Hi all!

Hoping someone can provide me with a 123 etc list of steps I need to take to drain, flush and refill the coolant.

Its a simple task in principle and something I've done on other cars before, I guess im just wanting to ensure I do it right first time. Not only that, I've seen competing advice across forums on whats best to do.

Any comments/advise is always welcome!

Here are the pages from a copy of the owners manual covering coolant change:

7-4-6 1991 OM Nissan 300ZX.pdf

The drain on the engine block can be awkward to get to and open. A full drain refill will need 10 litres of new anti-freeze/coolant.

You want to be using "Traditional" Inorganic Additive Technology (IAT) Ethylene Glycol base. In this country (winter) 50/50 mix with distilled water is satisfactory. I change mine every two years and get it premixed from Nissan - L248 Premix Engine Coolant/Antifreeze KE902-99945.

Thanks for the tip Andrew - I need to get mine done, so will look up that Nissan product👍

I can reply now 😅

Thanks for the info @AndrewG - I've seen information online saying that this can be flushed without touching the drain on the block and just do it through the rad? Any thoughts on this?

Don't forget that the thermostat will be closed impeding the flow.

I've seen people talking about flushing it with a hose and the engine running for a couple of cycles, to really get rid of any sludge. The water in this is quite brown, so wanting to clean it best I can.

Obvs, to me that sounds interesting to say the least, but equally does make sense. So in my head, I was going to do the following:

1. Take off radiator cap, remove radiator drain plug

2. Look at the rate of water coming out the drain plug, match a rate of water from the hose.

3. Put the hose into the radiator fill cap hole

4. Start the engine and get up to temp

5. Leave it doing that until the water drains out clear. 

6. Stop the engine

7. Let all the water drop out the drain plug

8. Wash through with distilled water

9. Put drain plug back

10. Fill up with coolant. 

Does this make sense? Good or bad idea?

There was a thread a while back taking that approach (scroll down):

https://www.300zx-owners.club/forums/topic/70784-engine-block-coolant-drain-bolt/

I've not done that so can't comment on how well it works.

Edited May 12May 12 by AndrewG