4.0l XJ Overheating

[Billnick]

Originally Posted by junglejuice

but now the temp is all over the place from just over 1/4 (around 70*) up to the normal 90's range according to the guage, it doesn't look like a lot on the guage but when it never used to move at all it is a little odd.
.

Sounds like those fans are cooling the water temp down too much. You could cut down the airflow with a bit of removable plywood, rework the fans or put a piece of tape over the gauge.

[junglejuice]

Originally Posted by Billnick

Sounds like those fans are cooling the water temp down too much. You could cut down the airflow with a bit of removable plywood, rework the fans or put a piece of tape over the gauge.

The fan mod went in back in about 2009 so I seriously doubt that will be the issue, the first sign of any fluctuation albeit only minor ie you could detect on the guage when the t/stat would open and close was after doing the engine swap but at the same time I had to put in a new temp sensor as it broke but it was minor not like now, if I have the AC on which means the fans are both on full speed the temp stays around the 70 mark, if I leave the AC off the fans run on low speed the temp will eventually come up higher but still not quite to where it used to.
I am thinking it may be the t/stat, I still have the original from my engine even though it is at least 8.5yrs old but was always stable and I still have the t/stat from the new motor which is ??yrs old so it will be interesting to swap them back in and see what happens....

[Billnick]

The point I was making is now the rad is super efficient and doesn't require the same amount of air pulled through it to maintain a stable temp. I'm thinking one of those flow restrictors made out of a nylon cutting board would do the trick.

[junglejuice]

Good point, I will try the thermostat first before modding it....

[Rodgebone]

sounds like the t-stat is stuck open

[junglejuice]

Originally Posted by Rodgebone

sounds like the t-stat is stuck open

Sometimes maintenance doesn't help when you replace a perfectly fine working t/stat with a new potentially dodgy one....

[rastus2571]

When I did the scenic rim trip with the boys from the patrol 4x4 forum my xj was bubbling and overheating with about 2-3 hours of low range offroad hardcore rock crawling work.

The green machine was working hard with those lockers and centipede 31's.

Jason on here (who came out with us for the day) put me onto a tip of folding the wings
back and down from the vents under the bonnet, I did this mod and found it did slightly lower the temps running around at home.

I did not do this on the day.

However I did pop the bonnet on the day and left it on the safety latch for the rest of the day to get the hot air out under his advice.

So what I have done for mine now is left the main guts of the thermostat in and raised the back of the bonnet up with longer bolts and washers to let it get the hot air out at a 25mm raise and it sits on 70 now no matter how hard I push it.

And I do work the green machine. The bonnet raise gets the heat out.

I am also putting twin GU scoops on the bonnet at the front for more flow.




Worked a treat and dropped it from around 110 back to 90.