Changed every cooling system component - Jeep still overheats

99 Jeep Cherokee
4.0 Liter



Since last year gradually changed:

• Fan Clutch
• Electric Fan
• Thermostat (Super Stant 195)
• Water Pump
• Drive Belt
• Radiator

Been acting up recently so I finally changed the radiator.

Before installing the new rad, I did a super flush with preston flush, drove it for three days, drained and flushed it, super gross brown water. I must have flushed it once a day after that running just water for 5 days until all the brown water stopped coming out. Filled it with a a 50/50 mix currently.

Its 111 degrees today in Las Vegas. I ran the jeep up-hill on the highway, temp gradually climbed to 240 before I stopped and headed back home.

I honestly don't know what else to do. Every part I changed is brand new or less than a year old.

Any suggestions or troubleshooting is welcome. Thanks guys.

What radiator did you use ? the core thickness is vary important . OEM heavy duty towing radiator was 1 1/4 of a inch thick . and what fan clutch did you use ? all so check the a/c condenser to see that it is clean and that the fins are not plugged stopping air flow .

Both of my XJs have run Mopar's HD XJ radiator, #52080104AC for years with good results, even during the present heatwave, 110 here today.
http://www.factorymoparparts.com/52080104ac.html

Besides possible having too small radiator, the A/C condenser can also reduce cooling, even if the A/C is not used.
The condenser has very fine fins that can slowly plug up with debris up to the point where the air flow is significantly reduced and does not allow enough flow on a hot day.

Anytime the grill and/or the radiator is removed, I make sure to clean the condenser by spraying and saturating the condenser with a strong cleaning degreaser solution and letting it soak for a while and then gently using a water spray to wash the debris out. The fins are delicate, be careful not to damage them with too strong a spray. Straighten out any bent fins.

Any chance it has a head gasket leak into the cooling system.
A combustion leak test might be in order.

Running hot can be caused by many things. Here are a few

1) Running too lean, caused by vacuum leak such as intake, or vacuum booster, etc.

2) Exhaust back pressure caused by plugged cat or crimped exhaust pipe.

Hooking up a vacuum gauge can tell you a ton.

3) Cam not indexed correctly. While this can cause an engine to run hot, you would normally notice a change in performance.

4) No radiator shroud

5) Bad fan clutch

6) Wild card.....the wrong water pump. They look the same but the pump for a v-belt setup are designed to run the opposite direction.

7) Bad O2 sensor or bad O2 output due to crack in upstream header

8) Clogged injectors causing it to run too lean. A tailpipe sniffer can help diagnose a bunch.

9) Slipping transmission dumping heat into transmission cooler in radiator.

10) Various issues messing with ignition timing. Can be verified with an old school timing light.

11) Headgasket or cracked block allowing exhaust into cooling system. Can be diagnosed with a tailpipe sniffer but using it to see if hydrocarbons are in the coolant. You can also by a relatively cheap system that uses a liquid and a small bulb pump to sniff the radiator as well.

12) Plugged radiator.

13) Lower radiator hose that collapses when it gets hot.

14) A air bubble in coolant

15) Pull and do a reading on the spark plugs. Old school but it works.

16) A old worn out radiator cap. They should be changed every 2 years. Run a 16lb one.

Given all those, start with reading the plugs. It can diagnose a multitude of problems. Follow up by making sure it is actually overheating. Does it boil over? Use a non-contact IR meter and look at the thermostat housing.

tech1001 said:

What radiator did you use ? the core thickness is vary important . OEM heavy duty towing radiator was 1 1/4 of a inch thick . and what fan clutch did you use ? all so check the a/c condenser to see that it is clean and that the fins are not plugged stopping air flow .

Click to expand...

• This Radiator;Core thickness 1 Inch
• This Fan Clutch
• Will check the ac condensor for blockage

Thanks!

lazyxj said:

Both of my XJs have run Mopar's HD XJ radiator, #52080104AC for years with good results, even during the present heatwave, 110 here today.
http://www.factorymoparparts.com/52080104ac.html

Besides possible having too small radiator, the A/C condenser can also reduce cooling, even if the A/C is not used.
The condenser has very fine fins that can slowly plug up with debris up to the point where the air flow is significantly reduced and does not allow enough flow on a hot day.

Any chance it has a head gasket leak into the cooling system.
A combustion leak test might be in order.

Click to expand...

• Thanks for the link! This will be the next rad I get, but I dont think its a rad problem... i've owned the jeep for years and it's never had overheating problems like this.
• Will def clean out the condenser for peace-of-mind and preventative maintenance

lazyxj said:

Any chance it has a head gasket leak into the cooling system.
A combustion leak test might be in order.

Click to expand...

I had a freeze plug go bad a couple years back and had the engine overheat a few times as a result before I found the leak.

I replaced the head gasket, intake valve (cracked), Exhaust valve (cracked) and fuel injectors (cracking). However it's never ran the same... lack of power and random misfire codes.

I have yet to take it apart and figure out where I went wrong. But these overheating problems are a recent occurrence

@Old_man, thanks for taking the time to write that list! Here are my responses:

1) Running too lean, caused by vacuum leak such as intake, or vacuum booster, etc.

I def have vacuum leaks, When I accelerate on the highway I lose my AC until the RPM's drop back down and I'm cruising again.


2) Exhaust back pressure caused by plugged cat or crimped exhaust pipe.

Exhaust pipes are good to go. Cant speak for my cat.


3) Cam not indexed correctly. While this can cause an engine to run hot, you would normally notice a change in performance.

I have lack of performance ever since I put the engine back together, read my reply above^

4) No radiator shroud

Properly Installed.

5) Bad fan clutch

New clutch installed Jan 2018

6) Wild card.....the wrong water pump. They look the same but the pump for a v-belt setup are designed to run the opposite direction.

Installed Jan 2018

Pretty sure It's correct.

7) Bad O2 sensor or bad O2 output due to crack in upstream header

Both 02 sensors changed May 2017. Cracked Exhaust header replaced May 2017 as well.

8) Clogged injectors causing it to run too lean. A tailpipe sniffer can help diagnose a bunch.

This is a possibility. I bought the upgraded 4 hole injectors and one of them was initially bad and had to be replaced. How do I check if they are clogged?

9) Slipping transmission dumping heat into transmission cooler in radiator.

Transmission is shifting fine (thank god)

10) Various issues messing with ignition timing. Can be verified with an old school timing light.

I will research how to do this.

11) Headgasket or cracked block allowing exhaust into cooling system. Can be diagnosed with a tailpipe sniffer but using it to see if hydrocarbons are in the coolant. You can also by a relatively cheap system that uses a liquid and a small bulb pump to sniff the radiator as well.

Never heard of this, might be worth it to take to a mechanic to do this test.

12) Plugged radiator.

Nope, brand new, super flushed before install

13) Lower radiator hose that collapses when it gets hot.

Hmm, maybe, it looks a little cramped down there. I replaced it and doesn't have the spring in it.

14) A air bubble in coolant

Tried burping it, It seems to be at capacity. no air bubbles.

15) Pull and do a reading on the spark plugs. Old school but it works.

Might be a good time to do this, yes.

16) A old worn out radiator cap. They should be changed every 2 years. Run a 16lb one.

This one is maybe 6 months old. 16lbs.

Follow up by making sure it is actually overheating. Does it boil over?

It does. I used a bluetooth ODB II sensor and run the Dashcommand App on my phone to get an accurate reading of the temp.

Use a non-contact IR meter and look at the thermostat housing

Been planning on buying one of these, seems like this is a good excuse to get one.

Thanks again for all of this. Looks like I'll prioritize my list of to-do's starting with the plugs.

Well do something about that list!

I do not think a single 1 inch tube in the XJ radiator is going to cut it in hot weather going up hill,...but then again I have been wrong before.

A vacuum leak is most noticeable when on the gas and under load not on deceleration.

techno1154 said:

A vacuum leak is most noticeable when on the gas and under load not on deceleration.

Click to expand...

Not to clutter up this thread, but I've had a whistle under the hood for years, which has survived this recent engine replacement. Only happens when decelerating or coasting in neutral when hot after highway travel. Figured it was a vacuum leak but can never seem to locate it. Only ever heard it in the cabin and have never been able to reproduce it under the hood goosing the throttle. Where am I not looking?

First things first. Find and fix the vacuum leak. It can also mess with sensor readings and fool the ECU.

Do a plug reading and post up the pix.

I'd suggest you pull the head, pressure test the head, if OK then resurface and remount it. When I first bought my 88XJ, I had an overheating problem. I took it back to the dealer who pressure tested and found it to be OK. Then one hot day, while accelerating, I saw a puff of white exhaust smoke which then stopped after accelerating. Apparently, the head was lifting ever so slightly and hot exhaust gas was getting into the cylinder and coolant and then the head would reseal. I took it back to the dealer and explained what I saw. The dealer pulled the head, pressure tested, resurfaced it and remounted it. End of problem.

My 2000XJ was doing the same thing. I pulled the head, had it pressure tested, resurfaced, and remounted. End of problem.

Best regards,

CJR

You said it mostly happens at higher speeds/RPM's. You said you don't have the spring in the bottom radiator hose.

When that hose is new and pliable it can partially collapse from the pump suction. Pull the air box out so you can see, warm up the motor, gun it to 5 grand or so a few times watch that bottom hose. Pinch it between your fingers after it gets hot and see how it feels.

Those hoses can also separate in layers, outer layer, then the weave for strength and inner layer. The inner layer can separate from the weave and cause issues. I've seen it on really old hoses.

After the second time (once on mine and once on a buddies) I saw not having the spring inside the bottom radiator hose cause high RPM cooling issues, I made sure it was in there, positioned correctly and long enough.

Sometimes new hoses come with springs that are too short or a smaller diameter spring can shift downstream and partially enter the pump intake. When the spring is too sort or shifts it can leave enough hose un-reinforced enough to (partially) collapse. Mostly after market springs, the original spring may be a bit larger diameter and seems to stay in place better.

I didnt see you list a new radiator cap... I see you said you flushed it a few times, I have noticed the cap goes 'bad' and does not hold pressure when removed a few times

Well, I'll offer a slightly difference viewpoint.

At 111 deg, the surface temps can rise well about 140 deg. Climbing a hill at freeway speeds on top of that can generate a lot of heat.

I'm in Socal and occasionally take the I-15 through the Cajon pass. In summer time, I see lot's of overheated cars stopped on the side of the road. My own 88 get very hot. When it does I slow down, even shift into 3rd to keep the RPMs up and pull over for a few minutes when needed.

Here's a video I used to bleed air from my coolant system. Bought one of those big ass funnels and this way of bleeding has worked really well for me.

https://www.youtube.com/watch?v=nLvgRrak_5E&t=5s

You could always give Royal Purple "purple ice" a shot and see if it helps at all.

I have been on since 2000 ( I feel as if I am one of the grand fathers here) and I have seen probably over a thousand over heating thread. It seem to occur mostly in the summer in the hilly part of the country. Here in mostly flat Florida and Texas not so much. The one thing every XJ owner do in common is to replace the radiator. I am not saying the radiator do not or should not be replaced. I have owned my XJ some 13 years and getting ready to replace the radiator a second time.

Many posters here on replaces the radiator with a bargain brand radiator then chase their tails for months afterwards and spend countless $$ doing everything else that could be done to the cooling system with very little to show for it. Coming from a person who have installed dual electric cooling fans in place of the OEM mechanical and electric fans, I find the OEM cooling system to be up to the task in all but the harshest environment. It is true there are not a lot of extra cooling built into the system i.e. every part must be in good condition and properly maintained but a good OEM system does its job properly.

Take a look at lazyxj's posts over the years and borrow a page from him(he do not mind) in rebuilding your cooling system in the XJ. What I do not know about your XJ is whether or not other engine problems contribute to the over heating you are experiencing.

The_Punisher said:

Here's a video I used to bleed air from my coolant system. Bought one of those big ass funnels and this way of bleeding has worked really well for me.

https://www.youtube.com/watch?v=nLvgRrak_5E&t=5s

You could always give Royal Purple "purple ice" a shot and see if it helps at all.

Click to expand...

What amazes me here is the number of people who bleed an open cooling system. It is true the Renix with the closed cooling system as do all closed cooling system need or should be bled of air the open system is self bleeding.
It is all so simple:---- fill the radiator(and engine) with coolant.
fill the recovery bottle with coolant.
run the engine until it reaches operating temperature.
shut the engine off and allow it to cool.
top up the recovery bottle.
you are done.

There's a lot of experienced folks here. I'm new to XJ life, I bought a nearly perfect 99 4.0L. A few days after purchase it started slowly overheating when loaded (highway/hot day). After replacing every cooling system component, I did a block test with the engine HOT and the cooling system tested positive for exhaust gases (head gasket/cracked block). This is number 11 on old_man's list. See my picture below for how the fluid is no longer blue but has turned yellow. You can google how to do this, but it was very difficult to do with the engine hot like that.

See CJR's comments in the previous page. The point I want to make here is that if you are being optimistic and just trying to replace small things, that will all be a waste if you have a more serious issue lurking. I would pay to have the block checked before going too much further.

The kit ran less than $50 at NAPA.

I owe you guys an update:

old_man said:

First things first. Find and fix the vacuum leak. It can also mess with sensor readings and fool the ECU.

Do a plug reading and post up the pix.

Click to expand...

VACUUM LEAKS

• I pushed air and cigar smoke through my intake manifold and found air escaping from the #4 fuel injector
• Turns out the o-ring was a bit too small (left o-ring on pic)
• After this fix, the jeep is so much smoother and shifts much better.
• Drove it uphill on highway and jeep still seems to struggle keeping up with traffic (might be due to the tire/gear ratio)
• 101 Degrees out - jeep took a bit longer, but still overheated
• Stopped once it got near 230 and went back home

PLUG CHECK

• Pulled the plugs
• Overall they seem okay
• #4 plug had a few particles, i'm assuming from not having a perfect leak (small o-ring)
• Cleaned them off, checked the .035 gap, and re-installed with 27 ft lbs)

RADIATOR CAP AND HOSES

• forgot to mention in original post that the radiator cap, and hoses have also been replaced
• Lower radiator hose changed Jan 2018
• Upper Radiator Hose changed Jan 2018
• New 16lb Rad Cap installed Jan 2018

User: 8Mud Mentioned to watch the lower hose when hot.

8Mud said:

...warm up the motor, gun it to 5 grand or so a few times watch that bottom hose. Pinch it between your fingers after it gets hot and see how it feels.

Click to expand...

I did this and seems like it held rigidity well under high heat.

techno1154 said:

I have been on since 2000 ( I feel as if I am one of the grand fathers here) and I have seen probably over a thousand over heating thread. It seem to occur mostly in the summer in the hilly part of the country. Here in mostly flat Florida and Texas not so much. The one thing every XJ owner do in common is to replace the radiator. I am not saying the radiator do not or should not be replaced. I have owned my XJ some 13 years and getting ready to replace the radiator a second time.

Many posters here on replaces the radiator with a bargain brand radiator then chase their tails for months afterwards and spend countless $$ doing everything else that could be done to the cooling system with very little to show for it. Coming from a person who have installed dual electric cooling fans in place of the OEM mechanical and electric fans, I find the OEM cooling system to be up to the task in all but the harshest environment. It is true there are not a lot of extra cooling built into the system i.e. every part must be in good condition and properly maintained but a good OEM system does its job properly..

Click to expand...

Very good point. You may be 100% correct. I just moved from FL. So my jeep isn't used to this heat or hills. There is a current heat wave coming through now. High heat, in combination with cheap parts may be the reason behind my demise.

What I do notice is at night, it takes much longer to overheat (duh).

But additionally, the three days when I did the preston flush, I was running ONLY distilled water and the engine did not climb over 210 once. The problem started again after the flush was done and I introduced a 50/50 mix.

If my current engine issues are not contributing to this overheating problem then my choices are clear:

1. Buy better parts ($300 radiator instead of a $100 radiator)
2. Run distilled water/Water Wetter until winter time and then swap back to antifreeze 50/50