Overheating... STILL

[Tenny]

Not sure how accurate the gauge is, I've never had a infrared gun reader on it. Never noticed it actually boiling over either, but with the transmission boiling over I have to imagine it's at least some-what accurate... Though I have questioned this an awful lot.

My e-fan is hot wired, and usually on when I drive, esp if i think there is even a possibility of over-heating.

 

[TiRod]

(oh and I consider over-heating anywhere around midway between 210 and the red.)

It's not popping the cap and boiling over, tho. So, it's not actually overheating - just running hotter than you want based on a factory dash gauge.

Water boils at 212, plus the 15 degrees added from the cap, means the coolant might be boiling at 227 - which isn't marked on our gauges at all. Red starts at 240, IIRC, so halfway between 210 and 240 is 225, right on the money if the needle swings with no geometric progression and can be trusted.

I'd use a high quality block flush to increase heat transfer, and try Gojeep's flow restrictor. If a three core aluminum radiator isn't getting the job done, it's probably not capacity, it's too much flow. The coolant hasn't had enough time to dump heat before it returns.

As for the wire in the lower hose, it's only necessary because older radiators get so clogged they won't flow enough to keep up with the pump. The hose makers got tired of being blamed for the hose collaspsing when flow wasn't their fault. As far as I'm concerned they just add more rust to the coolant and don't fix the problem.

 

[heyhar]

Five years ago, at 130k miles, I took the head off my '92 to replace the lifters. While it was off, I took the opportunity to clean up the insides of stuff. The coolant passage at the back of the head was almost entirely clogged, with what looked like cooked-down antifreeze. I cleaned it out, and its corresponding passage in the block, and even though it hadn't had a cooling problem before, it ran much cooler after. The needle goes up to where it belongs, and never, no matter what, goes any higher, even when the A/C still worked. A drastic plan to be sure, but I'd bet you would find a similar thing. I'm just waiting to find an excuse to take the head off my '96, as it runs a little warmer than it should. There really is a reason that the coolant needs to be replaced periodically. And, of course, the clogged cat sounds plausible, and much easier to remedy.

 

[Tenny]

Alright... still having issues (duh)

So yesterday I put in a new thermostat (195*f Mr Gasket Balanced) and put a new sender unit for the dash gauge (just so I can be sure it's not off... (but the gauge itself could be off I realize)). Still have not replaced the cat though.

After that I left it idling with a shirt over the radiator to try and limit the flow... With A/C on and diff combo's, and it never got to 210*f. Idled for a total of around 1 hour. I held it at 2k rpm for about 3-4 minutes...

Now I drove it today, agreed in a hotter temp (80-100*f) over two hills. Almost the whole time it was at or above 210. Got to about 1/2 between 210 & the red on both hills. This is doing maybe 50-55mph.

Now I was thinking, maybe the Transmission is adding all the heat to the radiator thus it not being able to cool. So I was thinking about pulling the transmission fluid from going into the radiator, and have it only go into the auto-transmission cooler only. Then I realized if it's already adding that much heat with both, the little cooler probably wouldn't be able to cool it by itself.. (correct?) Now this is just a shot in the dark, but the radiator is now leaking transmission fluid (and I think the radiator is out of warranty, but I'll have to check later). So it kinda solves that leaking problem temporary..

So does the transmission add that much heat to the radiator?

BTW the transmission cooler is: B&M part #70268 - 19,000 GVW, 11'' x 7.5'' x .75''

 

[Tenny]

Well... I have time to burn right now, but not much soon. I am going to try running the transmission w/o the radiator... esp since the radiator leaking it... Still any comments or whatever are welcome... I'll check the thread once i finish and before I give it a test drive heh.

 

[Tenny]

well it seemed to run a tad bit cooler but not much

 

[joe_peters]

Did you ever add the ZJ HD fan clutch?

 

[Ecomike]

Alright... still having issues (duh)

So yesterday I put in a new thermostat (195*f Mr Gasket Balanced) and put a new sender unit for the dash gauge (just so I can be sure it's not off... (but the gauge itself could be off I realize)). Still have not replaced the cat though.

After that I left it idling with a shirt over the radiator to try and limit the flow... With A/C on and diff combo's, and it never got to 210*f. Idled for a total of around 1 hour. I held it at 2k rpm for about 3-4 minutes...

Now I drove it today, agreed in a hotter temp (80-100*f) over two hills. Almost the whole time it was at or above 210. Got to about 1/2 between 210 & the red on both hills. This is doing maybe 50-55mph.

Now I was thinking, maybe the Transmission is adding all the heat to the radiator thus it not being able to cool. So I was thinking about pulling the transmission fluid from going into the radiator, and have it only go into the auto-transmission cooler only. Then I realized if it's already adding that much heat with both, the little cooler probably wouldn't be able to cool it by itself.. (correct?) Now this is just a shot in the dark, but the radiator is now leaking transmission fluid (and I think the radiator is out of warranty, but I'll have to check later). So it kinda solves that leaking problem temporary..

So does the transmission add that much heat to the radiator?

BTW the transmission cooler is: B&M part #70268 - 19,000 GVW, 11'' x 7.5'' x .75''

Somebody here last summer found an exhaust leak blowing right onto the transmission housing, that was causing was there overheating problems.

 

[Mudderoy]

This sounds just like the problem I have had with my 1998 for the past couple of years. Going to the CSF 3 core fixed any running hot problem with the exception of summer time temps, or running down the highway at 70 mph.

I have changed to...

Radiator CSF 3 core.
High flow thermostat housing
High flow thermostat (180 degree)
NAPA ZJ HD fan clutch
All hoses
FlowKooler water pump
B&M transmission cooler (also has a OE cooler)
temp sensor
Cleaned condenser at the car wash. It looks good, didn't notice any bent fins.

The only thing I haven't changed is the heater core.

In the morning (air temp in the 80's) it takes 10 miles to reach 210. In the afternoon it takes about 2 miles to reach 210, then goes up to 222 (the first hash mark after 210) but usually stays about 215/216 (midway).

Driving is between 50 and 60 mph a couple of miles between slowdown or stops, not freeway driving.

I have verified gauge temps with a IR scanner.

The ZJ HD fan clutch helped the most. The engine runs more peppy, like it does in cooler weather. Before you could feel a slight loss in horse power when the air temps, and coolant temps were higher.

Since it takes so long to rise to the 210 temp in the mornings, and I froze my ass off during the winter (40's is cold in Houston) I'm going to go back to a 195 degree thermostat. No need running rich for 10 miles in the mornings!

I have noticed that if I'm running down the freeway at 75 mph (2800 rpm) if I turn off the A/C the temp will drop about 10 degrees.

 

[Ecomike]

This sounds just like the problem I have had with my 1998 for the past couple of years. Going to the CSF 3 core fixed any running hot problem with the exception of summer time temps, or running down the highway at 70 mph.

I have changed to...

Radiator CSF 3 core.
High flow thermostat housing
High flow thermostat (180 degree)
NAPA ZJ HD fan clutch
All hoses
FlowKooler water pump
B&M transmission cooler (also has a OE cooler)
temp sensor
Cleaned condenser at the car wash. It looks good, didn't notice any bent fins.

The only thing I haven't changed is the heater core.

In the morning (air temp in the 80's) it takes 10 miles to reach 210. In the afternoon it takes about 2 miles to reach 210, then goes up to 222 (the first hash mark after 210) but usually stays about 215/216 (midway).

Driving is between 50 and 60 mph a couple of miles between slowdown or stops, not freeway driving.

I have verified gauge temps with a IR scanner.

The ZJ HD fan clutch helped the most. The engine runs more peppy, like it does in cooler weather. Before you could feel a slight loss in horse power when the air temps, and coolant temps were higher.

Since it takes so long to rise to the 210 temp in the mornings, and I froze my ass off during the winter (40's is cold in Houston) I'm going to go back to a 195 degree thermostat. No need running rich for 10 miles in the mornings!

I have noticed that if I'm running down the freeway at 75 mph (2800 rpm) if I turn off the A/C the temp will drop about 10 degrees.

Did you ever test and verify your air manifold and coolant temp sensors for accuracy to see if they were affecting fuel mileage?

I was looking at $41 fiberglass/silicate pipe wraps for exhaust manifolds yesterday that are designed to decrease under the hood temps. Nearly bought one.

I noticed this past week that my hood temp (engine off) was 158 F, and after a 20 minute trip in the afternoon heat it was 153 F. I have no insulation on that hood.

 

[scottmcneal]

Is your's running lean? Check your plugs..Run it on a freeway or hill, when you see the temp going up pull over fast an pull a plug.. I would pull all of them to check ...I found i had 2 bad injectors, Ran lean in 3 and 5.. Plugged fuel injectors can cause this..I run chevron gas, plus a cleaner from cheveron that has techolene(spell check)..HTH

 

[Kinslayer]

that exhaust wrap stuff is kind of lame. It deteriorates and makes a mess and doesn't do much. It's more for hot rodders who are constantly cleaning their motors and what not.

As for the tranny cooler, I grabbed a factory one from a ZJ and mounted it right in front of my stock e-fan. I bypassed the tranny altogether...I did it at the same time as I changed my leaky rad and my truck actually runs warmer now for some reason. <shrug> doesn't overheat, the efan keeps it down to uh..the middle of the gauge.. Although I still want to rig up a taurus fan to replace the stock manual fan for multiple reasons - HP gains, more flow through, and controllable.

 

[Mudderoy]

Did you ever test and verify your air manifold and coolant temp sensors for accuracy to see if they were affecting fuel mileage?

I was looking at $41 fiberglass/silicate pipe wraps for exhaust manifolds yesterday that are designed to decrease under the hood temps. Nearly bought one.

I noticed this past week that my hood temp (engine off) was 158 F, and after a 20 minute trip in the afternoon heat it was 153 F. I have no insulation on that hood.

Well I replaced the coolant temp sensor. I did the IR scan on the therm housing and it was within 5 degrees.

I also replaced the air intake temp sensor, but didn't check it. I guess IR the intake near where the sensor goes in? I think I can pull that information from the OBD II scanner I bought. Yeah gas mileage isn't any better 12 to 13.8 city.

I wish I had wrapped my header before I put it in! If I'm not laid off in a couple of months I'll get the cowl induction hood and release the heat that way.

 

[jdougn]

My '98 4.0 XJ ran hotter than normal at highway speeds when the catalytic converter was going bad. Also, I didn't think that a bad fan clutch mattered at speeds over 45mph since that's all the faster the fan spins? hth, dn

 

[Mudderoy]

I have not replaced the injectors. I had them cleaned.

I have replaced the catalytic converter.

According to someone that read my OBD II information (here on ) I'm running a little rich. Dunno....

 

[joe_peters]

My '98 4.0 XJ ran hotter than normal at highway speeds when the catalytic converter was going bad. Also, I didn't think that a bad fan clutch mattered at speeds over 45mph since that's all the faster the fan spins? hth, dn

Fan clutch (standard or HD) locks up when the air temperature at the bi-metal spring on the front of the clutch reaches 170 degrees, which is 30 degrees less than coolant temp. Vehicle speed and engine RPM are not factors.

When engaged, a standard fan clutch will turn at 60-70 percent of the shaft speed. When engaged, a HD fan clutch will turn at 80-90 percent of shaft speed.

 

[Ecomike]

Fan clutch (standard or HD) locks up when the air temperature at the bi-metal spring on the front of the clutch reaches 170 degrees, which is 30 degrees less than coolant temp. Vehicle speed and engine RPM are not factors.

When engaged, a standard fan clutch will turn at 60-70 percent of the shaft speed. When engaged, a HD fan clutch will turn at 80-90 percent of shaft speed.

My ZJ clutch is turning a lot faster than the XJ stock clutch even at 150 F coolant temps.

 

[Ecomike]

I have not replaced the injectors. I had them cleaned.

I have replaced the catalytic converter.

According to someone that read my OBD II information (here on ) I'm running a little rich. Dunno....

I'd be real curious to see a full set of your current OBD-II data at several rpms.

 

[bc99xj]

This sounds just like the problem I have had with my 1998 for the past couple of years. Going to the CSF 3 core fixed any running hot problem with the exception of summer time temps, or running down the highway at 70 mph.

I have changed to...

Radiator CSF 3 core.
High flow thermostat housing
High flow thermostat (180 degree)
NAPA ZJ HD fan clutch
All hoses
FlowKooler water pump
B&M transmission cooler (also has a OE cooler)
temp sensor
Cleaned condenser at the car wash. It looks good, didn't notice any bent fins.

The only thing I haven't changed is the heater core.

In the morning (air temp in the 80's) it takes 10 miles to reach 210. In the afternoon it takes about 2 miles to reach 210, then goes up to 222 (the first hash mark after 210) but usually stays about 215/216 (midway).

Driving is between 50 and 60 mph a couple of miles between slowdown or stops, not freeway driving.

I have verified gauge temps with a IR scanner.

The ZJ HD fan clutch helped the most. The engine runs more peppy, like it does in cooler weather. Before you could feel a slight loss in horse power when the air temps, and coolant temps were higher.

Since it takes so long to rise to the 210 temp in the mornings, and I froze my ass off during the winter (40's is cold in Houston) I'm going to go back to a 195 degree thermostat. No need running rich for 10 miles in the mornings!

I have noticed that if I'm running down the freeway at 75 mph (2800 rpm) if I turn off the A/C the temp will drop about 10 degrees.

i have the same setup other than a real water pump Hescos works great here in phx. oh yeah i have a 195 balanced t-stat next winter i think im going to use a reg t-stat

 

[Mudderoy]

i have the same setup other than a real water pump Hescos works great here in phx. oh yeah i have a 195 balanced t-stat next winter i think im going to use a reg t-stat

Hesco was my first choice, but $169!!!! I may have said already, I'm going back to a 195 thermo.