Sign in to follow this  

Need information on back flushing coolant system and re-fresh anti freeze on my 1999 DeVille Northstar

Recommended Posts

I am a new forum member.

I need information on back flushing coolant system and re-freshing anti freeze in my 1999 DeVille Northstar.

I would like to use the top heater hose at the heater core and install a back flush tee and use a garden hose to flush until clear water runs through. Does anyone have suggestions or reasons why this will not be advisable?

Thank you for any response.



Share this post

Link to post
Share on other sites

Unless the system is clogged, there is no need to flush it - a simple drain and refill with Dexcool mixed 50/50 with distilled water will do the job. You will not be able to remove all the coolant when draining it as there are no drain plugs on the block. Introducing water into the system will prevent you from reacing a 50% concentration when refilling the system as there will be more than half the system capacity of coolant remaining in the cooling system.

With this in mind, I drain and refill mine every 2-1/2 years. You could also drive the car for a few weeks and then repeat the drain and refill process again to get most of the old coolant out.

'93 Fleetwood Brougham
'05 Deville
'04 Deville
2013 Silverado Z71

Share this post

Link to post
Share on other sites

The reason you don't want to flush it is because tap water has minerals in it that you will not be able to remove, PLUS, you will not be able to get the tap water out of the block and you will have difficulty getting back to a 50/50 mix of coolant to water. Do as KHE recommends, drain and refill with 50/50 coolant to distilled water

Pre-1995 - DTC codes OBD1  >>

1996 and newer - DTC codes OBD2 >>

How to check for codes Caddyinfo How To Technical Archive >>

Cadillac History & Specifications Year by Year

Share this post

Link to post
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.

Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

Sign in to follow this  

  • Recently Browsing   0 members

    No registered users viewing this page.