Another overheating thread

[disco_nex]

Yes, I know it has been slaughtered to death on overheating. Got to love XJ's and overheating. If possible, I would like some experience to solve this problem.

The facts: Radiator was replaced less than 2000 km ago. The thermostat is now brand new (and has not fixed the issue), Water pump was replaced approx 25000 km ago. I can guarantee the temperature gauge is working correctly. I have a manual override switch for the A/C fan in case I want to personally turned it on (a great modification)

History: I have replaced the radiator less than 2000 km personally. It was refilled with a less than perfect 60/40 glycol water mixture, and it warmed up quicker than usual, but held the temperature as usual, with nowhere near any overheating. The XJ ran a solid 100-110 km/h trip out west for 1000 km before coming home for its usual trips to and from work.

I went for a fishing trip and it ran perfectly fine up to the location. The trip home is when the issues started to occur. It started overheating (close to redline) all the way home. The load was two persons and light camping gear. I got home and could not fine any issues. I ran it to and from work for a month with the manual overridden A/C fan on and the gauge always read between 75-105. Without the extra fan, it would run higher, closer to overheating.

Recent issues: After running the XJ with one person without issues, I picked up a mate and his camping gear for a fishing trip. With an extra approx 150 kg load, the XJ ran higher temps throughout the whole trip. The faster it went (60 km/h compared to 100 km/h), the higher then cooling temperature. When I hit the sand, that's when the temperature when to past overheat (overflow bottle was spitting water (ended up loosing 5L.). That was home time, where it drove as before the sand experience.

Question: I believe it's a water supply issue (blockage or water pump/impeller), while my father thinks it may be the catalytic converter (as it seems to be weeping a bit of water (1 drip per 15 sec at idle and parked). Lord knows how the catalytic converter can stuff around with the cooling system to me.

I'm looking for some ideas. I appreciate the time. Thanks!

[Big Dave]

Have you checked the fan clutch?

[anthonygubbin]

Are you losing coolant?

regards A

[tazwegion]

my father thinks it may be the catalytic converter

A damaged (ie. broken or clogged) catalytic converter causes additional strain on the engine thereby altering it's running temperature, additionally MPG gets worse (this happened to my last XJ) ;)


Did you flush out the cooling system when you performed the radiator and/or water pump swap?

+1 on checking out the clutch fan operation too! :mrgreen:

[ruffy01]

Water in the exhaust? surely that implies a head gasket.

[Doctor W]

Water in the exhaust? surely that implies a head gasket.

You always have a bit of water in the exhaust.....for every gallon of petrol you'll also have a gallon of water (exactly how much depends on humidity, water in the atmosphere) going thru the engine and as part of combustion process - that's why engines run better in higher humidity and colder air. Most engines will have light pinging in dry, hot air if timed optimally for "normal" temps and humidity.

A third vote for checking your fan clutch!

But it shouldn't make a difference at speed, so this could be something else or more than one cause......maybe fan clutch AND a disintegrating/ed Cat ???

[tassiecj6]

pull the water pump of and check the impeller blades .
they have been known to disintergrate in harsh water .my 95 did .
does it have addative in it ?

[disco_nex]

Thanks for the replies. I appreciate it. There seems to no sign of a cracked head, as I have checked for those symptoms. I'm going to have a crack to the clutch fan as it seems the next logical progression. If not, it looks like checking out the water pump again.

[BLU-125]

Fan clutch or are you sure the torque convertor is locking up?

[anthonygubbin]

Thanks for the replies. I appreciate it. There seems to no sign of a cracked head, as I have checked for those symptoms. I'm going to have a crack to the clutch fan as it seems the next logical progression. If not, it looks like checking out the water pump again.

In the workshop manual it talks about a reverse impeller on the pump for some models. I know it is a long shot but that could be the problem. To check its says turn on your heater and if it does not get hot then that could be the issue.

regards A

[disco_nex]

Fan clutch or are you sure the torque convertor is locking up?

The torque convertor is locking up nicely. Thanks.

[disco_nex]

In the workshop manual it talks about a reverse impeller on the pump for some models. I know it is a long shot but that could be the problem. To check its says turn on your heater and if it does not get hot then that could be the issue.

regards A

Cheers. If it was the pump impeller, it should of manifested itself a long time ago. I cannot check it anyway. The heater core is bypassed after it failed a few months ago. It's been a cold winter

[Doctor W]

In the workshop manual it talks about a reverse impeller on the pump for some models. I know it is a long shot but that could be the problem. To check its says turn on your heater and if it does not get hot then that could be the issue.

regards A

All Aussie 4.0L I6's were the later (than the early "Renix" 1984-91) engines which have the reverse flow pumps.....the genuine Jeep pumps have "Reverse Flow" stamped on the impeller.

[anthonygubbin]

All Aussie 4.0L I6's were the later (than the early "Renix" 1984-91) engines which have the reverse flow pumps.....the genuine Jeep pumps have "Reverse Flow" stamped on the impeller.

Can't be that then?? Like I said it was a long shot. Unless someone has put the wrong pump on although that seems unlikely. I know they sold me the wrong pump for my XJ just the other day. Maybe someone has imported one and fitted that? Although from what has been said so far this seems like only a recent problem, so should really rule out the wrong pump theory.

Regards A

[Doctor W]

Can't be that then?? Like I said it was a long shot. Unless someone has put the wrong pump on although that seems unlikely. I know they sold me the wrong pump for my XJ just the other day. Maybe someone has imported one and fitted that? Although from what has been said so far this seems like only a recent problem, so should really rule out the wrong pump theory.

Regards A

Impeller blades could have slowly rotted away due to bad/incorrect type/strenght coolant mix......could possibly be the problem - how old is the pump?

Although bad fan clutch is most likely, except that it happens at speed also when ther's good air flow.

[quints]

I'll echo the fan clutch. Replacing the clutch on mine fixed my hot running well and truly (thanks, Wooders). Gee, and isn't that a fun job to do.

Just a quick comment on the coolant ratio. Generally, the specific gravity of the ethylene glycol based products is off the planet. Try picking up a 20 litre drum of the stuff sometime. At anything over 50 / 50, it starts to struggle to dissapate heat. At ratios like 60 / 40, the vehicle will run hotter. How much hotter? Well, a Gp C touring car I used to know would sit on about 98 C all day around a certain mountain at Bathurst on a '33 / 66' mix. One of the geniusses on the car's crew -- figuring the label on the drum meant something more than it did -- decided to put straight anti-freeze / anti-boil in the radiator. It went three laps before it spewed every drop out going up the mountain.

[tazwegion]

All Aussie 4.0L I6's were the later (than the early "Renix" 1984-91) engines which have the reverse flow pumps.....the genuine Jeep pumps have "Reverse Flow" stamped on the impeller.


Are the OEM impellers cast OR folded steel? I ask because I had for many years been under the impression that cast impellers were of inferior performance, the aftermarket units appear to offer both styles ;)

[Gtscott]

what do you consider to be signs of a cracked head? as in what did you check for?
id do a compression test and tk test just to be sure its not the head gasket as you said it was overheating for a full trip home (though didnt say distance travelled in that trip)
also what temperature thermostat did you replace it with when you changed it?

[Deezelweazel]

Start with cheap things. Take out the thermostat and throw it into vegetable oil. Heat it up and measure the opening temperature, check the thermostat movement.

[anthonygubbin]

Start with cheap things. Take out the thermostat and throw it into vegetable oil. Heat it up and measure the opening temperature, check the thermostat movement.

Does that really work? I have heard a few people say something similar. But how does a mechanical device compress the spring simply by heat? Is there fluid inside the thermostat core that expands? I have seen a few people test that method and I have never seen one open yet.

Regards A

[tazwegion]

I have seen a few people test that method and I have never seen one open yet.


Then the thermostat was defective... this test (in water) works for me everytime, get a few odd looks from the missus though :mrgreen:

[anthonygubbin]

Then the thermostat was defective... this test (in water) works for me everytime, get a few odd looks from the missus though :mrgreen:

Ok then I believe it. I just don't understand how it could work, unless there is some sort of fluid inside thermostat core.

regards A

[Deezelweazel]

Oh trust me, it will. There is wax inside the chamber. It expands and opens the valve. Put a bit string on the valve so you can lift it to see the opening process.

It should start to open around 80°C. You can use a caliper to measure closed and opened valve difference. Water will work too, but the bubbles make the progress difficult to see at 100°C- use veg. oil instead.

[anthonygubbin]

I just cut mine open and no wax. A bit of rubber though. I just rang a mate who manufactures specialised car parts for overseas vehicles and he said it does work. He suggested something to do with the expansion of brass when it reaches a certain temp.
I am still baffeld but have been converted. I might look into it some more, why, because I get annoyed when I can't work out why something does what is does. LOL

Sorry for diverting the thread for a bit there Disco.

From what you have said it does sound more like a non performing fan as when you turn on the aux fan it cools.

I read in the manual that some of the fans have silicone in them and that they should always remain vertical or damage can occur to the fan, by the grease and silicone mixing together. Could that be a possibility?

Regards A

[Deezelweazel]

The manual describes also the test procedure for the fan...

[disco_nex]

what do you consider to be signs of a cracked head? as in what did you check for?
id do a compression test and tk test just to be sure its not the head gasket as you said it was overheating for a full trip home (though didnt say distance travelled in that trip)
also what temperature thermostat did you replace it with when you changed it?

The signs I checked for a cracked head were: Excessive water in the exhaust, an unexplained loss of coolant, spark plugs overly white in colour and milky engine oil.

The compression test will be done tomorrow. See how it goes from there. The thermostat is a 195F unit, and it was changed only yesterday, for the same problems occuring.

Someone mentioned the water pump, it is roughly 1.5 years old.

[disco_nex]

I just cut mine open and no wax. A bit of rubber though. I just rang a mate who manufactures specialised car parts for overseas vehicles and he said it does work. He suggested something to do with the expansion of brass when it reaches a certain temp.
I am still baffeld but have been converted. I might look into it some more, why, because I get annoyed when I can't work out why something does what is does. LOL

Sorry for diverting the thread for a bit there Disco.

From what you have said it does sound more like a non performing fan as when you turn on the aux fan it cools.

I read in the manual that some of the fans have silicone in them and that they should always remain vertical or damage can occur to the fan, by the grease and silicone mixing together. Could that be a possibility?

Regards A

A copper srping within the thermostat heats up and once a certain temperature is reached, it opens a valve, allows water to flow through the radiator.

[Deezelweazel]

How does the thermostat in a car's cooling system work?

http://auto.howstuffworks.com/question248.htm

:rolleyes:

[anthonygubbin]

Thanks Deezel, now I understand. But I have scewed this thread enough, so it might be best to see if we can help Disco work out why his XJ is overheating.

Regards A

[disco_nex]

Thanks Deezel, now I understand. But I have scewed this thread enough, so it might be best to see if we can help Disco work out why his XJ is overheating.

Regards A

No harm done. Always good to see other people learning!

[Deezelweazel]

Check the orientation of the thermostat too, Disco.
In my opinion you have to recheck every item step-by step. Did you alter anything? Like belt running orientation? Don't laugh, I have seen belts mounted in the wrong direction- so the water pump was running reversed.
Do you still have the fan shroud mounted?

[disco_nex]

Check the orientation of the thermostat too, Disco.
In my opinion you have to recheck every item step-by step. Did you alter anything? Like belt running orientation? Don't laugh, I have seen belts mounted in the wrong direction- so the water pump was running reversed.
Do you still have the fan shroud mounted?

The orientation of the thermostat is correct. It can only go in one way. The belt is correct, because it has been running the same direction since it was replaced with the water pump. The problem would of manifested itself a long time ago if it was the issue.

[disco_nex]

Well, problem solved. It was the clutch fan.

Thanks for you help people. I appreciate it.

[Doctor W]

Then the thermostat was defective... this test (in water) works for me everytime, get a few odd looks from the missus though :mrgreen:

Doesn't our missus know how to cook a thermostat?......bring to boil and gently simmer for a few minutes.....serve with Sirloin steak, Bearnaise sauce and some nice veges.....a really nice dish!

[tazwegion]

Doesn't our missus know how to cook a thermostat?

It's that disapproving look you get when using some special cooking vessel for automotive diagnosis...

[Antiferret]

i know the prob is now sorted, but i will round this thread for completeness.

2 other items that need to be checked are belt tension and rediator cap.
both these have caused dramas in the past..

[Mopar69/95]

how can you tell if your clutch fan is buggered?

I dont advise adding grill mesh, i did last sunday, drove monday morning and uninstalled monday night. Ok when cruisin but doesn't allow enough flow in stop start traffic causing the temp to rise to 110/120.

I have recently changed my radiator and temp stays normal on the highway but city driving gets to temp and drops by half when thermostat opens(95deg). Will adding gojeep's restrictor fix this, im just worried it may fix for city driving but will stuff highway driving or with load?
Any ideas?

[Billnick]

My understanding is that any hole moving in the wind has turbulence around it restricting the flow. The more individual holes you have in a grille the more turbulence you create. Vertical slots like the Jeep allow more air through than mesh of the same size. You get the same effect with a flyscreen door, you can get a lot more air flowing, particularly in a stiff breeze by opening the door, even though the physical area of the wire is relatively small.

[carvesdodo]

how can you tell if your clutch fan is buggered?


General rule of thumb & guestimation ....

1/. When the engine is cold ... the fan will be firm for the first few spins by hand ... and then it will free up and spin easily.

2/. After the vehicle has been running and the coolant temp is above about 80* ... switch off engine and spin the fan ... It should should be firm and not free up after a few spins.

If its constantly firm ... or constantly free spinning ... Its not working as intended.

Constantly firm is acceptable ... as it will be performing like the old style, "non-thermal" fanclutches .... but it will be costing you a small percentage loss in fuel & horsepower in the course of your daily driving.


I dont advise adding grill mesh, i did last sunday, drove monday morning and uninstalled monday night. Ok when cruisin but doesn't allow enough flow in stop start traffic causing the temp to rise to 110/120.


Sounds more like your fanclutch is an issue .... coz there is minimal flow regardless - in stop/start conditions.

If and when you get round to needing a new fanclutch ... try the mesh again for a comparison.


I have recently changed my radiator and temp stays normal on the highway but city driving gets to temp and drops by half when thermostat opens(95deg). Will adding gojeep's restrictor fix this, im just worried it may fix for city driving but will stuff highway driving or with load?
Any ideas?


The temp drops from 100* to 50* ???? .... bit hard to do if the thermostat is working properly ...

Does it go 100 - 50 - 100 - 50 .... or just drop to 50 ? ..

If you do enough city driving ... does the temp stabilise at a higher temp ?

How many temp sensors does yours have .. One or Two ??

Personally ... I'd make sure that the thermostat functions properly ... Maybe even see what happens with the heater on and off - if yours has a tap control on the heater hoses.

and if you only have the one temp sensor ... Make sure the system has enough coolant in it so that the temp sensor, which is mounted higher than the thermostat .... is definitely submerged in coolant ... before buggerising around with unnescessary restrictors.

[Mopar69/95]

General rule of thumb & guestimation ....

0The temp drops from 100* to 50* ???? .... bit hard to do if the thermostat is working properly ...

Does it go 100 - 50 - 100 - 50 .... or just drop to 50 ? ..

If you do enough city driving ... does the temp stabilise at a higher temp ?

How many temp sensors does yours have .. One or Two ??

Personally ... I'd make sure that the thermostat functions properly ... Maybe even see what happens with the heater on and off - if yours has a tap control on the heater hoses.

and if you only have the one temp sensor ... Make sure the system has enough coolant in it so that the temp sensor, which is mounted higher than the thermostat .... is definitely submerged in coolant ... before buggerising around with unnescessary restrictors.

i have a 95 limited 4.0, im pretty sure its just the one sensor. coolant is full and uses the overflow bottle properly.

I drive 15km to work at 11:30pm most nights with the heater on full and home at 8.30am with just vent. either way makes no difference, the temp will raise to just below half, maybe stay for a bit then drop quickly to half that, pretty much on the 1/4 line. then slowly raise again to just below half and so on all the way to and from work.

i just cruise to work at 60, usualy with cruise control and the revs sit on about 1100/1200rpm so its def not having to work hard. when cruising at 110 on the highway normal temp is constant.

the thermostat is prob only 2 years old maybe. cant remember exaclty but should still be good.

[Billnick]

i have a 95 limited 4.0, im pretty sure its just the one sensor. coolant is full and uses the overflow bottle properly.

I drive 15km to work at 11:30pm most nights with the heater on full and home at 8.30am with just vent. either way makes no difference, the temp will raise to just below half, maybe stay for a bit then drop quickly to half that, pretty much on the 1/4 line. then slowly raise again to just below half and so on all the way to and from work.

i just cruise to work at 60, usualy with cruise control and the revs sit on about 1100/1200rpm so its def not having to work hard. when cruising at 110 on the highway normal temp is constant.

the thermostat is prob only 2 years old maybe. cant remember exaclty but should still be good.

Oddly enough my 98 XJ with a new radiator and no A/C radiator does the same. I can get the gauge to read normal if I gun it off the lights. When the temps were cooler I put a 12" x 9" piece of flat tin in between the rad and elec fan which fixed it. Seems to be the thermostat shutting down because the engine is running too cool.

[disco_nex]

i know the prob is now sorted, but i will round this thread for completeness.

2 other items that need to be checked are belt tension and rediator cap.
both these have caused dramas in the past..

Thanks for that. Always a good idea if someone uses it for reference

[Mopar69/95]

did the test and im pretty sure my clutch fan is buggered. that would explain gettin warmer when not moving.

also i've never actualy seen or heard my thermo come on either...?

my aircon use to work but as far as i can remember it hasnt worked since i installed my head unit so im thinkin i stuffed something with the controls in the dash. by moving the knob to air con nothin happens at all.

if the relays for the aircon are stuffed or something else isnt right with the aircon system(electicly) will the thermo still work when the temp reaches 105?

[nixon]

how can you tell if your clutch fan is buggered?

I dont advise adding grill mesh, i did last sunday, drove monday morning and uninstalled monday night. Ok when cruisin but doesn't allow enough flow in stop start traffic causing the temp to rise to 110/120.

I have recently changed my radiator and temp stays normal on the highway but city driving gets to temp and drops by half when thermostat opens(95deg). Will adding gojeep's restrictor fix this, im just worried it may fix for city driving but will stuff highway driving or with load?
Any ideas?

You'll know it buggered because you'll hear it, mine went and you know it's gone all it takes is to lift the bonnet and u can hear where it's coming from. It's like a $90 fix though, but it's a pain to pull out and replace.

[disco_nex]

Well, not to kick this thread again, but I thought I would do it for reference. The clutch fan DID need replacing, but it has not fixed the problem. Just from a practical point of view, this is an example of how the most recent overheating issue occurred:

I drive at a continuous 80-100 km/h with the air conditioning on for 20 km with the temperature sitting at near 100 C. The outside air temperature is near 30 C. As traffic slows, I switch the air con off and switch on the auxiliary fan via my override switch while driving at a mixture of city and open road driving for 10 km. The operating temperature increases to near boiling temp.

My theory is that it is the water pump now. Seems to be little water pressure through the top radiator hose while at operating temperature.

Other people believe it could be a head gasket. I have considered it, but there has been no water out of the exhaust, no mystery coolant loss and the spark plugs are clean.

[Easy Rollins 1]

Wrong temp range thermostat?
Clogged radiator?

[junglejuice]

i have a 95 limited 4.0, im pretty sure its just the one sensor.



The 94's & 95's have two temp sensors, one at the front near the thermostat and one at the rear of the head near the intke manifold, the rear one is for the guage the front is for the ECU...

[disco_nex]

Thanks for suggestions Easy Rollins and JJ.

The thermostat is brand new and is the correct model. The radiator cannot be clogged, as it is relatively new, plus I had back-washed it recently.

I will consider the temp sensors as well, but I am pretty sure they are working correctly from my experience