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overheat............sometimes

R

rifle6

NAXJA Forum User
Location
UTAH!
hey, I have a problem , hope some of you guys may have seen this before.
I did search the millions of old threads and came up with alot of info, but nothing sounded like what i have going on.

Xj 92, 4.0
2inch rubicon lift with 30 in maxxis.

the problem.
last fall at highway speed my temp neared red line, i shut it down and after an hour everything was ok, and it never overheated again,
during the winter i did notice thet the heater was cooler than normal, but i'm ok with that, but i did buy a new thermostat.

yesterday, same exact thing after about an hour of normal highway driving it got hot, i shut it down and everything was fine for the rest of the day.

so last night i replaced the thermostat, and figured that was that,
today i load up and get about 30 miles from home nice temp then WHAM. it spiked, so i let it cool. but this time it overheated again, so i shut it down, played this game all night, finally got it home.

my guess is water pump, but before this there has never been a drop of leakage. can a pump go bad and not leak?

any ideas, suggestions welcomed .
thanks.
 
Other than the gauge, any other signs of overheating?

When was the last time you flushed the cooling system--not with water, but with a commercial flush the kind you put in and leave for 500 miles?

At highway speeds AIRFLOW alone is usually enough to keep the engine within normal operating temperatures. If the airflow is restricted--bugs, mud, dead birds in the fins--cooling will be reduced.

Problems with coolant FLOW will cause overheating. Hence, the flush I described above. Also, what is the condition of the lower heater hose? OEM hoses had a spring in them to prevent collapse of the lower hose and restriction of coolant flow. If there is no spring I recommend replacing the lower use with a "universal" fit ribbed hose that has the spring built into it.

When was the last time you changed the radiator cap? Good for about two years, once the cap won't hold pressure the boiling point of the coolant is lowered.

How is the mix of the coolant? When was it changed last? Are you using coolant and distilled water 50/50?

Have you been loosing any coolant?
 
Thanks for the reply,
The air flow is clean, no debris, other than the guage, it puke its guts, filled the overflow, and a heater hose clamp.

To my knowlage the pump and hoses are stock.. I guess I will just replace the upper,lower hoses. And the pump. I would like to flush the system, what is a way to do that? Undo the top hose stick garden hose in radiator?

Thanks
 
Do yourself a favor and rent a coolant tester to check for combustion gasses--you pay for the test fluid and rent the tester. That way you can be pretty sure you don't have a headgasket problem.

If Ok, then buy Prestone/Bar's Leak/Zerex radiator CLEANER--the stuff you put in and leave for a specified amount of time/miles, like 3-6 hours of driving (can be over multiple days) and just follow the directions. The 15 minute stuff is bunk. Once done, before putting in the new coolant do the hoses and WP.

Good luck, post up your results.
 
Well I got the pump in, thermostat and new upper and lower hoses,and a new 4way cross for the heater hoses, it idled for 20 mins at 180, so I took it out on the free way,at about 10 miles it overheated again. I put the flush in 250 miles then replace coolant,

I'm out of ideas, unless my heater core is plugged, I could bypass it and run the one hose back into the pump right? When it cools off that's my next step.
 
Cap...... I wonder , maybe I pick one up .

Can a plugged heater core cause overheating,

Right now the mix is 90 percent coolant
 
rifle6 said:
Well I got the pump in, thermostat and new upper and lower hoses,and a new 4way cross for the heater hoses, it idled for 20 mins at 180, so I took it out on the free way,at about 10 miles it overheated again. I put the flush in 250 miles then replace coolant,

I'm out of ideas, unless my heater core is plugged, I could bypass it and run the one hose back into the pump right? When it cools off that's my next step.
Click to expand...

Worth a shot, two clamps and a few inches of hose is all it takes.

EDIT: there is a point of diminishing returns with coolant mix, anything past 70/30 is a waste. Check this table: http://www.magers.org/handy/antifreeze.html
 
Last edited:
Well , crap. Not the radiator cap either. Now I am officially out of ideas............... This sucks.
 
do you get HEAT when the HVAC controls are set for it?

Ok, try this: remove both heater hoses, one from the thermostat housing is the heater core input, the one from the WP is the heater core outlet. Use a garden hose--please don't get carried away with the pressure--and backflush the heater core by putting the garden hose to the heater core output--the hose from the WP. Switch back and forth, flush, back flush, see if the flow improves any.

Did you test for combustion gasses yet?

One wild a** guess is the mechanical fan clutch EXCEPT it only turns at 30 percent of shaft speed if the airflow through the radiator and hitting the bi-metal spring is less than 170 degrees--in other words, the regular air flow should be adequate for cooling at highway speeds. Even if the fan clutch was so bad it totally freewheeled, I don't think it would make any difference on the highway.
 
Last edited:
rifle6 said:
Right now the mix is 90 percent coolant
Click to expand...

joe_peters said:
EDIT: there is a point of diminishing returns with coolant mix, anything past 70/30 is a waste. Check this table: http://www.magers.org/handy/antifreeze.html
Click to expand...


Have you addressed the percentage mix of the anti-freeze/water mix yet ??

Ethylene-Glycol is not a cooling agent - Its added to water to prevent water freezing.

Water alone cools better than an anti-freeze mix.

Too much anti-freeze can increase temps .... thats why the recommended mix in the FSM is 50/50 for general use. ( eth-gly to water )

For colder area operation the mix can be increased safely to a bit over 60% eth-gly ...

And for hotter area operation the mix can be safely lowered as much as you want ... as long as you keep in mind the nescessity for corrosion inhibitors due to the effects of water on components, minimum daily ambient temps, etc.
 
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the mix is roughly 80-20 now, i expected a large BURP, and have not seen it yet,
no on the conbustable gases,
exhaust is black, not white, so i don't think i am burning coolant, the oil is black and looks and smells like oil.

i will try the hose to garden hose.
 
Mine is doing the same thing. I had the waterpump, t-stat lower hose all replaced when they did the head gasket from it overheating. After about an hour at highway speeds, it spiked and runs about 15-20* higher now. ONly thing left that isn't new is the radiator and heater core. It runs at 210 around town no problem. Thought about having the radiator boiled out since the heater gets hot when i turn it on. Ideas?
 
egotripp said:
Mine is doing the same thing. I had the waterpump, t-stat lower hose all replaced when they did the head gasket from it overheating. After about an hour at highway speeds, it spiked and runs about 15-20* higher now. ONly thing left that isn't new is the radiator and heater core. It runs at 210 around town no problem. Thought about having the radiator boiled out since the heater gets hot when i turn it on. Ideas?
Click to expand...

Normal temps around town ... Higher temps on highway .... Are generally indicative of a poorly performing radiator.
 
Ok, blown headgasket presents in a number of different ways--depends on where and how bad it is.

1. White plume of steam from the exhaust pipe.

2. Milkshake in the crankcase.

3. Combustion gases in the coolant system OR pumping coolant out of the recovery bottle.

4. Different combinations of 1/2/3.

You say your coolant mix is 80 anti-freeze to 20 water? Way in the wrong direction for Summer use. A 50/50 mix is a good thing for Winter, but in summer you need to reduce the amount of ethylene glycol, more like 30 anti-freeze and 70 water or even as much as 10 anti-freeze and 90 water.

Some more reading for you: http://www.challengers101.com/CoolantMix.html
 
learning lots of stuff i thought i new about coolant.
i always thought more coolant is better, since the XJ now has ZERO fluids i will do the 50-50 mix.

results of today. took it to a shop my buddy runs, they checked combustion gases, and cylinder compression. good news is the head and gasket are good to go.

they were going to power flush it, but got looking into it and he called and said the radiator was shot. no use flushing it. so for 20 bucks i was on my way.

also said my fan clutch was shot...... now not knowing JACK SHI& about a fan clutch i said ok, i will get one of those too.

so tonight the radiator came out...... surprisingly simple other than the lower trans fluid line fitting..... what a pain in the arse. got the fan a clutch off, flushed the whole thing out untill clear H2o came out the lower hose.

i will put it all back together after work, and post results.
thanks to all.
 
Your XJ has the exact same symptoms my '92 did.. I checked over everything, and found the fan clutch was bad. I changed it, and never had a problem after that. Good luck with the rad and clutch, should solve your problem..
 
Last edited:
rifle6 said:
learning lots of stuff i thought i new about coolant.
i always thought more coolant is better, since the XJ now has ZERO fluids i will do the 50-50 mix.
Click to expand...

Its a common misconception ....

Mainly because Eth-Gly is constantly referred as coolant ...... When its actually an anti-freeze agent.

A correct mix of eth-gly and water for the vehicles operating conditions is coolant .... ;)

Radiator and fanclutch are commonly the main cause of overheating issues ... Replace those in addition to what you have already done ... and you should be problem free for quite some time.
 
well, that did the trick, i road tested it for about 30 miles, it was cool out tonight, but i ran it about 60 miles an hour, and it never got over 170 ish.

it might be my imagination but it sounds and runs better, even a little more power.
so it was the fan clutch and radiator, when i pulled the old one out it weights about 25 lbs more than the new one. must be full of crap.

running about a 40-60 mix .

thanks for all the help.

300 dollar fix includes:
radiator
cap
water pump
fan clutch
new hoses
4 way cross for heater hoses
thermostat
test head gasket

cool running XJ................priceless!!!!
 
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