put in there (obviously Chinese) actually rusted enough to partially disintegrate. Then again when another spring migrated partially into the water pump and left a section of hose without support (wrong diameter). Then again on a top hose when the layers in the hose separated, the inner layer had the consistency of a condom and would partially interrupt flow.

Most of an engine's heat is created in the head. Could it be possible that during the engine rebuild, the headgasket was installed incorrectly? (Covering some of the coolant passages)

I mention this because of all the other solutions that have been tried...

I feel your pain. The hottest part of the engine is the head. If it were my engine, I'd pull the head, have it cooked-out chemically (to clear any head blockages), have it magna-fluxed for visible cracks, and then have it pressure-tested for no-visable internal cracks.
If OK, I'd have the head resurfaced and install the head with a new premium head gasket and ARP head bolts. I would not use the standard available Torque-to-Yield head bolts.

Best regards,

CJR

All great ideas, that I wish weren't. I have wondered about running lean. Is there a sensor I can trick to get it to rich up a little?
At this point I fear I my have to pull the head and check. The engine builder had a good rep, but.... Last time I don't build it myself.
It's frustrating because I built this for camping and I am afraid to push it that far.

Milner said:

All great ideas, that I wish weren't. I have wondered about running lean. Is there a sensor I can trick to get it to rich up a little?
At this point I fear I my have to pull the head and check. The engine builder had a good rep, but.... Last time I don't build it myself.
It's frustrating because I built this for camping and I am afraid to push it that far.

Click to expand...

The O2 sensor would be the most likely sensor to cause a lean condition.

I'd also strongly consider a lean burn condition. Being a 98 it should have two 02 sensors, precat and after cat. If the computer is still reading the second sensor as if the cat is still there it could be pulling fuel trims. I can't remember exactly but the second 02 sensor checks the condition of the cat and adjusts fuel trims based on that.

I hate to say this but what cam did the builder use is it stock ? and how is the cam timing and the timing chain ?