The infamous air in the cooling question

In my search I have found so many hits on this topic but I still have to ask. I just changed all my hoses, t-stat, bottle etc... and filled up the system or so I thought. I also followed the advise of from the service guy from Jeep who suggested I fill the bottle up and remove the sending unit next to the valve cover to bleed out the air. So I did this (and made a nice mess ) but didn't see much air coming out. I then started it up again and stopped at the gas station before I go to work and saw coolant was almost at the top of the bottle! This leads me to believe there is air caught in the system. Did I need a good run to get the air at or around the temp sensor? Do you think I should bleed the air out this way? I was unsuccessful at finding the block drain. MAybe too much crud...

Thanks

burpin

You can ask 20 people this question,and you will get 20 different
answers.

Thanks for the reply. I guess I will go out the next few mornings and crack open the sensor to bleed out any air, and bring the bottle back up to the 1/2 way mark. Then when I get to work massage the upper radiator hose to hopefully get the air out. I'll continue this until all the air seems to be out.

One question is I hear the t-stat housing should have an air hole in it? I just replaced mine with one from the dealer and do not have this? Should I have this and can be drilled out??

One final note off topic: tomorrow I will be replacing the O2 sensor and an oil change. Then I'm going to take it for the emmissions test again after getting it nice and hot. I got my fingers crossed that it will pass this time.

Do a search and you will spend a long time reading posts on this topic.
If you burp through the sensor, the rear of the truck needs to be higher (to move the traped air to the back of head). And, you won't see air come out, only coolant.
If you fill using upper radiator hose, the front of the truck needs to be higher.
If you don't use either method, the truck needs to go through a few temp cycles to burp the air.
The t-stat housing doesn't have a hole. It is the OEM t-stat itself that has a hole that needs to be oriented at 12 o'clock position.

Good luck ... Maz

Ditto what Maz wrote.

Use only OEM thermostat. None of the aftermarket units have the check valve. You can drill a hole in the flange of an aftermarket t-stat, but that doesn't make it the equivalent of the OEM.

I was shown how to "burp" the system by a friend who was for many years the service manager of a Jeep dealership. Fill the bottle half way, leave cap loose, start engine and let idle until coolant in bottle boils. Shut off engine. Watch the bottle while it cools. After a few minutes it will suddenly start to suck coolant back into the system. At this point start adding coolant to replace what's being sucked in -- keep level at 1/2. When it stops sucking, repeat the process. You'll probably need to do this between four and siz cycles.

You can do the same thing by driving it and then checking the coolant level each time before you start up again.

Thanks Maz and Eagle for the information. I started trying the boil method but was boiling out alot of coolant. Since I'm no coolant pro and was making a bit of a mess I decided to go with removing the sensor. Since my driveway is inclined backing it in brings the rear up higher then the front. When the jeep is warm I notice the coolant level is higher then when its cold. Is this a good indication of trapped air?
Thanks

OEM tstat

Oh just remembered I did get the OEM 195 t-stat and pointed the arrow up for the install.

mudhound32 said:

When the jeep is warm I notice the coolant level is higher then when its cold. Is this a good indication of trapped air?
Thanks

Click to expand...

No, it's an indication that the laws of physics haven't changed.

The liquid expands when hot. That's why the bottle is only supposed to be filled halfway when cold. When hot it will be almost filled -- and under pressure. Just watch it for several days. Take a look every morning before starting it and add enough to bring it back to the halfway level. After a couple or so days you shouldn't need to add any more.

FWIW, the remove the temp sensor method doesn't really work, because the sensor is lower than the bottle. It's better than nothing, but it doesn't purge all the air from the system.