overheat

Hi guys,

I don’t usually ask questions on a forum I don’t contribute to, but since my XJ is bought, not built, I don’t have too much you would be interested in. I have read and searched a lot though and gotten a few answers that helped fix things.

I have a problem that has been addressed multiple times in various forums, but still cannot figure it out. I want to stay loyal to my independent Jeep mech, but he cannot figure this out either. I've read at least 8 hours of threads but nothing seems to directly apply to what is going on.


2001 XJ Sport
142,000 miles all by me
Auto 4.0
Stock other than:
KN cone filter
Throttle body spacer
High flow exhaust

About a year ago I had coolant spray all over inside of hood, loosing coolant.
Dark sludge/sediment in coolant overflow tank, but looks perfect green in radiator.
NO water in oil.
Had mech replace radiator & thermostat, he used a plastic model as opposed to metal.
Still have gunk coming out into overflow, and heater not working.

Flush and fill the heatercore and rad about 3 times, heater now working again but weak. Tried new rad cap, but it is listed at 18psi, not 16, problem?

Now overheating at idle and heavy load. Pulling up 1-70 hills will overheat, especially if AC on. Turning AC off brings it back down usually.

Going from steady 210 with no slow rise, but rather one big jump up to 240ish, idiot light comes on.

Reduce load and turn off ac (or wintertime defroster) and needle jumps right back down. Not a slow decrease, but boom, back down to 210.

Replaced thermostat again, E fan seems to be working as it should (comes on with AC, comes on at about 215)



Everything I have read pointed to the fan clutch so I had it replaced.

No apparent leakage from waterpump. Rad totally full when cold, overflow where it should be. Overflow water still dark, but looks great in rad.

Still broke.

Waterpump?

> seems that if I am right at 210 on the road generally that the pump is working.



Replace brand new rad?



Hoses?



I’ve looked for the 0331 code near the third spark plug, but can’t find the code, not looking in the right spot I guess.



Is the stock transmission cooler a potential problem? If it had blockage, would the water just bypass it, or is it mandatory that the water flow through there?


Is the fact that I have lots of rocks stuck in my AC condenser a potential problem? Ac still works fine, but could be limiting flow to the radiator.

Thanks.

Sludge and low heat output point to still clogged cooling system. Coolant should be replaced every 2 years or 30,000 miles no matter it looks like. You cannot determine the condition of coolant by its appearance. The water pump may not be leaking, but some people have reported that when changed out, the pump vanes on their old water pump were significantly worn down which would result in low coolant flow volume. I would replace it with a top quality, brand name, water pump. Jumping thermostats from 210* to high temps and back again suggests that the radiator cap needs to be replaced. If you remember Physics 101, liquids under pressure (16lbs sound familiar ?) have a higher boiling point. You are seeing the coolant flash to steam and stalling the flow of coolant.

Make sure the A/C condenser and the radiator are clean and free from excessive mud, grass, bugs, or other debris.

You have a 2001 so you have an 0331 head.

Thanks Tim,
Coolant is only 2 months old. There could still be sludge that was in the engine block or hoses though I suppose. There have been three flush and fills since the new rad installed.

Rad cap is only a couple weeks old, but he put a 18psi on instead of 16. It that a potential problem being too much (as opposed to not enough)?

aldous said:

Still have gunk coming out into overflow, and heater not working.

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Heater core plugged??

aldous said:

Flush and fill the heatercore and rad about 3 times, heater now working again but weak. Tried new rad cap, but it is listed at 18psi, not 16, problem?

Click to expand...

Did you flush the heater core independently, back & forth several times. Sounds like there WAS an issue there that was partially fixed.

aldous said:

Everything I have read pointed to the fan clutch so I had it replaced.

Click to expand...

That would be my best guess, but if you covered that you should be good.

...

aldous said:

Replace brand new rad?

Click to expand...

I would always prefer an all metal radiator...that may just be me.

aldous said:

Hoses?

Click to expand...

If they look to be in good shape...doubtful

aldous said:

I’ve looked for the 0331 code near the third spark plug, but can’t find the code, not looking in the right spot I guess.

Click to expand...

The casting number is on the drivers side by the throttle body, between the 3-4th injector. The place to look for a crack in the head is usually between 3 & 4. You'd see an obvious crack just looking through the valve cover with the cap off.

aldous said:

Is the stock transmission cooler a potential problem? If it had blockage, would the water just bypass it, or is it mandatory that the water flow through there? .

Click to expand...

The tranny fluid and the water don't come into contact or share lines, so no! Coolant goes one way, tranny fluid is limited to the driver's side "tank" in the radiator and any external cooler. The radiator cooler can be eliminated altogether and you can plumb it to an external, either stock or aftermarket cooler.

aldous said:

Is the fact that I have lots of rocks stuck in my AC condenser a potential problem? Ac still works fine, but could be limiting flow to the radiator.

Click to expand...

Yes. XJ cooling systems need all the ducks in a row, including air flow.

Drain and fill or Chemical Flush and fill ? You can drain, save and re-use the 2 month old coolant after you use a flushing additive.

16 lbs is the specified radiator cap.

ParadiseXJ said:

Did you flush the heater core independently, back & forth several times. Sounds like there WAS an issue there that was partially fixed.

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Do you also post on a ski message board? Familiar avatar. Rideski here.

Anyway, yes I think the heater core got plugged around the time of the first radiator problem. Either during that problem, or subsequently when the new one was put on and perhaps enough gunk was left in the hoses or something to then stick in the heatercore. This is the cause of all of the flush and fills. The heatercore was flushed independently and it has helped, quite a bit.

I am in the process of trying to find out what radiator the mech put back in as the replacement. I just found out that the xj with towing package may have come stock with a two core and without the towing package came with one core. Maybe he put on a one core... (I have the factory towing package)

If the plugged condenser is the problem that would be an expensive fix, but I can't just leave it as is.

Tim_MN said:

Drain and fill or Chemical Flush and fill ? You can drain, save and re-use the 2 month old coolant after you use a flushing additive.

16 lbs is the specified radiator cap.

Click to expand...

The mech did a chemical flush and fill, and then the last time we actually left the chemicals in for about 80 miles of driving, then flushed and filled after with new coolant. That finally freed up the heater core to blow hot air in Winter.

It would be great if the rad cap was the problem. Guess I will just try that now.

I suspect that your 0331 head is cracked like mine. Do you steadily use coolant so that you have to top up the bottle regularly to keep it at the line? Do you have milky residue on the bottom (inside) of the oil fill cap?

Tim_MN said:

Make sure the A/C condenser and the radiator are clean and free from excessive mud, grass, bugs, or other debris.

You have a 2001 so you have an 0331 head.

Click to expand...

I missed this yesterday, bummer, I thought the 0331's were made in year 2000, I bought mine in December of 01.

The ac condenser is full of gravel and has many many bent vanes.

winterbeater said:

I suspect that your 0331 head is cracked like mine. Do you steadily use coolant so that you have to top up the bottle regularly to keep it at the line? Do you have milky residue on the bottom (inside) of the oil fill cap?

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I read up on the 0331 issue, it sounded like if you made it past 100,000 miles without a crack, you were supposed to be in the clear? I had 120,000 before the first radiator blew.

I do not have to add much if any coolant, and there is definitely not any milk in the oil. But from what I read, if it is cracked, it could be just a one way leak, pushing oil into the coolant, but not vice versa?

My mechanic seemed to think that the compression test he did ruled out blown head gasket.
I guess I should go back and have him test for hydrocarbons.


I put the new rad cap on, but won't be able to get it super heated for a couple of days.

Thanks for the ideas.

aldous said:

I missed this yesterday, bummer, I thought the 0331's were made in year 2000, I bought mine in December of 01.

The ac condenser is full of gravel and has many many bent vanes.

Click to expand...

That would definetely be part of your problem.

Hi guys, just wanted to report back. Knock on metal, I seem to have this fixed.
Replaced the waterpump, belt, and hoses and did yet another flush and fill. Seems to have done the trick. The waterpump looked fine inside, fins were all intact and original size. Who knows, maybe a bearing was getting stiff? Hoses had a small amount of buildup, btu that couldn't have been the problem, I just replaced them since I was in there anyway and wanted to eliminate the chance of a burst. Some chance that is was from remnants of the solvent I used to try to clear gunk out of the heatercore and the flush and fill eliminated it, but seems logical it was more the waterpump. Glad (at the moment) that I did not do the ac condenser.

Probably not the time of year to do this, especially in Denver, but when you can w/o freezing weather put in a commercial flush product, like Prestone, not the quickie crap but the kind you put in and leave for 500 miles. Follow the directions on the product, but when it comes time to neutralize and flush pull the heater hoses and flush the heater core backwards FIRST then FORWARDS, and keep alternating the flush until the water is clear. Use a garden hose on LOW pressure, you don't want to blow the heater core and flood the cabin.

Thanks Joe. I did that in the middle of this Summer. I flushed it well, but had no reason to explain the still present overheats, even after the new fan clutch. Fan clutch was by far the common denominator of everything I read here and on a couple other forums. Water pump showed no big trouble signs like the worn out fins I have seen in pictures.

Anyway, let's hope it gets me through the Winter, then it will have been a good investment. I should be at about 175,000 miles by then.