7ate9

Just not sure if this is my coolant sensor (pic below) I'm actually trying to burp my system after a thermostat and WP change.
Thanks

Rockfrog

what you are pointing at is the IAT (Inlet Air Temp) sensor. There is no coolant anywhere in the intake.




The engine Temperature Guage sensor is on the backside of the cylinder head near the firewall, you can almost see it in the first picture, single lead, purple wire.





That's what you want to pop to burp the system if you want to do it that way.

7ate9

Thanks I'll have to move some wires out of the way and get a better look tomorrow .
Is there another way to burp the system ?
I never drained the block, and I back flushed the heater core, pretty clean.
I filled the radiator and coolant reservoir it's a closed system new WP and thermostat .90 xj i6L
Thanks

7ate9

Found it ! Man that's tight back there what size is it??

Rockfrog

IIRC it is either 7/16" or 1/2"

7ate9

Thanks! Wonder if I even need to burp it this way? Heh?

DFlintstone

I think the temp sender is 3/4, (same as 19mm). Not worth the trouble and it might break. I prefer the front of the jeep up about a foot, but level works. Just fill it cold, slow or fill it and come beck after a bit. (50/50 mix). The deal is air needs to weep out that little hole that's up at 12:00 on the thermostat. Then start it and add as it warms up. If it sputters and makes a scene, stop, let it cool some and repeat. That's an expansion bottle to be left at least 1/2 empty so the air in it can compress. Then check it for a day or two.

7ate9

Hey Dflintstone , just got everything back together!
I filled the radiator up and reserve bottle half way.
Thanks for your last post it just confirms everything I've been researching thanks!
Also thanks to Cruiser,thank you!

There should still be water in the block too bc all I did was drain the radiator right?
And I leave the cap off the reserve bottle while it gets up to temp right? (90 xj i6 d-35s 242 TC closed cooling system)

DFlintstone

Yea, leave the cap off while it warms. The coolant in the block drains when you remove the radiator hoses btw. They can be a little stubborn, but it will fill.

7ate9

I just let it run for awhile annnd can't get the electric fan aux to kick on?? I ran it almost to 210* shut her down cause I got scared . Cant get pressure to upper/ lower hose? Anything ? Should I pop the upper of and fill again? Thanks

DFlintstone

The E-fan doesn't come on till it gets pretty hot, like 217*. 210* is what allot of people report running at. Idling with the cap off it will start to boil and spit if it's not done burping. Just turn it off, let it cool some, start it again and keep it filled to 1/2 tank. If it's being extra stubborn you can pull the inner heater hose, (actually right in the center), off the T-stat housing for a minute. Shouldn't be necessary though.

7ate9

When should it have pressure in the upper hose?
I

DFlintstone

After it's burped and the cap is back on.

Rockfrog

I added a fitting to burp my system on my XJ, have the same thing on my 88 MJ as well. $12 off eBay and $2 for a petcock from home Depot.


Saved me a lot of headaches bleeding the cooling system on both vehicles. The 4.0 just has a habit of trapping air in the head. Quick and easy to get it out at the high point now.

7ate9

I can squeeze the bottom hose when it's cooled
And a bubble comes back to the res tank 90 xj 4.0 closed cooling system

How how much longer should I run it, before I drive it?