4.0l XJ overheating? Start here - the basics!

[werd]

I went for a drive today and the temp gauge was nudging at the top end of the scale. I relocated the relay coil power source and it's all good now.
After a big workout the gauge is sitting on about 107C

[hillsjeep]

Can I get your opinion on this, I'm not sure if I have a heating issue or just a "hit and miss" gauge.

I've just put a lower mileage second hand engine in my XJ. The old one used to always sit just around 100, but I regularly got low engine temp codes. The new engine sat between 100 and 3/4 but still got low engine temp codes, so I swapped the 82* t/stat for a 92* and now the gauge sits right on 3/4 but no more low temp codes.

It has 2 coolant temp sensors so the gauge is fed from the rear sensor and the PCU from the front.

My TJ always sits on 100 or just below/above. I took it for a long drive today and then measured the temp on the block near where the rear sensor would be, the top heater hose and t/stat housing and the numbers match the XJ almost exactly.

So could the difference in gauge reading just be the difference between the t/stat sensor in the TJ and the rear sensor in the XJ or is it more likely the gauge just isn't that accurate?

The XJ has never shown any other signs of overheating and has a good quality after market radiator and is maintained well and sits around 3/4 (112.5*) regardless of weather, accent or decent, speed etc.

Is it possible to connect the gauge to the t/stat housing sensor and see if it matches the TJ then?

[hillsjeep]

well I've found the issue. I replaced a stuffed t/stat with a new cheap t/stat from ebay which was also rooted.

after taking it back out and heating both t/stats I found the old one opened at 82* but didn't close properly which explains the previous low temp alerts and the fact that when decending Mt Lofty the temp reported below 1/4 on the gauge on cold mornings.

The new 91* t/stat barely opened at 100* which explains the higher temps I had with it.

I purchased a new expensive 82* t/stat like my old one and now the temp is sitting just over half even going up Mt Lofty with the A/C on.

Hopefully now that it closes properly there will be no more low temp codes.

[wikchi]

Sorry to bump a older thread but i did the cooling system on mine a couple of weeks ago and its still heating up to about 100-105 while on the beach.

Thinking of making a hood scoop and vents is there anything else i can do for improved airflow?

[kyphonii]

Originally Posted by wikchi

Sorry to bump a older thread but i did the cooling system on mine a couple of weeks ago and its still heating up to about 100-105 while on the beach.

Thinking of making a hood scoop and vents is there anything else i can do for improved airflow?

What did you do so far.



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[wikchi]

New clutch fan
New Electric fan
New 3 core alum rad
New pipes
new waterpump
New thermostat
all gaskits done in cooling system
holds water fine but still overheats enough that it feels pretty hot especially at t he back of the firewall and at the footwells at the front, would more airflow through the bonnet and sides help?

[kyphonii]

Originally Posted by wikchi

New clutch fan
New Electric fan
New 3 core alum rad
New pipes
new waterpump
New thermostat
all gaskits done in cooling system
holds water fine but still overheats enough that it feels pretty hot especially at t he back of the firewall and at the footwells at the front, would more airflow through the bonnet and sides help?

Dose it get over 105 degree Celsius.
One mark right (hotter) then the middle. Of the gauge.
It's suppose to run about one mark either side of the middle.
It's a cast iron head and block. Not critical on temp like aluminium heads.
The exhurst will hear the floor.


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