Overheating and already replaced all the usual suspects

[techno1154]

So far I can only get about 2 gallons in my system and .5 in the overflow tank... maybe I need to bleed the system better to get that .5 in there still.

It is quite normal for the XJ radiator to take only 2 gallons. My 1996 XJ only took 2 gallons when I bought it, and that is after a water pump and thermostat change and completely draining the radiator including the recovery bottle. It had an unending overheating problem when driven fast on the highway. The problem went away with a radiator change. The new radiator took 2.5 gallons plus the .5 gallon in the recovery bottle. My guess is, 2 gallons may be enough for manual shift XJ's but not good enough when the AW4 is added to the mix.

Then again, a 2 gallon radiator may not be normal.

 

[Tony_SS]

oem better than a new napa rad?

Maybe that's why I'm overbeating a bit too now.

OEM as any plastic tanked OEM replacement radiator...not necessarily a dealer Mopar brand.

I have a Spectre brand from Rock Auto...so far so good. Last brand was a Vista.

 

[yossarian19]

I think the Mopar branded radiator is the safest bet, though any OEM replacement should, I think, adhere to the tube / fin configuration of the Mopar design. NAPA isn't known for selling bullshit parts, as an aside.
CSF 3-row is, so far, the only after market "upgrade" radiator I'd trust.
Any updates from the OP?

 

[rockclimber]

Stick with mopar.


I've fixed a number of overheating XJs by putting a mopar rad into it.

I swapped in a knock-off oem and it is not nearly as efficient. It was cheap though.

 

[Qban]

Ok now that I got my infrared temp gun mailed in from amazon today I got some numbers.

I ran the jeep around the street to get it up to running temp, then pushed it about 65-70mph on the freeway for about 10min, came home parked and took the measurements while idling. Once I was up to running temp the temp gauge didn't change much at all the whole time.

Upper Radiator Hose (next to tstat housing): 210.5
Lower Radiator Hose: 173
Tstat Housing Itself (right below the sensor): 220
Temp Gauge Read Aprox. 195

 

[yossarian19]

That all sounds correct-ish, maybe a bit high on the housing (not sure, really) maybe a bit low on the gauge.
None of that sounds like overheating, exactly.

 

[Qban]

That all sounds correct-ish, maybe a bit high on the housing (not sure, really) maybe a bit low on the gauge.
None of that sounds like overheating, exactly.

Thanks
The "overheating" part happens when I'm on the highway for about 15 minute at 65-70mph.

I was thinking that I could slip a thermocouple from one of my multimeters into the upper radiator hose at the tstat housing and cause the overheating on the freeway, then I can see if the coolant is really that temperature.

Also from the recommendation of a previous post I marked the coolant at the recovery bottle, it seems that I did loose a little but it didn't boil out of the recovery, and also my oil looked clean (no milk shake or water)

 

[Tony_SS]

I really like my Scangauge II... I get real time temp readings right from the computer so I'm not guessing by looking at my gauges.

 

[CobraMarty]

Is there anything blocking your grill? Lights? Winch? Oil cooler? Bull bar? etc?

 

[yossarian19]

I'm trying to figure out a way to prove / disprove its insufficient radiator flow causing the overheat. The theory is that at higher RPM & higher power produced, the radiator isn't keeping up with the higher BTU output of the motor while around town, it can. It doesn't make it easier that it only has a problem at highway speed - difficult to duplicate the symptom with the hood open & hands on it.

Is the lower hose in good shape? If it's sucking down at all when you blip the throttle by hand, that could be the problem.

 

[Qban]

Is the lower hose in good shape? If it's sucking down at all when you blip the throttle by hand, that could be the problem.

Yes, the lower radiator hose is a brand new dealer part with the metal spring inside.

 

[Digger87xj]

I'm trying to figure out a way to prove / disprove its insufficient radiator flow causing the overheat. The theory is that at higher RPM & higher power produced, the radiator isn't keeping up with the higher BTU output of the motor while around town, it can. It doesn't make it easier that it only has a problem at highway speed - difficult to duplicate the symptom with the hood open & hands on it.

Is the lower hose in good shape? If it's sucking down at all when you blip the throttle by hand, that could be the problem.

I think it has more to do with fins per inch than water flow.

If the rad companies are skimping on the number of fins to the bare minimum they think is needed, it's going to have an effect especially when we are talking lifts and larger tires.

 

[CobraMarty]

How is the cooling in the rain?

Maybe rig some tubing and spray some water on the radiator and see if that helps cool it down.

Try another cap. I just had a bad one that didn't leak and 'seemed' to work right.

 

[Qban]

How is the cooling in the rain?

Maybe rig some tubing and spray some water on the radiator and see if that helps cool it down.

Try another cap. I just had a bad one that didn't leak and 'seemed' to work right.

At this point I've had 2 radiator caps I've tried. A napa cap which was the first thing I tried when I started having this problem and the one that came with the champion radiator. Both of them didn't change anything. I'm sticking with the napa one right now as I feel it's better constructed.

Last night I back removed the tstat and flushed Every part of the system independently. I did have a blockage in the heater core but I got most of the crap out. I just filled it up with prestone flush/cleaner and I'm going to run it for a few days and backflush it again. I'll change out the thermostat to an oem factory one since the gauge reading didn't match my thermometer readings very well.

After this I'll run it some more and see if I can check the temps with an IR temp gun if I get an overheat again.

 

[Qban]

Sorry I should have proofread that last message

Corrections:

Last night I removed the tstat and back flushed Every part of the system independently.

I'll change out the temp sensor to an oem dealership one since the gauge reading didn't match my thermometer readings very well.

 

[Qban]

Ok, So I back flushed the entire system. I did each section independently then the entire system, filled with a bottle of prestone flush/cleaner (they merged the two now), ran it for 2 days (the bottle says thats ok to do). Then back flushed the system once more.

The one place I had the most crap coming from was the heater core and while flushing I noticed a good drip coming from a hole in the bottom frame rail under the heater core. Is it safe to assume I have a leak in the heater core?

Whats the right way to bypass the heater core, disconnect the two hoses and connect them together or cap both sides? Since the outlet of the engine goes to the heater core then to the water pump it would seem to make sense that its better to cap the two hoses so that all your coolant goes through the radiator but I haven't read anything about doing it that way.

The other thing I did was get an oem temp sensor, I'm happy to say that the new sensor reads more correctly according to my ir temp gun, the bad news is that it's actually a higher temp than before =) haha, I'll just be happy that I feel I can trust my gauge now.

 

[techno1154]

Ok, So I back flushed the entire system. I did each section independently then the entire system, filled with a bottle of prestone flush/cleaner (they merged the two now), ran it for 2 days (the bottle says thats ok to do). Then back flushed the system once more.

The one place I had the most crap coming from was the heater core and while flushing I noticed a good drip coming from a hole in the bottom frame rail under the heater core. Is it safe to assume I have a leak in the heater core?

Whats the right way to bypass the heater core, disconnect the two hoses and connect them together or cap both sides? Since the outlet of the engine goes to the heater core then to the water pump it would seem to make sense that its better to cap the two hoses so that all your coolant goes through the radiator but I haven't read anything about doing it that way.

The other thing I did was get an oem temp sensor, I'm happy to say that the new sensor reads more correctly according to my ir temp gun, the bad news is that it's actually a higher temp than before =) haha, I'll just be happy that I feel I can trust my gauge now.

You need to connect both hoses together. The hot water that bypasses the thermostat should be re-routed into the water pump and re-circulated into the engine block.

 

[Qban]

Alright, so I bypassed the heater core, bleed the system, have a temp sensor that I trust and I overheated according to the gauge again. Time to go with an OEM radiator =) I already put in for the RMA on the champion and hopefully they will take it back, otherwise I'll be making a phone call to the credit card company.

 

[Qban]

Ok, so I put back in my old stock radiator. Unfortunately I'm overheating about that same which is after 65-70mph on the freeway for about 10min with no ac. I still need to measure the temperature difference across the rad, but I'm just too annoyed at the thing at this point.

I feel like bypassing the heatercore has only made things a bit worse. I bypassed it to remove the possibility of a heater core leak as being a problem. BTW I'm running without the tstat to make life easier with the flushing and coolant burping. I also did a block test this morning, autozone rents them including the fluid for free so why not, luckily the liquid stayed blue so I guess its safe to assume I'm not getting any combustion gases in the coolant, that's good at least.

I'm starting to think that this is primarily an airflow problem. My overheating started a while after I lifted the front an inch higher than the rear, my fan shroud is also missing the bottom section (it was like that when I bought it). And when I did the radiator work the "gasket/seal" around it fell apart so I'm running without one of those too, and I also don't have my bumper on.

Is there any merit to replacing the fan shroud with a complete one (hopefully from the junkyard), fixing up that around the radiator seal thingy, putting back on the bumper, and maybe putting the stock front skid plate on to lessen the air from coming in from the bottom. This is the only reasonable thing I can think of next.

Hopefully my stupidity can help anyone else before wasting their time too chasing ghosts. Thanks!

 

[yossarian19]

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.