Jeep Grand Cherokee WK2 Diesel Thermostat fault

Wk2 diesel running hotter than it used to?

I have a theory and i think i have almost got to the bottom of it.

We have probably replaced thousands of thermostats on jeeps over the years and only ever used genuine Jeep parts.

Some customers reported that the car still behaved as normal but now it runs hotter with the temp gauge getting up to three quarters or close before the fans kick in.

We compared lots of Jeeps and we spoke to Jeep Australia who all said it’s normal.

The knock on effect is that whilst the coolant temp runs a few degrees hotter, the engine oil temp also exceeds 100degrees.

Our theory is …….

The thermostats fitted to the wk2 on the production line opens at 87-90degrees Celsius.

For what ever reason the genuine Jeep sold off the shelf in Australia (in a box, not fitted to the car) opens at 95-98 degrees.

I have tested several of these now and have confirmed this fact. Genuine Jeep fitted to the car and genuine Jeep sold from the dealer parts department consistently have 8-10 degree variations. I cant explain why.

The dayco product (part number to be confirmed, i left the box at work) opens at 88 degrees.

I have now run two jeep wk2s with all three thermostats and as a test with no thermostat and found the dayco and the original fitted thermostat eliminated the warmer temp and the oil temp exceeding 100 degrees. The genuine jeep part from jeep parts departments introduced this problem.

Don’t fit genuine thermostats from part departments.

But if your jeep is running warmer after cooling system work get the Dayco 88 degree thermostat. They Dayco part number needed is DT248D

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