Jump to content

How do you..flush, fill and burp the closed cooling system

Recommended Posts

I searched the How to Forums..may have missed it but. How do you flush this type of system. Then how do you fill it back up..properly and then burp out the air.

Seems this system, if done wrong, would lend itself to air bubble problems etc.

I know many have swapped to an open system but that is not in the financial cards JUST YET:-)


The previous owner did not run much if any coolant..looks like straight water...judging by the rusty color of the coolant.


I do not have overheating issues as of the moment but...I want to flush out whatever the PO had been running. Heck I HOPE he was smart enough to atleast use distilled water...but I am not too sure. Anyway, any guidance would be a great help. I have bookmarked the swap to an open system but that is a few months away.

By the way this in an 89 Comanche Sport 4.0L


Link to comment
Share on other sites

If the coolant looks rusty, he most likely used tap water. Tap water with iron in it (hard water) will turn rust brown. With a lot of iron will actually leave brown gunk all over the place. This is regardless of whether he used it straight or added antifreeze to it.

Link to comment
Share on other sites

The best way I've found to get that last bit of air out is raise up the back of the truck so the sir will naturally rise to the back of the engine and then use the temp sensor at the back of the head as the air escape valve. If you unscrew it carefully, the air can escape before you pull the sensor completely off :thumbsup: Be very careful and use gloves and eye protection as well as drape a rag over the temp sensor so anitfreeze doesn't spray all over the place.

Link to comment
Share on other sites

...That is kinda how I figured it. Bleed it with engine off. Then start it up with the sensor just loose enough to bleed off air while it runs under pressure. Kinda like bleeding air off of my pressure tank on my pool:-)

I have the service manual but it just says to keep filling the pressure bottle...i could not see how that would ever get all the air out.

Thanks.....time to get cover in coolant.


Link to comment
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now

  • Create New...